JPH1080716A - Manufacture of high-strength high-carbon steel wire excellent in elongation characteristic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a steel wire being the element wire of a high-strength and slender-diameter wire rope whose diameter is <=1mm and a high-strength bead wire. SOLUTION: By using dies made of high-carbon steel wire >=80% in the area factor of pearlite structure and whose approach angle is >=6 deg. to <12 deg. and by setting an area-reducing factor per dies to >=20% to <30%, the wire drawing is performed with a wire drawing strain quantity of >=2.5 which is shown in formula (wire drawing strain quantity = 2×1n (Do/Dn)) (wherein, Do: wire diameter before wire drawing (mm), Dn: wire diameter after wire drawing (mm)), and then blueing treatment is performed in a temperature area of >=380 deg.C to <430 deg.C. By appropriately controlling wire drawing condition and blueing condition, the high-carbon steel wire with high strength and high elongation can be manufactured, and an industrial effect is very much remarkable.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a steel wire and a high-strength bead wire which are used as a strand of a thin high-strength wire rope having a wire diameter of 1 mm or less.

[0002]

2. Description of the Related Art In recent years, from the viewpoint of reducing the weight of wire ropes, tires, and the like, steel wires have been required to have higher strength. As a method for realizing high strength, there are a method of adding an alloy element and a method of increasing the amount of wire drawing. The former has a problem that heat treatment characteristics change and wire drawing workability is reduced, and is not practical. For this reason, usually, a method of increasing the amount of wire drawing when increasing the strength is adopted.

On the other hand, in the case of a wire rope, a bead wire, etc., one of the important characteristics is the elongation of the steel wire as well as the strength. If the steel wire does not have sufficient elongation, a stable product shape cannot be produced. However, "machine research"
As shown in Vol. 9, No. 10 (1957), pp. 57-65, the elongation of the steel wire becomes a very small value as the amount of wire drawing increases, and the wire drawing strain that can realize high strength is obtained. In the region where the amount is 2.5 or more, the elongation is 3% or less.

Conventionally, the elongation has been recovered by performing a bluing process at 400 to 450 ° C. for several seconds after the drawing process. However, in a region where the amount of strain of the drawing process is 2.5 or more, the bluing process is performed. Did not achieve high growth. Further, Japanese Patent Publication No. 4-4392 discloses a stainless steel thin wire having improved elongation characteristics by adjusting the composition, but in the case of a high carbon steel wire, when a high-temperature annealing treatment such as stainless steel is performed, Although the elongation recovers, the strength is greatly reduced by the spheroidization of the cementite, so that it cannot be applied to a high carbon steel wire.

[0005]

SUMMARY OF THE INVENTION According to the present invention, a die approach angle in a wire drawing process, a reduction ratio per die and a bluing temperature are optimized.
An object of the present invention is to provide a method for producing a high-strength high-carbon steel wire having excellent elongation characteristics.

[0006]

The inventors of the present invention have analyzed the effects of wire drawing conditions on the elongation of a high carbon steel wire after drawing and after bluing in detail, and have found that the die approach angle, It has been found that the elongation can be improved by optimizing the area reduction rate per die. Furthermore, it was found that the bluing temperature at which the elongation was the best changed depending on the drawing conditions, and by optimizing the bluing temperature in accordance with the drawing conditions, the amount of drawing strain was 2.5 or more. It has been found that high elongation can be obtained also in the region.

That is, the gist of the present invention is as follows.
(1) Using a high carbon steel wire having an area ratio of pearlite structure of 80% or more, using a die having an approach angle of 6 ° or more and less than 12 °, and reducing the area reduction per die to 20% or more and less than 30%. A high-strength, high-carbon high-strength carbon having excellent elongation characteristics, wherein after performing wire drawing with a strain amount of 2.5 or more shown in the formula, blueing treatment is performed in a temperature range of 380 ° C or more and less than 430 ° C. In the method of manufacturing steel wire.

[0008] Wire drawing strain = 2 x ln (Do / Dn) (1) Do: wire diameter before drawing (mm), Dn: wire diameter after drawing (mm)

[0009]

First, the reason why the area ratio of the pearlite structure is limited to 80% or more will be described. If the area ratio of the pearlite structure is less than 80%, work hardening by wire drawing is small, and high strength cannot be realized even if the wire drawing amount is increased. For this reason, the area ratio of the pearlite structure was set to 80% or more.

Further, even if the area ratio of the pearlite structure is 80% or more, if the drawing strain is less than 2.5, the tensile strength becomes 2000 MPa or less. Insufficient strength. For this reason, the drawing strain amount was set to 2.5 or more. Next, the reasons for limiting the approach angle of the die will be described. If the die approach angle is less than 6 °, it becomes difficult to introduce a lubricant into the dies during wire drawing, and poor lubrication results in low elongation of the steel wire. On the other hand, when the approach angle of the die is 12 ° or more, the elongation after the wire drawing becomes 3% or less in the region where the wire drawing strain is 2.5 or more. Sufficient elongation cannot be obtained. For this reason, the approach angle of the die is set to 6 ° or more and less than 12 °.

