US20040151616A1

US20040151616A1 - Lead-free alloys, composition thereof, methods of preparation and uses for soldering and babbitting

Info

Publication number: US20040151616A1
Application number: US10/357,848
Authority: US
Inventors: Daniel Sabarese; Harold Stuhler; Mark Sabarese
Original assignee: CHEMICAL AND MEDICAL TECHNOLOGIES Inc
Current assignee: CHEMICAL AND MEDICAL TECHNOLOGIES Inc
Priority date: 2003-02-04
Filing date: 2003-02-04
Publication date: 2004-08-05

Abstract

Lead-free alloys comprising tin, copper, antimony, silver and a lanthanide metal are disclosed. Also disclosed are methods of preparing the lead-free alloys and their use for soldering and babbitting. The lead-free solder alloys exhibit improved tensile and shear strength, and they exhibit flow characteristics similar to those of 50:50 tin:lead alloys.

Description

1. FIELD OF THE INVENTION

The present invention relates to lead-free alloys comprising tin, antimony, copper, silver, and a lanthanide metal, wherein the alloys are substantially free of group IVA elements, group VA elements, bismuth, nickel, and zinc. The lead-free alloys are useful for joining metal surfaces such as brass, bronze, copper, steel, stainless steel, monel and galvanized metal in soldering applications such as plumbing, refrigeration, and roofing. The lead-free alloys are also useful as babbitt alloys. The present invention also relates to methods of preparing the lead free-alloys of the invention.

2. BACKGROUND OF THE INVENTION

Traditional lead-based solder used to join metal water supply pipe is an alloy containing 50 wt. % tin and 50 wt. % lead (hereinafter referred to as “50/50 solder”). The harmful of effects of lead are well known, and recent studies have highlighted risks posed by plumbing systems containing 50/50 solder. Many local plumbing codes now prohibit the use of lead-containing solders in potable water systems. As a result there is considerable effort directed at lead-free alloys useful as replacements for 50/50 solder.

A suitable replacement for 50/50 solder should have physical properties similar or superior to those of the lead-based solder. For example, 50/50 solder exhibits a melting range from about 182° to about 216° C. The lower temperature is referred to as the solidus point, corresponding to the temperature at the onset of melting. The upper temperature is referred to as the liquidus point, corresponding to the temperature at which the alloy is fully liquified. Within this range, 50/50 solder forms a “mush” or “slush” that exhibits good gap-filling capabilities. However, if the temperature of the molten alloy is too high, e.g., above the liquidus point, the gap-filling capabilities of the alloy are diminished due to decreased viscosity.

Lead-free solder alloys comprising tin as the base metal are known, but such alloys tend to have higher melting points than 50/50 solder. For example, a lead-free solder alloy containing 95 wt. % tin and 5 wt. % antimony exhibits a solidus point of 252° C. and a liquidus point of 262° C.

By replacing all or part of the antimony, the melting range of the tin-based lead-free solder alloys can be altered. A lead-free solder alloy containing 95.5 wt. % tin, 4 wt. % copper and about 0.5 wt. % silver exhibits a solidus point of 239° C. and a liquidus point of 359° C.

A solder alloy containing 95 wt. % tin, 3 wt. % antimony, 1.5 wt. % bismuth, and 0.5 wt. % silver exhibits a solidus point of 233° C. and a liquidus point of 252° C.

A lead-free solder alloy containing about 95.5 wt. % tin, 4.7 wt. % copper, and 0.13 wt. % selenium and/or tellurium exhibits a solidus point of 224° C. and a liquidus point of 234° C.

A lead-free solder alloy containing 94.5 wt. % tin, 3.0 wt. % antimony, 0.5 wt. % silver, 1.5 wt. % zinc, and 0.5 wt. % copper exhibits a solidus point of 230° C. and a liquidus point of 249° C.

Lead-free solder alloys containing tin, silver, and a lanthanide metal are known. Inclusion of a lanthanide metal in the tin-based alloys allegedly lowers the melting point and improves the mechanical properties of the tin-based alloys. To avoid oxidizing the lanthanide metal, the alloys are often prepared under a non-oxidizing atmosphere.

Inclusion of elements of group IVa and/or a group Va, particularly titanium, allegedly increases the wetting power of the lead-free tin-based alloys and further serves to reduce the surface tension of the molten alloys. However, the group IVa and/or a group Va elements present in these alloys are prone to oxidation, so a sacrificial element such as a lanthanide metal is often used as an oxygen scavenger in these alloys. However, the resultant lanthanide metal-oxygen complexes have no effect on the properties or performance of the resultant alloys.

Lead alloys and tin alloys are also used in babbitting applications, typically where metal surfaces are subject to abrasion. Babbitt alloys are typically divided into high lead alloys (≧70% lead by weight) and high tin alloys (>80% tin by weight), wherein the high tin babbitt alloys typically contain 10 wt. % or less of lead.

High tin babbitt alloys exhibit relatively high complete liquefaction temperatures (˜370-425° C.) as compared to the high lead alloys (˜270-280° C.). Babbitt alloys are heated to a temperature above the complete liquefaction temperature before they are applied to a metal substrate, so the high tin babbitt alloys also require higher pouring temperatures than do high lead babbitt alloys. Concerns with release of lead into the environment, however, have caused the babbitting industry to favor tin alloys over lead alloys.

There remains, however, a need for improved lead-free solder alloys and babbitt alloys.

3. SUMMARY OF THE INVENTION

The present invention relates to lead-free alloys, uses of the lead-free alloys, and methods of preparing the lead-free alloys.

In one embodiment, the present invention relates to lead-free solder alloys useful for plumbing, refrigeration, and roofing applications, wherein the alloys comprise tin, antimony, copper, silver, and a lanthanide metal; and the alloys are substantially free of group IVa elements, group Va elements, bismuth, nickel, and zinc. Preferably, the lanthanide metal is selected from the group consisting of lanthanum, cerium, neodynium, samarium, europium, and mixtures thereof. More preferably, the lanthanide metal is cerium.

