JPS60152659A - Wire rod for hyperfine wire having superior workability - Google Patents

Abstract

PURPOSE:To obtain a wire rod for a hyperfine wire having superior workability by adding specified percentages of C, Si and Mn to Fe and reducing the amounts of P, S, Cu, Ni, Cr, O and N contained to a specified value each. CONSTITUTION:A wire rod consisting of, by weight, 0.60-0.90% C, 0.10-0.50% Si, 0.30-1.00% Mn, <0.010% P, <0.005% S, <0.10% in total of Cu, Ni and Cr, <=30ppm total oxygen, <=30ppm total nitrogen and the balance Fe is manufactured. When the wire rod is used, a wire of <=about 0.4mm.phi suitable for use as a material for a tire cord or a belt cord is obtd.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is an ultra-fine material with excellent workability used in reinforcing materials for rubber products such as tires and industrial belts, i.e., tire cords and Peltoco-P (1). This relates to wire rods.

(Prior art and its problems) The ultra-fine steel wire used as a rubber reinforcing material is drawn to a wire diameter of 0.4 to 0.10 m+a by repeated heat treatment and wire drawing of the wire rod, and then subjected to a special twisting process. The steel cord is assembled into a steel cord with a predetermined configuration by the machine.

However, in the process of twisting Co-P strands, productivity is low because the Co-P strands are thin. Therefore, increasing the efficiency of stranded wire processing has become an extremely important industrial issue.

As a way to increase the productivity of stranded wire processing, the current twisted υ
It is conceivable to further increase the wire processing speed, but an increase in the twisted wire processing speed will naturally increase the strain rate due to torsional stress and tensile stress applied to the steel cord wire. When applying P wire, the twisting process leads to frequent wire breaks. Therefore, methods for increasing the processing speed of stranded wire to improve the productivity of steel cords have not necessarily yielded effective results.

(2) On the other hand, in order to increase the tensile strength of steel cord strands, methods such as increasing the carbon content or increasing the area reduction processing rate up to the finished wire have been adopted. Although it is relatively easy to increase the tensile strength of cord tension, it is impossible to avoid deterioration of toughness value due to high tension. Difficult to improve.

Conventionally, well-known wire rods applied to steel cord regulations usually have C: 0.65 to 0.854, St: 0.
．． 15-0.40%, Mn: 0.30-0.90
S, P: 0.010-0.030%, S
: 0.005 to 0.020%. Therefore, with the composition as described above, P and S limit the improvement of the toughness of the steel wire, and hence the improvement of fatigue properties when used at high tension levels or cold processing such as cord twisting. It is difficult to speed up the interforming process, which poses a problem when used as a wire material for ultra-fine wires such as steel cords.

(Purpose of the Invention) In order to solve such problems, the present inventors have investigated the mechanical properties and twisting processing characteristics of high carbon steel wires to be wire-drawn. In order to ensure the toughness of carbon steel wire, p, s.

It was confirmed that reducing so-called impurities such as 0 and N and so-called high purification is effective, and as a result, significant improvements in fatigue properties at high tension levels and wire stranding workability at high speeds can be obtained.

P segregates at grain boundaries or ferrite/IP-lite interfaces, increases the susceptibility to crack generation during fatigue, and inhibits slippage of the ferrite/IP-lite interface during plastic working.

On the other hand, S mostly exists as sulfide in steel, and this becomes a stress concentration source when subjected to repeated stress such as fatigue loading, or when neutral deformation is rapid, leading to cracking. have a significant impact on

As described above, it can be seen that the toughness, fatigue properties, and high-speed twisting workability of ultrafine high carbon steel wires can be greatly improved by lowering the level of impurities such as P and S, so-called high purity. ,
The purpose is to propose wire materials for ultra-fine wires such as steel cord wire.

(Structure and operation of the invention) That is, the gist of the present invention is as follows.

Weight I: C: 0.60-0.90% si: Q, IQ-0.50 coefficient Mn: 0.30-1. Contains O0% and P content: less than 0.010 S content -: 0. O0505 Total content of Cu, Ni, Cr: less than 0.101 Total oxygen content: 30 ppm or less Total nitrogen content: 30 ppm or less, the remainder being iron A wire rod for ultra-fine wires with excellent workability.

Next, the effect of each element defined in the present invention and the reason for limiting the content will be explained.

Reason for limiting C: 0.60 to 0.90; Generally, the tensile strength of wire-drawn steel wire increases with the carbon content (5), so it is desirable to increase the amount as much as possible. Steel cord wire rods for reinforcing rubber are used with a carbon content of 0.601 or more due to the required strength. On the other hand, if the carbon content exceeds 0.901, a large amount of pro-eutectoid cementite will precipitate, and the drawability of wires with high area reduction ratios such as steel cord wires or the toughness of mechanical properties after wire drawing will deteriorate significantly. do. Therefore, carbon content is 0.6
The ratio was 0 to 0.90.