Next, the reason for limiting the area reduction rate per die will be described. When the area reduction rate per die is less than 20%, the deformation of the steel wire by wire drawing concentrates on the surface layer,
The deformation of the steel wire becomes uneven and the elongation becomes small. Also,
Even when the bluing process is performed, the structural change due to the bluing process is uneven in the cross section of the steel wire, and the elongation is not sufficiently recovered. On the other hand, when the area reduction rate per die is 30% or more, strain aging occurs due to heat generated during wire drawing, and thus elongation is deteriorated. For this reason, the area reduction rate per die is set to 20% or more and less than 30%.

Next, the reasons for limiting the bluing treatment temperature will be described. When wire drawing is performed under the wire drawing conditions described above, if the bluing treatment temperature is lower than 380 ° C., the structural change due to the bluing treatment is not sufficient, and the recovery of elongation is small. On the other hand, if the bluing treatment temperature is 430 ° C. or higher, the strength is reduced and the spheroidization of cementite proceeds more than necessary, resulting in low elongation. For this reason, the bluing treatment temperature is set to 380 ° C. or higher4
It was less than 30 ° C.

[0013] The bluing treatment time is not particularly limited because it differs depending on whether a lead bath is used for heating during bluing, when a salt bath is used, or when heating is performed in air.

[0014]

EXAMPLES Hereinafter, the effects of the present invention will be described more specifically with reference to examples. Table 1 shows a die approach angle of 10
° Wire drawing at 25% reduction in area per die
It shows the relationship between the area ratio of the pearlite structure, the amount of wire drawing strain, and the elongation when a bluing treatment is performed at 400 ° C. for 5 seconds in a lead bath.

No. 1 of the present invention. 3, No. No. 4 realizes high tensile strength of 2000 MPa or more and high elongation of 6% or more. No. 1, No. No. 2 has good elongation, but has a low tensile strength due to a low area ratio of the pearlite structure. No. 5, no. In No. 6, the area ratio of the pearlite structure is 80% or more, and the elongation is good, but the tensile strength is low due to a small amount of wire drawing strain.

No. 7, no. No. 8 is the case where the wire drawing amount was increased for the one having a low area ratio of the pearlite structure. For No. 7, the tensile strength is low even when the amount of drawing strain is increased. On the other hand, No. For No. 8, tensile strength can be achieved by increasing the amount of wire drawing strain, but the ferrite phase precipitated at the former austenite grain boundary is coarsened, ductility after wire drawing is deteriorated, and elongation is reduced. Lower.

Table 2 shows that the area ratio of the pearlite structure is 96%,
It shows the relationship between the die approach angle, the area reduction rate per die, and the bluing temperature in the case of a wire drawing strain amount of 2.85. The bluing treatment was performed in a lead bath for 5 seconds. No. 10, 11, 12, 15,
16, 17, 20, 21, and 22 are examples of the present invention, and others are comparative examples.

As can be seen from the table, all of the examples of the present invention have a tensile strength of 2000 MPa or more and an elongation of 6% or more,
High strength and high elongation are realized. On the contrary,
No. of Comparative Example. In No. 9, since the die approach angle is small, poor lubrication occurs and the elongation is small. On the other hand, N
o. 13 has a small elongation due to a large die approach angle. No. No. 14 has a small area reduction rate per die, so that non-uniform deformation occurs and elongation is small. No. No. 18 causes strain aging due to the large area reduction rate per die,
Low elongation. No. In No. 19, the recovery of elongation is not sufficient because the bluing treatment temperature is low. No. In No. 23, since the bluing treatment temperature was high, a structural change occurred more than necessary and the elongation was low.

[0019]

[Table 1]

[0020]

[Table 2]

[0021]

As is apparent from the above embodiments, the present invention makes it possible to produce a high-strength, high-elongation, high-carbon steel wire by optimizing the wire drawing and bluing conditions. The industrial effect is extremely remarkable.

Claims (1)

[Claims] 1. A high carbon steel wire having an area ratio of pearlite structure of 80% or more is used with a die having an approach angle of 6 ° or more and less than 12 °, and the area reduction rate per die is 20%.
380 ° C. or more 430
A method for producing a high-strength high-carbon steel wire having excellent elongation characteristics, wherein a blueing treatment is performed in a temperature range of less than ° C. Wire drawing distortion = 2 × ln (Do / Dn) (1) Do: wire diameter before drawing (mm), Dn: wire diameter after drawing (mm)