JPH0364593B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to high-tensile strength steel wires, and particularly to high-tensile strength steel wires used for various steel cords and the like. (Prior Art) In recent years, high-tensile steel wires have been widely used in suspension bridge cables, wire ropes, and steel cords that increase the strength of automobile tires. Piano wire is a long-known representative example of such high-tensile steel wire. For example, as can be seen on page 362 of the Steel Materials Handbook (published by Maruzen Co., Ltd. on June 30, 1962), wire rods made of symbiotic steel containing about 0.8% C are patented and drawn. Strength is imparted through work hardening. However, this piano wire also suffers from breakage during wire drawing and poor properties after wire drawing, so for example, a steel wire with a diameter of 2 mm has a strength of 230 Kg/mm ^{2, and a steel wire with a diameter of 0.3 mm has a strength of 230 Kg/mm 2} .
It is said that it is not possible to make products with a weight of 320 kg/mm ² or more. On the other hand, from a structural design standpoint, there is a strong demand for weight reduction, and there is a need to develop wire materials with higher strength. (Problems to be Solved by the Invention) In view of the above-mentioned situation, the present invention has been developed to achieve properties that have not been achieved in the past, especially strength and ductility, without causing deterioration of the material even if it is work hardened by wire drawing. The purpose is to provide a rolled wire rod that can be coated. (Means for solving the problem) That is, the present invention consists of a core part and an outer layer part surrounding it, and the area ratio of the core part in the cross section to the whole cross section is in the range of 0.01 to 0.80, and the core part Part is weight%
C0.01~0.60%, Mn0.3~1.5%, Al0.005~0.10
%, limited to Si 0.5% or less, S 0.03% or less, and other Fe and unavoidable impurities.
%, Mn0.3~1.5%, Al0.005~0.10%,
A high-tensile steel wire characterized by being made of steel containing Fe and other unavoidable impurities, and consisting of a core part and an outer layer part surrounding it, and the area ratio of the core part to the whole cross section in the cross section is 0.01 to 0.80. is within the range of
The core part has C0.01~0.60% and Mn0.3~1.5 in weight%.
%, contains Al0.005~0.10%, Si0.5% or less,
Made of steel with S limited to 0.03% or less and other Fe and other unavoidable impurities, the outer layer is C0.7~ by weight%.
1.0%, Si0.1~2.0%, Mn0.3~1.5%, Al0.005~
Contains 0.10%, Cr0.2~2.0%, and further contains Ti, Nb,
A total of 0.005 to 0.3% of one or more of V and Zr
This is a high-tensile steel wire characterized by being made of steel containing Fe and other unavoidable impurities. The present invention will be explained in detail below. (Function) FIG. 1 shows one embodiment of the cross section of the steel wire according to the present invention. The core part 1 in the figure has a low carbon content and has a composition similar to ordinary steel, and the outer layer part 2 has a high carbon content and has a basic composition similar to that used in so-called piano wire. . The reason why the wire of the present invention is constructed of a core portion and an outer layer portion surrounding the core portion as shown in FIG. 1 is as follows. That is, when conventional steel wires are repeatedly drawn, small cracks occur near the central axis, which gradually increase in size, and eventually become large cracks and break. At this point, the steel wire cannot be strengthened any further. However, if the structure is made up of a core part and an outer layer part surrounding it as shown in Figure 1, the ductility near the steel wire core part is high, so small cracks are unlikely to occur, and even if small cracks do occur, they will not occur. Since it has the ability to resist the development of large cracks, it has much higher workability than conventional steel wires.
What's more, even after processing, the frequency of defects is much lower, and it has high tensile and torsional ductility. The area ratio of the core part 1 to the entire cross section is 0.01 to 0.80.
This is because if it is less than 0.01, the occupied area is too small and workability cannot be improved, and if it exceeds 0.80, the overall strength will be insufficient. Next, the reason for limiting the range of components in the core portion will be described. It is impractical to make C less than 0.01% based on existing industrial standards, and on the other hand, if it exceeds 0.6%, ductility decreases and properties are impaired, so it is set to 0.01 to 0.6%. Next, if the Mn content is less than 0.3%, deoxidation will be insufficient, and if it exceeds 1.5%, workability will decrease. Furthermore, if Al is less than 0.005%, the crystallinity will become coarser, and if it exceeds 0.10%, inclusions will increase and workability will deteriorate. On the other hand, Si is used to prevent early wire breakage and deterioration of mechanical properties due to material deterioration due to wire drawing.
Limit to 0.5% or less. Furthermore, if the S amount exceeds 0.03%, a decrease in torsion value becomes a problem, so it is limited to 0.03% or less. On the other hand, the reasons for limiting the components of the outer layer are as follows. First, C is an indispensable component for ensuring the strength of the steel wire, so it should be 0.7% or more. However, if it exceeds 1.0%, mesh-like cementite will be generated and the wire drawability will be significantly reduced, so the upper limit was set at 1.0%. Next, Si is added as a deoxidizing and strengthening element for steel, but if it is less than 0.1%, deoxidizing will be insufficient.
The lower limit is %. On the other hand, if Si exceeds 2%, the steel becomes brittle, so the upper limit is set at 2%. Also, like Si, Mn is an essential element for deoxidation.
Add 0.3% or more. In addition, since Mn has the effect of delaying pearlite transformation, it is desirable to have a large amount of Mn in order to form a homogeneous pearlite structure throughout the outer periphery, but if it exceeds 1.5%, the effect is saturated, so 1.5% is the upper limit. Furthermore, if Al is less than 0.005%, crystal grains will become coarser, and if it exceeds 0.10%, inclusions will increase and workability will deteriorate. The above is the basic component system of the outer layer, but in addition to these compositions, Cr, Ti, Nb, V, Zr
When one or more of these are added, the strength of the outer peripheral portion is further increased. First, Cr increases the strength of steel by making the lamella spacing of pearlite finer, but if it is less than 0.2%, this effect is insufficient, while if it exceeds 2%, the ductility of pearlite decreases and wire drawability deteriorates. The upper limit is 2%. Furthermore, Ti, Nb, V, and Zr all precipitate as fine carbonitrides, thereby making the austenite grains finer and strengthening the steel. These elements 1
If the total content of more than one species is less than 0.005%, the effect is insufficient, while if it exceeds 0.3%, the effect is saturated, so it was set at 0.005 to 0.3%. Manufacturing methods for such steel wire include, for example, performing composite casting of different types of molten steel during casting, or inserting round steel into a steel pipe and integrating it by welding, shrink fitting, cold fitting, press fitting, or other means. Possible methods include rolling after that. In order to impart a predetermined strength to the steel wire thus obtained, it may be subjected to a conventional high-tensile strength wire manufacturing process in which the wire is drawn after patenting. Furthermore, it is also possible to use a recently developed means of omitting patenting through the salting immediately after hot rolling. The effects of the present invention will be illustrated in more detail by way of examples below. (Example) Table 1 shows the components contained in the core part and the outer layer part. In the same table, A, B, D, E, F, G, H, and L are examples of the present invention, and C, I, J, and K are comparative examples. These steel wires are prepared by preparing various steel pipes with an outer diameter of 100 mm and an inner diameter of 31.6 mm to 91.3 mm. After pickling a round steel tube with an outer diameter slightly smaller than the inner diameter, the latter is inserted into the former and heated in a vacuum. It is made from a material whose ends are electron beam welded and hot-rolled to a diameter of 11 mm. However, K
The steel wire shown in is not a composite structure, but a single steel wire, which is the same as conventional piano wire. These steel wires were patented and drawn at 560°C. As an example, FIG. 2 shows the relationship between the area reduction rate and the mechanical properties of the steel wire of Example A of the present invention and conventional steel wire K. In addition, Table 2 shows the strength, reduction of area, and twisting values when each steel wire was drawn to a diameter of 5 mm. The same table also shows the percentage reduction in area from the material when the wire is broken by repeated wire drawing. According to FIG. 2, the strength after drawing when the steel wire A of the present invention is used is not much different from that of the conventional steel wire K, but the drawing and twist values are greatly improved. In relation to this, the cross-sectional reduction rate at the wire drawing limit is increasing. The improvement in strength due to this is approximately 30Kg/mm ²
It is clear that the present invention can provide a wire rod with higher strength. Further, as is clear from Table 2, the other invention examples B, D, E, F, G, H, and L all have approximately the same strength as K and are superior in other properties. However, C, which is a proportional example, lacks strength, and I, J
It can be seen that the workability and ductility were not improved at all.

