JPH0780008B2 - Metal wire drawing method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a method for drawing a metal wire.

[0002]

2. Description of the Related Art Generally, work is hardened when a metal wire is subjected to die drawing or roller rolling. The degree of work hardening depends on the characteristics of the metal, the degree of drawing work (each area reduction rate and total area reduction rate), and the wire drawing method. The relationship of (tensile strength) is grasped for each metal, and the bus diameter with respect to the finished diameter is calculated based on this relationship and standardized. For example,
When a stainless steel wire is drawn at room temperature, the relationship between the drawing rate and the tensile strength of each steel type is shown in different graphs as shown in FIG. In particular, austenitic stainless steel wire is complicated in terms of each of the constituent elements contained therein, and therefore various factors affecting work hardening and strength and factors governing them are complicatedly mixed, and it is difficult to simply define.

For this reason, particularly in the case of stainless steel wires for springs and 1 / 2-hard stainless steel wires, a bus bar having a start size with respect to the finished diameter has been previously determined, and the total area reduction rate due to the drawing process during that time has been previously determined. A predetermined strength is obtained by work hardening corresponding to. In the case of spring wire, the allowable range of strength for each size is 25 kg / m ² ,
Considering changes in component values and temperature, it is necessary to narrow the range of the drawing rate in order to enter the target value in this range. That is, it is necessary to design the busbar diameter to be substantially constant.

Therefore, in order to diversify the finished size diameter, it is necessary to prepare and hold as many busbars as that, and in the case of a single delivery, there may be a case where orders are lost if the busbars are not in hand.

[0005]

DISCLOSURE OF THE INVENTION The present inventor has conducted earnest research to solve such problems. That is, the work hardening of the austenitic stainless steel wire is influenced by the amount of martensite induced by working and the Ni
Equivalent (parameter indicating the stability of austenite; N
i + 0.65Cr + 0.98Mo + 1.05Mn + 0.
38Si + 12.6 (N + C)% ... Hirayama's formula (1))
It is clear that is involved in a different form from the work hardening caused by the usual accumulation of dislocations.

On the other hand, the generation of processing-induced martensite is easily affected by heat. That is, in order to control the work hardening in the wire drawing of various austenitic stainless steel wires, the drawing rate and drawing temperature are controlled according to the Ni equivalents derived from the components, and the martensite generation state controlled by them is controlled. If you can control the, you can control the strength of the line as a result.

FIG. 2 shows that the Ni equivalent is 21.9%,
34.2% and 26.0% steel types are selected, and the drawing rates are 35%, 57% and 71% respectively, and in that case the processing temperature is room temperature, 80 ° C, 140 ° C and 210 ° C. The amount of martensite produced was investigated. Figure 3
Indicates the drawing work ratio and the amount of martensite generated for the Ni equivalent of 21.9%.

As shown in FIG. 3, the amount of martensite generated with respect to the drawing rate is significantly affected by the heating temperature. That is, when the drawing process is performed at a temperature of 200 ° C. or higher, when the working rate is 71%, only about 10% of martensite is generated and the work hardening becomes lower.

FIG. 4 shows the relationship between the drawing temperature and the yield strength for each Ni equivalent for each drawing work ratio. Table 1 shows the change in yield stress per 1 ° C of the drawing temperature (kg /
mm ² / ° C.). From the above, it is understood that if various Ni equivalents are determined, a product having a predetermined strength can be produced by appropriately controlling the heating temperature even if the drawing rate is not determined.

The present invention has been made on the basis of the above findings, and an object of the present invention is to finish a metal wire (product) having a desired diameter and a desired strength from a bus bar having an arbitrary diameter in wire drawing of the metal wire. Therefore, it is an object of the present invention to provide a wire drawing method by controlling the heating temperature during wire drawing to an optimum temperature.

[0011]

Means for Solving the Problem That is, the present invention provides a metal wire drawing method for drawing a bus bar to produce a finished metal wire having a desired diameter and a desired strength. The relationship between the drawing work ratio and the strength of the finished metal wire in the case of changing the above is investigated in advance for each Ni equivalent.

