Method for manufacturing low-strength and high-plasticity wire rod and method for manufacturing high-strength fine steel wire

Abstract

The present invention discloses a method for manufacturing a low-strength and high-plasticity wire rod and a method for manufacturing a high-strength fine steel wire. The method for manufacturing the wire rod is as follows: mixing and melting the components of the wire rod in proportion, and casting the obtained molten steel to obtain a billet; performing hot rolling on the billet to obtain a wire rod; cooling the wire rod and controlling the phase transformation process at a temperature of 660-700°C for a time of 15-30 s. The method for manufacturing the fine steel wire is as follows: the above-mentioned wire rod is prepared through drawing, austenitizing heat treatment and final drawing. The deformation performance of the wire rod produced by this method is improved, and the comprehensive performance of the ultra-fine steel wire after drawing can be optimized, reducing the tissue defects while not losing the strength of the steel wire. Due to the good deformation ability of the wire rod, the wire breakage rate of the steel wire is significantly reduced during the production process, reducing die wear and energy consumption, and greatly reducing the production cost.

Description

Technical Field

[0001] The present invention relates to a method for preparing round steel wire rods and a method for preparing steel wires, and particularly to a method for manufacturing low-strength and high-plasticity wire rods and a method for manufacturing high-strength and thin steel wires. Background Art

[0002] Steel cord wire, as a kind of high-strength pearlitic steel wire, is widely used as the skeleton material of automobile tires. With the development of technology, its strength has been continuously improved, the specifications have gradually become thinner, and the problem of a relatively high wire breakage rate has become prominent accordingly.

[0003] Traditional SWRH82B hot-rolled wire rods contain the following components by mass percentage: C: 0.80% - 0.85%, Si: 0.15% - 0.30%, Mn: 0.45% - 0.60%, Cr: 0.01% - 0.03%, P≤0.02%, S≤0.01%, and the rest are Fe and inevitable impurities. The wire rods are required to have a tensile strength of 1070 - 1120 MPa and an area reduction rate ≥38%. Among them, the finished steel wire with a diameter of 0.30 mm has a strength reaching 3300 MPa level; the finished steel wire with a diameter of 0.20 mm has a strength reaching 3600 MPa level.

[0004] Traditional ultra-fine steel wires are produced by a three-stage method: drawing → austenitizing heat treatment → drawing → austenitizing heat treatment → final drawing. In order to reduce production costs, it is changed to a two-stage method: drawing → austenitizing heat treatment → final drawing. Since one drawing process is reduced, the total deformation amount of the steel wire in each drawing process increases, and the requirement for the deformation ability of the wire rod is significantly improved. The drawing process before the final drawing is to refine the steel wire specifications and obtain intermediate wires, and the increased strength disappears after austenitizing heat treatment. Therefore, the strength of the finished steel wire depends on the deformation amount in the final drawing stage.

[0005] Traditional high-strength wire rods have relatively poor plasticity, more tissue defects occur during drawing, the wire breakage rate is relatively high, and the die wear and energy consumption are also relatively high. And the traditional wire drawing die matching method will also cause relatively fast plastic loss and poor torsion performance. Therefore, it is necessary to propose new tissue control processes and drawing processes to reduce the strength of the wire rod, improve the deformation ability of the wire rod, reduce the wire breakage rate while reducing die wear and energy consumption, and reduce production costs. Summary of the Invention

[0006] Object of the Invention: The object of the present invention is to provide a method for manufacturing low-strength and high-plasticity wire rods with a simple process;

[0007] The second object of the present invention is to provide a method for manufacturing high-strength and thin steel wires with fewer defects and a low wire breakage rate.

[0008] Technical Solution: The method for manufacturing low-strength and high-plasticity wire rods according to the present invention includes the following steps:

[0009] (1) Mix the wire rod components in proportion and carry out smelting, and pour the molten steel obtained from smelting to obtain a billet;

[0010] (2) Carry out hot rolling on the billet to obtain a wire rod;

[0011] (3) Cool the wire rod and control the phase transformation process at a temperature of 660 - 700 °C for a time of 15 - 30 s to obtain a low-strength and high-plasticity wire rod.

[0012] Among them, in step (3), the cooling rate is controlled at 5 - 15 °C / s. By increasing the phase transformation temperature and time and controlling the cooling rate, the initial structure of the pearlite wire rod can be regulated, and the drawing performance of the wire rod can be improved. If the phase transformation temperature is too low or the phase transformation time is too short, the structure of the pearlite wire rod is not conducive to subsequent drawing.

[0013] Among them, in step (2), the heating process of the billet includes a heating section and a soaking section; the temperature of the heating section is 980 - 1030 °C, and the heating time is 25 - 35 min; the temperature of the soaking section is 1080 - 1130 °C, and the soaking time is 40 - 55 min. In this temperature and time range, the tissue uniformity is better and the defects are fewer.

