JP6945906B1 - γ-based stainless steel wire and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stainless steel wire in which the amount of γ remaining in the finished metal wire is maintained at a high value to improve workability, and a practical manufacturing method thereof. SOLUTION: In mass%, C: 0.08% or less, Si: 1.00% or less, Mn: 2.00% or less, P: 0.045% or less, S: 0.030% or less, Ni: It has a composition of 8.0 to 10.50%, Cr: 18.0 to 20.00%, and the balance Fe, has a wire diameter of 0.08 mm or more and 2.60 mm or less, and has a tensile strength of 1550 N / mm 2 or more and 3500 N. A γ-based stainless steel wire having a γ content of 30% by volume or more and 90% by volume or less of / mm2 or less. The manufacturing method was generated by arranging at least two drawing jigs in the front and rear along the drawing direction of the γ-based stainless steel bus, and drawing the γ-stainless steel bus with the drawing jig in the previous stage. This is a method of heat drawing with a drawing jig in the subsequent stage using the processing heat. [Selection diagram] Fig. 4

Description

In the present invention, two drawing jigs (dies) are arranged in the drawing direction, and the heat generated by the drawing by the drawing jig in the previous stage is used to draw the wires in the drawing jig in the subsequent stage. The present invention relates to a γ-based stainless steel wire in which an austenite structure remains and a method for producing the same.

The wire drawing process of stainless steel is performed for the purpose of obtaining a desired wire diameter and obtaining a desired strength. The wire diameter is determined by the hole diameter of the jig (die) used for wire drawing. In addition, the strength is determined by the degree of processing. The degree of processing is determined by various experiments in advance on the relationship between the degree of decrease in the cross-sectional area of the wire diameter due to processing, that is, the surface reduction rate "(1- (d ₁ ² ÷ d ₂ ^{2)) x 100%" and the strength.} Secure and utilize this in actual production. That is, the strength is controlled by the surface reduction rate.

By the way, when γ-based stainless steel wire is processed, γ → α ′ processing transformation occurs. This γ → α'working transformation is significantly affected by the temperature immediately before being machined, and even if it is subjected to strong machining (cutting surface rate 90%) by heating at about 150 ° C., it is only about 30% of that during normal temperature machining. Does not progress, and 70% of the volume remains as a γ structure, enabling further processing. Therefore, for wire drawing of γ-based stainless steel wire, it is preferable to perform strong processing in a heating state of about 150 ° C.

However, the technical problem that becomes a practical problem here is that the wire drawing process is for a γ-based stainless steel wire that travels at a high speed of several meters per second. How to raise the temperature to the above-mentioned temperature in the vicinity of the die BOX is an issue of the wire drawing process of the present invention.
It is not so easy to heat a γ-based stainless steel wire running at a high speed of several meters per second in a short time of 1 second or less, even if it is heated to about 150 ° C. at most.

The present inventor has previously proposed a heating wire drawing method using an induction heating device as a method for heating a stainless steel wire, and a patent has been granted (Patent Document 1: Patent No. 2050506, and the content of the invention). Please refer to the official gazette No. 07-080008).
However, the induction heating device (IH), which is indispensable for carrying out this invention, is very expensive at 6 million yen per set, and it is not enough to set multiple units in front of the die of each pot of the continuous wire drawing machine. Unless it showed a good track record, it could not be put into practical use, and there were many problems in the transition to commercial production.
As one of the measures, the present inventor has developed a heat-resistant lubricating oil method (see Patent Document 2: Japanese Patent Application Laid-Open No. 2012-81502) and filed an application as a heating wire drawing method using heat-resistant lubricating oil. With this method, for example, an austenitic stainless steel wire having a tensile strength of 2200 N / mm can be obtained (see paragraph 0022,0024). However, although the invention of Patent Document 2 has been established experimentally like the invention of Patent Document 1, it is a requirement to be solved such as development of a heat-resistant lubricating oil capable of adapting to a high temperature of 150 ° C. or higher for a long time. As in Patent Document 1, there were many problems in the transition to commercial production.
Under these circumstances, at present, it is not possible to obtain a stainless steel wire in which the amount of γ remaining in the finished metal wire is maintained at a high value to improve workability and a practical manufacturing method thereof. ..

