Processing technology of fine blanking steel for seat adjuster

Abstract

The invention discloses a processing technology of fine blanking steel for a seat adjuster, which comprises the following steps: S1, longitudinal shearing: longitudinally cutting a hot-rolled strip steel wide coil into narrow strip steel through a pair of disc scissors; s2, acid pickling is conducted, specifically, iron rust and oxide skin on the surface of the narrow strip steel are removed through acid pickling; s3, calendaring: calendaring the pickled narrow strip steel by adopting a large compression ratio of 40-60%; s4, spheroidizing annealing is conducted, specifically, the narrow strip steel treated in the step S3 is heated to the annealing temperature, heat preservation is conducted, and then furnace cooling is conducted to the room temperature; the annealing temperature is lower than the critical temperature of the narrow strip steel; and S5, flattening is conducted, specifically, the narrow strip steel obtained after spheroidizing annealing is rolled with the small compression ratio smaller than or equal to 3%, and the fine blanking steel for the seat adjuster is obtained. By means of the method, banded structures can be reduced or even eliminated, carbide distribution is homogenized, the stability of the stamped part in the heat treatment process is guaranteed, and the defects such as breakage of the stamped part are avoided.

Description

Technical Field

[0001] The present invention relates to the field of fine blanking steel processing, and more specifically, to a processing technology for fine blanking steel used in seat regulators. Background Art

[0002] Fine blanking belongs to non-chip processing technology and is a precision blanking method developed on the basis of ordinary punching technology. It can obtain high-quality fine blanking parts with higher dimensional accuracy, smoother blanking surfaces, less warping, and better interchangeability than ordinary punching parts in one stamping stroke, and improve product quality at a lower cost. At present, three major fine blanking part manufacturing centers, namely Europe, the United States, and Japan, have been formed in the world, and a complete fine blanking industrial chain has been formed.

[0003] Fine blanking materials are one of the core elements of fine blanking technology. The seat regulator, as the core part of the seat, is precisely processed by the fine blanking process. However, at present, defects such as fracture often occur during the heat treatment process after material stamping. After a large number of part failure analyses, the reason for such defects lies in the uneven distribution of carbides, that is, obvious banded structures exist.

[0004] In view of the above situation, it is urgent to study a processing technology for fine blanking steel used in seat regulators, which can solve the problem of fracture failure during the heat treatment process of parts after stamping caused by the uneven distribution of carbides. Summary of the Invention

[0005] Aiming at the above-mentioned defects existing in the prior art, the purpose of the present invention is to provide a processing technology for fine blanking steel used in seat regulators, which can reduce or even eliminate banded structures, make the distribution of carbides uniform, ensure the stability of the heat treatment process of parts after stamping, and avoid defects such as fracture of parts after stamping.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions:

[0007] The present invention provides a processing technology for fine blanking steel used in seat regulators, including the following steps:

[0008] S1, slitting longitudinally, slitting the wide coil of hot-rolled strip steel into narrow strip steel by a circular shear;

[0009] S2, pickling, removing rust and scale on the surface of the narrow strip steel by pickling;

[0010] S3, rolling, rolling the pickled narrow strip steel with a large reduction ratio of 40 - 60%;

[0011] S4, spheroidizing annealing, heating the narrow strip steel processed in step S3 to the annealing temperature and holding for a certain time, and then cooling it in the furnace to room temperature; the annealing temperature is lower than the critical temperature of the narrow strip steel;

[0012] S5. Flattening: The narrow strip steel after spheroidizing annealing is rolled with a small reduction ratio of ≤3% to obtain fine blanking steel for seat adjusters.

[0013] Preferably, in the step S1, during the hot rolling and slitting process, the width of the wide coil of the hot rolled strip steel is 1000 - 1500 mm, and the width of the narrow strip steel ≤550 mm.

[0014] Preferably, in the step S2, hydrochloric acid is used during the pickling process, and its concentration is 15 - 30 wt%.

[0015] Preferably, in the step S3, the surface roughness R of the rolling rolls used during the rolling process a is 1.0 - 2.0.

[0016] Preferably, in the step S4, during the spheroidizing annealing process, the annealing temperature is 680 - 700 °C, and the holding time is 30 ± 5 h.