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【table】

[Table] (Effects of the invention) As is clear from the above examples, according to the present invention, it is possible to provide a high-strength steel wire that could not be obtained conventionally, and it is also possible to provide a steel wire with the same strength as the conventional one. Even in the case of drawing, the effect of reducing material yield and productivity due to breakage is much lower than in the past, which greatly contributes to the development of industry.

[Brief explanation of drawings]

Figure 1 is a sectional view showing the structure of the steel wire of the present invention, Figure 2
The figure is a diagram showing changes in mechanical properties with respect to area reduction rate. 1...Core part, 2...Outer layer part.

Claims (1)

[Claims] 1. Consisting of a core part and an outer layer part surrounding it, the area ratio of the core part in the cross section to the whole cross section is 0.01 to 0.80.
The core contains C0.01~0.60%, Mn0.3~1.5%, Al0.005~0.10%, and is limited to less than 0.5% Si and less than 0.03% S. , other Fe and other unavoidable impurities, and the outer layer contains C0.7~1.0%, Si0.1~2.0%, Mn0.3~1.5%, Al0.005~0.10% by weight, A high-tensile steel wire characterized by being made of steel containing Fe and other unavoidable impurities. 2 Consists of a core part and an outer layer part surrounding it, and the area ratio of the core part in the cross section to the whole cross section is 0.01 to 0.80
The core contains C0.01~0.60%, Mn0.3~1.5%, Al0.005~0.10%, and is limited to less than 0.5% Si and less than 0.03% S. , other Fe and other unavoidable impurities, the outer layer has a weight percentage of C0.7~1.0%, Si0.1~2.0%, Mn0.3~1.5%, Al0.005~0.10%, Cr0.2 ~2.0%, further contains one or more of Ti, Nb, V, and Zr in a total of 0.005 to 0.3%, and also contains Fe and unavoidable impurities. .