A high-speed wire rolling method for soft magnetic stainless steel wire rod

Abstract

The present invention relates to the field of stainless steel wire rolling, and specifically to a high-speed wire rolling method for soft magnetic stainless steel wire rods. The method of the present invention includes billet heating, high-speed rolling and controlled cooling. The present invention optimizes the design and precise control of the billet heating temperature, the start rolling temperature, the temperature of the finishing mill, the wire laying temperature, the rolling speed and the rolling reduction. After the wire laying, the Stelmor air cooling line is used to achieve a cooling speed of ≥8°C / S, so that the soft magnetic stainless steel wire rod is prepared without cracking during rolling, and the rolling yield is improved. The comprehensive rolling yield is ≥96%, and the prepared soft magnetic stainless steel wire rod has excellent surface quality; and the problem of coarse metallographic structure in the core of the soft magnetic stainless steel wire rod is solved, so that the metallographic structure in the core is homogenized, and the obtained soft magnetic stainless steel wire rod has good plasticity and mechanical properties, tensile strength ≤580MPa, elongation ≥25%, and shrinkage ≥50%.

Description

Technical Field

[0001] The invention relates to the field of stainless steel wire rolling, and in particular to a high-speed wire rolling method for soft magnetic stainless steel wire rods. Background Art

[0002] Soft magnetic material is a kind of magnetic material with high magnetic permeability, high saturation magnetic induction intensity, low coercive force. It is easy to magnetize under the action of magnetic field and easy to demagnetize after the magnetic field is removed. Therefore, it is widely used in the manufacture of magnetic conductors, transformers, relay cores, household appliance solenoid valves, automotive control system solenoid valves, etc. Since soft magnetic stainless steel not only has good magnetic properties but also good corrosion resistance, it is widely favored by users. In recent years, with the rapid development of home appliances and automobile industries, the demand for soft magnetic stainless steel has also increased, but there are few domestic manufacturers of soft magnetic stainless steel, mainly because it is difficult to produce. At present, China still mainly relies on imports from Italy, Japan and other countries. Soft magnetic stainless steel materials are mainly ferritic stainless steel. In order to improve its magnetism, plasticity, corrosion resistance, weldability, etc., ultra-low carbon content and high Si content are required. At the same time, other alloy elements such as Ni, Ti, Al, etc. are often added. The most common steel grades are 430FR from the United States, KM series from Japan, MG series from Italy, etc. This type of steel is difficult to roll, which is mainly reflected in rolling cracking, resulting in low rolling yield and surface warping defects of the finished product; after rolling, the core structure is uneven and the plasticity is poor, which is not conducive to subsequent cold processing.

[0003] At present, there are few reports on the rolling of soft magnetic stainless steel wire rods in China. Patent CN107099653 A is a production method for high-silicon stainless steel wire rods, and discloses a ferritic stainless steel whose Si content is required to be 2.5-3.5% and Cr is 12.5-15.0%. The product has great limitations. The main problem it solves is the yield rate of high-silicon ferritic stainless steel. It cannot completely solve the problem of coarse central grains and poor plasticity during rolling of ferritic stainless steel, and is difficult to apply to the soft magnetic stainless steel wire rod described in the present invention. Patent CN106636909A is a corrosion-resistant soft magnetic ferrite stainless steel, which does not describe the rolling method in detail and is not suitable for high-wire production. Patent CN106636894 A is a low-carbon ferritic soft magnetic easy-to-cut stainless steel and its production method. This method cannot solve the problem of coarse core structure of the material. The plasticity of the material after production is poor, which is not conducive to subsequent wire drawing processing, and this invention is mainly aimed at sulfur-containing steel with an S content of more than 0.15. Patent CN106583449A discloses a method for rolling ferritic stainless steel, which is mainly for stainless steel plates. Plates are quite different from wire rods and are not suitable for the production and processing of wire rods. Therefore, it is still one of the difficulties and pain points in this field to study a suitable rolling method for preparing soft magnetic stainless steel wire rods with excellent surface quality, uniform metallographic structure, good plasticity and mechanical properties and high yield. Summary of the invention

[0004] The purpose of the present invention is to solve the problems of the prior art and provide a high-speed wire rolling method for soft magnetic stainless steel wire rods. The method does not cause cracking during rolling, improves the rolling yield, and the prepared soft magnetic stainless steel wire rods have excellent surface quality, uniform core metallographic structure, and good plasticity.