At the time of wire drawing, the drawing ratio is obtained from the diameter of the bus bar to be drawn and the desired diameter of the finished metal wire, and the Ni of the above bus bar is obtained from the obtained drawing ratio.
Using the relationship between the drawing rate at the equivalent weight and the strength of the finished metal wire, find the heating temperature during wire drawing to obtain the finished metal wire with the desired diameter and strength, and perform the wire drawing at the obtained heating temperature. This is a method for drawing a metal wire. To give a specific example of treatment, the bus bar is an austenitic stainless steel wire, the wire drawing process is repeatedly performed at a heating temperature in the range of 100 to 500 ° C., and the finished metal wire has a tensile strength of 80 to 200 kg. / Mm ² .

The present invention can be applied to all metal busbars to be drawn, but in particular, JI in which a predetermined strength is specified for an austenitic stainless wire whose work hardening behavior is complicated.
SG 4314 Stainless Steel Wire for Spring, JIS G 4
It is more effective when applied to 309 stainless steel wire soft No. 2 and 1/2 hard, and further to soft No. 1 etc.

[0014]

According to the present invention, a bus bar having an arbitrary diameter, for example, a bus bar having a size larger than the standard bus bar diameter is used for wire drawing, and the heating temperature is controlled between the processes,
The work hardening amount due to the surface reduction ratio exceeding the standard surface reduction ratio is reduced, and finally, a product having the target strength can be obtained even though a thicker bus bar is used. For example, FIG.
FIG. 3 is a diagram illustrating a relationship of heating temperature-pulling rate-yield strength for a bus bar having a Ni equivalent of 21.9% based on the above.

Now, assume that a finished metal wire (product) having a yield strength of 140 kg / m and a finished diameter of 2.00 mm is manufactured.
In the normal standard process, a drawing ratio of 39% at room temperature drawing, that is, a 2.55 mm bus bar must be used. However, there is no handhold of this bus bar and it is 3.32mm or 3.9.
If you own a 2 mm bus bar, 80% at 64% processing
If a hot wire drawing is carried out or a hot wire drawing is carried out at 140 ° C. with a processing of 74%, a predetermined product can be obtained.

The above effects are more effective in the following points. In the present invention, in the wire drawing process, the heating is performed in the initial stage of the process, that is, the bus bar is not yet processed and is heated in a single structure of austenite or under a state where martensite is slightly generated by the processing. By controlling the strength, the effect is to be achieved. That is, in the case of a γ structure state, at most 200 is required in order to minimize the generation of processing-induced martensite.
Even if it is heated to about 0 ° C., there is a remarkable effect, and the degree of the effect becomes more effective when high working degree is performed as shown in Table 1. However, the structure that has undergone the martensitic transformation by work at room temperature and is work-hardened is softened only by heating at about 200 ° C. due to the accumulation of dislocations. These states are shown in FIGS. 6 and 7.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is carried out by an apparatus as shown in FIG. This device includes an induction heater 1, a die or roller die 2, a take-up pot 3, an induction heater 4, a die or roller die 5, a take-up pot 6, ... Induction heater 7, a die or roller die 8, a take-up pot 9 And the induction heater 10 in the final process.

First, the bus bar M is firstly connected to the induction heater 1
(Or other heating device) to heat to an appropriate temperature of 100 to 500 ° C. to soften, immediately process with a die or roller die 2, and wind up in a winding pot 3.

The heating and wire drawing processes are repeated to produce a finished metal wire (product) having a predetermined strength. Further, when softness is required, it is guided to the induction heater 10 in the final process of wire drawing and heated to a high temperature (600 to 1200 ° C.) in an atmosphere of an ammonia cracking gas to perform bright annealing. Bright annealing at the end of the process of the present invention allows in-line production of soft wires.

Now, it is possible to reduce each area reduction rate by heating wire drawing at least 25%, and the total area reduction rate will be 93% if continuous drawing is performed 9 times. Therefore, if the area reduction ratio is within the range of 93%, the work hardening that exceeds the area reduction ratio standardized in conventional room temperature processing can be reduced by heating wire drawing. Can be used.

By applying the above idea to WPB type of JIS G 4314 (stainless steel wire for spring), the method of the present invention was carried out to obtain a product having a finished diameter of 0.5 mm to 3.0 mm. Table 2 shows the finished wire diameter, the diameter of the busbars, and the number of buses in this case. For comparison, Table 2 also shows the diameter and the number of busbars in the conventional method. From Table 2, it was confirmed that it was possible to reduce the conventional 15-size bus bar to 4 sizes in the present invention, the production process was remarkably rationalized, and the delivery date could be shortened. Further, the annealing and wire-drawing operations for producing the busbar are partially omitted or the cost is reduced because the busbar is finished to be thick.