In another embodiment, the present invention also relates to lead-free solder alloys useful for plumbing, refrigeration, and roofing applications, wherein the alloy consists essentially of tin, antimony, copper, silver, and cerium; and the alloy is substantially free of group IVa elements, group Va elements, bismuth, nickel, and zinc.

The present invention also relates to methods of preparing lead-free solder alloys.

In one embodiment, the invention relates to methods of preparing lead free-alloys useful for plumbing, refrigeration, and roofing applications comprising the steps of:

preparing a molten first alloy comprising tin, antimony and copper;

optionally adding a scavenger to the molten first alloy to form a scavenger-contaminant complex; and

removing the scavenger-contaminant complex from the molten first alloy;

adding a lanthanide metal-containing second alloy to the molten first alloy to form a molten lead-free alloy;

processing the molten lead-free alloy into a shape; and

cooling the lead-free alloy to form a solid form of said shape; wherein

the lead-free alloy is substantially free of group IVa elements, group Va elements, bismuth, nickel and zinc. Optionally, the tin used in the molten first alloy is high purity tin.

The invention also relates to methods of using a lead-free solder alloy for joining metal surfaces in plumbing, refrigeration, and roofing applications, wherein the alloy comprises tin, antimony, copper, silver, and a lanthanide metal; and the alloy is substantially free of group IVa elements, group Va elements, bismuth, nickel, and zinc.

The present invention is also directed to lead-free babbitt alloys. In one embodiment, the present invention relates to lead-free babbitt alloys, wherein the alloy comprises tin, antimony, copper, silver, and a lanthanide metal; and the alloy is substantially free of group IVa elements, group Va elements, bismuth, nickel, and zinc.

In another embodiment, the invention relates to methods of preparing a lead free-babbitt alloy comprising the steps of:

preparing a molten first alloy comprising tin, antimony and copper;

optionally, adding a scavenger to the molten first alloy to form a scavenger-contaminant complex; and

removing the scavenger-contaminant complex from the molten first alloy;

processing the molten lead-free alloy into a shape; and

cooling the lead-free alloy to form a solid form of said shape; wherein

The present invention also relates to methods of using lead-free alloys for babbiting, wherein the alloy comprises tin, antimony, copper, silver, and a lanthanide metal; and the alloy is substantially free of group IVa elements, group Va elements, bismuth, nickel, and zinc.

The present invention may be understood more fully by reference to the following detailed description and illustrative examples, which are intended to exemplify non-limiting embodiments of the invention.

4. DETAILED DESCRIPTION OF THE INVENTION

4.1 Definitions

As used herein, the term “babbitt” refers to a “soft” alloy which is applied to a metal substrate. As used herein, the term “babbitting” refers to a process whereby a “soft” alloy coating is applied to a metal substrate. [0038]
As used herein, the phrase “complete liquefaction point or temperature” refers to the temperature at which a babbitt alloy passes from a mush or pasty state to a liquid state. [0039]
As used herein, the phrase “group IVa metals” refers to metals of the titanium triad in the Periodic Table of the Elements, i.e., titanium, zirconium, and hafnium. [0040]
As used herein, the phrase “group Va metals” refers to metals of the vanadium triad in the Periodic Table of the Elements, i.e., vanadium, niobium, and tantalum. [0041]
As used herein, the phrase “lanthanide metal” refers to lanthanum and the fourteen elements that follow lanthanum in the Periodic Table of the elements, i.e., lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium. [0042]
As used herein, the phrase “lead free” means the maximum lead content is 0.15 wt. %. [0043]
When used to describe a solder alloy, the phrase “melting range” refers to the temperature range at which the alloy begins to melt (solidus point) up to the temperature at which the alloy is in a liquid state (liquidus point). When used to describe a babbitt alloy, the phrase “melting range” refers to the temperature range at which the alloy begins to melt (melting point) up to the temperature at which the alloy is in a liquid state (liquefaction point). [0044]
As used herein, the term “paste” refers to a composition comprising a flux and a powder form of the lead-free alloy of the invention. [0045]
As used herein, the term “preform” refers to a solder composition comprising solder in a specific shape or design, e.g., a ring or triangle. [0046]
As used herein, the phrase “proper pouring temperature” refers to the temperature of a babbitt alloy at which it becomes suitable for application to a substrate. This temperature is above the complete liquefaction temperature of the babbitt alloy. [0047]
As used herein, the term “scavenger” refers to a material which removes contaminants or impurities from a molten alloy. [0048]
As used herein, the acronym “SEM” means scanning electron microscope. [0049]
As used herein, the phrase “substantially free” means that the maximum content of an impurity metal is 1 wt. %, preferably 0.5 wt. %, most preferably 0.1 wt. % based on the weight of alloy. The maximum content of impurity metals will typically be 0.03 wt. % based on the weight of alloy. [0050]