Special Fair 07-08008 Gazette Japanese Unexamined Patent Publication No. 2012-81502

In view of the above circumstances, the present inventors have conducted diligent research to solve the above problems, and as a result, utilize the processing heat generated by the processed stainless steel bus itself to reduce the γ → α'processing transformation and improve the workability. The present invention is an epoch-making invention that can contribute to the improvement of productivity, cost reduction, and the development of new products by performing wire drawing with a large amount of excellent γ structure remaining and extending the processing limit to the maximum. We have succeeded in developing a "γ-based stainless steel wire" in which a large amount of the γ-structure remains and a "method for manufacturing this γ-based stainless steel wire by wire drawing". Hereinafter, the present invention will be specifically described.

First, an outline of "a method for producing a γ-based stainless steel wire (having a composition of SUS304)" according to the present invention will be described.
In general, when a metal is processed, elements move on the sliding surface of the crystal unique to the metal, deformation progresses and internal stress is accumulated, and at the same time, dislocations also accumulate and become inactive dislocations, making processing difficult. do. Furthermore, in addition to these deformation mechanisms, the structure of γ-based stainless steel wire is processed, causing γ → α ′ processing transformation, and hardening proceeds.
In this case, the processing transformation is significantly affected by the temperature immediately before the processing, and the change hardly progresses by heating at about 200 ° C., and the strength is hardly improved. However, since the machining speed of the continuous wire drawing machine is as high as 2 to 8 m / s, it is difficult to set the heating device on the platform of the narrow continuous wire drawing machine.

Therefore, as a new method completely different from these countermeasures, the method of the present invention (hereinafter, referred to as "double die heating wire drawing method" in the present specification) has been developed.
Hereinafter, refer to "Overview of the double die heating wire drawing method" in FIG. 1, "Temperature dependence of drawing and martensite generation" in FIG. 2, and "Relationship between machining temperature-reduction rate-tensile strength" in FIG. Then, the outline of the "double die heating wire drawing method" according to the method of the present invention will be described.
Note that FIG. 1 is a schematic view showing a specific example thereof in order to facilitate understanding of the present invention. In FIG. 1, an example of arranging two dice is shown in the upper row, and the heating temperature is attached to a numerical value or the like in the lower row. I will point out that it is not.
Further, FIG. 2 shows that the higher the processing temperature, the lower the rate of martensite generation can be pressed, and FIG. 3 shows that the higher the processing temperature, the more the increase in tensile strength can be suppressed. There is.

As is clear from the description in FIG. 1, two dies (wire drawing jigs) are arranged at intervals of, for example, 100 mm to 150 mm, and the heat generated by the wire drawing process with the No. 1 die in the previous stage remains as it is. The method of bringing it to the No. 2 die in the latter stage and performing the heating wire drawing here, preferably the method of preheating in the preheating zone before the wire drawing process with the No. 1 die, can be said to be an ideal method. ..

(Preheating)
More specifically, in order to reduce the γ → α'working transformation during wire drawing with the No. 1 die in the previous stage, γ-based stainless steel wire is used before entering the No. 1 die, for example. If preheated to about 70 ° C to 130 ° C and the preheated wire is introduced into the No. 1 die, the γ → α'working transformation when passing through the No. 1 die is significantly suppressed, and the No. 1 die is further suppressed. If the temperature just before entering the No. 2 die in the latter stage can be raised to nearly 200 ° C, the γ → α'heating transformation will be drastically reduced, the strength improvement will be halved, and the ideal heating wire drawing will be realized. You will be able to do it.
As the preheating method placed in front of the No. 1 die, direct heating (energization, heat-resistant lubricating oil, etc.) or indirect heating (hot air, passing through a heating furnace, etc.) can be considered. Assuming that the state in which the preheating and the No. 1 die and the No. 2 die are arranged is one set of double dice, the state in which six sets are arranged is shown in FIG. If the preheating is around 130 ° C., the temperature can be sufficiently raised even if the linear velocity is high.