[0014] Among them, in step (2), during the rolling process, the rough rolling starting temperature is 1090 - 1120 °C; the surface temperature of the rough rolling and medium rolling rolls is controlled at 35 - 65 °C; the temperature entering the finishing mill is 950 - 980 °C, and the outlet temperature is below 1060 °C; the wire rod laying temperature is controlled at 930 - 980 °C.

[0015] Among them, the wire rod contains the following components by mass percentage: C: 0.82% - 0.84%, Si: 0.10% - 0.15%, Mn: 0.30% - 0.45%, Cr: 0.05% - 0.10%, P ≤ 0.01%, S ≤ 0.01%, Cu ≤ 0.08%, Ni ≤ 0.08%, and the rest are Fe and unavoidable impurities; the pearlite lamellar spacing distribution range in the wire rod structure is 110 - 200 nm, the average value of the lamellar spacing is 140 - 160 nm, and the grain size of the wire rod is 7 - 8 grades. The pearlite colony size is larger, the lamellar spacing is larger, the loss of the die during drawing is smaller, and the generated tissue defects are fewer. If the pearlite structure is relatively fine, it is easy to break the wire during large-strain drawing, and the energy consumption and die loss are increased.

[0016] The preparation method of the high-strength ultra-fine steel wire described in the present invention is prepared by drawing, austenitizing heat treatment and final drawing of the low-strength and high-plasticity wire rod prepared by the above method.

[0017] Specifically, it includes the following steps:

[0018] (1) The wire rod is drawn in multiple passes to obtain intermediate wire; the die allocation for wire drawing: small reduction ratios are used in the 1st to 6th passes, large reduction ratios are used in the 7th to 10th passes, and small reduction ratios are used in the 11th to the last pass;

[0019] (2) The intermediate wire is subjected to austenitizing heat treatment;

[0020] (3) The intermediate wire after austenitizing heat treatment is finally drawn to obtain finished steel wire.

[0021] Among them, in step (1), the area reduction ratios in the 1st to 6th passes are 12% - 14%, 13% - 15%, 14% - 16%, 12% - 14%, 13% - 15%, 14% - 16%. At this time, the area reduction ratio is small, the strain is low, the pearlite clusters are easy to rotate, and the structure is relatively uniform; if the area reduction ratio is large, there are more structural defects.

[0022] Among them, in step (1), the area reduction ratios in the 7th to 10th passes are 17% - 19%, 18% - 20%, 19% - 21%, 20% - 22%. At this time, the area reduction ratio is large, and the work hardening effect is good; if the area reduction ratio is low, more passes of wire drawing are required, increasing energy consumption and reducing production efficiency.

[0023] Among them, in the present invention, it is preferably drawn a total of 14 passes; preferably, the area reduction ratios in the 11th to 14th passes are 12% - 14%, 13% - 15%, 11% - 13%, 14% - 16%. At this time, the area reduction ratio is low, the friction with the die is small, and the wire breakage rate is low. If the area reduction ratio is high, due to the small diameter, the wire breakage rate increases significantly.

[0024] Beneficial effects: Compared with the prior art, the present invention has the following remarkable effects: (1) By adjusting the production process of the wire rod, controlling the grain size and pearlite lamellar spacing of the wire rod, optimizing the structure of the wire rod, improving the deformation performance of the wire rod, the process is simple, and the prepared wire rod has low strength and high plasticity. (2) Using the die matching method with low - high - low compression ratios for this wire rod, the continuity of cementite in the structure of the produced steel wire is better, the defects are fewer, the plastic loss of the steel wire is reduced, and the torsion performance is improved. (3) The wire breakage rate of the steel wire produced by this method is reduced by 10% - 15%, the die loss is reduced by 15% - 20%, the energy consumption is reduced by more than 10%, the production continuity is improved, and the production cost is saved. Brief Description of the Drawings

[0025] Figure 1 is the process diagram of the preparation and drawing of the wire rod of the present invention;

[0026] Figure 2 is the SEM diagram of the wire rod of Example 1 and Comparative Example 1;

[0027] Figure 3 SEM images of the wire rods after drawing in Example 1 and Comparative Example 1 Detailed implementation manners

[0028] The present invention will be further described in detail below.