4.2 The Lead-Free Alloys

4.2.1 Solder Alloys

The present invention is directed to lead-free solder alloys. The lead-free solder alloys of the present invention exhibit improved tensile and shear strength compared to other known lead-free solder alloys used for plumbing, refrigeration, and roofing applications. The lead-free solder alloys of the present invention also exhibit melting ranges and flow characteristics similar to those of 50:50 tin:lead solder, and provide a joint that is bright and shiny. In addition, the alloys meet or exceed all state and federal regulations for potable water applications. [0051]
In one embodiment, the present invention relates to lead-free solder alloys useful for plumbing, refrigeration, and roofing applications, wherein the alloy comprises tin, antimony, copper, silver, and a lanthanide metal; and the alloy is substantially free of group IVa elements, group Va elements, bismuth, nickel, and zinc. [0052]
The base metal of the lead-free solder alloys is tin, and it typically comprises more than 95 wt. % of the alloy. Tin is a relatively soft metal. Without being limited by theory, it is believed that the addition of antimony, copper, and silver hardens the tin base. [0053]
The alloys of the present invention further require a lanthanide metal. Preferably, the lanthanide metal is selected from the group consisting of lanthanum, cerium, neodynium, samarium, europium and mixture thereof. More preferably, the lanthanide metal is cerium. [0054]
Without being limited by theory, it is believed that inclusion of the lanthanide metal in the alloy hardens the tin base and improves the tensile strength, elasticity, and flowability of the alloy. Without wishing to be bound by theory, it is believed that the improved elasticity is the result of a lowering of the coefficient of expansion of the tin base. For example, the lead-free solder alloys of the present invention exhibit a tensile strength in the range from about 5500 to about 8500 psi. In a preferred embodiment, the tensile strength of the lead-free solder alloys of the present invention ranges from about 6500 to about 7500 psi. More preferably, the tensile strength is about 7100 psi. [0055]
The lead-free solder alloys of the present invention exhibit a Brinell hardness ranging from about 15 to about 25. In a preferred embodiment, the Brinell hardness ranges from about 18 to about 25. More preferably, the Brinell hardness is about 20. [0056]
The lead-free solder alloys of the present invention also exhibit an elongation in the range from about 25 to about 40%. In a preferred embodiment, the elongation ranges from about 30 to about 35%. [0057]
In one embodiment, the lead-free solder alloy comprises at least 96 wt. % tin, 0.25 to 1% wt. % antimony, 0.25 to 4 wt. % copper, 0.05 to 0.5 wt. % silver, and 0.01 to 0.3 wt. % lanthanide metal, preferably 0.03 to 0.1 wt. % lanthanide metal. [0058]
In a preferred embodiment, the lead-free solder alloy comprises at least 96 wt. % tin, 0.25 to 1% wt. % antimony, 0.25 to 4 wt. % copper, 0.05 to 0.5 wt. % silver, and 0.01 to 0.3 wt. % cerium, more preferably 0.03 to 0.1 wt. % cerium. [0059]
In another embodiment, the present invention also relates to lead-free solder alloys useful for plumbing, refrigeration, and roofing applications, wherein the alloy consists essentially of tin, antimony, copper, silver, and cerium; and the alloy is substantially free of group IVa elements, group Va elements, bismuth, nickel, and zinc. [0060]
The melting range of the lead-free solder alloy is defined by the solidus and liquidus points or temperatures. The lead-free solder alloy of the present invention exhibits a melting range of from about 190° C. (solidus point) to about 320° C. (liquidus point). In a preferred embodiment, the melting range of the lead-free solder alloy is from about 210° C. (solidus point) to about 280° C. (liquidus point). [0061]

4.2.2 Babbitt Alloys

Babbitt alloys are divided into high tin alloys (>80% by weight tin) that are substantially lead-free, and high lead materials that contain ≧70% lead by weight (see Kirk-Othmer: [0062] Encyclopedia of Chemical Technology 24:119-129 (1997)). Standard specifications for babbitt alloys or “metals” and methods of testing the babbitt alloys are disclosed in ASTM B 23 (1999).
In one embodiment, the present invention relates to lead-free babbitt alloys which exhibit improved strength, resistance to cracking, and improved grain restructuring without loss of anti-friction properties. [0063]
In a preferred embodiment, the yield point of the lead-free babbitt alloys of the present invention ranges from about 3400 to about 7500 psi. More preferably, the yield point is about 7100 psi. [0064]
The lead-free babbitt alloys of the present invention also exhibit a Brinell hardness (20° C.) ranging from about 15 to about 27. In a preferred embodiment, the Brinell hardness ranges from about 18 to about 25. More preferably, the Brinell hardness is about 20. [0065]
In another embodiment, the invention relates to lead-free babbitt alloys, wherein the alloy comprises tin, antimony, copper, silver, and a lanthanide metal; and the alloy is substantially free of group IVa elements, group Va elements, bismuth, nickel, and zinc. [0066]
Preferably, the lanthanide metal is selected from the group consisting of lanthanum, cerium, neodynium, samarium, europium and mixture thereof. More preferably, the lanthanide metal is cerium. [0067]
In one embodiment, the lead-free babbitt alloy of the present invention comprises at least 84 wt. % tin, 3 to 8 wt. % antimony, 3 to 8 wt. % copper, 0.05 to 0.5 wt. % silver, and 0.01 to 0.30 wt. % lanthanide metal, preferably 0.03 to 0.1 wt. % lanthanide metal. [0068]
In a preferred embodiment, the lead-free babbitt alloy of the present invention comprises at least 84 wt. % tin, 3 to 8 wt. % antimony, 3 to 8 wt. % copper, 0.05 to 0.5 wt. % silver, and 0.01 to 0.30 wt. % cerium, preferably 0.01 to 0.1 wt. % cerium. [0069]
In another embodiment, the invention relates to lead-free babbitt alloys, wherein the alloy consists essentially of tin, antimony, copper, silver, and cerium; and the alloy is substantially free of group IVa elements, group Va elements, bismuth, nickel, and zinc. [0070]
The melting range of the lead-free babbitt alloy is defined by the melting and complete liquefaction points or temperatures. The lead-free babbitt alloys of the present invention exhibit a melting range from about 275° C. (melting point) to about 375° C. (complete liquefaction point). In a preferred embodiment, the melting range of the lead-free babbitt alloy is from about 300° C. (melting point) to about 350° C. (complete liquefaction point). [0071]

4.3 Methods of Preparing the Lead-Free Alloys

The present invention is also directed to methods of preparing lead-free alloys useful for soldering and babbiting. [0072]