(Double die heating wire drawing method)
The method of the present invention is characterized in that the operation in the wire drawing process is changed from the conventional "surface reduction rate strength control method" to the "heating temperature control method".
Hereinafter, this point will be specifically described.
The operation in wire drawing is to match the diameter of the outlet by passing a wire through a wire drawing jig called a tie, which has a large entrance and a small outlet. By this operation, it is possible not only to make the wire diameter a predetermined diameter but also to improve the strength by processing at the same time as processing.
Factors governing the increase of the intensity of this case, the area reduction rate ^{_{(1- (d 1 2 ÷ d}} 0 2)) × 100%), 25~20% from previous experiments and results in a normal ambient temperature drawing If this is repeated and the total surface rate is processed to around 85%, the wire cannot withstand further processing and the wire breaks. Even if it does not break, internal cracks may occur, resulting in a defective product. In many wire manufacturers, as a work standard, each surface reduction rate is standardized at 20 to 25%, and the total surface rate is standardized at about 80 to 82%. The wiring is driven and continuous wire drawing is performed.
As for the surface reduction rate adopted by each wire drawing machine, it is appropriately selected whether to adopt the same surface reduction rate (parallel draft) for each wire drawing machine or to gradually reduce the surface reduction rate (tapered draft) in consideration of the pulling force. It is possible.
After that, it is brightly annealed and softened, and the same wire drawing is repeated again to reduce the wire diameter and increase the strength.

In order to compare with the wire drawing process of the present invention, first, the conventional wire drawing process is shown in FIG. 5 (current wire drawing / annealing process).
For example, when a 5.5 mmφ rolling rod (material) is used as an example to manufacture a 0.90 mmφ thin wire, two types of continuous wire drawing machines are used as shown in FIG. 5, and a primary wire drawing machine and a secondary wire drawing machine are used. Primary annealing (one bright annealing) is performed in the middle of the wire drawing to produce the desired 0.90 mmφ. FIG. 6 shows the surface reduction rate and strength improvement in this case for Ni equivalent 21.9 ^{Note 1} . All the strength control of conventional γ-based stainless steel wire is controlled by the surface reduction rate, and in order to produce the required strength, the start size is determined by the surface reduction rate-strength relationship diagram, and the processing rate is calculated to produce the product. Aim for conversion.
Note 1: Ni equivalent is a formula that considers the influence of contained elements for the occurrence of processing transformation of γ → α', that is, the stability of γ, and generally adopts the formula called Hirayama's formula. The larger the Ni equivalent, the more stable the γ.
Hirayama's formula:
Ni equivalent (%) = Ni (%) +0.65Cr (%) +0.98Mo (%) + 1.05Mn (%) + 0.35Si (%) + 12.6C (%)
On the other hand, there are two JIS standards for γ-based stainless steel wires, JIS G 4309 (stainless steel wire) and JIS G 4314 (stainless steel wire for springs), which are W1, W2, W1 / 2H and WPA, WPB, respectively. There are five strength standards, and the strength standards for intermediate wire processing are the other four standards except W1. Strength standards are set in the size range. FIG. 7 shows the relationship between the JIS standard and the wire diameter in an easy-to-understand manner.

FIG. 6 is a diagram showing the relationship between the surface reduction rate and the strength. When the surface reduction rate for creating the strength lines of 4 standards is obtained from this figure, W2 is calculated at around 20%, W1 / 2H at around 40%, and WPA at around 70%, depending on the wire diameter. WPB standard products can be produced at around 82%. However, the production of strength standard products that depend on the surface reduction rate requires precise support, and there are many types of JIS standard sizes (wire diameters), and the start size and wire drawing that meet all of these are complicated.

