JP2002294346A - Method for producing steel wire rod having excellent cold workability - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a steel wire rod having excellent cold workability by which the production cost in the production process for a wire rod can be reduced, and further, the production cost in the production process for a steel ball or the like can be reduced. SOLUTION: A wire rod produced by subjecting a slab having a composition containing, by mass, 0.6 to 1.2% C, 0.1 to 0.5% Si, 0.2 to 0.6% Mn and 1.0 to 2.0% Cr, and the balance Fe with inevitable impurities to hot rolling is coiled in the temperature range of 700 to 850 deg.C. The wire rod is next subjected to spheroidizing annealing, and, after that, strain is applied thereto within a range where the strain amount ε=100×d/(D+d) satisfies 2.5 to 15.0 by using a modification roller. Further, pickling and surface treatment are performed thereto; wherein, D is the diameter (mm) of the modification roller, and (d) is the diameter of the wire rod ×1/2 (mm).

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 rod having excellent cold workability and used as a material for steel balls and rollers.

[0002]

2. Description of the Related Art When manufacturing steel balls and rollers (hereinafter referred to as steel balls, etc.) generally used for bearings, a high-carbon chromium steel wire is used as a raw material. The process is roughly divided into the manufacturing process of steel balls and the like. In the manufacturing process of a steel wire, a slab having a predetermined component is hot-rolled to produce a steel wire, then wound into a coil, spheroidized annealing of the coil is performed, and the coil is unwound and pickled. And surface treatment, then cold drawing, and rewinding into a coil.

[0003] In the manufacturing process of steel balls and the like, the steel wire rod wound around the coil is unwound and cut, and further cold forged. In recent years, in order to reduce the manufacturing cost of steel balls and the like, cold drawing has been omitted in the manufacturing process of steel wire rods. When omitting cold drawing in the manufacturing process of steel wire, after performing spheroidizing annealing of the steel wire manufactured by hot rolling and wound into a coil, it is subjected to pickling and surface treatment, and again. Wind up the coil.

[0004] The technique of using such a steel wire rod without the cold drawing as a raw material is not limited to the production of steel balls or the like, but is being studied for various products. For example, JP-A-2000-212691 discloses a steel wire rod for cold forging and a method for producing the same. This technique omits wire drawing in a manufacturing process of a wire rod used as a material for manufacturing a bolt. That is, a steel wire rod manufactured by hot rolling is further annealed and pickled, and then subjected to cold forging to manufacture a bolt.

[0005] In these techniques, since cold drawing is omitted, spheroidizing annealing (or annealing) causes the steel wire rod to be wound around a coil in a softened state, so that the packed shape is not collapsed. I can't. Therefore, when unwinding and cutting or cold forging the coil in the manufacturing process of steel balls or the like (or bolts), it becomes difficult to take out the tip of the coil or tangling of the steel wire occurs. Failure to do so may result.

[0006] Therefore, spheroidizing annealing,
There is known a method of winding a high-carbon chromium steel wire, which has been subjected to pickling and surface treatment, onto a coil, and then rewinding the coil to improve the packing appearance (so-called recoiling). However, according to this method, even if the cold drawing is omitted, since the recoiling is performed, a significant reduction in the manufacturing cost of the steel wire rod cannot be expected.

On the other hand, in a manufacturing process of a steel ball or the like, a steel wire or the like is cut and then cold forged to manufacture a steel ball or the like. The production volume is about 10,000 per hour, and it is manufactured at high speed and continuously. Therefore, it is necessary to extend the tool life of cutting and cold forging, and the material of the tool and the lubricant are devised. However, when the surface scale remains on the steel wire material, seizure occurs and the tool life is shortened.

For the purpose of optimizing the pickling conditions in the wire rod manufacturing process, various techniques such as addition of a chemical solution for preventing excessive pickling, adoption of vibration pickling, and high pressure water cleaning after pickling are used. Has been implemented, which causes an increase in manufacturing cost.

[0009]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and eliminates cold drawing and recoiling in the manufacturing process of a steel wire to reduce the manufacturing cost of the steel wire.
Moreover, it is an object of the present invention to provide a method of manufacturing a steel wire rod having excellent cold workability, which can also reduce costs in a manufacturing process of steel balls and the like.

