JPH10147844A - Wire rod for steel wire - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To improve the scale adhesion and peelability of a steel wire. SOLUTION: In weight%, C: 0.70 to 1.1%, S
i: 0.10 to 0.40%, Mn: 0.20 to 0.90
%, P: 0.003-0.02%, S: 0.002-
0.01%, Cr: 0.02 to 0.3%, the balance being Fe and unavoidable impurities. At the interface between the scale and the steel attached to the surface of the steel after rolling, the Cr concentration is 0.1%. The concentration region of 07% or more is 0.2 μm or more and 2 μm
The present invention is characterized in that it is present, thereby obtaining a steel wire having good scale adhesion and peelability.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a steel wire having good scale properties.

[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. At the same time, a scale mainly composed of iron oxide adheres to the surface of the wire. Since the scale causes flaws, it must be removed at the time of wire drawing.
It is desirable to easily peel off by a scale removal (mechanical descaling) method by a stress load as disclosed in JP-A-10829. If the scale is not peeled off by mechanical descaling, the scale is removed by pickling with dilute hydrochloric acid or the like, but acid treatment equipment is required and the process becomes complicated. Conventionally, scale control has been performed by focusing on scale releasability and adjusting the components by adding elements such as S.

[0003]

However, if the scale releasability is simply improved, the scale will peel off in the process from the wire rod manufacturing process to the wire drawing process, exposing the ground iron on the surface, causing rust. It was a problem to get it. That is, there has been a demand for a scale which is hard to peel off during the movement between processes, can be used for preventing rust, and can be easily peeled off by mechanical descaling immediately before wire drawing.

Accordingly, the present invention has been made to solve the above-mentioned problem, and has good adhesiveness under a stress generated during transportation between processes, and further applies a certain stress or more thereafter. This realizes a scale that can be easily peeled off by mechanical descaling.

[0005]

The gist of the present invention is as follows. (1) By weight%, Si: 0.10 to 0.40%, S:
0.002 to 0.01%, Cr: 0.02 to 0.3%, with the balance being Fe and unavoidable impurities. At the interface between the steel and the scale attached to the surface of the steel after rolling, 0.2 μm in the concentrated area where the concentration is 0.07% or more
A wire rod for a steel wire, characterized by having good scale adhesion at a stress load of not less than m and not more than 2 μm and not more than a predetermined value, and having good peelability of the scale at a stress load of more than that. (2) By weight%, C: 0.70 to 1.1%, Si: 0.
10 to 0.40%, Mn: 0.20 to 0.90%, P:
0.003-0.02%, S: 0.002-0.01
%, Cr: 0.02 to 0.3%, with the balance being Fe and unavoidable impurities, and the Cr concentration at the interface between the steel and the scale attached to the surface of the steel after rolling is 0.1%.
A steel wire characterized in that a concentrated region of 07% or more exists in a range of 0.2 μm or more and 2 μm or less. The scale wire has good adhesiveness under a stress load of a predetermined value or less, and has good peelability of the scale under a stress load of more than that. Wire. It is.

Here, in order to obtain the desired scale, the first scale
It is sufficient that the structure of the present invention is satisfied.However, in the case of soft wire, the adverse effect of scale at the time of drawing is not so remarkable, and it is hard steel wire that the effect is particularly remarkably exhibited by applying the present invention. This is the second invention.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The reasons for limiting the components of the present invention are described below. C preferably has a pearlite structure in order to obtain sufficient strength as a hard steel wire by heat treatment.
0% or more is necessary, but if it exceeds 1.1%, the tendency of graphitization increases, and the toughness is significantly reduced.

[0008] Si forms a solid solution in ferrite to increase the strength of the substrate, promotes the refinement of precipitated carbides, and is also effective in refining crystal grains. For this reason, the range of Si is set to 0.1% or more.
If it exceeds 0.4%, a large amount of composite oxide of Fe and Si is generated at the interface between the steel material and the scale, and the scale releasability is increased.
The range was set to 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%.