The method of the present invention requires precise measures for the above-mentioned problems of the prior art, that is, the production of strength standard products depending on the surface reduction rate, and there are many types of JIS standard sizes (wire diameters), which satisfy all of them. The start size and wire drawing process are designed to solve the problem of complexity, and the processing heat generated by the wire to be processed is used to reduce the processing transformation of γ (austenite structure) → α'(martensite structure). Innovative technology and new product development method that leaves a lot of γ structure with excellent workability, extends the processing limit to the maximum, improves productivity, reduces costs, and contributes to the development of new products. It is a suggestion.

That is, the γ-based stainless steel wire has a property of causing a γ → α ′ processing transformation when processed, but this processing transformation is significantly affected by the temperature immediately before processing, and the temperature is around 200 ° C. Only a few processing transformations occur. In other words, the present invention has been made focusing on the fact that only about 1/10 of the normal temperature processing occurs, the γ structure having excellent workability is maintained even when subjected to strong processing, and the strength improvement is halved.

Hereinafter, the outline of the present invention will be described with reference to the drawings. In the description here, specific numerical values and the like are presented to facilitate understanding of the invention, but the present invention is specified by the specific numerical values and means and the like described here. is not it. It is pointed out just in case that the present invention is an invention specified within the scope of claims, and the drawings show the invention more concretely.

In the double die wire drawing method according to the present invention, a normal die box is lengthened, and as shown in FIG. 1, two dies are placed in a die box containing a powder lubricant with an interval of about 150 mm. Install and place a preheating zone in front of it. The preheating (preheating) zone heats with electric heat, lubricating oil, hot water, or the like to raise the temperature of the wire entering the first die in the die box to about 50 ° C to 130 ° C.

As a result, the γ → α'processing transformation that occurs when wire drawing is performed is reduced as much as possible, and the processing heat generated by the first die is added to heat the wire at 130 ° C to 250 ° C. In this state, heat drawing is performed with the second die.
FIG. 8 shows the relationship between the surface reduction rate of the first die (No. 1 die) and the processing heat generation temperature. From this figure, a desired processing heat generation temperature can be obtained by appropriately controlling the surface reduction rate of the No. 1 die.

As described above, according to the method of the present invention, the heat generated by the processing heat generation (self-heating) generated by the wire drawing process can be effectively utilized as it is, so that it can be said to be a very energy-saving heating wire drawing method. Of course, if the development of heat-resistant lubricating oil progresses and a lubricating oil up to about 150 ° C. is produced, this may be utilized. The temperature prediction state in the preheating zone and the double die is shown in the lower part of FIG. If the preheating temperature exceeds, for example, 100 ° C., it can be expected that the heat generated by the No. 1 die is added, that is, the linear temperature reaches about 200 ° C. before entering the No. 2 die.

In Table 1 below, a die box (for example, the dible die set shown in FIG. 1) in which two dies are incorporated in one die box is arranged in a continuous wire drawing machine, and the first die of the double die set is reduced. The surface ratio is 20%, the surface reduction rate of the second die is 35%, and the transition of the total surface reduction rate when wire drawing is performed with a continuous wire drawing machine (6H) is shown in four types of start sizes (1.00 mm, 1.00 mm, 2.00 mm, 3.00 mm and 5.50 mm).