[0010]

According to the present invention, C is set to 0.6 to 1.
2% by mass, 0.1 to 0.5% by mass of Si, 0.2 to 0.6% by mass of Mn, 1.0 to 2.0% by mass of Cr, the remainder being Fe and unavoidable impurities. After winding the manufactured steel wire in the temperature range of 700 to 850 ° C, and then performing spheroidizing annealing, the strain amount ε calculated by the following formula (1) using a straightening roller satisfies 2.5 to 15.0. This is a method for producing a steel wire rod in which strain is imparted within the range, and further, pickling and surface treatment are performed.

Ε = 100 × d / (D + d) (1) ε: Amount of strain D: Diameter of straightening roller (mm) d: Diameter of wire rod × 1/2 (mm) As a preferred embodiment, in addition to the above-described composition, the steel wire rod has Mo: 0.5% by mass or less, N
It is preferable to contain one or more of i: 0.5% by mass or less and Cu: 0.5% by mass or less.

In a second preferred embodiment, the thickness of the surface scale of the steel wire rod produced by hot rolling is preferably 10 μm or less.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the reasons for limiting the components of a steel wire according to the present invention will be described. C: 0.6 to 1.2% by mass C is an element necessary to secure the strength of the steel wire. If the C content is less than 0.6% by mass, sufficient strength for use in applications such as steel balls cannot be obtained. On the other hand, when the content exceeds 1.2% by mass, retained austenite is generated and the hardness is reduced. Therefore, the C content must satisfy the range of 0.6 to 1.2% by mass.

Si: 0.1-0.5% by mass Si is an element having a deoxidizing effect. If the Si content is less than 0.1% by mass, a sufficient deoxidizing effect cannot be obtained. on the other hand,
If it exceeds 0.5% by mass, silicate-based inclusions are formed, and various defects are generated. Therefore, the Si content is 0.1
It is necessary to satisfy the range of 0.5% by mass.

Mn: 0.2 to 0.6% by mass Mn is an element that improves the strength of a steel wire rod as in C. If the Mn content is less than 0.2% by mass, sufficient strength for use in applications such as steel balls cannot be obtained. On the other hand, if it exceeds 0.6% by mass, cracks occur in the manufacturing process of steel balls and the like. Therefore, the Mn content must satisfy the range of 0.2 to 0.6% by mass.

Cr: 1.0 to 2.0% by mass Cr is an element that improves the strength of a steel wire rod like C. If the Cr content is less than 1.0% by mass, sufficient strength for use in applications such as steel balls cannot be obtained. On the other hand, when the content exceeds 2.0% by mass, a large amount of carbide is generated, and the cold workability in the production process of steel balls or the like is deteriorated. Therefore, the Cr content is
It is necessary to satisfy the range of 1.0 to 2.0% by mass.

Mo: 0.5% by mass or less, Ni: 0.5% by mass or less, Cu: 0.5% by mass or less Mo, Ni and Cu are elements that improve the corrosion resistance of steel wire rods. Even if these elements are added in excess of 0.5% by mass, the effect of improving the corrosion resistance is saturated and the production cost is increased. Therefore, when adding one, two or more types of Mo, Ni, and Cu, the content is set to 0.5% by mass or less of Mo:
0.5 mass% or less, Cu: 0.5 mass% or less is preferable.

The smaller the amount of the impurity elements P and S, the better the fatigue life can be improved.
Is preferably 0.010% by mass or less. After hot rolling a slab having the above composition to produce a steel wire, 700
Wound on a coil at a temperature range of ~ 850 ° C. Here, the reason for limiting the winding temperature of the steel wire will be described.