[0005] The technical solution adopted by the present invention to solve its technical problem is:

[0006] A high-speed wire rolling method for soft magnetic stainless steel wire rod comprises the following steps:

[0007] (1) Billet heating: The billet is heated in three stages: in the first stage, the billet is heated to 800±20°C at a rate of 10-15°C / min and kept at this temperature for 15-25min; in the second stage, the billet is heated to 1000±15°C at a rate of 8-10°C / min and kept at this temperature for 15-25min; in the third stage, the billet is heated to 1060±10°C at a rate of 6-8°C / min and kept at this temperature for 20-25min; wherein the billet is a square billet of 160×160-180×180 (unit: mm) or a round billet of Φ150-Φ180 (unit: mm);

[0008] (2) High-speed rolling: The heated billet is rolled and laid by a rough rolling mill, No. 1 flying shear, intermediate rolling mill, No. 2 flying shear, pre-finishing rolling mill, No. 3 flying shear, finishing rolling mill and laying mill, and the rolling reduction of each pass is controlled to be no more than 35%;

[0009] (3) Cooling: After rolling, the steel is rapidly cooled to a temperature not higher than 250°C to obtain a soft magnetic stainless steel wire rod.

[0010] Preferably, in step (1), the surface of the blank is required to be flat and free of defects visible to the naked eye.

[0011] Preferably, in step (1), the blank is placed in a furnace at room temperature for heating.

[0012] Preferably, in step (1), the temperature of the blank is raised to 800°C at a rate of 10-15°C / min, and kept at 800±20°C for 15-25 min; the temperature is raised to 1000°C at a rate of 8-10°C / min, and kept at 1000±15°C for 15-25 min; the temperature is raised to 1060°C at a rate of 6-8°C / min, and kept at 1060±10°C for 20-25 min. This method can further ensure that the blank is heated evenly and fully.

[0013] Preferably, the high-speed rolling in step (2) includes 6 passes of rough rolling, flying shearing with No. 1 flying shear, 12 passes of intermediate rolling, flying shearing with No. 2 flying shear, 6 passes of pre-finishing rolling, flying shearing with No. 3 flying shear, 10 passes of finishing rolling and spinning.

[0014] Preferably, in step (2), the starting rolling temperature is 1050-1080°C, the temperature of the finishing mill is controlled at 850-900°C, and the spinning temperature is 850-880°C.

[0015] Preferably, in the step (2), the final rolling speed is required to be: 50-65 m / s for specifications of Φ5.5-Φ8.0 mm; 30-48 m / s for specifications of >Φ8.0-Φ11.0 mm; 20-28 m / s for specifications of >Φ11.0-Φ14.0 mm; 10-18 m / s for specifications of >Φ14.0-Φ20.0 mm.

[0016] Preferably, in step (2), the No. 1 flying shear only cuts 100-200 mm from the head, the No. 2 flying shear cuts 200-300 mm from the head and tail, and the No. 3 flying shear cuts 350-500 mm from the head and tail, thereby further preventing the head and tail from rotting and causing steel pile accidents.

[0017] Preferably, the cooling rate of the rapid cooling in step (3) is ≥8°C / s, and more preferably, the spinning is cooled through a Stelmore air cooling line; more preferably, the spinning is cooled to a temperature ≤250°C for coiling, and then naturally cooled to room temperature after coiling.

[0018] Preferably, the soft magnetic stainless steel wire rod obtained by the high-speed wire rolling method has excellent surface quality, uniform core metallographic structure, good plasticity, tensile strength ≤580MPa, elongation ≥25%, surface reduction ≥50%, and rolling yield ≥96%.

[0019] Preferably, the soft magnetic stainless steel wire rod obtained by the high-speed wire rolling method has a specification of Φ5.5 to Φ20 mm.