Further, according to the present invention, many merits can be obtained by utilizing the combination of heating wire drawing and room temperature wire drawing in the wire drawing process. That is, it is possible to shift the epoch-making production technology from the conventional strength control by the processing reduction rate to the strength control by the heating temperature.
Further, FIG. 9 shows the tensile strength of each wire drawn up to 0.77 mm (heated wire drawing 6Pass) starting from 5.50 mm in Table 1 for each heating temperature. This table shows the case where double dice and heating wire drawing are performed in all the die boxes, but if this is applied, one start size can be obtained by combining with normal wire drawing from the Pass in the middle of the continuous drawing machine. It can be said that this is a wire drawing method having a wide range of applications, such as being able to obtain a wire rod having an arbitrary finished wire diameter and tensile strength from the wire diameter.
Then, according to the method for producing γ-based stainless steel according to the present invention, C: 0.08% or less, Si: 1.00% or less, Mn: 2.00% in mass% according to claims 1 and 2. Hereinafter, P: 0.045% or less, S: 0.030% or less, Ni: 8.0 to 10.50%, Cr: 18.0 to 20.00%, and the composition of the balance Fe (composition of SUS304). It has a wire diameter of 0.08 mm or more and 2.60 mm or less, a tensile strength of 1550 N / mm2 or more and 3500 N / mm2 or less, and 30% by volume or more, 90% by volume or less, or 40% by volume or more. A γ-based stainless steel wire having a γ content of 70% by volume or less can be produced.

Hereinafter, examples of the present invention (Examples 1 to 6) will be described.
As described in detail below, Example 1 is an example relating to a method for producing an arbitrary JIS standard strength wire by changing only the heating temperature in a machining process of the same bus, the same double die set continuous drawing machine, and the same surface reduction rate. be.
The second embodiment is a production method of an arbitrary strength JIS standard product by selecting a heating temperature with an arbitrary double die set in the same bus, the same double die set continuous drawing machine, and the same surface reduction rate processing process.
Example 3 is an example of one operation (heat treatment omitted, reduction in the number of wire drawing machine hooks) by increasing the processing reduction rate.
Example 4 is an example of a method of producing a piano wire-grade high-strength wire with SUS304 by utilizing the heating wire drawing method.
Example 5 is an example of a method for manufacturing a fatigue resistant strength wire.
Example 6 is an example of a method for producing a SUS304 wire having a tensile strength of 1,600 N / mm ² or more and a γ content of 30% or more.

Example 1: Same bus wire, same double die set continuous wire drawing machine, arbitrary JIS standard strength wire production method by changing only the heating temperature in the processing process with the same surface reduction rate Double die continuous wire drawing machine (6 kettles) is used. FIG. 10 shows an example of each surface reduction rate, heating temperature, and increase in tensile strength when wire drawing is performed. The experimental results show the experimental results at 200 ° C., 140 ° C., and 80 ° C.
On the right side of this graph, the standard value of tensile strength for each wire diameter is matched with the scale of tensile strength. Looking at FIG. 10, the temperature of the heating wire to be applied to each standard value in the set of double dies can be found. As another example, consider the case where the finished wire diameter of 0.77 mm is drawn with 6 sets of double die continuous drawing machines.
From Table 1, it is necessary to prepare a start size of 5.50 mm. From FIG. 10, the range of four standard strengths of 0.77 mm may be read, and the heating temperature suitable for each may be selected by comparing with the JIS standard. In this case, 0.77 mm W1 / 2H is drawn at a heating temperature of 200 ° C, WPA is drawn at 140 ° C, WPB is drawn at 80 ° C, and if it is drawn, the three strength standards are drawn in exactly the same process. Nevertheless, it is possible to be satisfied.
As can be seen from this, the present invention can be said to be a conversion from the surface reduction rate control method, which has been practiced today, to the heating temperature control reel method according to the present invention.

Example 2: The same bus, the same double die set continuous drawing machine, the same surface reduction rate machining process, the heating temperature is selected with any double die set, and the production method of any strength JIS standard product. This production method is shown in the figure. As shown in No. 11, it is a method of selecting the heating temperature for each No. of the double die set to secure the target strength. For example, in order to secure W1 / 2H, all 6 sets of heated wire drawing at 200 ° C. are adopted for wire drawing, and in the case of producing WPB, heating wire drawing at 200 ° C. is No. Adopted up to 4 double die sets and then No. 5-No. The double die set of 6 is drawn at room temperature. In this case, only the die after the double die may be used, and the strength may be secured by processing with a surface reduction rate of about 20%. Similarly, WPB can be produced by adopting heating wire drawing at 140 ° C. up to double die set No. 5, and then adopting normal temperature wire drawing.

