JPH10137803A - Diameter reducing method of stainless wire rod - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the manufacturing costs of a stainless wire rod by setting the wire rod temperature in the outlet side of a continuous rolling mill at a specified value or above in the case of cold reducing the outer diameter of a stainless steel raw wire rod with the continuous rolling mill. SOLUTION: The outer diameter of the raw wire rod SW in the ordinary temperature state made from stainless steel difficult to work, which is recoiled with a recoiling machine 1 and continuously fed through the inlet guide 2, is continuously cold rolled to reduce with the continuous rolling mill 3 and the wire rod is coiled with a coiling machine 4. At this time, the wire rod is rolled under the condition that the material temperature in the outlet side of the continuous rolling mill 3 becomes >= (Md point +50) deg.C. When the material temperature in the outlet side of the continuous rolling mill 3 is >= (Md point +50) deg.C, the higher the better. However when it becomes too high, since seizure is possibly generated between the material and a pass roll depending on a material, the upper limit is preferable kept at e.g. (Md+150) deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a stainless steel wire,
Specifically, the present invention relates to a method for reducing the diameter of a stainless steel wire having a wire diameter of 5 mm or less.

[0002]

2. Description of the Related Art A stainless steel wire having a wire diameter of 5 mm or less is
Usually, it is manufactured as described below. That is, 2
A wire rod having a wire diameter of 9 to 6 mm is obtained by hot rolling by a wire rod rolling machine in which a roll stand is arranged in tandem. Next, the wire is passed through a die peeling device or a bite peeling device to remove scratches on the surface and rough finish to a wire diameter of about 5 mm. Thereafter, a product wire having a desired wire diameter is finished in a cold state by a die drawing method.

[0003] The above-mentioned die drawing method is a cold working method of reducing the wire diameter by drawing a wire through a hole die, and is widely used as a method of working not only for stainless steel wires but also for small diameter wires of various materials. Used.

In the die wire drawing method, in processing with a single hole die, the area reduction rate determined by the following equation is limited in order to prevent the wire itself from breaking due to the drawing force on the exit side.

Reduction area (%) = {(S0−S) / S0} × 100 where S0: cross-sectional area of wire before processing (mm ² ) S: cross-sectional area of wire after processing (mm ² ) Usually, a necessary total area reduction rate is ensured by using a continuous drawing method.

FIG. 3 is a schematic diagram showing an example of the continuous drawing method. As shown in FIG. 3, a plurality of hole dies 31, 31,... And take-up pots 32, 32, ... are used.

In the continuous wire drawing method, wire drawing is performed in a state where the wire S is wound several times around a take-up pot 32 that is rotatably driven and disposed on the exit side of each hole die 31. And the tensile force in each hole die 31 is added by the frictional force between the winding hook 32 and the wire S. In addition, the wire tension between each winding pot 32 and the hole die 31 on the downstream side thereof is adjusted by controlling the rotation speed of the winding pot 32 so that the wire S is not loosened. Therefore, the tension acting on the wire S during wire drawing is only the pulling force at each hole die 31, and the pulling force at the upstream hole die is superimposed on the wire S being processed at the downstream hole die. Never do. As a result, in this continuous drawing method, not only continuous drawing with a plurality of hole dies is possible, but also the drawing force in each hole die does not overlap the wire being processed, so that It is possible to increase the area reduction rate.

[0008] Apart from the above-mentioned die drawing method, there is also a method of reducing the diameter by a rolling mill equipped with a grooved roll as disclosed in, for example, JP-A-63-168202.

FIG. 4 is a diagram for explaining the method disclosed in Japanese Patent Application Laid-Open No. 63-168202. That is, the method includes, as shown in FIG. 4, a substantially circular roll hole type formed by a plurality (four in the illustrated example) of hole type rolls 11 arranged around the pass line, Roll stand 12, 12, 12,... Of A arrangement and B arrangement (see FIG.
Using a continuous rolling mill alternately arranged in the pass line direction,
This is a method in which the outer diameter of the strands 13 is sequentially reduced and rolled.