4.3.1 Lead-Free Solder Alloys

In one embodiment, the invention relates to methods of preparing lead free-alloys useful for plumbing, refrigeration, and roofing applications comprising the steps of: [0073]
preparing a molten first alloy comprising tin, antimony and copper; [0074]
optionally adding a scavenger to the molten first alloy to form a scavenger-contaminant complex; and [0075]
removing the scavenger-contaminant complex from the molten first alloy prior to addition of the second alloy; [0076]
adding a lanthanide metal-containing second alloy to the molten first alloy to form a molten lead-free alloy; [0077]
forming the molten lead-free alloy into a shape; and [0078]
cooling the lead-free alloy to form a solid form of said shape; wherein [0079]
the lead-free alloy is substantially free of group IVa elements, group Va elements, bismuth, nickel and zinc. Preferably, the tin used in the molten first alloy is high purity tin. [0080]
Preferably, the lanthanide metal is selected from the group consisting of lanthanum, cerium, neodynium, samarium, europium and mixtures thereof. More preferably, the lanthanide metal is cerium. [0081]
In one embodiment, the lead-free solder alloy prepared by the method of the present invention comprises at least about 96 wt. % tin; 0.25 to 4 wt. % antimony; 0.25 to 4 wt. % copper; 0.05 to 0.5 wt. % silver, and 0.01 to 0.3 wt. % lanthanide, preferably 0.03 to 0.1 wt. % lanthanide. [0082]
In a preferred embodiment, the lead-free solder alloy prepared by the method of the present invention comprises at least about 96 wt. % tin; 0.25 to 4 wt. % antimony; 0.25 to 4 wt. % copper; 0.05 to 0.5 wt. % silver, and 0.01 to 0.3 wt. % cerium, preferably 0.03 to 0.1 wt. % cerium. [0083]
The first alloy is prepared by charging about 1.5 to 6.0 parts by weight copper, about 0.5 to 2.0 parts by weight antimony, and 92 to 98 parts tin to a kettle; heating the contents of the kettle to about 350°-400° C. and mixing to form the molten first alloy. [0084]
In the present invention, a second alloy comprising a lanthanide metal is added to the molten first alloy. In one embodiment the second alloy is prepared by charging about 1-10 parts by weight cerium, about 3-30 parts silver, and 60 to 96 parts tin to a crucible. The contents of the crucible are heated and mixed with a graphite rod as a molten mass forms. The heating is continued until the contents of the crucible reach a temperature of about 600 to 800° C., preferably about 700° C. The molten second alloy is then charged to ingot molds (one to two lbs.) and cooled to ambient temperature to provide a solid form of the second alloy comprising 1-10 wt. % cerium, 3-30 wt. % silver, and the balance tin. [0085]
In another embodiment, the method further comprises addition of a third alloy to the molten first alloy, wherein the second alloy comprises 1-10 wt. % cerium and the balance tin; and the third alloy comprises 3-30 wt. % silver and the balance tin. The second alloy is prepared by adding 1-10 parts by weight cerium to a tin bath containing 90-99 parts tin at a temperature of 600 to 800° C., preferably about 700° C. The third alloy is prepared by adding 3-30 parts by weight silver to tin bath containing 70-97 parts tin at a temperature of 600 to 800° C., preferably about 700° C. The resultant second and third alloys are then formed into ingots as described above. [0086]
The lead-free solder alloy of the invention is prepared by adding sufficient quantity of the second alloy, and optionally the third alloy, to the molten first alloy to form a lead-free alloy comprising at least about 96 wt. % tin; 0.25 to 4 wt. % antimony; 0.25 to 4 wt. % copper; 0.05 to 0.5 wt. % silver, and 0.01 to 0.3 wt. % cerium, preferably 0.03 to 0.1 wt. % cerium. The molten lead-free solder alloy is then cast or extruded into the desired shape and cooled to form the solid form of the cast or extruded shape. [0087]
In another embodiment the lead-free alloy of the present invention may be prepared by charging about 0.05 to 0.5 parts by weight silver to a kettle containing 0.25 to 4 parts copper, 0.25 to 4 parts antimony and 92-98 parts tin. The contents of the kettle are mixed and heated to 350 to 400° C. Cerium (0.01 to 1.0 parts by weight) is then added to the resultant melt via a plunger. The resultant lead-free alloy is mixed for an additional 2-5 minutes or until all metals have melted. The molten lead-free alloy is then charged to ingot molds as described above to provide a solid form of the lead-free alloy comprising at least about 96 wt. % tin; 0.25 to 4 wt. % antimony; 0.25 to 4 wt. % copper; 0.05 to 0.50 wt. % silver, and 0.01 to 0.3 wt. % cerium, preferably 0.03 to 0.1 wt. % cerium. [0088]
Typical cast or extruded shapes of the lead-free solid solder include wire, bar, foil, preform or powder. Powder forms of the alloy may be prepared by, e.g., atomizing the molten form of the alloy or milling a solid form of the alloy. [0089]
In one embodiment, the powder form of the lead-free alloy is combined with a flux to form a paste. [0090]
Methods of preparing the lead-free alloys may optionally comprise addition of a scavenger to the molten first alloy. Without being limited to theory, it is believed that the scavenger removes contaminants present in the molten first alloy which would otherwise react with the lanthanide metal present in the second alloy. For example, metals used to prepare the first alloy may contain contaminants such as, e.g., carbon, silicon, halides, oxides, sulfides, phosphides, other nonmetals; and metal contaminants such as the oxides of iron and copper. These contaminants can adversely affect the beneficial properties of the lanthanide metal component of the lead-free alloy by forming a complex with the contaminants, particularly at elevated temperature (see, e.g., Cotton and Wilkinson: Inorganic Chemistry 990 (1980)). The resultant lanthanide metal-contaminant complexes will “float” to the surface of the molten alloy and will not be incorporated into the alloy. It is highly desirable that the metals used to prepare the lead-free alloy of the present invention are of high purity, preferably at least 99.85% pure, more preferably at least 99.95% pure, most preferably 99.99% pure. Such high purity metals are readily available from commercial suppliers. [0091]
Scavenger complexes useful in the invention are well-known in the art of metal alloys. The scavenger is typically a metal or metal salt which forms a complex or “dross” with the contaminants in preference to the first alloy metals. The resultant scavenger-contaminant complex is then separated from the molten first alloy prior to addition of the lanthanide metal-containing second alloy and, optionally, the silver-containing third alloy. In a preferred embodiment the scavenger-metal complex floats on the surface of the molten first alloy and is skimmed off the surface prior to addition of the second alloy. [0092]
The types of contaminants present in the molten first alloy dictate the specific scavenger(s) to be employed. For example, residual zinc may be removed by use of a caustic soda scavenger, while acid residues, e.g., sulfate or phosphate, may be removed with a soda ash scavenger. A non-limiting example of a scavenger useful in the invention comprises 5 wt. % sodium chloride, 5 wt. % potassium chloride, 10 wt. % caustic and the balance soda ash. [0093]
In another embodiment, the invention relates to methods of preparing lead free-alloys useful for plumbing, refrigeration, and roofing applications consisting essentially of: [0094]
preparing a molten first alloy comprising tin, antimony and copper; [0095]
adding a scavenger to the molten first alloy to form a scavenger-contaminant complex; and [0096]
removing the scavenger-contaminant complex from the molten first alloy; [0097]
adding a lanthanide metal-containing second alloy to the molten first alloy to form a molten lead-free alloy; [0098]
forming the molten lead-free alloy into a shape; and [0099]
cooling the lead-free alloy to form a solid form of said shape; wherein [0100]
the lead-free alloy is substantially free of group IVa elements, group Va elements, bismuth, nickel and zinc. Preferably, the tin used in the molten first alloy is high purity tin. [0101]