[0029] Example 1

[0030] A low-strength and high-plasticity wire rod contains the following components by mass percentage: C: 0.82%, Si: 0.10%, Mn: 0.30%, Cr: 0.05%, P: 0.006%, S: 0.005%, Cu: 0.08%, Ni: 0.08%, and the balance is Fe and unavoidable impurities. The preparation method of the low-strength and high-plasticity wire rod includes the following steps:

[0031] (A1) Smelting: Mix the wire rod components in proportion and carry out smelting, and cast the molten steel obtained by smelting to obtain a casting blank;

[0032] (A2) Continuous casting and rolling: Heat the casting blank to obtain a heated casting blank; The heating includes a heating section and a soaking section. The temperature of the heating section is 980 °C and the heating time is 35 min; The temperature of the soaking section is 1130 °C and the soaking time is 40 min; Roll the heated casting blank, and the rough rolling starting temperature is 1120 °C; The surface temperature of the rough rolling and medium rolling rolls is controlled at 35 °C; The temperature entering the finishing mill is 950 °C, and the outlet temperature is below 1060 °C; The wire rod spinning temperature is controlled at 930 °C;

[0033] (A3) Wire rod controlled cooling: Cool the wire rod, control the cooling rate at 5 °C / s, control the time at 15 s, and the phase change process at a temperature of 700 °C.

[0034] The method for preparing high-strength ultra-fine wire using the above low-strength and high-plasticity wire rod includes the following steps:

[0035] (B1) Drawing: Draw the wire rod for 14 passes to obtain an intermediate wire. The distribution of the wire drawing die matching passes: For the 1st to 6th passes, small reduction ratios are adopted, and the area reduction ratios are 12%, 15%, 16%, 12%, 15%, and 16% respectively; For the 7th to 10th passes, large reduction ratios are adopted, and the area reduction ratios are 19%, 20%, 19%, and 22% respectively; For the 11th to 14th passes, small reduction ratios are adopted, and the area reduction ratios are 14%, 13%, 13%, and 16% respectively.

[0036] (B2) Heat treatment: Perform austenitizing heat treatment on the intermediate wire and then perform final drawing.

[0037] (B3) Final drawing: Perform final drawing on the intermediate wire after austenitizing heat treatment to obtain the finished wire. The wire rod production and drawing processes are as Figure 1 shown.

[0038] The wire rod has a diameter of 5.5 mm, the pearlite lamellar spacing distribution range is 110 - 200 nm, the average lamellar spacing is 159 nm, and the grain size is grade 8. The tensile strength of the wire rod is 1017 MPa, and the reduction of area is 44%. The tensile strength of the finished steel wire is about 3329 MPa, and the fracture elongation is 2.5%. The number of torsion turns reaches 48 turns.

[0039] Example 2

[0040] Based on Example 1, the difference from Example 1 is that the wire rod contains the following components by mass percentage: C: 0.84%, Si: 0.15%, Mn: 0.45%, Cr: 0.10%, P: 0.005%, S: 0.006%, Cu: 0.05%, Ni: 0.05%, and the rest is Fe and inevitable impurities.

[0041] Example 3

[0042] Based on Example 1, the difference from Example 1 is that the wire rod contains the following components by mass percentage: C: 0.83%, Si: 0.12%, Mn: 0.40%, Cr: 0.08%, P: 0.008%, S: 0.008%, Cu: 0.06%, Ni: 0.05%, and the rest is Fe and inevitable impurities.

[0043] In step (A3), the cooling rate is controlled at 15 °C / s, the phase transformation time is 30 s, and the phase transformation temperature is 660 °C.

[0044] Example 4

[0045] Based on Example 1, the difference from Example 1 is that the wire rod contains the following components by mass percentage: C: 0.82%, Si: 0.13%, Mn: 0.43%, Cr: 0.06%, P: 0.007%, S: 0.006%, Cu: 0.06%, Ni: 0.05%, and the rest is Fe and inevitable impurities.

[0046] In step (A3), the cooling rate is controlled at 5 °C / s, the phase transformation time is 15 s, and the phase transformation temperature is 700 °C.

[0047] Example 5

[0048] On the basis of Example 1, the difference from Example 1 is that in step (B1), for wire drawing die matching pass distribution: for the 1st to 6th passes, small reduction ratios are adopted, and the area reduction ratios are 14%, 13%, 14%, 14%, 13%, and 14% respectively; for the 7th to 10th passes, large reduction ratios are adopted, and the area reduction ratios are 17%, 18%, 21%, and 20% respectively; for the 11th to 14th passes, small reduction ratios are adopted, and the area reduction ratios are 12%, 15%, 11%, and 14% respectively.

[0049] Comparative Example 1

[0050] On the basis of Example 1, the difference from Example 1 is that in step (B1), for the 1st to 6th passes, the area reduction ratios are 18%, 10%, 17%, 18%, 10%, and 11% respectively;

[0051] Comparative Example 2

[0052] On the basis of Example 1, the difference from Example 1 is that in step (B1), for the 7th to 10th passes, the area reduction ratios are 15%, 22%, 16%, and 24% respectively;

[0053] Comparative Example 3

[0054] On the basis of Example 1, the difference from Example 1 is that in step (B1), for the 11th to 14th passes, the area reduction ratios are 15%, 16%, 15%, and 9% respectively;

[0055] Comparative Example 4

[0056] On the basis of Example 1, the difference from Example 1 is that in step (A3), the phase change time is 10 s.