[0020] Preferably, the high-speed wire rolling method specifically comprises the following steps:

[0021] 1) Billet preparation: Use square billets of 160×160~180×180 (unit: mm), or round billets of Φ150~Φ180 (unit: mm). The surface of the billet should be flat and free of visible defects.

[0022] 2) Billet heating: heating is divided into three stages. In the first stage, the billet is put into the furnace at room temperature, and the temperature is raised to 800°C at a rate of 10-15°C / min, and kept at 800±20°C for 15-25min; in the second stage, the temperature is raised to 1000°C at a rate of 8-10°C / min, and kept at 1000±15°C for 15-25min; in the third stage, the temperature is raised to 1060°C at a rate of 6-8°C / min, and kept at 1060±10°C for 20-25min. This method can ensure that the billet is heated evenly and fully;

[0023] 3) High-speed rolling: The rolling process includes 6 passes of rough rolling → No. 1 flying shear → 12 passes of intermediate rolling → No. 2 flying shear → 6 passes of pre-finishing rolling → No. 3 flying shear → 10 passes of finishing rolling → wire laying, and the maximum rolling reduction of each pass is ≤35%;

[0024] 4) Controlling cooling: After spinning, all the insulation covers of the Stelmore air cooling line are opened, and the air volume is adjusted to ensure that the cooling rate is ≥8°C / s, and the wire is cooled to a temperature of ≤250°C and then rolled up. After rolling up, it is naturally cooled to room temperature to obtain the soft magnetic stainless steel wire rod.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. During the heating process, the temperature is reasonably designed and gradually increased in three stages. A reasonable holding time is retained in each stage to make the billet temperature uniform, avoid cracking caused by uneven billet temperature during the rolling process, and improve the surface quality of the finished product.

[0027] 2. During high-speed rolling, the starting rolling temperature, finishing rolling temperature and wire laying temperature are precisely controlled, and the rolling speed is strictly limited to avoid the coarse and uneven core structure caused by excessively high core temperature of the rolled piece, so as to homogenize the metallographic structure and improve the plasticity.

[0028] 3. During high-speed rolling, the flying shears at each part should be reasonably designed to cut the head and tail, so as to avoid steel pile accidents caused by head and tail rot and avoid losses caused by excessive cutting of the head and tail.

[0029] 4. During high-speed rolling, control the maximum rolling reduction of each pass to ≤35% to avoid cracking of the rolled piece due to excessive deformation.

[0030] 5. After spinning, the wire is cooled quickly with a cooling rate of ≥8℃ / S. It is cooled to a temperature of ≤250℃ and then rolled up, which effectively avoids the precipitation temperature range of the σ phase, prevents the precipitation of the σ phase, and further improves the plasticity and mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Schematic diagram of the blank heating process in the method of the present invention;

[0032] Figure 2 Surface macroscopic image of the soft magnetic stainless steel KM-31 wire rod prepared in Example 1;

[0033] Figure 3 The core metallographic structure of the soft magnetic stainless steel KM-31 wire rod prepared in Example 1;

[0034] Figure 4 Surface macroscopic image of the soft magnetic stainless steel 430FR wire rod prepared in Example 2;

[0035] Figure 5The core metallographic structure of the soft magnetic stainless steel 00Cr13Si2 wire rod prepared in Example 4;

[0036] Figure 6 The core metallographic structure of soft magnetic stainless steel 00Cr13Si2 wire rod produced by conventional process. DETAILED DESCRIPTION

[0037] The following examples are provided to further illustrate the technical solution of the present invention in detail in conjunction with the accompanying drawings. The following examples are only a more detailed description of the best implementation scheme of the present invention and do not limit the scope of the present invention in any way.

[0038] Embodiment 1:

[0039] The rolled material in this embodiment is soft magnetic stainless steel KM-31 with a specification of Φ6.5mm. The chemical composition, by weight, includes C: 0.018%, Si: 1.2%, Mn: 0.3%, P: 0.030%, S: 0.02%, Ni: 0.10%, Cr: 15.05%, N: 0.018%, and the rest is iron and unavoidable impurities.

[0040] The specific preparation steps are as follows:

[0041] 1) Billet preparation: Use a 160×160 (unit: mm) square billet with a smooth surface and no visible defects.