4.3.2 Lead-Free Babbitt Alloys

The present invention also relates to methods of preparing lead free-babbitt alloys. Such alloys can be prepared by methods similar to those used to prepare the lead-free solder alloys. [0102]
In one embodiment, the invention relates to methods of preparing lead free-babbitt alloys comprising: [0103]
preparing a molten first alloy comprising tin, antimony and copper; [0104]
optionally adding a scavenger to the molten first alloy to form a scavenger-contaminant complex; and [0105]
removing the scavenger-contaminant complex from the molten first alloy; [0106]
adding a lanthanide metal-containing second alloy to the molten first alloy to form a molten lead-free alloy; [0107]
forming the molten lead-free alloy into a shape; and [0108]
cooling the lead-free alloy to form a solid form of said shape; wherein [0109]
the lead-free alloy is substantially free of group IVa elements, group Va elements, bismuth, nickel and zinc. Preferably, the tin used in the molten first alloy is high purity tin. [0110]
Preferably, the lanthanide metal is selected from the group consisting of lanthanum, cerium, neodynium, samarium, europium and mixtures thereof. More preferably, the lanthanide metal is cerium. [0111]
In one embodiment, the lead-free babbitt alloy prepared by the method of the invention comprises at least about 96 wt. % tin; 0.25 to 4 wt. % antimony; 0.25 to 4 wt. % copper; 0.05 to 0.5 wt. % silver, and 0.01 to 0.3 wt. % lanthanide, preferably 0.03 to 0.1 wt. % lanthanide. [0112]
In a preferred embodiment, the lead-free babbitt alloy prepared by the method of the invention comprises at least about 96 wt. % tin; 0.25 to 4 wt. % antimony; 0.25 to 4 wt. % copper; 0.05 to 0.5 wt. % silver, and 0.01 to 0.3 wt. % cerium, preferably 0.03 to 0.1 wt. % cerium. [0113]
The first alloy is prepared by charging about 3 to 8 parts copper, about 3 to 8 parts antimony, and about 85 to about 94 parts by weight tin to a kettle; and heating the contents of the kettle to a temperature of about 350° to about 400° C. while mixing to form a molten first alloy. [0114]
In the present invention a second alloy comprising a lanthanide metal is added to the molten first alloy to form the lead-free babbitt alloy of the invention. [0115]
Preferably, the lanthanide metal is selected from the group consisting of lanthanum, cerium, neodynium, samarium, europium and mixtures thereof. More preferably, the lanthanide metal is cerium. [0116]
In another embodiment, the second alloy is prepared by charging about 1-10 parts by weight cerium, about 3-30 parts silver, and 60 to 96 parts tin to a crucible. The contents of the crucible are heated and mixed with a graphite rod as a molten mass forms. The heating is continued until the contents of the crucible reach a temperature of about 600 to 800° C., preferably about 700° C. The molten second alloy is then charged to ingot molds (one to two lbs.) and cooled to ambient temperature to provide a solid form of the second alloy comprising 3-30 wt. % cerium, 10-30 wt. % silver, and the balance tin. [0117]
In another embodiment, the method further comprises addition of a third alloy to the molten first alloy, wherein the second alloy comprises 1-10 wt. % cerium and the balance tin; and the third alloy comprises 3-30 wt. % silver and the balance tin. The second alloy is prepared by adding 1-10 parts by weight cerium to a tin bath containing 90-99 parts tin at a temperature of 600 to 800° C., preferably about 700° C. The third alloy is prepared by adding 3-30 parts by weight silver to tin bath containing 70-97 parts tin at a temperature of 600 to 800° C., preferably about 700° C. The resultant second and third alloys are then formed into ingots as described above. [0118]
The lead-free babbitt alloy is then prepared by adding sufficient quantity of the second alloy, and optionally the third alloy, to the molten first alloy to form a lead free alloy comprising at least about 85 wt. % tin, 3 to 8 wt. % antimony, 3 to 8 wt. % wt. % copper; 0.05 to 0.5 wt. % silver, and 0.01 to 0.3 wt. % cerium, preferably 0.03 to 0.1 wt. % cerium. The molten lead-free babbitt alloy is then cast or extruded into the desired shape as described above. [0119]
A scavenger as described above for the lead-free solder alloys may optionally be added to the molten first alloy to remove contaminants. [0120]
In one embodiment, the invention also relates to methods of preparing lead free-babbitt alloys consisting essentially of: [0121]
preparing a molten first alloy comprising tin, antimony and copper; [0122]
optionally adding a scavenger to the molten first alloy to form a scavenger-contaminant complex; and [0123]
removing the scavenger-contaminant complex from the molten first alloy; [0124]
adding a lanthanide metal-containing second alloy to the molten first alloy to form a molten lead-free alloy; [0125]
forming the molten lead-free alloy into a shape; and [0126]
cooling the lead-free alloy to form a solid form of said shape; wherein [0127]
the lead-free alloy is substantially free of group IVa elements, group Va elements, bismuth, nickel and zinc. Preferably, the tin used in the molten first alloy is high purity tin. [0128]