Example 3: One operation by increasing the processing reduction rate (heat treatment omitted, number of wire drawing machine hooks reduced)
In general wire drawing work, a wire is passed through a jig called a jig that has a conical hole with a large entrance and a small exit. To measure. In this case, in order to represent the degree of processing, it represents the reduction degree of the cross-sectional area of the line at the call with each reduction of area ^{_{(1- (d 1 2 ÷ d}} 0 2)) × 100%), which was continuously Repeat 7 to 8 times to perform continuous wire drawing. Start size and cross-sectional area reduction rate of the finished diameter is referred to as a total reduction of area, expressed by _{^{(1- (d 0 2 ÷ d}} 8 2)) × 100%).
What percentage of each surface reduction rate and total surface reduction rate should be determined by complicated factors such as the problem of friction between the wire and the die, the material, and the structure of the wire drawing machine, which is a secret matter of each manufacturer, but in general. Generally, each surface reduction rate is about 20 to 25%, and the total surface reduction rate is about 80 to 85%. If finer wire drawing is required, intermediate annealing is performed to soften the wire, and then the wire is drawn again. I do.
In the double die heating wire drawing method according to the present invention, the surface reduction rate of the No. 1 die of the double die set in which two dies are set is set to about 20%. Table 1 shows an example of the Pass schedule of the 6H continuous wire drawing machine with 2 dice as 35%. In the case of the double die heating wire drawing method, as shown in Table 1, one set of double dies can be processed with a total surface reduction rate of 48%, and if three sets are installed (total 6 Pass), 85% and five sets are installed (total). If it is 10Pass), it will be about 96%, and it will be possible to perform continuous wire drawing in 16 blocks at each exemption rate of 21% in the case of normal room temperature wire drawing, and strong processing equivalent to the processing of two continuous drawing machines. Moreover, since the wire can be continuously drawn without intermediate annealing, it is possible to significantly rationalize production and reduce costs. Moreover, by utilizing the processing heat generated by the wire to be processed itself, it is expected that energy saving and cost reduction will be incomparable even when compared with the utilization of an induction heating device.

Example 4: A method of producing a piano wire-grade high-strength wire with SUS304 by utilizing the heating wire drawing method.
As described above, the γ-based stainless steel wire cannot be strongly machined because the work-induced martensite increases with the work. At present, in order to secure the strength equivalent to that of piano wire with stainless steel wire, only measures can be taken by changing the contained elements by increasing the amount of Mn or the like or decreasing the amount of Ni. Therefore, in order to obtain the strength equivalent to that of a piano wire with pure SUS304, the heating wire drawing method according to the present invention is utilized.
Now, when the heating temperature is 140 ° C. using 5 sets of double dies, wire drawing, and processing with a total surface reduction rate of 96%, the tensile strength is ^{only about 1,700 N / mm 2,} but it remains. The amount of γ is more than 70% of the total, and it is in a state where it can sufficiently withstand further strong machining. When the intermediate line with a total surface reduction rate of 96% at 140 ° C. is processed again with a double die wire drawing machine, the tensile strength is 2,600 N / mm ² or more at the second wire drawing as shown in FIG. Can be obtained.
That is, in the conventional SUS304 against most up 2,400N / mm ^2, is capable of further improvement in strength by applying the present invention, the tensile referred 2,600N / mm ² obtained in the second wire drawing The intensity value is well comparable to the piano wire (WPA) species.
This process is only an example, and by applying the present invention, there is a sufficient possibility of ensuring strength higher than that of piano wire by combining heating wire drawing and room temperature wire drawing.