[0010]

However, stainless steels, especially SUs with a high C content for high strength,
Austenitic stainless steels, such as S201, SUS202, and SUS303, which are difficult to work, have poor cold workability and a large decrease in ductility due to working.

Therefore, when such a difficult-to-work stainless steel wire made of austenitic stainless steel is reduced in diameter by the above-described continuous drawing method, the material on the exit side of the hole die, particularly on the downstream side of the hole die exit side, is obtained. Breakage easily occurred, and the total area reduction rate could not be so large. That is, among the above-mentioned hard-working austenitic stainless steels, SUS303, which is particularly hard-working, can only work at a total area reduction rate of about 60%, and performs processing at a total area-reduction rate higher than that. Required an intermediate annealing treatment.
As a result, there is a disadvantage that not only the cost for the intermediate annealing treatment is increased, but also that the productivity is reduced and the production cost of the product is increased.

On the other hand, in the case of the above-mentioned continuous rolling method, although it is possible to perform processing without tension between stands, in practice, a slight amount of material (wire) is prevented between stands. Rolling is performed under tension, but the tension to be applied can be extremely small as compared with the continuous drawing method. For this reason, the material that has been processed by the upstream roll stand and has reduced ductility hardly breaks at the downstream roll stand. Therefore, in this continuous rolling method, even with the above-mentioned difficult-to-work stainless steel, the total area reduction in one pass can be made larger than that in the continuous drawing method.

However, the total area reduction rate that can be obtained is
It is considerably smaller than general austenitic stainless steel having good workability such as SUS304 and SUS316.
That is, for example, SUS304 can reduce the diameter at a total area reduction rate of 90% or more, whereas SUS304 can reduce the diameter.
In the case of No. 03, diameter reduction processing could only be performed at a total area reduction rate of about 75%.

For this reason, there has been a demand for the development of a method capable of reducing the diameter of a difficult-to-process stainless steel wire represented by the SUS303 with a higher total area reduction.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and has as its object to provide a stainless steel wire which is difficult to process, such as SUS303, and which can be reduced in diameter with a higher total area reduction rate. It is to provide a diameter reduction processing method.

[0016]

The gist of the present invention resides in the following method for reducing the diameter of a stainless steel wire.

A stainless steel roll is formed by a continuous rolling mill in which a plurality of four-roll stands each having a substantially circular shape are formed in a tandem direction along the pass line. When the diameter of the wire is reduced while the outer diameter of the wire is cold, the temperature of the wire at the exit side of the continuous rolling mill is (Md
Point +50) A method for reducing the diameter of a stainless steel wire, the method comprising reducing the diameter of the stainless steel wire under a condition of not less than 50 ° C.

In the above-mentioned method of the present invention, the roll groove form is such that the distance between the opposed groove bottoms of the four hole rolls is D.
m, and the dimension between the groove edges is Dh, and the ratio (Dh / D
m) is preferably a roll-hole type having 1.02 to 1.06.

The present inventors have conducted many experiments and found the following, and have accomplished the present invention.

That is, when stainless steel, especially austenitic stainless steel, undergoes plastic deformation during cold working, the structure becomes martensitic and work hardens, resulting in loss of cold workability. On the other hand, the material temperature is Md, which is a transformation temperature at which martensitization occurs with the above-mentioned cold working.
In the case where the temperature is higher than the point, martensite formation is suppressed, and a decrease in cold workability due to working is suppressed.

When a metal material is subjected to cold working, processing heat is generated and the material temperature rises. The temperature rise increases as the degree of working applied increases.

From the above, it is conceivable to increase the degree of processing to be applied and increase the temperature of the material during processing to the Md point or higher to perform processing.