4.4 Methods of Using the Lead-Free Alloy

The invention also relates to methods of using a lead-free alloy for soldering and babbitting. [0129]

4.4.1 Methods of Soldering

When used for soldering metal surfaces, the lead-free alloy can be used in accordance with methods well-known in the art. In a typical soldering application, the metal surfaces to be joined are cleaned to remove surface contaminants, and a flux is applied to the surface to further remove residual oxide film from the surfaces. The metal surfaces are then aligned in the desired manner to form a joint. A heat source, e.g., a propane or an acetylene torch, is applied to the joint, and the joint is heated to sufficient temperature to cause the solder to form a liquid. A sufficient amount of solder is applied to the heated joint, the resultant liquified alloy flows into the joint through capillary action, and the liquid solder bridges the solid surfaces. The solder is then allowed to cool, causing the solder to solidify to form a hardened joint. [0130]
In one embodiment the invention relates to methods of using a lead-free solder alloy for joining metal surfaces in plumbing, refrigeration, and roofing applications, wherein the alloy comprises tin, antimony, copper, silver, and a lanthanide metal; and the alloy is substantially free of group IVa elements, group Va elements, bismuth, nickel, and zinc. [0131]
In one embodiment, the metal surfaces are selected from the group consisting of brass, bronze, copper, steel, stainless steel, monel and galvanized metal. As used herein the term “monel” refers to a nickel-copper alloy comprising 66 wt. % nickel and 31 wt. % copper. Galvanized metal refers to the zinc-based coating applied to the surface of certain metals to inhibit corrosion. [0132]
The choice of flux is determined by the metals to be joined and the service to which the joined metal(s) will be used, i.e. plumbing, refrigeration, or roofing applications (see, e.g., ASTM B32 (1999)). Preferably, the flux is a water-soluble paste flux that contains no zinc, ammonium chloride, petrolatum or metals and can be used for joining all metal surfaces except aluminum and stainless steel. One example of a flux that can be used for the present invention is ORANGE CRUSH paste flux, available from Precise Alloys, Bronx, N.Y. Aluminum and stainless steel are joined using any conventional flux used for soldering such metals. [0133]

4.4.2 Methods of Babbitting

The present invention also relates to methods of using a lead-free alloy for babbitting. A babbitt alloy is typically applied to the surface of a substrate metal, where the substrate metal may cause wearing or scoring of another metal part. For example, the babbitt alloy may be applied to a sleeve or support of a rotating or sliding metal shaft. The softer babbitt layer wears preferentially, thereby increasing the service life of the moving metal part. Kirk-Othmer: [0134] Encyclopedia of Chemical Technology 24:119-129 (1997)) describes methods of babbitting, and further discloses that babbitt alloys are divided into high tin alloys (>80% tin by weight) that are substantially lead-free, and high lead materials (>70% lead by weight).
U.S. Pat. No. 4,117,580 to Heck discloses methods of applying a babbitt alloy to a substrate. The surface to be coated with the babbitt alloy is cleaned, a flux is applied to the cleaned metal surface, and the surface is coated with molten tin. Excess tin is removed, and the babbitt alloy is applied to the “tinned” surface. U.S. Pat. No. 4,117,580 also discloses a method of babbitting where a tin powder/flux slurry is applied to cleaned substrate metal surface, the coated substrate is heated to the tinning temperature, i.e., at or above the melting point of tin, and a flux/water mixture is sprayed on the heated tin coating. The molten form of the babbitt alloy is then applied to the tin coating followed by cooling or quenching. [0135]
U.S. Pat. No. 6,117,565 to Wengler et al. describes methods for applying babbitt alloys to a substrate including statically casting, centrifugally casting or tig welding. [0136]
Once applied, the excess babbitt alloy may be removed by any known method used in the art such as machining or polishing to produce the babbitted material with the desired size and shape. [0137]
The following examples are set forth to assist in understanding the invention and should not, of course, be construed as specifically limiting the invention described and claimed herein. Such variations of the invention, including the substitution of all equivalents now known or later developed, which would be within the purview of those skilled in the art, and changes in formulation or minor changes in experimental design, are to be considered to fall within the scope of the invention incorporated herein. [0138]
A number of references have been cited, the entire disclosures of which are incorporated herein by reference. [0139]

5. EXPERIMENTAL

5.1 Example 1

Example 1 describes the preparation and properties of a lead-free solder alloy of the invention. [0140]
A pre-formed cerium-containing second alloy was prepared by charging 5 parts by weight cerium, 15 parts silver, and 80 parts tin to a crucible. The contents of crucible were mixed with a graphite rod as they were heated to a temperature of 700° C. After about 2-5 minutes of mixing all the metals were dissolved, and the resultant molten cerium-containing second alloy was charged to ingot molds (one or two pound molds) and allowed to cool to ambient temperature to form solid ingots. [0141]
A first alloy was prepared by charging of 2.75 parts by weight copper, 1 part antimony, and 96.25 parts tin to a kettle. The contents of the kettle were heated to a temperature of 350°-400° C. with mixing. A scavenger was added to the molten first alloy, and the resultant “dross” was skimmed off the top of the molten first alloy. [0142]
The cerium-containing second alloy (1.63 parts) was added to the molten first alloy, and the resultant molten lead-free solder alloy was mixed for five minutes. The molten alloy was then cast into ingots or extruded to provide a lead-free solder alloy (Table 1). [0143]

TABLE 1

Composition of the lead-free alloy of Example 1.

