JPH10158785A - Wire rod for steel wire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the scale adhesion and peeling properties of a wire rod for a steel wire and to make better the scale adhesion at the time of carrying and the scale peeling properties at the time of mechanical descaling thereof. SOLUTION: This wire rod for a steel wire has a compsn. contg., by weight, 0.70 to 1.1% C, 0.10 to 0.40% Si, 0.20 to 0.90% Mn, 0.003 to 0.02% P, 0.002 to 0.01% S, and the balance Fe with inevitable impurities, and in which, in scale adhered to the surface of the steel by the observation of the cross-section by an optical microscope, empty holes of 1 to 3μm are allowed to exist by 1 to 5% area ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wire for a steel wire having good scale adhesion when transporting a steel material and having good scale peelability during mechanical descaling.

[0002]

2. Description of the Related Art A steel wire is manufactured by drawing a wire rod obtained by rolling a steel slab. The heat treatment immediately after rolling from the steel material to the wire material forms a metallurgical structure of the steel material that greatly affects the subsequent drawability. A scale mainly composed of iron oxide adheres to the surface of the wire. At the time of wire drawing, the scale must be removed because it causes flaws, and it is desirable that the scale be removed easily by applying a stress to the steel material and removing the scale (mechanical descaling). If the scale does not peel off due to mechanical descaling, acid removal equipment is required to remove it by pickling with diluted hydrochloric acid, etc.
The process becomes complicated. Conventional scale control has been performed by focusing on scale releasability and adjusting the components by adding an element such as S.

[0003]

However, by improving the scale releasability, the scale is peeled off during the transportation and transporting process from the wire rod manufacturing process to the wire drawing process, exposing the ground iron to the surface and causing rust. Has been a problem. Therefore, there has been a demand for a scale which is hardly peeled off during the movement of the process, can be used for preventing rust without exposing the surface of the base iron, and can be easily peeled off by mechanical descaling immediately before wire drawing. Therefore, a scale that has good adhesion under stress generated during transportation between processes and that easily peels off by mechanical descaling or the like that applies a certain level of stress has been studied.

The present invention advantageously solves the above-mentioned problems, and an object of the present invention is to provide a steel wire having a scale having optimal adhesion and peelability on its surface.

[0005]

The gist of the present invention is to provide a steel component containing Si: 0.10 to 0.40% S: 0.002 to 0.01% by weight, or C: 0.70 to 1.1% Si: 0.10 to 0.40% Mn: 0.20 to 0.90% P: 0.003 to 0.02% S: 0.002 to 0.01% The balance is steel consisting of Fe and unavoidable impurities. Observation of the cross section with an optical microscope shows that pores of 1 μm or more and 3 μm or less exist in the scale attached to the steel material surface in an area ratio of 1% or more and 5% or less. Characteristic wire rod for steel wire.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the reasons for limiting the components of the present invention will be described. Si enhances the strength of the base by forming a solid solution in ferrite and promotes the refinement of precipitated carbides,
Further, it is also effective in refining crystal grains. For these reasons, the range of Si is set to 0.1% or more, but the range of 0.4%
Beyond, Fe and Si are brittle at the interface between steel and scale
Since a large amount of the composite oxide is generated and scale peeling during transportation increases, the range is set to 0.10 to 0.40%.

S has a function of facilitating embrittlement of the interface between the scale and the iron base, and increases the scale exfoliation property in removing the scale by mechanical stress (mechanical descaling).
Although it was set to 002% or more, if it exceeds 0.01%, the scale score is remarkably reduced.

Here, in order to obtain the scale of the object of the present invention, it is sufficient that the structure of the first invention is satisfied. However, in the case of a soft wire, the adverse effect of the scale upon drawing is not so remarkable. Is particularly remarkable in a hard steel wire, and the necessary component in that case is the second invention.
Hereinafter, the reasons for limiting the component system will be described.

C is preferably a pearlite structure in order to obtain sufficient strength as a hard steel wire by heat treatment.
It is necessary to be 0.7% or more, but if it exceeds 1.1%, the tendency of graphitization increases, and the toughness significantly decreases. Therefore, the range is set to 0.7 to 1.1%.

Mn is an element for enhancing hardenability and obtaining strength, and it is necessary to contain 0.2% or more. However, if it exceeds 0.9%, toughness is impaired.
2 to 0.9%.

[0011] P contributes to the improvement of the strength of the steel material.
003% or more, but the addition causes embrittlement,
If it exceeds 0.02%, it cannot be used for wire drawing, so it is made 0.02% or less.