FIG. 1 shows the winding temperature (° C.) of the hot-rolled steel wire and the thickness (μm) of the surface scale adhered to the steel wire.
6 is a graph showing the result of investigating the relationship with. As is apparent from FIG. 1, as the winding temperature increases, the thickness of the surface scale increases. Especially when the winding temperature exceeds 850 ° C, the surface scale exceeds 10 μm. As the surface scale becomes thicker, the pickling time to remove it increases proportionately. If pickling is performed to remove a surface scale having a thickness of more than 10 μm, it takes a long time, so that the surface roughness of the steel wire becomes rough and the cold workability in the manufacturing process of steel balls and the like deteriorates.

On the other hand, in order to wind the hot-rolled steel wire at a temperature lower than 700 ° C., it is necessary to forcibly cool the steel wire rod using a large-scale cooling device such as a water cooling device after the completion of the hot rolling. In such a case, various measurement and control devices are required to maintain the cooling capacity of the large-scale cooling device at a constant level and to ensure the stability of the winding temperature of the steel wire rod, and the steel wire rod manufacturing process is required. Causes an increase in manufacturing costs.

Therefore, the coiling temperature of the hot-rolled steel wire must be in the range of 700 to 850 ° C. The thickness of the surface scale attached to the steel wire is preferably 10 μm or less as described above. After winding the steel wire rod into the coil in the above temperature range, spheroidizing annealing is performed. The spheroidizing annealing is a process for spheroidizing carbides in a steel wire and improving cold workability in a manufacturing process of a steel ball or the like.

Next, using a straightening roller, the steel wire is strained while unwinding the coil, and then wound again on the coil. This distortion is imparted for the purpose of removing the surface scale attached to the steel wire by the spheroidizing annealing and improving the strength of the steel wire. In order to achieve these objects, it is necessary to maintain the amount of strain applied to the steel wire using a straightening roller in an appropriate range.

Therefore, as a result of a detailed study of the amount of strain, the surface roughness was removed to reduce the surface roughness of the steel wire rod by shortening the pickling time in the post-process, and to reduce the coldness in the manufacturing process of steel balls and the like. An appropriate amount of distortion that can improve workability was found. That is, the distortion amount ε per straightening roller calculated by the following equation (1) is in the range of 2.5 to 15.0.

Ε = 100 × d / (D + d) (1) ε: strain amount D: diameter of straightening roller (mm) d: diameter of wire rod × 1/2 (mm) If strain amount ε is less than 2.5, In addition, the surface scale of the steel wire is not sufficiently removed, and the strength of the steel wire wound around the coil is insufficient, resulting in tangling. On the other hand, if the strain amount ε exceeds 15.0, the effect of removing the surface scale saturates, so that the residual amount of the surface scale does not change even if an excessive strain is applied, and the strength of the steel wire is excessively increased, and The life of the forging tool may be shortened. Therefore, the strain amount ε needs to satisfy the range of 2.5 to 15.0.

The above-mentioned amount of distortion ε is the amount of distortion per correction roller, and within the above-mentioned range, there is no problem even if the distortion is repeatedly applied using a plurality of correction rollers. After winding the steel wire rod to which the distortion was given using a straightening roller, it is pickled and surface-treated.

When the steel wire is manufactured in this way, since the cold drawing and recoiling can be omitted, the manufacturing cost of the steel wire can be reduced. In addition, since the strength of the steel wire is improved by applying the distortion using the straightening roller, the problem that the package of the coil is broken does not occur. As a result, entanglement of the high carbon chromium steel wire can be prevented in the manufacturing process of steel balls and the like, so that stable operation can be achieved. Moreover, since high carbon chrome steel wire has excellent cold workability,
The productivity of the manufacturing process of steel balls and the like is improved, and cost reduction in the manufacturing process of steel balls and the like can be achieved.

[0027]

EXAMPLES Four types of high carbon chromium steel satisfying the component range of the present invention shown in Table 1 were melted and cast into continuous cast pieces (width 560 m).
m, thickness 400 mm). The cast slab was subjected to soaking diffusion annealing, and then rolled to produce a round billet having a diameter of 170 mm. Further, surface flaws were inspected to repair surface flaws, and then hot-rolled to produce a steel wire rod having a diameter of 6.5 mm. The steel wire is water-cooled on the outlet side of hot rolling, and the winding temperature is 800 ℃, 920
° C. The thickness of the surface scale attached to the steel wire rod thus wound was measured.