However, in the above-described continuous drawing method, if the working temperature is set so that the material temperature during working can be higher than the above Md point, the wire is easily broken. Even if the material temperature becomes higher than the Md point, the heat is removed by the take-up pot provided on the exit side of the hole die, and the material temperature on the entry side of the next-stage hole die becomes lower than the Md point. For this reason, in the case of using the continuous drawing method, it is necessary to provide a heating device for heating the material to a temperature equal to or higher than the Md point on the entry side of each hole die, which increases equipment cost and is not practical. Furthermore, in the die wire drawing method, the slip between the hole die and the material is large, and in the case of a material that is easily seized such as the above-mentioned difficult-to-work stainless steel, the seizure occurs when the material temperature increases, particularly when the material temperature rises above the Md point. Since it occurs remarkably, it is difficult to process at the Md point or higher.

However, when the continuous rolling method is used in place of the continuous drawing method, the material is successively passed through a downstream roll stand while generating heat while working without slipping between the roll and the roll. Lined. Therefore, in the continuous rolling method, unlike the continuous drawing method, the material temperature once raised by the processing heat does not drop during the processing, so that the heat generated by the processing is gradually accumulated. As a result, the material temperature after processing is much higher when using the continuous rolling method than when using the continuous drawing method.

Then, as the continuous rolling mill, a continuous rolling mill in which a plurality of roll stands in which four round rolls forming a circular groove are arranged around a pass line are arranged in tandem in the pass line direction is used. When continuous rolling is performed under the condition that the material temperature at the exit side of the rolling mill is (Md point + 50) ° C. or more, the formation of martensite in the material structure during rolling is reliably suppressed, and the reduction in workability due to rolling is reduced. It has been found that the total area reduction rate in one pass, which can be suppressed and processed without surface cracking, can be increased.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a diameter reducing method according to the present invention will be described below in detail with reference to FIGS. 1 and 2 and FIGS.

FIG. 1 is a schematic side view showing an example of an embodiment of the present invention. In the drawing, reference numeral 1 denotes a rewinding machine, 2 denotes an inlet guide, 3 denotes a continuous rolling mill, and 4 denotes a winding machine. , SW is the strand material, W
Is the above difficult-to-work stainless steel wire.

The continuous rolling mill 3 comprises a plurality of roll stands 3a arranged in tandem with a stand center interval M in the pass line direction. Each roll stand 3
As shown in FIG. 4A, similar to the conventional continuous rolling mill shown in FIG. 4 and FIG. 5, there are provided four grooved rolls 11 forming a substantially circular roll die, and the rolling direction of the rolls is 45 °. As shown in FIG.

Although not shown in the drawing, the entry side (left side in the figure) of each roll stand 3a is provided with a wire S of a material to be rolled.
For W, a nozzle for applying a water-soluble rolling lubricating oil such as a solven oil is provided.

Further, although not shown, the four hole-type rolls 11 incorporated in each roll stand 3a are:
The roll shafts of one of the four hole type rolls are connected to each other by a gear, and can be rotationally driven in the same direction by a drive source connected to the roll shaft.

As shown in FIG. 2, the roll stand shape of each of the roll stands 3a has a slightly smaller edge diameter Dh than a groove bottom diameter Dm in order to prevent the material from biting into the roll gap G4. It has a large substantially circular shape. Then, the dimension Dm (D
h) is gradually reduced, so that the outer diameter of the wire SW can be reduced.

Here, as the shape of the roll hole type, the diameter ratio (Dh / Dm) of the edge diameter Dh to the groove bottom diameter Dm is 1.
It is desirable that the shape be in the range of 02 to 1.06. That is, when the diameter ratio (Dh / Dm) exceeds 1.06,
The roundness of the wire W after the diameter reduction processing is deteriorated. Conversely, if the diameter ratio (Dh / Dm) is less than 1.02, material biting occurs, and the reduction in area per stand that can be rolled is reduced, and it is necessary to obtain a desired reduction in area. This is because it is not practical because the number of stands increases and the manufacturing cost of the continuous rolling mill increases.