[0057] Comparative Example 5

[0058] On the basis of Example 1, the difference from Example 1 is that in step (A3), the cooling rate is controlled at 20 °C / s.

[0059] Comparative Example 6

[0060] On the basis of Example 1, the difference from Example 1 is that in step (A3), the phase change temperature is 640 °C / s.

[0061] The wire rods prepared in Examples 1 - 5 and Comparative Examples 1 - 6 of the present invention were compared in terms of tissue performance parameters, and the results are shown in Table 1 below.

[0062] Table 1 shows the tissue performance parameters of the examples and comparative examples

[0063]

[0064] As shown in Table 1, after adjusting the heat treatment process, the wire rod has a smaller grain size and a wider lamellar spacing, resulting in better deformation ability during drawing. The microstructural morphologies of different wire rods are compared as Figure 2 shown. At the same time, a wire drawing die matching method with a small-large-small reduction ratio is adopted, which increases the strength of the low-strength wire rod significantly. Under the same deformation amount, the tensile strength of Example 1 increased by 2312 MPa, which is higher than that of Comparative Example 4, Comparative Example 5, and Comparative Example 6. Since the microstructure of the wire rod is more conducive to subsequent processing and forming, the cementite continuity of the finished wire is better and the microdefects are fewer, so the torsion performance is better, as Figure 3 shown. Moreover, the wire breakage rate, die loss, and energy consumption of the examples are lower than those of the comparative examples.

Claims

1. A method for preparing high-strength fine steel wire, characterized in that, It is prepared by drawing, austenitizing heat treatment and final drawing of low-strength and high-plasticity wire rods; the wire rods contain the following components by mass percentage: C: 0.82% - 0.84%, Si: 0.10% - 0.15%, Mn: 0.30% - 0.45%, Cr: 0.05% - 0.10%, P≤0.01%, S≤0.01%, Cu≤0.08%, Ni≤0.08%, and the rest are Fe and inevitable impurities; the pearlite lamellar spacing distribution range in the microstructure of the wire rods is 110 - 200 nm, the average value of the lamellar spacing is 140 - 160 nm, and the grain size of the wire rods is 7 - 8 grades; The preparation method of the low-strength and high-plasticity wire rods includes the following steps: (1) Mix the wire rod components in proportion and carry out melting, and cast the molten steel obtained by melting to obtain a billet; (2) Carry out hot rolling on the billet to obtain wire rods; (3) Cool the wire rods, and control the phase transformation process at a temperature of 660 - 700 °C for 15 - 30 s to obtain low-strength and high-plasticity wire rods; the cooling rate is controlled at 5 - 15 °C / s; The preparation method of the high-strength fine steel wire includes the following steps: (1) Carry out multi-pass drawing on the wire rods to obtain intermediate wires; the die allocation for wire drawing: small reduction ratios are adopted for the 1st - 6th passes, large reduction ratios are adopted for the 7th - 10th passes, and small reduction ratios are adopted for the 11th - last passes; the area reduction ratios for the 1st - 6th passes are 12% - 14%, 13% - 15%, 14% - 16%, 12% - 14%, 13% - 15%, 14% - 16%; the area reduction ratios for the 7th - 10th passes are 17% - 19%, 18% - 20%, 19% - 21%, 20% - 22%; a total of 14 passes of drawing are carried out, and the area reduction ratios for the 11th - 14th passes are 12% - 14%, 13% - 15%, 11% - 13%, 14% - 16%; (2) Carry out austenitizing heat treatment on the intermediate wires; (3) Carry out final drawing on the intermediate wires after austenitizing heat treatment to obtain finished steel wires.

2. The preparation method of the high-strength fine steel wire according to claim 1, characterized in that, In step (2) of the preparation method of the low-strength and high-plasticity wire rods, the heating process of the billet includes a heating section and a soaking section; the temperature of the heating section is 980 - 1030 °C, and the heating time is 25 - 35 min; the temperature of the soaking section is 1080 - 1130 °C, and the soaking time is 40 - 55 min.

3. The preparation method of the high-strength fine steel wire according to claim 1, characterized in that, In step (2) of the preparation method of the low-strength and high-plasticity wire rods, during the rolling process, the rough rolling starting temperature is 1090 - 1120 °C; the surface temperature of the rough rolling and medium rolling rolls is controlled at 35 - 65 °C; the temperature entering the finishing mill is 950 - 980 °C, and the outlet temperature is below 1060 °C; the wire rod laying temperature is controlled at 930 - 980 °C.

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