JP3340698B2 - High strength steel wire and small diameter high strength steel wire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-tensile steel wire rod and a small-diameter steel cord used for reinforcing a rubber tire of a truck, a bus, a passenger car or the like or a belt cord used for reinforcing a belt. The present invention relates to a high tensile strength steel wire obtained by twisting a high tensile strength steel wire and a high strength thin wire.

[0002]

2. Description of the Related Art Steel wire manufacturing methods utilizing pearlite transformation have been used for a long time. Generally A ₃ point or more temperature region heated to (750 to 1100 ° C.), was treated γ of, to obtain a pearlite structure performs isothermal transformation treatment at a temperature range of the quenching to five hundred fifty to six hundred eighty ° C., further the tissue Is drawn and used as a wire (steel wire).

[0003] As a method of controlling the pearlite transformation, there is a method described in JP-A-1-316420.
This cools to 900-800 ° C in the austenitic range,
This is a method for producing a high-strength, high-fatigue-strength cord wire that is plastically worked at a working degree of 20 to 40% in this temperature range and then immersed in lead.

[0004]

The most important factor in producing a high-strength steel wire is a structure formed in final patenting. Generally, the heat treatment process is adjusted so as to form a uniform pearlite structure by a patenting process. However, in the conventional patenting treatment, even in the hypereutectoid steel, a thin ferrite or pseudo-pearlite structure precipitates along the old γ grain boundary. This phase becomes a starting point of a crack in the wire drawing process, and therefore needs to be suppressed as much as possible. Therefore, the emergence of a high-strength steel wire rod that renders this phase harmless and excellent in wire drawing workability is expected.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and the gist of the present invention is as follows.

(1) In weight%, C: 0.90% to 1.10%, Si: 0.4% or less, Mn: 0.5%
Hereinafter, P: 0.020% or less, S: 0.020% or less,
Cu: contains not less than 0.10% and not more than 0.80%, the balance being iron and inevitable impurities, and the inevitable Al content is 0.003% or less. Excellent high tensile steel wire.

(2) By weight%, Cr: 0.1
0% to 0.30%, Ni: 0.10% to 1.0
The high-strength steel wire according to the above (1), which contains 0% or less of one or two types.

[0008] (3) The high-strength steel wire according to the above (1) or (2), which has a uniform pearlite structure and is excellent in wire drawing workability.

(4) The high-strength steel wire excellent in wire formability according to any one of the above (1) to (3), wherein microcracks do not occur during wire drawing.

(5) A small-diameter high-tensile steel wire excellent in ductility, characterized by being manufactured using the steel wire rod according to any one of the above (1) to (4).

(6) The small-diameter high-strength steel wire excellent in ductility according to the above (5), wherein delamination does not occur in a twist test.

(7) A high-strength twisted steel wire obtained by twisting the small-diameter high-strength steel wire according to any one of (5) and (6).

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The reasons for limiting the steel composition of the present invention are as follows.

C is an economical and effective strengthening element,
In order to sufficiently exhibit the effect of C, the amount of addition should be 0.90.
% Or more. However, if it is too high, the ductility decreases and the drawability deteriorates, so the upper limit is set to 1.10%.

[0015] Si is an element necessary for deoxidizing steel, and if its content is too small, the deoxidizing effect becomes insufficient. Also, Si forms a solid solution in the ferrite phase in pearlite formed after heat treatment and increases the strength after patenting, but decreases the ductility of ferrite,
0.4% or less to reduce the ductility of the ultrafine wire after drawing.

Mn is desirably added in a small amount to ensure the hardenability of steel. However, the addition of a large amount of Mn causes segregation, and during patenting, bainite,
A supercooled structure such as martensite is generated, which impairs the drawability thereafter, so that the content is 0.5% or less.

Since Cu is an element for improving the corrosion fatigue characteristics of the wire, it is desirable to add Cu in an amount of 0.10% or more to exhibit its effect. If the added amount of Cu is too large, the ductility of the ferrite phase is reduced.
%.

One or two types of Cr and Ni are added for the following reasons.

In the case of hypereutectoid steel, a cementite network is likely to be generated in the structure after patenting,
Thick cementite tends to precipitate. In order to realize high strength and high ductility in this steel, it is necessary to make pearlite fine and eliminate the cementite network and thick cementite as described above. Cr has the effect of suppressing the appearance of such abnormal portions of cementite and further reducing pearlite. However, the addition of a large amount increases the dislocation density in the ferrite after the heat treatment, and significantly impairs the ductility of the ultrafine wire after the drawing. Therefore, the amount of Cr added is set to 0.10% or more where the effect can be expected, and 0.30% or less which increases the dislocation density in ferrite and does not impair ductility.

Since Ni also has the same effect as Cr, if necessary, 0.10% or more which exerts the effect is added. Ni
If the addition amount is too large, the ductility of the ferrite phase is reduced, so the upper limit is made 1.00%.