[0017] Preferably, in the step S5, the surface roughness R of the rolling rolls used during the rolling process a is 1.0 - 2.0.

[0018] Preferably, the spheroidization rate of the fine blanking steel for seat adjusters reaches over 95%, and the banded structure ≤ grade 1.

[0019] The present invention has the following beneficial effects:

[0020] 1. The processing technology of the fine blanking steel for seat adjusters of the present invention, by adopting a large reduction ratio in the rolling ratio, maximally eliminates the influence of the banded structure of the base material, and greatly reduces the risk of the banded structure being inherited to the finished product;

[0021] 2. The processing technology of the fine blanking steel for seat adjusters of the present invention, during the spheroidizing annealing treatment process, adopts a long-time holding at a temperature below the critical temperature, which not only ensures a spheroidization rate of over 95% and mechanical properties of the fine blanking steel, but also greatly improves the uniformity of the spheroidized structure and reduces the risk of the banded structure;

[0022] 3. The processing technology of the fine blanking steel for seat adjusters of the present invention, through processes such as hot rolling and slitting, pickling, rolling, spheroidizing annealing, and flattening, ensures the mechanical properties while reducing the banded distribution of carbides, and finally greatly reduces the cracking risk of the material after stamping and heat treatment. Specific Embodiments

[0023] In order to better understand the above technical solutions of the present invention, the following further illustrates the technical solutions of the present invention in combination with embodiments.

[0024] A processing technology of fine blanking steel for seat adjusters of the present invention includes the following steps:

[0025] S1, Slitting longitudinally: longitudinally slit the wide coil of hot-rolled strip into narrow strip steel by using circular shears.

[0026] Specifically, use circular shears to longitudinally slit and divide the wide coil of hot-rolled strip with a width of 1200 - 1500 mm into narrow strip steel with a width ≤ 550 mm. The specific dimensions will be set according to the side wire ratio and the width required by the user. Among them, the wide coil of hot-rolled strip can use hot-rolled strip with the grade of 20MnB5, and its components are shown in the following table:

[0027] C Si Mn P S Cr Al B N 0.12-0.23％ ≤0.5％ 0.9-1.4％ ≤0.035％ ≤0.04％ ≤0.35％ ≤0.06％ 0.0008-0.0005％ ≤0.006％

[0028] S2, Pickling: remove the rust and scale on the surface of the narrow strip steel by pickling.

[0029] Specifically, use hydrochloric acid to pickle the narrow strip steel processed in step S1. The purpose is to remove the rust and hot-rolled scale on its surface through the oxidation reaction between hydrochloric acid and the surface of the narrow strip steel to ensure the surface quality of the subsequent rolling process. Among them, the concentration of hydrochloric acid is 10 - 30 wt%.

[0030] S3, Rolling: roll the pickled narrow strip steel with a large reduction ratio of 40 - 60%.

[0031] Specifically, use a rolling mill to roll the pickled narrow strip steel back and forth and finally roll it into the target thickness. Among them, the rolling mill can use a single-stand reversible rolling mill, and the surface roughness R of the rolls on the rolling mill a is 1.0 - 2.0. The main purpose is to prevent the roughness of the copied plate surface from being too low, resulting in sticking phenomenon during the annealing process. In a specific embodiment, control the gap between the upper and lower rolls of the rolling mill to ensure the thickness of the rolled narrow strip steel. During the rolling process, control the large reduction ratio to be 40 - 60%. The main purpose is to refine the grains, destroy the original banded structure, prepare for spheroidizing annealing, and reduce the thickness fluctuation.

[0032] S4, Spheroidizing annealing: heat the narrow strip steel processed in step S3 to the annealing temperature and keep it warm, and then cool it in the furnace to room temperature; the annealing temperature is less than the critical temperature of the narrow strip steel.