[0042] 2) Billet heating: The heating is divided into three stages. In the first stage, the temperature of the billet is raised to 800℃ at a rate of 11℃ / min and kept at 800±20℃ for 16min. In the second stage, the temperature is raised to 1000℃ at a rate of 9℃ / min and kept at 1000±15℃ for 15min. In the third stage, the temperature is raised to 1060℃ at a rate of 7℃ / min and kept at 1060±10℃ for 23min.

[0043] 3) High-speed rolling: The rolling process includes 6 passes of rough rolling → No. 1 flying shear → 12 passes of intermediate rolling → No. 2 flying shear → 6 passes of pre-finishing rolling → No. 3 flying shear → 10 passes of finishing rolling → wire laying, the maximum rolling reduction of each pass is 30%, the starting rolling temperature is 1055°C, the finishing rolling temperature is controlled at 860°C, the wire laying temperature is 856°C, the final rolling speed is 63m / s, the No. 1 flying shear only cuts 130mm at the head, the No. 2 flying shear cuts 280mm at the head and tail, and the No. 3 flying shear cuts 400mm at the head and tail.

[0044] 4) Controlled cooling: After spinning, all the insulation covers of the Stelmore air cooling line are opened, and the air volume is adjusted to achieve rapid cooling. The average cooling rate is 9°C / S. The wire is cooled to a temperature of 230°C and rolled up. After rolling up, it is naturally cooled to room temperature.

[0045] The surface macroscopic picture of the soft magnetic stainless steel wire rod in this embodiment is as follows: Figure 2 As shown, the surface is excellent, the rolling yield, plasticity and mechanical properties are shown in Table 1, and the core metallographic structure is shown in Figure 3 As shown, the heart tissue is uniform.

[0046] Embodiment 2:

[0047] The rolled product in this embodiment is Φ12mm soft magnetic stainless steel 430FR, and the chemical composition, by weight, includes C: 0.012%, Si: 1.35%, Mn: 0.4%, P: 0.032%, S: 0.21%, Ni: 0.20%, Cr: 17.8%, N: 0.034%, Ti: 0.21%. The specific preparation steps are as follows:

[0048] 1) Billet preparation: Use a 180×180 (unit: mm) square billet with a smooth surface and no visible defects.

[0049] 2) Billet heating: The heating is divided into three stages. In the first stage, the temperature of the billet is raised to 800℃ at a rate of 12℃ / min and kept at 800±20℃ for 19min. In the second stage, the temperature is raised to 1000℃ at a rate of 10℃ / min and kept at 1000±15℃ for 18min. In the third stage, the temperature is raised to 1060℃ at a rate of 8℃ / min and kept at 1060±10℃ for 24min.

[0050] 3) High-speed rolling: The rolling process includes 6 passes of rough rolling → No. 1 flying shear → 12 passes of medium rolling → No. 2 flying shear → 6 passes of pre-finishing rolling → No. 3 flying shear → 10 passes of finishing rolling → wire laying, the maximum rolling reduction of each pass is 28%, the starting rolling temperature is 1075°C, the finishing rolling temperature is controlled at 880°C, the wire laying temperature is 870°C, the final rolling speed is 25m / s, No. 1 flying shear only cuts 180mm at the head, No. 2 flying shear cuts 230mm at the head and tail, and No. 3 flying shear cuts 350mm at the head and tail.

[0051] 4) Controlled cooling: After spinning, all the insulation covers of the Stelmore air cooling line are opened, and the air volume is adjusted to achieve rapid cooling. The average cooling rate is 10℃ / S. The wire is cooled to a temperature of 240℃ and rolled up. After rolling up, it is naturally cooled to room temperature.

[0052] The surface macroscopic picture of the soft magnetic stainless steel wire rod in this embodiment is as follows: Figure 4 As shown, the surface is excellent, and the rolling yield, plasticity and mechanical properties are shown in Table 1.