In the present invention, the rewinding machine 1
SUS303 continuously supplied through the entrance guide 2
The continuous diameter of the wire SW made of a difficult-to-work stainless steel at room temperature is reduced by continuous rolling in the cold state by the continuous rolling mill 3 configured as described above. At this time, it is necessary to perform rolling under the condition that the material temperature at the exit side of the continuous rolling mill 3 becomes (Md point + 50) ° C. or more.

The reason is as follows. That is, the material temperature at the exit side of the continuous rolling mill 3 is (Md point +
If the temperature is less than 50) ° C., the heat generated during the processing by the upstream roll stand is largely removed between the stands, and the material temperature is Md.
The number of processing stands in the temperature range that does not exceed the point increases. For this reason, the material structure progresses to martensite in the early stage of rolling and the workability of the material deteriorates, and surface cracks are likely to occur at the time of processing in the subsequent stands, and the number of subsequent stands that can be processed without surface cracks Is reduced, and as a result, the total area reduction rate in one pass cannot be increased.

On the other hand, when the material temperature at the output side of the continuous rolling mill 3 is set to (Md point + 50) ° C. or more, heat removal between the stands of the processing heat generated by the upstream roll stand is suppressed as much as possible. As a result, the number of processing stands in a temperature range where the material temperature does not exceed the Md point is reduced. For this reason, a decrease in workability of the material due to the progress of martensitization of the material structure in the early stage of rolling is suppressed, and surface cracks are less likely to occur at the time of working in the latter stage, so that the latter stage that can be processed without surface cracks This is because the number increases, and as a result, the total area reduction rate in one pass can be increased.

The material temperature at the outlet side of the continuous rolling mill 3 is preferably higher as long as it is (Md point + 50) ° C. or higher. It is preferable that the upper limit be kept at (Md point + 150) .degree.

The rolling conditions for setting the material temperature at the exit side of the continuous rolling mill 3 to (Md point + 50) ° C. or more are determined by the specifications of the continuous rolling mill 3 to be used and the working degree (reduction surface area) given per stand. Although it varies depending on the rate, it can be ensured by controlling the material speed at the entry side of the continuous rolling mill 3.

For example, there are 27 stands, 1 to 19
Up to the stand, the roll diameter and the distance M between the centers of the stands are all 100 mm. Up to the 20 to 27 stands, a continuous rolling mill having the roll diameter and the distance M between the centers of the stands of 70 mm is used. In the case of performing continuous rolling with the area reduction rate at each stand excluding 9.5%, the material speed at the entry side of the continuous rolling mill 3 is set to 30 m / min or more, so that the continuous rolling mill 3 The material temperature on the outlet side can be set to (Md point + 50) ° C. or higher.

In this case, by setting the material speed at the entry side of the continuous rolling mill 3 to less than 400 m / min, the material temperature at the exit side can be made (Md point + 150) ° C. or less.

Further, the area reduction rate applied per stand is not particularly limited, but is preferably 5 to 15%. However, when a final finishing stand for adjusting the cross-sectional shape of the product stainless steel wire W after rolling is installed as in the above example, the roll hole dimension of the final finishing stand is the roll diameter of the immediately preceding roll stand. Preferably, it is the same as the groove size.

[0041]

EXAMPLE First, a wire made of SUS303 (Md point = 40 ° C.) having a diameter of 5.2 mm was prepared as a wire.