[0033] Specifically, the narrow strip steel after calendering is heated to the annealing temperature and held for a certain time, and then cooled in the furnace to room temperature to obtain the fine blanking steel for seat adjusters. Among them, the annealing temperature during the annealing process is lower than the critical temperature of the narrow strip steel (the critical temperature of the narrow strip steel is 720 °C - 750 °C). In this process, a structure with spherical or granular carbides uniformly distributed on the ferrite matrix is mainly obtained, thereby reducing hardness, increasing toughness, and improving the cutting performance. The annealing temperature is mainly below the critical temperature to prevent the appearance of lamellar pearlite. Because after the carbide dissolves sufficiently above the critical temperature, during the subsequent slow cooling process, due to the lack of core carbides in some areas, cores have to be regenerated in the relatively uniform austenite, resulting in the appearance of lamellar pearlite. Therefore, in a specific embodiment, the annealing temperature is 680 - 700 °C, and the holding time is 30 ± 5 h.

[0034] S5, leveling, the narrow strip steel after spheroidizing annealing is rolled with a small reduction ratio of ≤ 3% to obtain the fine blanking steel for seat adjusters.

[0035] Specifically, the narrow strip steel after spheroidizing annealing is rolled by a rolling mill to the final finished thickness. Among them, a single-stand reversible rolling mill can be used for the rolling mill, and the surface roughness of the rolls used on the rolling mill is guaranteed to be Ra ≤ 0.4, mainly to ensure that the surface roughness of the final product meets the customer requirements. Among them, the thickness of the narrow strip steel after rolling is ensured by controlling the gap between the upper and lower rolls of the rolling mill. During the rolling process, the reduction ratio is controlled to be ≤ 1.5%.

[0036] The spheroidization rate of the fine blanking steel for seat adjusters prepared by the above processing technology reaches more than 95%, and its banded structure is ≤ grade 1, greatly reducing the risk of heat treatment cracking of the parts after stamping.

[0037] The processing technology of the fine blanking steel for seat adjusters of the present invention will be further introduced below with specific examples.

[0038] Example 1

[0039] The processing technology of the fine blanking steel for seat adjusters in this example is as follows:

[0040] (1) Select a hot-rolled strip steel wide coil with a grade of 20MnB5, a width of 1000 mm, and a thickness of 7.5 mm. The preliminarily spheroidized wide coil strip steel is longitudinally cut into narrow strip steel with a width of 500 ± 2 mm by a circular shear.

[0041] (2) The narrow strip steel is pickled with hydrochloric acid with a concentration of 15% to remove the rust and hot-rolled scale on its surface.

[0042] (3) The pickled narrow strip steel is rolled back and forth with rolls of Ra2.0 until the target thickness of 4.5 mm. The reduction ratio during the rolling process is 40%.

[0043] (4) Heat the hot-rolled strip after rolling to 700 °C and hold for 25 h, then cool it in the furnace to obtain fully spheroidized narrow strip steel;

[0044] (5) Roll the fully spheroidized annealed narrow strip steel once with a roll of Ra0.3 to the finished thickness of 4.48 mm. The reduction ratio used in this process is 0.5%, and the thickness tolerance reaches within ±0.03 mm.

[0045] In this example, the spheroidization rate of the fine blanking steel for seat adjusters prepared reaches 95 - 100%, and its banded structure is grade 0. The parts of the fine blanking steel for seat adjusters do not show fracture failure during the heat treatment process.

[0046] Example 2

[0047] The processing technology of the fine blanking steel for seat adjusters in this example is as follows:

[0048] (1) Select a wide coil of hot-rolled strip with a grade of 20MnB5, a width of 1200 mm, and a thickness of 11.0 mm. Longitudinally cut and strip the preliminarily spheroidized wide coil strip into narrow strip steel with a width of 400 ± 2 mm through a circular shear;

[0049] (2) Pickle the narrow strip steel with 20% hydrochloric acid to remove the rust and hot-rolled oxide scale on its surface;

[0050] (3) Roll the pickled narrow strip steel back and forth with a roll of Ra1.5 until the target thickness of 4.5 mm. The reduction ratio during the rolling process is 59%;

[0051] (4) Heat the hot-rolled strip after rolling to 680 °C and hold for 35 h, then cool it in the furnace to obtain fully spheroidized narrow strip steel;

[0052] (5) Roll the fully spheroidized annealed narrow strip steel once with a roll of Ra0.3 to the finished thickness of 4.48 mm. The reduction ratio used in this process is 0.5%, and the thickness tolerance reaches within ±0.03 mm.

