JP3476321B2 - Wire rod for steel wire - Google Patents

Description

Description: 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 excellent scale peelability during a mechanical descaling. [0002] The production of steel wire is performed by drawing a wire rod obtained by rolling from a billet. 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. At the same time, a scale mainly composed of iron oxide adheres to the surface of the wire. Since scale causes flaws, it must be removed in advance during wire drawing. Scale is removed by stress load (mechanical descaling)
It is desirable that the film be easily peeled off. If the scale is not peeled off by mechanical descaling, the scale is removed by pickling with dilute hydrochloric acid or the like, but an acid treatment facility is required and the process becomes complicated. So conventionally,
Control of the scale has been carried out by placing an emphasis on the releasability of the scale and adjusting the components by adding elements such as S. However, simply improving the scale releasability causes the scale to peel off during the process from wire manufacturing to wire drawing, exposing the ground iron to the surface, The problem is that rust is generated.
Therefore, there has been a demand for a scale which is hard to peel off during the movement of the process, can be used for preventing rust, and easily peels off immediately before wire drawing. [0004] The present invention can solve this problem, and has good adhesion under stress generated during transportation between processes.
In addition, the present invention provides a steel material having a scale that is easily peeled off by mechanical descaling or the like in which a certain level of stress is applied. [0005] [Means for Solving the Problems] gist of the present invention, the components of the steel material in weight% C: 0.60~1.2% Si: 0.10~0.40 % Mn: 0. 20 to 0.90% P: 0.02% or less S: 0.003% or less, the balance being Fe and unavoidable impurities ,
Of the interface between the scale and the steel attached to the surface of the steel after rolling
When the maximum value of S is 0.07% or less in the S enrichment region,
This is a wire rod for a steel wire characterized by having good scale adhesion and peelability . The reasons for limiting the components of the present invention are described below. As a result of previous studies, it has been found that S exists in the scale only at the detection limit of 0.0001% or less, and is concentrated at the interface between the scale and the steel material. This is because Fe is preferentially oxidized during scale growth in a temperature range of 1000 to 900 ° C. in a cooling process immediately after rolling of steel, and S is discharged from the scale. When the cooling rate is changed, the passage time in the temperature range of 1000 to 900 ° C. changes,
The S maximum value of the thickening section changes. The S-enriched region at the interface is E
By scanning an electron beam with a diameter of 0.1 μm in a direction perpendicular to the interface between the scale and the steel material by PMA, the S
The concentration can be measured and the maximum value determined. This S
When the maximum value is 0.07% or less, the adhesiveness of the scale becomes high, and the impact such as contact during transportation is sufficiently provided. This time, it was found that the interface yielded and the peelability was improved. Here, in order to obtain the scale of the object of the present invention, it is sufficient to satisfy the structure of the first invention. However, the adverse effect of the scale upon drawing a soft wire 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 preferably has a pearlite structure in order to obtain sufficient strength as a hard steel wire by heat treatment.
It is necessary to be 0.60% or more, but if it exceeds 1.2%, the tendency of graphitization increases, and the toughness significantly decreases. Therefore, the range is set to 0.60 to 1.2%. [0009] Si forms a solid solution in ferrite to increase the strength of the base material, promotes the refinement of precipitated carbides, and is also effective for the refinement of crystal grains. For this reason, the range of Si is set to 0.1% or more.
If it exceeds 0.4%, Si oxide S will be present at the interface between steel and scale.
iO ₂ Many occur, since the scale peelability becomes large, and the range as from 0.1 to 0.4%. Mn is an element for enhancing hardenability and obtaining strength as a steel wire, and is required to be 0.2% or more.
If the content exceeds 0.9%, the toughness is impaired. Therefore, the range is set to 0.2 to 0.9%. [0011] P contributes to the improvement of the strength of the steel material, but at the same time increases the brittleness. If it exceeds 0.02%, it cannot be used for wire drawing. S has the function of facilitating embrittlement of the interface between the scale and the iron base, and enhances the scale releasability in scale removal (mechanical descaling) due to stress load. If the element that improves the adhesion of the scale is not added,
If the content exceeds 0.003%, the scale score is remarkably reduced. Therefore, the range is set to 0.003% or less. The above is a description of the S concentration in the scale and the basic components of the steel of the present invention. At the time of this production, a wire can be obtained through the steps of ordinary steelmaking, ingot making or continuous casting, slab rolling, further bar rolling or wire rod 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. EXAMPLES Table 1 shows the chemical composition (% by weight), scale rating, and residual scale amount of the test steel. In Table 1, A1 to A6 are steels of the present invention, and B1 to B6 are comparative materials. A bloom (cross section: 300 mm x 500 mm) obtained by ordinary converter refining and continuous casting was rolled into a wire (cross section: 7 mmφ) through slab rolling and wire rolling. When the cooling rate after rolling is changed, the passage time in the temperature range of 1000 to 900 ° C. changes, and the thickness of the scale layer changes. The scale score and residual scale amount of the obtained wire were measured. 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 term "residual scale amount" means a scale remaining on the surface of a steel material after a method of removing stress by applying a stress to the steel material (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. [Table 1] According to the steel material of the present invention, scale adhesion during transportation between processes is improved, so that it is possible to omit the application of a rust preventive agent, thereby saving labor. 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. Not only cost merit but also environmentally advantageous effects can be obtained.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-6-322442 (JP, A) Corrosion prevention technology, 1989, Vol. 38 No. 3, pages 177 to 184, Kawasaki Steel Engineering Reports, 1981, Vol. 13 No. 2, pages 258-267 (58) Fields investigated (Int. Cl. ⁷ , DB name) C22C 38/00-38/60 B21C 1/00

Claims (1)

(57) [Claims 1] The composition of steel material is as follows: C: 0.60 to 1.2% Si: 0.10 to 0.40% Mn: 0.20 to 0.90 by weight% % P: 0.02% or less S: 0.003% or less , the balance being Fe and unavoidable impurities,
For a steel wire, wherein in a concentrated region of S at the interface between the scale and the steel attached to the surface of the steel after rolling, the maximum value of S is 0.07% or less, and the scale has good adhesion and peelability. wire.