Further, when the present invention is applied when a bus bar of 5.5 mmφ is processed with a high reduction ratio to finish it to 0.38 mmφ, 5.5 mm → 1.45 mm (primary wire drawing) →
It was possible to carry out wire drawing while omitting the intermediate annealing of 0.38 mm (secondary wire drawing). On the other hand, when the conventional wire drawing method is applied, 5.5 mm → 2.2 mm (primary wire drawing) → intermediate annealing → 0.80 mm (secondary wire drawing) → intermediate annealing → 0.38 mm Requires intermediate annealing twice.

In the method of the present invention, some or all of the steps can be performed by computer control. For example, the relationship between the drawing rate and the strength of the finished metal wire when the heating temperature during wire drawing is changed is investigated in advance for each Ni equivalent, and the data is input in advance in the memory of the computer. When the bus bar to be used for wire drawing is determined, the Ni equivalent and diameter of the bus bar and the diameter of the metal wire to be finally finished are input to this computer. From the Ni equivalent of the input busbar, the computer extracts data on the relationship between the drawing rate and the strength of the finished metal wire when the heating temperature during wire drawing at that Ni equivalent is changed.
Based on this data, the total area reduction rate is calculated from the value of the busbar diameter and the value of the finished metal wire diameter, the optimum heating temperature during wire drawing is set, and the number of drawing steps in the pass line, The area reduction rate in each drawing step is calculated. Then, a heating temperature setting signal is output to a temperature control device (not shown) of each induction heater 1, 4, 7 ... And each induction heater 1, 4, 7 ... Is controlled to a predetermined set temperature by this temperature control device. To do. Further, a signal corresponding to the calculated surface reduction rate is output to an adjusting device (not shown) for each die 2, 5, 8 ... Be set to rate. In this way, it is possible to automatically perform the drawing process of the metal wire.

[0024]

As is apparent from the above embodiments, according to the present invention, the following effects can be exhibited. 1. The required busbar for the production of the spring wire is greatly reduced.

2. The annealing and wire drawing operations for producing the spring wire busbars are partially omitted or the cost is reduced because the busbars are finished thick. 3. Bright annealing at the end of the process allows in-line production of soft wires. 4. High area reduction processing is possible and intermediate annealing can be omitted.

[0026]

[Table 1]

[0027]

[Table 2]

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a drawing rate and a tensile strength when various stainless steel wires are drawn.

FIG. 2 is a diagram showing a relationship between a processing temperature and a martensite generation state when the drawing rate of various stainless steel wires having different Ni equivalents is changed.

FIG. 3 is a diagram showing a relationship between a drawing workability and a temperature dissimilarity of martensite generation in a stainless steel wire having a Ni equivalent of 21.9%.

FIG. 4 is a diagram showing a change in yield strength for each processing rate with respect to a drawing processing temperature in various materials having different Ni equivalents.

FIG. 5 is a diagram showing a relationship between a drawing workability and a yield strength when the wire drawing temperature is changed.

FIG. 6 is a diagram showing a relationship between a preheating temperature and a tensile strength of a stainless steel wire.

FIG. 7 is a diagram showing the results of a high temperature tensile test of a stainless steel wire that has been 64% drawn.

FIG. 8 is an explanatory view showing an example of an apparatus for carrying out the method of the present invention.

[Explanation of symbols]

1, 4, 7, 10 ... Induction heater, 2, 5,
8 ... Die or die roller, 3, 6, 9 ... Winding pot

Claims (2)

[Claims] 1. A metal wire drawing method for producing a finished metal wire having a desired diameter and a desired strength by drawing a bus bar, and a drawing rate and a finish when a heating temperature during wire drawing is changed. The relationship with the strength of the metal wire is investigated in advance for each Ni equivalent, and the drawing rate is calculated from the diameter of the bus bar to be drawn and the desired diameter of the finished metal wire. From the calculated drawing rate, Using the relationship between the drawing rate in the Ni equivalent of the busbar and the strength of the finished metal wire, the heating temperature during wire drawing to obtain the finished metal wire with the desired diameter and strength is obtained, and the obtained heating temperature Wire drawing method for metal wire. 2. The bus bar is an austenitic stainless steel wire, the wire drawing is repeatedly performed at a heating temperature within a range of 100 to 500 ° C., and the finished metal wire has a tensile strength of 8
The method for drawing a metal wire according to claim 1, wherein the method is 0 to 200 kg / mm ² .