As in the case of the conventional ultrafine steel wire,
The content of S is set to 0.020% or less, and P is also similar to S.
Since it impairs the ductility of the wire, its content should be 0.020% or less
It is desirable that Causes of reduced ductility of extra fine wires
Al_TwoO_Three, MgO-Al _TwoO_ThreeAl_TwoO_ThreeThe main component
And the presence of non-ductile inclusions. Therefore, the present invention
In order to avoid the decrease in ductility due to non-ductile inclusions,
The l content is 0.003% or less.

As shown in FIG. 1, the steel wire of the present invention is manufactured through the steps of hot rolling → drawing → patenting → drawing → final patenting → brass plating → drawing.
In such a manufacturing process, it is desirable to adjust the heat treatment process in the final heat treatment to obtain a uniform pearlite structure,
In normal heat treatment, a ferrite phase or a pseudo-pearlite phase precipitates along the prior austenite grain boundaries. Since this phase becomes a starting point of cracking during wire drawing, it is necessary to suppress precipitation as much as possible or to change the precipitation form to a form in which cracks are unlikely to occur. This precipitation cannot be suppressed in the ordinary patenting treatment. Therefore, it is necessary to make the deposit harmless by changing the form of the deposition. In order to render the precipitation form harmless, it is necessary to change the site of precipitation from a plane to a point by imparting strain to the prior austenite grain boundaries. For this purpose, most enters easily the work strain, with the A ₁ transformation temperature below the temperature after the austenitizing, it is necessary to perform the final patenting treatment while giving the process the steel wire in the transformation start before or transformation.

The above-mentioned processing may be any processing as long as processing distortion can be given. For example, any of rolling, bending, swaging, etc. is effective. Further, since the bending process hardly changes the shape of the wire due to the bending process, the wire can be easily introduced. However, since bending deformation introduced into the wire in bending is small, it is necessary to perform bending that satisfies at least D / d ≦ 20 (D: roll diameter, d: wire diameter).

According to the high-strength steel wire of the present invention, it is possible to suppress a precipitation phase which is a starting point of a crack during wire drawing or to make a precipitation form in which a crack is hardly generated. No cracks occur. In addition, a thin high-strength steel wire having excellent ductility and free from delamination even in a twist test after drawing can be obtained. And a high tensile strength steel wire can be manufactured by twisting a small diameter high tensile strength steel wire.

[0025]

EXAMPLES As shown in Table 1 (chemical composition) and Table 2 (processing conditions and properties), tests were carried out on steels having 1 to 4 chemical compositions according to the present invention. The manufacturing process of the steel wire is as shown in FIG. 1, and the wire rod manufactured by the hot rolling is subjected to the final patenting process shown in Table 2 by the wire drawing process and the LP process to obtain a wire diameter of 5.50 to 2.50 mmφ. Wire. The heat treatment shown in Table 2 was performed using this wire. Thereafter, a wire (steel wire) having a final wire diameter of 0.060 to 2.00 mmφ was formed by wire drawing using a die having a die approach angle of 14 °. At this time, the number of micro cracks having a wire width was measured at a 1/2 part of the L section when the area reduction rate in the wire drawing became about 1.0 in true strain. Also,
The tensile test and the torsion test were performed on the final wire, and the mechanical properties of the final wire were investigated.

No. 1 to No. 4 of the present invention show no microcracks in the middle of drawing, and even in a wire produced by the subsequent drawing, a wire free of delamination was obtained by a torsion test. I have. By twisting such small diameter wires, a high tensile strength steel wire can be manufactured.

[0027]

[Table 1]

[0028]

[Table 2]

[0029]

According to the present invention, a wire (steel wire) excellent in wire drawing property can be obtained by the final patenting process, and a thin-diameter high-tensile steel wire having more excellent ductility can be obtained by subsequent wire drawing. it can.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an example of a manufacturing process of a high-tensile steel wire of the present invention.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C22C 38/00 301 C22C 38/16 C22C 38/42

Claims (7)

(57) [Claims] C .: 0.90% or more and 1.10% by weight
% Or less, Si: 0.4% or less, Mn: 0.5% or less,
P: 0.020% or less, S: 0.020% or less, Cu:
Excellent drawability, characterized by containing 0.10% or more and 0.80% or less, the balance being iron and unavoidable impurities, and the unavoidable Al content being 0.003% or less. High tensile steel wire. 2. The composition according to claim 1, further comprising one or more of Cr: 0.10% to 0.30% and Ni: 0.10% to 1.00% by weight. Claim 1
A high-strength steel wire rod with excellent drawability as described. 3. The high tensile strength steel wire according to claim 1, wherein the high tensile strength steel wire has a uniform pearlite structure. 4. The high tensile strength steel wire according to claim 1, wherein microcracks do not occur during wire drawing. 5. A high-strength, small-diameter, high-strength steel wire produced using the steel wire according to any one of claims 1 to 4. 6. The steel wire according to claim 5, wherein delamination does not occur in the torsion test. 7. A high-strength twisted steel wire obtained by twisting the small-diameter high-strength steel wire according to any one of claims 5 and 6.