Example 5: Manufacture of fatigue-resistant strength wire When producing a stainless steel wire for a spring, a state in which a large amount of γ structure is contained, that is, a wire drawn by heating a heated wire to 140 ° C. to 250 ° C. is fatigued. It was confirmed that the fatigue strength in the test was more than doubled. This is shown in FIG. The reason why the fatigue strength in the fatigue test is more than double is that cracks occur when fatigue fracture occurs, and when the tip propagates, the stress at the tip causes γ → α'transformation and hardens. It is considered to prevent further propagation and prevent fatigue fracture.
According to the experimental data in the fatigue fracture test, when comparing the room temperature wire drawing and the heated wire drawing material at 140 ° C., the room temperature wire drawing has a large tensile strength and wire diameter, but the fatigue test result shows in FIG. As you can see, it can be seen that the heated wire drawing material is nearly twice as good. From this example, it was confirmed that the fatigue-resistant strength wire can be manufactured by the manufacturing method of the additional wire drawing material according to the present invention.

Example 6: Manufacture of SUS304 wire having a tensile strength of 1,600 N / mm ² or more and a γ content of 30% or more.
When SUS304 is processed at room temperature with a total surface reduction rate of 50% or more, as shown in FIG. 14, 80% or more of the total volume of the structure is α'martensite. Looking at this from the viewpoint of strength, as shown in FIG. 15, it shows around ^{1,500 N / mm 2.}
That is, at 1,600 N / mm ² or more, the amount of α'martensite is 80% or more and the amount of austenite is 20% or less in the case of normal temperature wire drawing. On the other hand, when the wire is drawn by heating, at 140 ° C., the surface reduction rate ^{reaches 1,600 N / mm 2} at 96%, but the residual γ is 75% or more and α'is 25% or less.
That is, it can be said that a product processed by the heat drawing method has a high strength of 1,600 N / mm ^{2 or more and contains 75% of γ.}
Table 2 shows the elements contained in SUS304, but SUS304 contains many elements other than the components listed in Table 2, and these elements are γ → α'work transformation, that is, γ. Affects stability. Furthermore, the content of each element has an allowable range, which intricately affects the γ → α ′ processing transformation. There are many studies on the stability of γ, but the most commonly used formula is called the Hirayama formula.
For reference, the effects of the heating wire drawing of this Ni equivalent are shown in FIGS. 16 and 17. As can be seen from this figure, the Ni equivalent clearly has an effect on the machining transformation in the room temperature wire drawing, but in the case of the heating wire drawing, the effect becomes small at around 200 ° C. and 100 N / mm ² There is only a degree. In addition, martensite can be suppressed to about 10%.

According to the present invention, the γ → α'working transformation is reduced, a large amount of γ structure having excellent workability remains, the processing limit is extended to the maximum degree, and wire drawing is performed to improve productivity and reduce costs. Furthermore, it is possible to provide a method for manufacturing an austenitic stainless steel wire that can contribute to the development of a new product.

Double die heating wire drawing method schematic diagram Diagram showing the temperature dependence of drawing and martensite generation Diagram showing the relationship between heating temperature, tensile strength, and exemption rate The figure which shows the double die heating wire drawing process Diagram showing the current wire drawing / annealing process Diagram showing the relationship between exemption rate and strength Diagram showing the relationship between wire diameter and strength according to JIS standards The figure which shows the relationship between the surface reduction rate with the No. 1 die and the processing heating temperature. Diagram showing the relationship between heating temperature, tensile strength, and exemption rate The figure which shows the production example of the JIS standard strength wire by changing only the heating temperature in the processing process of the same bus, the same double die set continuous drawing machine, and the same exemption rate. The figure which shows the production example of the arbitrary JIS standard strength standard line by selecting the heating temperature of an arbitrary double die set in the processing process of the same bus, the same double die set continuous drawing machine, and the same exemption rate. Diagram showing an example of production of high-strength stainless steel wire The figure which shows the S-N curve (normal wire drawing and heating wire drawing) Diagram showing the relationship between the exemption rate and the amount of martensite Diagram showing the relationship between heating temperature, reduction / exemption rate, and tensile strength Figure showing the effect of heating wire drawing of Ni equivalent (No. 1) Figure showing the effect of heating wire drawing of Ni equivalent (Part 2)