S has a function of making the interface between the scale and the base iron brittle, and enhances the scale peeling property in the scale removal (mechanical descaling) by the stress load.
Although it was set to 002% or more, if it exceeds 0.01%, the scale score is remarkably reduced.

The above are the basic components of the steel of the present invention. Further, the present invention employs a scale control means for controlling the porosity in the scale, thereby increasing the adhesiveness of the scale, producing a stable scale, and improving the peelability. Usually, the thickness of the scale is 5 to 20 μm,
By controlling the cooling rate and atmosphere of the rolled steel material, pores of 1 μm or more are formed in the scale. The pores in the scale can be obtained by polishing the cross section of the wire and observing the scale portion with an optical microscope. Originally, gas components such as CO exist inside the pores in the scale, but are observed as simple pores in the cross section. If the size of the pores in the scale exceeds 3 μm, cracks tend to be formed in the scale starting from the pores, and the adhesion is significantly deteriorated.
On the other hand, it was revealed that pores of less than 1 μm in the scale did not contribute to the propagation of cracks and did not contribute to the peelability under stress.

As a result of the above investigation, the porosity existing at the interface between the scale and the base iron was reduced by reducing the area ratio of porosity of 1 μm to 3 μm in the scale to 5% or less, and the adhesion of the scale was reduced. The performance is improved. Further, it was found that when the area ratio of the holes in the scale was 5% or less, the propagation of cracks due to the stress during transportation was not performed through the holes. On the other hand, it was found that when the pore area ratio in the scale was 1% or more, cracks at the interface were easily propagated when a stress in mechanical descaling was applied, and easily peeled off from the interface.

At the time of this production, a wire can be obtained through ordinary steps of steel making, ingot making or continuous casting, slab rolling, bar rolling or wire rolling. After that, through a wire drawing process including a descaling process, a final product having a predetermined wire diameter is obtained. Next, the effects of the present invention will be specifically described with reference to examples.

[0016]

EXAMPLES Table 1 shows the chemical composition of the test steel. In Table 1, A1 to A6 are steels of the present invention, B1 to B6
Is a comparative material. A bloom (cross section 300 mm × 500 mm) obtained by ordinary converter refining and continuous casting was rolled into a wire (cross section 7 mmφ) through slab rolling and wire rod rolling. The obtained wire was evaluated by an ordinary method. Table 2 shows the porosity, scale rating, and residual scale rating of the test steel.

The porosity is an average value obtained by observing a cross section perpendicular to the rolling direction of the wire rod after rolling the test steel with an optical microscope and measuring the porosity area of 10 cross sections. All of the steels of the present invention fall within a predetermined area ratio range.

The scale score is an index of the ratio of the area where the scale has peeled to the entire surface of the steel material. The higher the number, the greater the scale peeling. If the scale score is 1.5 or less, it is not necessary to apply a rust preventive.
It can be seen that the scale score is reduced by the present invention, and the scale is stably attached.

The residual scale amount refers to the scale remaining on the surface of the steel material after a method of applying a stress to the steel material to remove the scale (mechanical descaling). Usually, after mechanical descaling, pickling with dilute hydrochloric acid is performed, and the difference in weight before and after pickling is defined as the residual scale amount. Usually, the residual scale index is indicated by a value obtained by indexing the ratio of the residual scale to the weight of the steel material, and the larger the index, the worse the index. If the residual scale index is 0.2 or less, no pickling is required. It can be seen that the present invention significantly improves the residual scale.

[0020]

[Table 1]

[0021]

[Table 2]

[0022]

According to the present invention, the adhesion of the scale is improved during the transportation between processes and the like, so that the application of the rust preventive agent can be omitted and the labor can be saved. Further, environmental pollution due to chemical substances required for applying and peeling the rust preventive can be prevented. Further, by using mechanical descaling for the scale removing step, labor saving by omitting the pickling step and eliminating the acid treatment equipment can be achieved. It is an excellent invention not only for industrial advantages but also for the environment.

Claims (2)

[Claims] 1. A scale composed of a steel component containing, by weight%, Si: 0.10 to 0.40% S: 0.002 to 0.01%, and adhered to the surface of a steel material by observing a cross section with an optical microscope. 1 μm or more 3
A steel wire having pores having a size of 1 μm or less and an area ratio of 1% or more and 5% or less. Wire. 2. The steel component is as follows: C: 0.70 to 1.1% Si: 0.10 to 0.40% Mn: 0.20 to 0.90% P: 0.003 to 0. 2. The steel wire according to claim 1, wherein the wire contains 0.002 to 0.01% of S, and the balance consists of Fe and unavoidable impurities.