[0010] P contributes to the improvement of the strength of the steel material, so is made 0.003% or more. At the same time, to increase brittleness,
If it exceeds 0.02%, it cannot be used for wire drawing, so the content is made 0.01% or less.

S has the function of making the interface between the scale and the iron base material brittle, and increases the scale exfoliation property in removing the scale by mechanical stress (mechanical descaling).
002% or more. However, if the content exceeds 0.01%, the scale score is significantly reduced.
1% or less.

[0012] Cr has a function of strengthening the interface between the scale and the base iron. When Cr is present in an amount of 0.02% or more, it is concentrated at the interface of the scale to enhance the adhesion. If it exceeds 0.3%, the Cr-concentrated region becomes too thick, and the releasability at the time of removing the scale by mechanical stress (mechanical descaling) is significantly reduced. Therefore, the range is set to 0.3% or less.

[0013] As a result of previous research, C
It was found that r was present only at the detection limit of 0.002% or less and concentrated at the interface between the scale and the steel material. This is because the cooling process immediately after rolling of the steel material is 1000-90.
This is because Cr is preferentially oxidized during scale growth in a temperature range of 0 ° C., and only the oxide layer of iron grows on the surface layer because the Cr oxide controls the diffusion of Cr. When the cooling rate is changed, the passage time in the temperature range of 1000 to 900 ° C. changes,
The thickness of the oxide layer changes. The Cr concentration 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 Cr concentration can be measured and the width of the enriched region can be specified. The present inventors have found that when the concentration region having a Cr concentration of 0.07% or more exists in a range of 0.2 μm or more and 2 μm or less, the adhesiveness of the scale and the peelability under a stress load are improved.

The above are the basic components of the steel of the present invention and the Cr concentration in the scale. 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.

[0015]

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. 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 Cr oxide layer changes.
The scale score and residual scale amount of the obtained wire were measured. Table 2 shows the results.

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.
The steel of the present invention has a small scale score, indicating that the scale is stably adhered. On the other hand, steel B4 ~ B
6, Si or S is high, the scale is easily peeled,
The scale score is higher.

On the other hand, the residual scale amount refers to the scale remaining on the steel material surface after a method of removing the scale by applying a stress to the steel material (mechanical descaling). Washing was performed, and the difference in weight before and after pickling was defined as a residual scale amount. 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. 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. On the other hand, steel B1 has too low Cr and poor adhesion of the scale, and the scale score is high. On the other hand, steels B2 and B3, on the other hand, have too high Cr to increase residual scale.

[0018]

[Table 1]

[0019]

[Table 2]

[0020]

According to the steel of the present invention, since the scale adhesion between the steps is improved, it is possible to omit the application of a rust preventive agent, thereby achieving labor saving. 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 before wire drawing, labor saving and equipment cost reduction can be achieved by omitting the pickling step. As a result, the present invention is an excellent invention in consideration of not only industrial merits but also the environment.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C22C 38/18 C22C 38/18

Claims (2)

[Claims] 1. The composition contains, by weight%, Si: 0.10 to 0.40% S: 0.002 to 0.01% Cr: 0.02 to 0.3%, with the balance being Fe and unavoidable impurities. Become
At the interface between the scale and the steel attached to the surface of the steel after rolling, the concentration region having a Cr concentration of 0.07% or more is 0.2%.
A wire for a steel wire, characterized in that the scale has good adhesiveness under a stress load of not more than a predetermined value of not less than 2 μm and not more than 2 μm, and has good peelability of the scale under a stress load of more than that. 2. C: 0.70 to 1.1% in weight% Si: 0.10 to 0.40% Mn: 0.20 to 0.90% P: 0.003 to 0.02% S: 0.002 to 0.01% Cr: 0.02 to 0.3%, the balance being Fe and unavoidable impurities,
At the interface between the scale and the steel attached to the surface of the steel after rolling, the concentration region having a Cr concentration of 0.07% or more is 0.2%.
A wire for a steel wire, characterized in that the scale has good adhesiveness under a stress load of not more than a predetermined value of not less than 2 μm and not more than 2 μm, and has good peelability of the scale under a stress load of more than that.