Claims (12)

By mass%, C: 0.08% or less, Si: 1.00% or less, Mn: 2.00% or less, P: 0.045% or less, S: 0.030% or less, Ni: 8.0 to 10.50%, Cr: 18.0 to 20.00%, balance Fe composition, wire diameter 0.08 mm or more and 2.60 mm or less, tensile strength 1550 N / mm ² or more, 3500 ^{N / mm 2} A γ-based stainless steel wire having an austenite structure and a work-induced martensite structure, wherein the austenite structure is 30% by volume or more and 90% by volume or less. The γ-based stainless steel wire according to claim 1, which has an austenite structure of 40% by volume or more and 70% by volume or less. At least two drawing jigs are arranged in the front-rear direction along the drawing direction of the γ-based stainless steel bus, and the γ-based stainless steel wire is passed through the drawing jig in the previous stage to draw the wire, and then the rear stage. The method for producing a γ-based stainless steel wire according to claim 1 or 2, wherein a plurality of steps of heat drawing are performed at a predetermined heating temperature set in advance with a drawing jig.
The heating wire drawing with the drawing jig in the latter stage is performed at the above-mentioned predetermined heating temperature by utilizing the processing heat generated by the drawing processing of the γ-based stainless steel wire with the drawing jig in the previous stage. The method for producing a γ-based stainless steel wire according to claim 1 or 2, wherein the γ-based stainless steel wire is produced. 3. The third aspect of the present invention is that the temperature of the γ-based stainless steel wire is raised by 100 ° C. to 250 ° C. from the temperature before the wire drawing process by the drawing process jig in the previous stage by the wire drawing process by the drawing process jig in the previous stage. The method for manufacturing a γ-based stainless steel wire according to. At least two drawing jigs are arranged in the front-rear direction along the drawing direction of the γ-based stainless steel bus, and the γ-based stainless steel wire is passed through the drawing jig in the front stage to draw the wire, and then the rear stage. When performing multiple steps of heat drawing at a predetermined heating temperature set in advance with the drawing jig, at least some of the steps are performed before passing the γ-based stainless steel wire through the drawing jig in the previous stage. The method for producing a γ-based stainless steel wire according to claim 3 or 4, wherein the step of preheating the γ-based stainless steel wire is provided. The method for producing a γ-based stainless steel wire according to claim 5, wherein the preheating step is a step of raising the temperature of the γ-based stainless steel bus by 50 ° C. or higher. The method for producing a γ-based stainless steel wire according to claim 6, wherein the preheating step is a step of raising the temperature of the γ-based stainless steel bus by 50 ° C. to 200 ° C. The γ-based stainless steel bus heated in the preheating step is passed through the drawing jig in the previous stage, and the temperature is raised by 100 ° C to 250 ° C from the temperature before drawing by the drawing jig in the previous stage. The γ-based stainless steel wire according to any one of claims 5 to 7, wherein the γ-based stainless steel bus is passed through a drawing jig in the subsequent stage at a predetermined heating temperature to perform heat drawing. Manufacturing method. A die box containing a drawing jig applied to the method for manufacturing a γ-based stainless steel wire according to any one of claims 3 to 8, and is an inlet of a γ-based stainless steel bus wire to be drawn. A die box characterized in that a drawing jig in the front stage and a drawing jig in the rear stage are installed in order from the side to the outlet side. A die box containing a drawing jig applied to the method for manufacturing a γ-based stainless steel wire according to any one of claims 5 to 8, wherein the γ-based stainless steel wire is drawn. A die box characterized in that a preheating means, a drawing jig in the front stage, and a drawing jig in the rear stage are installed in order from the inlet side to the outlet side. The dice box according to claim 10, wherein the preheating means is one or more of the direct heating means and / or the indirect heating means. The die box according to any one of claims 9 to 11, wherein the area in which the drawing jig in the first stage is installed and the area in which the drawing jig in the second stage is installed are filled with a powder lubricant. ..

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