Metal Content in alloy, wt. %

Cerium 0.08

Silver 0.25

Antimony 0.98

Copper 2.71

Tin balance

5.2 Example 2

A lead-free alloy was prepared by adding 10.8 parts copper, 3.9 parts antimony, and 1 part silver to a kettle containing 384 parts by weight tin. The contents of the pot were mixed at 350° C. Cerium (0.32 parts by weight) was then added to the resultant melt via plunger. The resultant lead-free alloy was mixed for an additional 2-5 minutes at which point all the cerium had dissolved. The molten lead-free alloy was then charged to ingot molds as described in Example 1 provide a solid form of the lead-free alloy. [0144]

5.3 Example 3

A pre-formed cerium-containing second alloy was prepared by charging 5 parts by weight cerium to a molten tin bath (95 parts tin) at 700° C. The contents of the bath were held at 700° C. while the contents were stirred with a graphite rod. The resultant cerium-containing second alloy was charged to ingot molds (one or two pound molds), and the second alloy was allowed to cool to ambient temperature to form solid ingots. [0145]
A pre-formed silver-containing third alloy was prepared by charging 15 parts by weight silver to a molten tin bath (85 parts) at 700° C. The contents of the bath were held at 700° C. and stirred with a graphite rod. The resultant silver-containing third alloy was charged to ingot molds (one or two pound molds), and the third alloy was allowed to cool to ambient temperature to form solid ingots. [0146]
A first alloy was prepared by charging of 2.75 parts by weight copper, 1 part antimony, and 96.25 parts tin to a kettle. The contents of the kettle were heated to 350°-400° C. and mixed to form a molten mass. A scavenger was added to the molten first alloy, and the resultant “dross” was skimmed off the top of the molten first alloy. [0147]
The cerium-containing second alloy (1.65 parts) and the silver-containing third alloy (1.65 parts) were added to the molten first alloy, and the resultant molten lead-free solder alloy was stirred for five minutes. The molten alloy was then cast into ingots or extruded to provide a lead-free solder alloy: [0148]
All patents cited in the foregoing text are expressly incorporated herein by reference in their entirety. [0149]
It will be understood that the claims are intended to cover all changes and modifications of the preferred embodiments of the invention, herein chosen for the purpose of illustration, which do not constitute a departure from the spirit and scope of the invention. [0150]

Claims

We claim:

1. A lead-free solder alloy useful for plumbing, refrigeration, and roofing applications, wherein the alloy comprises tin, antimony, copper, silver, and a lanthanide metal; and the alloy is substantially free of group IVa elements, group Va elements, bismuth, nickel, and zinc.

2. The lead-free alloy of claim 1, wherein the lanthanide metal is selected from the group consisting of lanthanum, cerium, neodynium, samarium, europium and mixtures thereof.

3. The lead-free alloy of claim 2, wherein the alloy comprises at least 96 wt. % tin, 0.25 to 1 wt. % antimony, 1 to 4 wt. % copper, 0.05 to 0.5 wt. % silver and 0.1 to 0.3 wt. % lanthanide metal.

4. The lead-free alloy of claim 3, wherein the lanthanide metal content is 0.03% to 0.1 wt. % based on the weight of the alloy.

5. The lead-free alloy of claim 2, wherein the lanthanide metal is cerium.

6. The lead-free alloy of claim 5, wherein the alloy comprises at least 96 wt. % tin, 0.25 to 1% wt. % antimony, 1 to 4 wt. % copper, 0.05 to 0.5 wt. % silver, and 0.01 to 0.3 wt. % cerium.

7. The lead-free alloy of claim 6, wherein the cerium content is 0.03% to 0.1 wt. % based on the weight of the alloy.

8. The lead-free alloy of claim 7, wherein the melting range is from about 190° C. to about 300° C.

9. The lead-free alloy of claim 8, wherein the melting range is from about 210° C. to about 280° C.

10. A lead-free solder alloy useful for plumbing, refrigeration, and roofing applications wherein the alloy consists essentially of tin, antimony, copper, silver, and cerium; and the alloy is substantially free of group IVa elements, group Va elements, bismuth, nickel, and zinc.

11. A method of preparing a lead free-alloy useful for plumbing, refrigeration, and roofing applications comprising:

preparing a molten first alloy comprising tin, antimony and copper;

adding a lanthanide-containing second alloy to the molten first alloy to form a molten lead-free alloy;

processing the molten lead-free alloy into a shape; and

cooling the lead-free alloy to form a solid form of said shape; wherein

the lead-free alloy is substantially free of group IVa elements, group Va elements, bismuth, nickel and zinc.

12. The lead-free alloy of claim 11, wherein the lanthanide metal is selected from the group consisting of lanthanum, cerium, neodynium, samarium, europium and mixtures thereof.

13. The method of claim 12, wherein the lanthanide metal is cerium.

14. The method of claim 12, wherein the first alloy is prepared from 1.5 to 6 parts by weight copper, 0.5 to 2 parts by weight antimony, and 92 to 98 parts by weight tin.

15. The method of claim 14, wherein the second alloy comprises 1-10 wt. % cerium, 3-30 wt. % silver and 60 to 96 wt. % tin.

16. The method of claim 14, further comprising adding a third alloy to the molten first alloy, wherein the second alloy comprises 1-10 wt. % cerium and the balance tin; and the third alloy comprises 3-30 wt. % silver and the balance tin.

17. The method of claim 11, further comprising:

adding a scavenger to the molten first alloy to form a scavenger-contaminant complex; and

removing the scavenger-contaminant complex from the molten first alloy prior to addition of the second alloy.

18. The method of claim 11, wherein the shape of the solid form of the lead-free alloy is selected from the group consisting of a wire, bar, paste, foil, preform and powder.

19. The method of claim 18, further comprising the step of combining the powder with a flux to form a solder paste.

20. A method of using a lead-free solder alloy for joining metal surfaces in plumbing, refrigeration, and roofing applications, wherein the alloy comprises tin, antimony, copper, silver, and a lanthanide metal; and the alloy is substantially free of group IVa elements, group Va elements, bismuth, nickel, and zinc.

