RU2055928C1 - Method for manufacturing blanks from quick-cutting steel - Google Patents

Abstract

FIELD: production of blanks. SUBSTANCE: method involves obtaining porous blanks of required shape and size by sintering; spraying gas-tight layer of iron onto blanks; imparting final shape, density, texture to blanks by hot plastic working. EFFECT: increased efficiency and improved quality of blanks.

Description

 The invention relates to powder metallurgy, in particular to the manufacture of piece blanks from high-speed steel powder of any given shape and mass, determined by the technological capabilities of the equipment.

 An analogue of the proposed method is described in US patent N 3664008 "Method for the production of elongated high-density products from metal powders" (John Haller. Nortwill Mich. Filed June 12, 1969, Ser N 83257).

The inventive method consists in an analog that is made of welded elongate sheath in translation container is evacuated after the powder filling, sealed, heated to 1150 ^{° C,} compacted in a matrix punch smaller than the matrix; the part of the box and powder that is removed into the waste is squeezed into the gap during compaction.

 The disadvantages of the method: the need to manufacture a gas-tight container and evacuate it, the resulting workpiece is very far in size and shape from the workpieces of specific parts; after compaction, it is necessary to peel (grind) the container with a part of the compacted metal and obtain piece blanks of parts from the processed workpiece by various methods of hot deformation.

 According to the considered method, it is impossible to obtain blanks of complex configuration and it is not economically justified to manufacture blanks of small mass due to the relatively high cost of evacuated containers for small blanks.

 The prototype of the proposed method may be a method called "New Technology" (Novel rosite to P / M vol. 15 high-speed steels / tool steels. "MPR Metall Powder Rept", 1988, v. 43, No. 3, p. 199- 200), including the manufacture of powders by gas spraying a melt of high-speed steels; then the powder is sifted, mixed and compacted up to 85% of theoretical density using high-energy methods of loading into the shell, in the translation of the container. A container filled with a powder charge is sealed by welding at the seams, and the container is not evacuated.

The container is heated to 1038 ^about C and the powder is compacted by extrusion at a compression ratio of 3: 1, which allows to achieve 100% of the theoretical density; the final step is carried out heating of the flowsheet of the extruded preform to a temperature ^about 1138 C, followed by straight rolling to various profiles. Complete the last stage of the process of annealing, finishing machining. The validity of the dissolution of oxygen from the volume of air contained in a powder compacted to 85% of the theoretical density is proved.

 The disadvantages of the prototype: the need to manufacture a gas-tight container, the resulting workpiece is a continuous profile, suitable for the manufacture of tools such as pivotal and unsuitable for the manufacture of tools such as disk cutters, dies; grinding is required (grinding) of the workpiece after extrusion, which leads to the loss of high-speed steel, because in the manufacture of piece stocks from rods, it is almost impossible to build forging technology so that the former container would go into the volumes of inlet and allowance.

 In the prototype under consideration, the main advantage of powder metallurgy is not being used is the possibility of obtaining a blank of complex shape with minimal losses on launches, because modern technologies do not allow for economically justified cost to manufacture containers for thin blanks, as well as small-weight blanks.

 The task is to obtain high-speed steel powder workpieces by universal weight forging and standard equipment that are as close as possible to the final product by mass and configuration, protect the working surface of the pressing tool from abrasive wear by high-speed steel carbides. For this purpose, a porous preform of the required shape, taking into account the possibility of using various methods of hot compaction with the required degree of deformation in the compaction process, is obtained by sintering from high-speed steel powder. The process of obtaining a porous sintered billet (ed. St. N 1382588), lies in the fact that the powder is poured into the mold, impregnated with a molten binder, the resulting briquette on the hardened binder is removed from the mold and sintered in protective atmospheres in the backfill from dispersed refractory powder, and for ligaments choose a material that is completely sublimated before the sintering process begins, for example, paraffin, a briquette mold duplicates the configuration of a porous preform taking into account shrinkage, dispersed refractory filling is a fixing medium for preserving the configuration of the workpiece in the temperature range from sublimation of the binder to the occurrence of mechanical bonds. After sintering, the porous preforms are cooled to temperatures that exclude the possibility of oxidation in air; at these temperatures, the flow of the protective atmosphere is stopped, the porous preforms are cleaned of the remnants of the refractory filling, and a gas-tight coating of iron, steel or joint spraying is applied to the entire surface by gas-thermal spraying.