On the other hand, the continuous rolling mill is composed of 27 roll stands provided with four hole-shaped rolls made of SKD11. The diameter of the hole-shaped roll, the distance M between the centers of the stands (see FIG. 1), and the roll hole of each stand. Table 1 shows the groove bottom diameter Dm of the mold.
A continuous rolling mill having the dimensions shown was prepared. The roll hole shape of each stand was a substantially circular shape with a diameter ratio (Dh / Dm) between the edge diameter Dh and the groove bottom diameter Dm of 1.04. The area reduction rate at each stand of the continuous rolling mill is 9.5%. However, since the final 27th roll stand is used as a finishing stand, the area reduction rate is 0 (zero).
And

[0043]

[Table 1]

The continuous wire is supplied to the continuous rolling mill at a normal temperature state, and the number of rotations of the grooved rolls of each stand is controlled so that the material temperature at the exit side of the continuous rolling mill is variously changed. The material speed at the entry side is 10 to 1000 m /
While various changes are made within the range of min, the number of roll stands to which the actual reduction is applied is increased by one and rolling is performed in a cold state, and the number of stands that can be rolled without surface cracking, in other words, the total area reduction rate ( Table 1) was also examined. The results are shown in Table 2.

The material to be rolled during the rolling was sprayed with a water-soluble lubricating oil (solvent oil) at room temperature from a nozzle arranged on the entry side of each stand.

[0046]

[Table 2]

As is evident from the results shown in Table 2, when the material temperature on the exit side of the continuous rolling mill is lower than (Md point + 50) ° C., surface cracking does not occur up to 13 stands, but rolling of 14 stands is performed. In this case, surface cracks occurred, and only processing at a total area reduction rate of 72.8% was possible.

On the other hand, when the material temperature at the exit side of the continuous rolling mill is set to (Md point + 50) ° C. or more, no surface cracks are generated up to a minimum of 15 stands, and surface cracks are generated by a minimum of 16 stands. However, processing with a total area reduction rate of 79.9% or more was achieved. However, when the temperature of the material on the output side of the continuous rolling mill was higher than (Md point + 150) ° C., although no surface cracking occurred, seizure occurred at a minimum of 13 stands of rolling.

In the case of the present embodiment, if the material speed on the entry side of the continuous rolling mill exceeds 30 m / min, (Md point + 5
0) It can be seen that an outlet material temperature of at least 0 ° C. can be secured.

[0050]

According to the method of the present invention, a difficult-working austenitic stainless steel stainless steel wire represented by SUS303 having an outer diameter of 5 mm or less is formed by a continuous rolling mill provided with an existing four-roll stand. In addition, it is possible to perform processing in one pass with a higher total area reduction ratio than before. As a result, since the intermediate annealing can be omitted, the manufacturing cost of the stainless steel wire can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic side view showing an example of an embodiment of the present invention.

FIG. 2 is a view for explaining a preferred roll hole shape;

FIG. 3 is a schematic side view for explaining a conventional continuous drawing method.

FIG. 4 is a schematic side view for explaining a conventional continuous rolling method.

FIG. 5 is a schematic front view for explaining an arrangement of a roll stand.

[Description of Signs] 1: Rewinding machine, 2: Guide on entry side, 3: Continuous rolling mill, 3a, 12: Roll stand, 4: Winding machine, SW: Elemental wire, S: Stainless steel wire, 11: Hole type Roll, G4: Roll gap, Dm: groove bottom diameter, Dm: edge diameter.

Claims (2)

[Claims] 1. A continuous rolling mill in which a plurality of four-roll stands, each of which has a substantially circular roll shape formed of four groove-type rolls disposed around a pass line, are arranged in tandem in the direction of the pass line. When the outer diameter of the wire made of steel is reduced while the outer diameter is cold, the temperature of the wire at the exit side of the continuous rolling mill is (Md
Point +50) A method for reducing the diameter of a stainless steel wire, the method comprising reducing the diameter of the stainless steel wire under a condition of not less than 50 ° C. 2. The roll-to-roll type has a ratio (Dh / Dm) of 1.02 to 1 where Dm is the distance between opposed groove bottoms and Dh is the distance between groove edges of the four grooved rolls. 2. The method for reducing the diameter of a stainless steel wire according to claim 1, wherein the diameter is 0.06.