[0028]

[Table 1]

The steel wire was subjected to spheroidizing annealing (soaking temperature 790).
℃, soaking time 10hr, cooling rate from 790 ℃ to 650 ℃ 10 ℃ /
hr), and then strain was applied using a straightening roller. As for the strain applied to the steel wire, the strain amount ε per straightening roller was set to 1.7 to 16.0, and the steel wire was passed through a plurality of straightening rollers. Next, pickling with a hydrochloric acid solution having a concentration of 20% by mass was performed, and further, a bonderite treatment (treatment temperature of 80%).
C., a treatment time of 10 min), followed by washing with water and drying. Note that a chemical solution for preventing excessive pickling was not added to the hydrochloric acid solution used for pickling. In this state, the amount of scale remaining on the steel wire was measured.

The steel wire thus produced was cut into a predetermined length and cold forged to produce a steel ball, and the material permeability and cold workability in the production process were evaluated. The passability was evaluated as 0 when the number of operation stoppages during the production of 1 ton of steel balls was 0.
And the case where it occurred one or more times was marked with △. The cold workability was evaluated as ○ when the number of times of seizure of the tool during the production of 10 tons of steel balls was 0, and as Δ when the number of occurrences was 1 or more.

The measured value of the thickness of the surface scale in the manufacturing process of the steel wire thus obtained, the measured value of the remaining scale amount, and the evaluation of the material permeability in the manufacturing process of the steel ball,
The evaluation of cold workability is shown in Table 2 as Invention Examples 1 to 5.

[0032]

[Table 2]

Table 2 shows Comparative Examples 1 to 3 for comparison with Inventive Examples 1 to 5. Comparative Example 1 is an example in which the winding temperature and the thickness of the surface scale are out of the range of the present invention, and Comparative Examples 2 and 3 are examples in which the strain ε is out of the range of the present invention. In each of Invention Examples 1 to 5, there was no problem in the material permeability and cold workability in the steel ball manufacturing process. However, Comparative Example 1
Due to the large amount of residual scale, cold workability deteriorated. In Comparative Example 2, since the strain amount ε was small, the material permeability and the cold workability were deteriorated. In Comparative Example 3, since the strain amount ε was large, the strength of the steel wire rod was excessively increased, and the cold workability was deteriorated.

That is, according to the present invention, it was confirmed that a steel wire rod manufactured without performing cold drawing or recoiling had excellent cold workability.

[0035]

According to the present invention, since the cold drawing and recoiling can be omitted, the manufacturing cost of the steel wire can be reduced. Moreover, the obtained steel wire has excellent cold workability,
The productivity of steel balls and rollers is improved. This has a great effect on improving quality and reducing manufacturing costs.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between a winding temperature of a steel wire and a thickness of a surface scale.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Keizo Taoka 1-chome, Mizushima-Kawasaki-dori, Kurashiki-shi, Okayama Pref. BA05 DA05 FA02 HA02 HA03 HA07

Claims (3)

[Claims] C. 0.6 to 1.2 mass% of C and 0.1 to 0.5 mass% of Si.
Mass%, Mn 0.2-0.6 mass%, Cr 1.0-2.0 mass%
The steel wire rod produced by hot-rolling a slab having a composition of Fe and unavoidable impurities
Winding in the temperature range of ° C., and then performing spheroidizing annealing, using a straightening roller to impart strain within a range in which the strain amount ε calculated by the following equation (1) satisfies 2.5 to 15.0,
A method for producing a steel wire, further comprising performing pickling and surface treatment. ε = 100 × d / (D + d) (1) ε: Strain amount D: Diameter of straightening roller (mm) d: Diameter of wire rod × 1/2 (mm) 2. The steel wire according to claim 1, further comprising: Mo:
The method for producing a steel wire according to claim 1, wherein the steel wire contains one or more of 0.5% by mass or less, Ni: 0.5% by mass or less, and Cu: 0.5% by mass or less. 3. The method for producing a steel wire according to claim 1, wherein a thickness of a surface scale of the steel wire produced by the hot rolling is 10 μm or less.