[0053] Embodiment 3:

[0054] The soft magnetic stainless steel MGC with a specification of Φ15 mm is rolled in this embodiment. The chemical composition, in terms of weight percent, includes C: 0.019%, Si: 0.85%, Mn: 0.45%, P: 0.020%, S: 0.30%, Ni: 0.15%, Cr: 17.9%, N: 0.02%, Nb: 0.27%. The specific preparation steps are as follows:

[0055] 1) Blank preparation: Use a 150×150 (unit: mm) round blank with a smooth surface and no defects visible to the naked eye.

[0056] 2) Billet heating: The heating is divided into three stages. In the first stage, the temperature of the billet is raised to 800℃ at a rate of 15℃ / min and kept at 800±20℃ for 23min. In the second stage, the temperature is raised to 1000℃ at a rate of 8℃ / min and kept at 1000±15℃ for 23min. In the third stage, the temperature is raised to 1060℃ at a rate of 6℃ / min and kept at 1060±10℃ for 22min.

[0057] 3) High-speed rolling: The rolling process includes 6 rough rolling passes → No. 1 flying shear → 12 intermediate rolling passes → No. 2 flying shear → 6 pre-finishing rolling passes → No. 3 flying shear → 10 finishing rolling passes → wire laying, the maximum rolling reduction for each pass is 26%, the starting rolling temperature is 1070°C, the finishing rolling temperature is controlled at 885°C, the wire laying temperature is 872°C, the final rolling speed is 17m / s, No. 1 flying shear only cuts 200mm at the head, No. 2 flying shear cuts 280mm at the head and tail, and No. 3 flying shear cuts 460mm at the head and tail.

[0058] 4) Controlled cooling: After spinning, all the insulation covers of the Stelmore air cooling line are opened, and the air volume is adjusted to achieve rapid cooling. The average cooling rate is 8°C / S. The wire is cooled to a temperature of 200°C and rolled up. After rolling up, it is naturally cooled to room temperature.

[0059] The soft magnetic stainless steel wire rod of this embodiment has a good surface, and the rolling yield, plasticity and mechanical properties are shown in Table 1.

[0060] Embodiment 4:

[0061] The rolled product in this embodiment is Φ8mm soft magnetic stainless steel 00Cr13Si2, and the chemical composition, by weight, includes C: 0.025%, Si: 1.7%, Mn: 0.48%, P: 0.018%, S: 0.05%, Ni: 0.2%, Cr: 13.5%, N≤0.02%. The specific preparation steps are as follows:

[0062] 1) Blank preparation: Use a 180×180 (unit: mm) round blank with a smooth surface and no defects visible to the naked eye.

[0063] 2) Billet heating: The heating is divided into three stages. In the first stage, the temperature of the billet is raised to 800℃ at a rate of 13℃ / min and kept at 800±20℃ for 20min. In the second stage, the temperature is raised to 1000℃ at a rate of 9℃ / min and kept at 1000±15℃ for 20min. In the third stage, the temperature is raised to 1060℃ at a rate of 7℃ / min and kept at 1060±10℃ for 20min.

[0064] 3) High-speed rolling: The rolling process includes 6 rough rolling passes → No. 1 flying shear → 12 intermediate rolling passes → No. 2 flying shear → 6 pre-finishing rolling passes → No. 3 flying shear → 10 finishing rolling passes → wire laying, the maximum rolling reduction for each pass is 29%, the starting rolling temperature is 1055°C, the finishing rolling temperature is controlled at 858°C, the wire laying temperature is 860°C, the final rolling speed is 51m / s, the No. 1 flying shear only cuts 150mm at the head, the No. 2 flying shear cuts 230mm at the head and tail, and the No. 3 flying shear cuts 400mm at the head and tail.

[0065] 4) Controlled cooling: After spinning, all the insulation covers of the Stelmore air cooling line are opened, and the air volume is adjusted to achieve rapid cooling. The average cooling rate is 9°C / S. The wire is cooled to a temperature of 200°C and rolled up. After rolling up, it is naturally cooled to room temperature.

[0066] The surface of the soft magnetic stainless steel wire rod in this embodiment is excellent, and the rolling yield, plasticity and mechanical properties are shown in Table 1. The core structure picture is as follows Figure 5 As shown, the core structure is uniform. The core structure of the same steel produced by conventional process is shown in Figure 6 As shown, the heart tissue is coarse and very uneven.