Reason for limiting Si: O, lO to 0.50: St requires 0.10% or more to strengthen the ferrite ground, but if it exceeds 0.501, it may cause ferrite decarburization and surface flaws. The danger is huge.

Therefore, the upper limit of St was set to 0.5096.

Mn: 0.50-1. Reason for limitation of OO'A: Mn is an element necessary to ensure hardenability during patenting treatment and to obtain tensile strength and toughness in coexistence with C.

Therefore, the lower limit of Mn was set to 0.304, which is adopted in industrial standards such as JIS. The upper limit was set at 1.0, which is the limit at which martensite tends to be locally generated during the No. 4 tenting treatment (6) and inhibits wire drawability.

Reason for limiting p: below the o, oio ratio: P segregates at grain boundaries or ferrite/-orite interfaces, increasing the susceptibility to crack generation during fatigue due to repeated loads. Furthermore, it impairs malleability during plastic working performed at high speeds. By reducing P to 0.010 coefficient or less, the fatigue test characteristics of ultra-fine wire drawn material (the fatigue life of the Hunter set rotary bending in the fatigue test), and the twisting workability at high speed (
It has been confirmed through numerous tests that the fracture resistance (rupture resistance) is significantly improved. Therefore, the upper limit of P in the steel cord wire was set at 0.010%.

S: Reason for limitation of less than 0.005 S: At room temperature, S hardly forms a solid solution in steel and exists as a sulfide. Sulfides become a non-uniform part of the stress field during repeated loads during fatigue tests and when high-speed plastic working such as twisting is performed, and can become the nucleus for crack generation due to stress concentration. To suppress this effect, the upper limit of S is set to 0.
It was set to less than 0.005%.

Total content of Cu + Ni + Cr: 0.10%
Reason for limitation: P is a common impurity element in steel.

In addition to S, O, and N, Cu, Ni, and Cr are present. These elements mostly dissolve in solid solution in ferrite and partially participate in carbide formation, and improve toughness by reducing the P and O contents to 0.010% or less and 0.0051% or less, respectively. It has the opposite effect. Since the effects of these elements such as Cu, Ni, and Cr that exist as impurities are considered to be additive at the component level where they exist as impurities, the upper limit of the total content was set at a factor of 0.10.

Total oxygen prohibition: 30 ppm or less Reason for limitation: At room temperature, most oxygen exists in steel as an oxide.

Since oxides are generally hard, they remain undeformed even after wire drawing, becoming a stress concentration source and deteriorating fatigue properties.

When oxygen exceeds 30 ppm, the amount of inclusions increases rapidly.

Therefore, the oxygen amount was set to 30 ppm or less.

Total nitrogen content: Reason for limiting to 30 ppm or less; Nitrogen was set to 30 ppm or less in order to suppress strain aging as much as possible at room temperature after wire drawing and prevent toughness deterioration. This effect is
This is particularly effective under conditions where the S amount is less than 0.010 and the S amount is less than 0.005.

The wire rod of the present invention is suitable for use in drawing ultra-fine wires having a diameter of 0.4 mm or less.

The effect of non-metallic inclusions is particularly large on small-diameter steel wires. This is because the occupancy rate of inclusions in the cross section of the steel wire becomes larger in the case of small diameter steel wires.

In the case of the wire rod of the present invention, by limiting the total amount of oxygen, the improvement in fatigue properties is remarkable, especially in ultra-fine steel wires of 0.4 mmφ or less, in relation to the size of generated inclusions.

Furthermore, in the manufacturing process of small-diameter steel wire, the speed of the processing process is being increased in order to increase productivity.

The effects of the components p and s are greater as the processing speed increases, and therefore, the wire rod of the present invention is more effective in high-speed processing steps. Industrially, it is important to apply a high-speed processing process to a diameter of 0.4 mm or less.

Next, examples of the present invention will be described while comparing them with comparison materials.

(9) Table 1 shows the chemical composition of the test materials.

The 5.5 mm diameter wire rod is made into 0.23 mm diameter or 0.5 mm diameter in two stages.
A steel wire of 175 mmφ was drawn.

As a heat treatment before each step of wire drawing, the wire rod or steel wire was subjected to lead tenting treatment. The first /4' tenting process was performed on the 5.5 simple diameter wire rod, and the 1 (1 (J
It was heated at u°C and kept cool in a lead bath at 550°C.

Thereafter, dry wire drawing was performed to a diameter of 1.16+mφ. Next, a second patenting process is performed under the same conditions as the first patenting process, dry wire drawing is performed to 0.7 wnφ, and the finished wire is 0.
．． Wet wire drawing was performed up to 23+nmφ and 0.175mmφ.

(10) <Example 1> 0.23m having the mechanical properties shown in the second figure and in Figure 1
Figure 2 shows the results of a fatigue test conducted on the φ finished crevice.