[0053] In this example, the spheroidization rate of the fine blanking steel for seat adjusters prepared reaches 95 - 100%, and its banded structure is grade 0. The parts of the fine blanking steel for seat adjusters do not show fracture failure during the heat treatment process.

[0054] Example 3

[0055] The processing technology of the fine blanking steel for seat adjusters in this example is as follows:

[0056] (1) Select a hot-rolled strip coil with a grade of 20MnB5, a width of 1500 mm, and a thickness of 9.0 mm. Longitudinally cut and strip the preliminarily spheroidized strip coil into narrow strip steel with a width of 300 ± 2 mm using a circular shear;

[0057] (2) Pickle the narrow strip steel with hydrochloric acid with a concentration of 30% to remove the rust and hot-rolled oxide scale on its surface;

[0058] (3) Roll the pickled narrow strip steel back and forth with a roll with a Ra of 1.0 until the target thickness of 4.5 mm is reached. The compression ratio during the rolling process is 50%;

[0059] (4) Heat the hot-rolled strip steel after rolling to 690 °C and hold it for 30 h, and then cool it in the furnace to obtain fully spheroidized narrow strip steel;

[0060] (5) Roll the fully spheroidized and annealed narrow strip steel once with a roll with a Ra of 0.3 to the finished thickness of 4.48 mm. The compression ratio used in this process is 0.5%, and the thickness tolerance reaches within ±0.03 mm.

[0061] In this embodiment, the spheroidization rate of the fine blanking steel for seat adjusters prepared reaches 95 - 100%, and its banded structure is grade 0. The parts of the fine blanking steel for seat adjusters do not undergo fracture failure during the heat treatment process after stamping.

[0062] In summary, the processing technology of the fine blanking steel for seat adjusters of the present invention can reduce or even eliminate the banded structure, make the carbide distribution uniform, ensure the stability of the heat treatment process of the parts after stamping, and avoid defects such as fracture of the parts after stamping.

[0063] It should be noted that those of ordinary skill in the art in this technical field should recognize that the above embodiments are only used to illustrate the present invention and are not used to limit the present invention. As long as it is within the scope of the essential spirit of the present invention, changes and modifications to the above embodiments will fall within the scope of the claims of the present invention.

Claims

1. Processing technology of fine blanking steel for seat adjuster, characterized in that, it includes the following steps: S1, longitudinal shearing, longitudinally shearing the wide coil of hot-rolled strip steel into narrow strip steel by a circular saw; S2, pickling, removing rust and scale on the surface of the narrow strip steel by pickling; S3, rolling, rolling the pickled narrow strip steel with a large reduction ratio of 40-60%; S4, spheroidizing annealing, heating the narrow strip steel processed in step S3 to the annealing temperature and holding for a period, and then cooling in the furnace to room temperature; the annealing temperature is lower than the critical temperature of the narrow strip steel; S5, temper rolling, rolling the narrow strip steel after spheroidizing annealing with a small reduction ratio of ≤3% to obtain fine blanking steel for seat adjuster.

2. The processing technology of fine blanking steel for seat adjuster according to claim 1, characterized in that, in step S1, during the hot-rolling longitudinal shearing process, the width of the wide coil of hot-rolled strip steel is 1000-1500 mm, and the width of the narrow strip steel ≤550 mm.

3. The processing technology of fine blanking steel for seat adjuster according to claim 1, characterized in that, in step S2, hydrochloric acid is used during the pickling process, and its concentration is 15-30 wt%.

4. The processing technology of fine blanking steel for seat adjuster according to claim 1, characterized in that, In the step S3, the surface roughness R of the rolling rolls used in the rolling process a is 1.0 to 2.

0.

5. The processing technology of fine blanking steel for seat adjuster according to claim 1, characterized in that, in step S4, during the spheroidizing annealing process, the annealing temperature is 680-700 °C, and the holding time is 30±5 h.

6. The processing technology of fine blanking steel for seat adjuster according to claim 1, characterized in that, In the step S5, the surface roughness R of the rolling roll used in the rolling process a is 1.0 to 2.

0.

7. The processing technology of fine blanking steel for seat adjuster according to any one of claims 1-6, characterized in that, the spheroidization rate of the fine blanking steel for seat adjuster reaches more than 95%, and the banded structure ≤ grade 1.