 It was experimentally established that bulk oxidation of porous preforms can occur during storage, heating in protective media and, to the greatest extent, during the extraction of the preform from the furnace and before the first compaction operation. The sprayed shell excludes the possibility of oxidation in the above cases.

1

• 100= 0,00124
Практически при любом исходном содержании кислорода повышение его количества на подсчитанную величину не повлияет на последующие свойства стали.The increase in oxygen content in steel due to air enclosed in the volume of the sintered sealed billet is approximately determined by the calculation:
thermal density P6M5K5 8.2 g / cm ³ ;
the minimum density of the sintered at 1200 ^about With the workpiece 6.0 g / cm ³ ;
air density at +20 ^о С 1.2 g / l;
relative weighted amount of oxygen in the air 23.2%
The increase in the percentage of oxygen in steel will be
O ₂ =

1

• 100 = 0.00124
For almost any initial oxygen content, an increase in its amount by the calculated value will not affect the subsequent properties of the steel.

 PRI me R. Obtaining a porous preform.

For subsequent pressure treatment operations, the dimensions of the porous preform are determined, for example:
⌀ Nar 75 mm / ⌀ int. 55 mm, height 30 mm A porous preform is obtained by sintering a briquette of powder on a sublimate binder (e.g. paraffin), during which shrinkage occurs, which is experimentally determined at 2.3%. To obtain a briquette, a mold of size
⌀ Nar.75 × 1,023 76.8 mm
⌀ ext. 55 × 1.023 = 56.4 mm;
height: 30 x 1,023 30.7 mm.

Powder of high-speed steel is poured into the mold, heated to the liquid fluidity temperature of paraffin, and the amount of paraffin should not exceed or be less than the pore volume in the powder compacted by shaking, which is calculated:
ρ _kpm 8.15 g / cm ³ , ρ _powder k. 5.88 g / cm ³ .

For 1 cm ^{3 of} powder you need 1-5.88 / 8.15 0.28 cm ^{3 of} paraffin or, with ρ _paraff. 0.8 g / cm ³ , for 1 kg of powder you need 48 g of paraffin.

After impregnation and cooling, the obtained briquettes are removed from the mold (usually squeezed out with a movable punch), installed in a tray of a sealed container in a cold oven, completely covered with dispersed aluminum oxide. Sealed muffle, fed dissociated ammonia and the temperature was raised to 1100 ^C. The heating schedule determined by the size and configuration of the briquettes. The first temperature during the heating stop is performed from beginning to end evaporation paraffin second exposure at 1100 ^{° C} in a container; Workpiece weight hundred grams of 1 hour. Cooling to muffle simple configuration with workpieces at the highest possible speed for the type of workpieces or rings of elements of different diameter to 800 ^{° C} with an oven, muffle and further cooling in air to ^about 60-90 C with continuous supply of a protective atmosphere.

 Spraying an iron shell onto a porous preform.

 The sprayed casing is removed by cutting from the finished workpiece and, if optimally, it should be equal to the allowance after the completion of hot forming operations. In our case, the allowance according to GOST 7505-83 is 0.4 mm.

The conditional thickness of the deposition is determined at a density of 7.8 g / cm ³ .

The surface of the end face of the sintered billet 20.4 cm ² . After precipitation in the mold to the dimensions of the outer diameter of 75 mm, the inner diameter of 15 mm, the end surface will become 42.5 cm ² ; the thickness of the sprayed shell at the ends before precipitation
δ 0.4 x 42.5 / 20.4 0.85 mm.

The height of the workpiece after upsetting will decrease from 30 mm at ρ 6 g / cm ³ to 10.5 mm at ρ 8.15 g / cm ³ .