Table 2 Mechanical Properties of Sample Materials Fatigue tests were conducted using a Hunter set rotary bending fatigue testing machine, which is often used in the case of ultra-fine wires. The measured fatigue life is stress 100y/-1 rotational speed 3000r, pm
This is the number of repetitions until rupture under the test conditions.

It has been recognized that reducing the amount of P and S, that is, increasing the purity, greatly improves both the torsion value and Hunter fatigue life.
The deterioration in toughness that accompanies high tension can be avoided by increasing the purity, and both properties of high strength and high toughness can be obtained. In particular, when P is less than 0.10% and S is less than 0.005%, the improvement in fatigue properties is remarkable.

<Example 2> 0.7%C level having the mechanical properties shown in Table 3,
Tests were conducted on the twisted υ processing characteristics of steel cord using finished wires of 0.1 to 5 mφ.

The twisting property test was carried out in accordance with the method described in Japanese Patent Application No. 76185/1985. That is, as shown in Fig. 3, In
A cord twisting simulation test machine with a mechanism in which double twist punchers of the -Out method and the Out -In method are arranged in series was used (13). Tension is applied via the electromagnetic brake 5, and twisting is performed on the four rotary plates 2. and,
The tension applied to the cord wire and the twisting speed can be arbitrarily varied during the twisting test, and the changes can be measured and recorded. In Examples, the breaking tension at each twisting speed was measured. The test conditions were two-strand twisting at a twisting force of 10 mF and a twisting speed of 6,000 rpm and 110,000 rpm. In the figure, T indicates tension and TW indicates twisting.

The test results are shown in Figure 4. By reducing the P content by 1° and the S content, that is, increasing the purity of the steel cord material, the breaking strength/tensile strength ratio during twisting is significantly improved. The improvement in breaking tension, that is, the improvement in winding properties, is most effective when the P content is less than 0.01i and the S content is less than 0.005S.

<Example 3> 0,8-chi C level 0 having the mechanical properties shown in Table 4
．． 175m1Eφ finish #) iIJ twisting property test results (14) The rice is shown in Figure 5.

Using the test method shown in Figure 3, the test method was as follows:
The twisting breaking strength at each twisting speed from 0 to 19000 r, p, and m was measured and expressed as a ratio to the tensile strength. The twisting breaking strength decreases with the twisting speed to about 30 degrees of the tensile strength, but the degree of decrease depends on the p of the test material,
It varies depending on the S content. PiO, 003%, Si0.
0011D Inventive steel (symbol J) has high breaking strength even at high twisting speeds, especially at 15000 r
, p, m or higher.

Furthermore, test sample I of the steel of the present invention, which has a slightly higher p and s content than test material J (p content 0.008%, S] 0.004%)
Also, the twisting breaking strength was at a twisting speed of 8000 r,
It is as good as the test sample J up to 11,000 r, p, and m over pm.

As described above, when the steel of the present invention contains a high carbon content of 0.8% C or more, a remarkable improvement in the twisting properties was observed.

(Effects of the Invention) v As explained above, the steel cord made of the steel of the present invention has excellent toughness and is therefore suitable for high-speed twisting in response to the demand for improved productivity in the cord knitting process. It has good cord processing properties and also maintains excellent fatigue properties even when the tensile strength is high.

As described above, when the steel cord is used as a reinforcing material for rubber products such as tires or industrial belts, the wire rod of the present invention exhibits (1) excellent workability (twisting) during manufacturing and (2) excellent strength (2) during use. It is an extremely useful material for wire rods for ultra-fine wires, such as steel cords, with excellent workability.

[Brief explanation of the drawing]

Figure 1 is a graph showing the relationship between tensile strength and torsion value due to changes in P and S content in 0.8% C material, and Figure 2 is a graph showing the fatigue life and twist value in a Hunter set fatigue test using the same sample. P,
A graph showing the relationship between samples of S content, Figure 3 is a Kinmei diagram showing an overview of the simulation test method and testing machine for evaluating the twisting characteristics in cord knitting, and Figure 4 shows the relationship between 0 and 0 in 0.7SC material. A graph showing the results of the twisted esimilation test of the 1751 mφ cord wire in terms of the relationship between the P and S contents and the (twisted breaking strength/tensile strength) ratio,
Figure 5 shows 0,175. , is a graph showing the relationship between the (twisting breaking strength - tensile strength) ratio and twisting speed of the φ cord wire. Patent applicant Nippon Steel Corporation (17) Figure 1 2nd Hayabusa page 3

Claims (1)

[Claims] Weight range: C: 0.60-0.90 Si: 0.10-0.50% Mn: 0.30-1.00 T. and P content: less than 0.010% S content: less than 0.005% Total oxygen content: 30 ppm or less Total nitrogen content: 30 ppm or less, and the remainder is iron with excellent workability. Wire rod for wire.