[0067] Table 1

[0068]

[0069] In summary, when the soft magnetic stainless steel wire rod is prepared by the method of the present invention, no cracking occurs during rolling, the rolling yield is improved, and the comprehensive rolling yield is ≥96%; the prepared soft magnetic stainless steel wire rod has excellent surface quality, solves the problem of uneven metallographic structure in the core of the soft magnetic stainless steel wire rod, has excellent plasticity and mechanical properties, tensile strength ≤580MPa, elongation ≥25%, and surface shrinkage ≥50%.

[0070] The above-described embodiments are only preferred solutions of the present invention and are not intended to limit the present invention in any form. Other variations and modifications are possible without exceeding the technical solutions described in the claims.

Claims

1. A high-speed wire rolling method for soft magnetic stainless steel wire rod, characterized in that: The following steps are involved: (1) Billet heating: The billet is heated in three stages: in the first stage, the billet is heated to 800±20°C at a rate of 10-15°C / min and kept at this temperature for 15-25min; in the second stage, the billet is heated to 1000±15°C at a rate of 8-10°C / min and kept at this temperature for 15-25min; in the third stage, the billet is heated to 1060±10°C at a rate of 6-8°C / min and kept at this temperature for 20-25min; wherein the billet is a square billet of 160×160-180×180 mm or a round billet of Φ150-Φ180 mm; (2) High-speed rolling: The heated billet is rolled and laid by a rough rolling mill, No. 1 flying shear, intermediate rolling mill, No. 2 flying shear, pre-finishing rolling mill, No. 3 flying shear, finishing rolling mill and laying mill, and the rolling reduction of each pass is controlled to be no more than 35%; (3) Cooling: After rolling, the steel is rapidly cooled to a temperature not higher than 250°C to obtain a soft magnetic stainless steel wire rod; Wherein, in the step (2), the starting rolling temperature is 1050-1080°C, the temperature of the finishing mill is controlled at 850-900°C, and the spinning temperature is 850-880°C; In the step (2), the final rolling speed is controlled as follows: for specifications of Φ5.5-Φ8.0 mm: 50-65 m / s; for specifications of >Φ8.0-Φ11.0 mm: 30-48 m / s; for specifications of >Φ11.0-Φ14.0 mm: 20-28 m / s; for specifications of >Φ14.0-Φ20.0 mm: 10-18 m / s; The cooling rate of the rapid cooling in step (3) is not less than 8°C / s.

2. A high-speed wire rolling method for soft magnetic stainless steel wire rod according to claim 1, characterized in that: In the step (1), the surface of the blank is smooth and has no defects visible to the naked eye.

3. A high-speed wire rolling method for soft magnetic stainless steel wire rod according to claim 1, characterized in that: In the step (1), the temperature of the blank is raised to 800°C at a rate of 10-15°C / min, and kept at 800±20°C for 15-25min; the temperature is raised to 1000°C at a rate of 8-10°C / min, and kept at 1000±15°C for 15-25min; the temperature is raised to 1060°C at a rate of 6-8°C / min, and kept at 1060±10°C for 20-25min.

4. A high-speed wire rolling method for soft magnetic stainless steel wire rod according to claim 1, characterized in that: The high-speed rolling in step (2) includes 6 passes of rough rolling, flying shearing with No. 1 flying shear, 12 passes of intermediate rolling, flying shearing with No. 2 flying shear, 6 passes of pre-finishing rolling, flying shearing with No. 3 flying shear, 10 passes of finishing rolling and wire laying.

5. The high-speed wire rolling method of soft magnetic stainless steel wire rod according to claim 1, characterized in that: In the step (2), the cutting head of No. 1 flying shear is 100-200 mm, the cutting head and tail of No. 2 flying shear are 200-300 mm, and the cutting head and tail of No. 3 flying shear are 350-500 mm.

6. A high-speed wire rolling method for soft magnetic stainless steel wire rod according to claim 1, characterized in that: The soft magnetic stainless steel wire rod has a specification of Φ5.5 to Φ20 mm.

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