21. The method of claim 20, wherein the lanthanide metal is selected from the group consisting of lanthanum, cerium, neodynium, samarium, europium and mixtures thereof.

22. The method alloy of claim 21, wherein the lead-free alloy comprises at least 96 wt. % tin, 0.25 to 1 wt. % antimony, 1 to 4 wt. % copper, 0.05 to 0.5 wt. % silver and 0.1 to 0.3 wt. % lanthanide metal.

23. The method of claim 22, wherein the lanthanide content is 0.03% to 0.1 wt. % based on the weight of the alloy.

24. The lead-free alloy of claim 21, wherein the lanthanide metal is cerium.

25. The method of claim 24, wherein the lead-free alloy comprises at least 96 wt. % tin, 0.25 to 1% wt. % antimony, 1 to 4 wt. % copper, 0.05 to 0.5 wt. % silver, and 0.01 to 0.3 wt. % cerium.

26. The method of claim 25, wherein the cerium content is 0.03% to 0.1 wt. % based on the weight of the alloy.

27. The method of claim 20, wherein the metal surface is selected from the group consisting of brass, bronze, copper, steel, stainless steel, monel and galvanized metal.

28. A lead-free babbitt alloy wherein the alloy comprises tin, antimony, copper, silver, and a lanthanide metal; and the alloy is substantially free of group IVa elements, group Va elements, bismuth, nickel, and zinc.

29. The lead-free babbitt alloy of claim 28, wherein the lanthanide metal is selected from the group consisting of lanthanum, cerium, neodynium, samarium, europium and mixtures thereof.

30. The lead-free babbitt alloy of claim 29, wherein the alloy comprises at least 84 wt. % tin, 3 to 8 wt. % antimony, 3 to 8 wt. % copper, 0.05 to 0.5 wt. % silver, and 0.01 to 0.3 wt. % lanthanide metal.

31. The lead-free babbitt alloy of claim 30, wherein the lanthanide metal content is 0.03 to 0.1 wt. % based on the total weight of the alloy.

32. The lead-free babbitt alloy of claim 29, wherein the lanthanide metal is cerium.

33. The lead-free babbitt alloy of claim 32, wherein the alloy comprises at least 84 wt. % tin, 3 to 8 wt. % antimony, 3 to 8 wt. % copper, 0.05 to 0.5 wt. % silver, and 0.01 to 0.3 wt. % cerium.

34. The lead-free babbitt alloy of claim 33, wherein the cerium-content is 0.03 to 0.1 wt. % based on the total weight of the alloy.

35. The lead-free babbitt alloy of claim 33, wherein the melting range is from about 275° C. to about 375° C.

36. The lead-free babbitt alloy of claim 35, wherein the melting range is from about 300° C. to about 350° C.

37. A method of preparing a lead free-babbitt alloy comprising:

preparing a molten first alloy comprising tin, antimony and copper;

forming the molten lead-free alloy into a shape; and

cooling the lead-free alloy to form a solid form of said shape; wherein

38. The method of claim 37, wherein the lanthanide metal is selected from the group consisting of lanthanum, cerium, neodynium, samarium, europium and mixtures thereof.

39. The method of claim 38, wherein the lead-free alloy comprises at least 84 wt. % tin, 3 to 8 wt. % antimony, 3 to 8 wt. % copper, 0.05 to 0.5 wt. % silver, and 0.01 to 0.30 wt. % lanthanide metal.

40. The method of claim 39, wherein the lanthanide metal content is 0.03 to 0.1 wt. % based on the total weight of the alloy.

41. The method of claim 38, wherein the lanthanide metal is cerium.

42. The method of claim 41, wherein the lead-free alloy comprises at least 84 wt. % tin, 3 to 8 wt. % antimony, 3 to 8 wt. % copper, 0.05 to 0.5 wt. % silver, and 0.01 to 0.3 wt. % cerium.

43. The method of claim 42, wherein the cerium content is 0.03 to 0.1 wt. % based on the total weight of the alloy.

44. The method of claim 41, wherein the molten first alloy is prepared from 3 to 8 parts by weight copper, 3 to 8 parts by weight antimony, and 85 to 94 parts weight tin.

45. The method of claim 44, wherein the second alloy comprises 1-10 wt. % cerium, 3-30 wt. % silver and 60 to 96 wt. % tin.

46. The method of claim 44, further comprising adding a third alloy to the molten first alloy, wherein the second alloy comprises 1-10 wt. % cerium and the balance tin; and the third alloy comprises 3-30 wt. % silver and the balance tin.

47. The method of claim 37, further comprising:

48. A method of using a lead-free alloy for babbiting wherein the alloy comprises tin, antimony, copper, silver, and a lanthanide metal; and the alloy is substantially free of group IVa elements, group Va elements, bismuth, nickel, and zinc.

49. The method of claim 48, wherein the lanthanide metal is selected from the group consisting of lanthanum, cerium, neodynium, samarium, europium and mixtures thereof.

50. The method of claim 49, wherein lead-free alloy comprises at least 84 wt. % tin, 3 to 8 wt. % antimony, 3 to 8 wt. % copper, 0.05 to 0.5 wt. % silver, and 0.01 to 0.3 wt. % lanthanide metal.

51. The method of claim 50, wherein the lanthanide metal content is 0.03 to 0.10 wt. % based on the total weight of the babbitt alloy.

52. The method of claim 49, wherein the lanthanide metal is cerium.

53. The method of claim 52, wherein lead-free alloy comprises at least 84 wt. % tin, 3 to 8 wt. % antimony, 3 to 8 wt. % copper, 0.05 to 0.5 wt. % silver, and 0.01 to 0.3 wt. % cerium.

54. The method of claim 53, wherein the cerium content is 0.03 to 0.10 wt. % based on the total weight of the babbitt alloy.