The outer cylindrical surface before precipitation F _n π x 7.5 x 3 70.8 cm ² after precipitation P _n π x 1.05 x 7.5 24.7 cm ² . the thickness of the sprayed coating δ 0.4 x 24.7 / 70.8 0.14 mm

Inner cylindrical surface: up to draft F _in π x 5.5 x 3 51.0 cm ² ; after precipitation F _in π x 1.05 x 1.5 4.95 cm ² ; the thickness of the sprayed coating δ 0.4 x 4.95 / 51.0 0.04 mm

 When it is impossible to practically obtain conventional spraying methods, a very thin gas-tight shell increases its thickness and, accordingly, increases the allowance.

 Spraying volume (in mass units).

Ends: 2 x 20.4 x 0.085 x 7.8 27 g;
outer cylindrical surface
70.8 x 0.014 x 7.8 77.5;
inner cylindrical surface
51.0 x 0.004 x 7.8 1.6 g
total weight 36.35 g
Material for spraying mild steel wire with a diameter of 1.5 mm.

 Spraying mode: I 300 A, U 30 V.

 The plant capacity is 12 kg / h or 3.3 g / s.

Loss of spraying material on small items up to 60%
Wire consumption per product: 36.35 x 1.6 60 g;
Machine time: 60 / 3.3 18 s.

The sequence of operations:
clamp in a cartridge with a clamp on the outside, dust on the inner surface and end;
clamp in the cartridge with fixing with cams from the inside, spray on the second end and the outer surface;
cover with preservative (dipping).

 Time for 1 pc. only 40 s or 0.67 min (according to the actual time spent in the deposition of prototypes).

 An example of protection by spraying an iron-aluminum shell according to the mode and time does not differ from the example of spraying an iron shell, therefore, it is not repeated. Protection with an iron-aluminum shell has additional advantages: aluminum in the shell absorbs part of the oxygen from the volume of the porous preform during oxidation, the resulting aluminum oxide has a larger volume than aluminum and reduces the gas permeability of the sprayed shell.

 In the samples obtained by the present method after compaction and in samples heated and sealed in vacuum on a head with a hot vacuum chamber, there was no difference in ductility characteristics during the bending test. A decrease in ductility is an indication of an increase in oxygen content.

 Distinctive features of the proposed method.

A new sequence of application of known technological operations, the use of known processing methods for a new purpose: the use of a porous billet obtained by sintering a briquette from high-speed steel powder on a sublimated binder, the full sublimation temperature of which is much lower than the sintering start temperature to obtain a compact billet; the use of a porous preform having a configuration and mass that is fully consistent with that necessary to obtain a compact preform that is as close to the product as possible; use to create a gas-tight shell not of sheet steel and welding, but of thermal spraying to obtain this sprayed shell according to the necessary configuration of the porous preform and the required thickness in various places; the use in the composition of the sprayed shell of materials capable of absorbing oxygen from the volume of a porous preform, for example aluminum;
the use of a sprayed shell to protect the working surface of the pressing tool from abrasion by carbides of high speed steel.

The advantages of the proposed method:
the shape and dimensions of the porous sintered preform are not limited by the possibility of manufacturing a container of the desired shape and size, as in other methods with evacuated and non-evacuated containers;
the thickness of the sprayed shell at each individual section of the workpiece is determined depending on the degree of subsequent deformation and can be equal to the allowance for machining or part of the allowance and, depending on the selected technology of hot pressure treatment, different thicknesses can be performed at different sections of the workpiece;
spraying on a porous preform, taking into account the cost of subsequent technological operations and the associated losses, is cheaper than manufacturing a container of rolled steel using welding;
the sprayed iron-aluminum shell performs the function of a getter when the porous preform is heated: aluminum in the layer is oxidized by oxygen in the volume of the porous preform; forming aluminum oxide is more aluminum in volume and reduces the porosity of the sprayed layer;
the sprayed shell of iron or steel on a billet of high-speed steel powder reduces the wear of dies, molds, i.e. does not contain solid carbides;
the cost of materials and working time when receiving a gas-tight shell is much less than that of sheet steel using welding.

Claims (1)

 METHOD FOR PRODUCING PREPARATIONS FROM HIGH-CUT STEEL POWDER, including obtaining a porous briquette in a gas-tight shell, hot pressure treatment, characterized in that the porous briquette is sintered from the powder, and the shell is obtained by thermal spraying of metal onto the surface of the briquette.