A wide bearing steel strip and its manufacturing method

Abstract

The present invention relates to the field of steel production technology, and in particular to a wide bearing steel strip and a manufacturing method thereof. The method comprises: subjecting a continuous casting billet that meets the GCr15 steel composition requirements to heat treatment; subjecting the heat-treated continuous casting billet to hot rolling treatment to obtain an initial steel strip; the reduction amount of the continuous casting billet during the rough rolling process accounts for more than 70% of the total reduction amount of the continuous casting billet during the hot rolling process; during the rough rolling process, the single-pass reduction rate is 18-40%; the initial steel strip is cooled to a coiling temperature and then coiled to obtain a wide bearing steel strip; the width of the steel strip is 1000-1400 mm, the thickness is 3.6-10 mm, the cooling rate is 10-20°C / s, and the coiling temperature is 580-620°C. The wide bearing steel strip obtained by the method of the present invention has a more uniform structure, no network cementite in the structure, better plastic deformation performance, and is more suitable for cold forming such as stamping.

Description

Technical Field

[0001] The present invention relates to the technical field of steel production, and in particular to a wide bearing steel strip and a manufacturing method thereof. Background Art

[0002] With the rapid development of the manufacturing industry, the demand for steel for bearings and bearing rings is increasing. Bearing rings can be made from round steel or wire through forging, annealing, turning, quenching and tempering, grinding, and assembly. This process for producing bearing rings has the disadvantages of lengthy processes, low efficiency, and high costs. The recently developed cold stamping process for producing bearing rings offers the advantages of simplified production processes, high efficiency, and low energy consumption. The raw material used is now bearing steel strip, rather than round steel or wire. Bearing steel used to produce bearing rings must exhibit excellent stamping properties. However, only a few companies are currently capable of producing narrow widths (<1000mm) of bearing steel strip, which results in high production efficiency and costs. Therefore, there is a need to develop wider widths of bearing steel strip for the production of stamped bearing rings. Existing wide bearing steel strips produced using existing technologies exhibit uneven microstructure and mechanical properties. The presence of network carbides in the microstructure increases the steel strip's strength and reduces its plastic deformation properties, making it unsuitable for cold forming processes such as stamping. Summary of the Invention

[0003] The technical problem solved by the present invention is that the wide bearing steel strip produced by the existing technology has uneven structure and mechanical properties. The network carbides present in the structure will increase the strength of the steel strip and reduce the plastic deformation performance of the steel strip, making the steel strip unsuitable for cold forming such as stamping.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0005] A method for manufacturing a wide bearing steel strip, comprising:

[0006] Step S1, heating the continuous casting billet that meets the GCr15 steel composition requirements;

[0007] Step S2, subjecting the continuous casting slab that has undergone the heating treatment to hot rolling to obtain an initial steel strip; wherein the hot rolling treatment includes a rough rolling treatment and a finish rolling treatment, and the reduction of the continuous casting slab during the rough rolling treatment accounts for more than 70% of the total reduction of the continuous casting slab during the hot rolling treatment; the rough rolling treatment is performed in multiple passes, and the reduction rate of each pass is 18-40%;

[0008] Step S3: Cool the initial steel strip to the coiling temperature and then coil it to obtain a wide bearing steel strip; wherein the width of the wide bearing steel strip is 1000-1400 mm, the thickness is 3.6-10 mm, the cooling rate is 10-20°C / s, and the coiling temperature is 580-620°C.

[0009] Preferably, in step S2, six rough rolling passes are performed during the rough rolling process, wherein the reduction ratio of each of the first three rough rolling passes is 18-21%, and the reduction ratio of each of the last three rough rolling passes is 30-40%.

[0010] Preferably, in the step S2, 7 passes of finishing rolling are performed during the finishing rolling process, wherein the reduction ratio of each of the first 4 passes of finishing rolling is 25-43%.

[0011] Preferably, the reduction rate of each of the last three finishing passes is 10-20% and decreases in order from front to back, the total reduction rate of the last three finishing passes is 45-50%, and the reduction rate of each of the seventh finishing passes is 10-11%.

[0012] Preferably, in step S2, the starting rolling temperature of the rough rolling process is 1110-1170°C, and the finishing rolling temperature is 1060-1080°C.

[0013] Preferably, in step S2, the start rolling temperature of the finishing rolling process is 1000-1050°C, and the final rolling temperature is 830-870°C.

[0014] Preferably, in step S1, the temperature of the heating treatment is 1110-1170° C., the time is 160-200 min, and the soaking time is 30-40 min.

[0015] Preferably, the method for manufacturing the wide bearing steel strip further comprises: slowly cooling the wide bearing steel strip obtained in step S3 to 400-500° C., wherein the slow cooling rate is less than 1° C. / s.

[0016] The present invention also provides a wide-width bearing steel strip, which is manufactured according to the manufacturing method of the wide-width bearing steel strip as described above.

[0017] Preferably, the components of the GCr15 wide-width bearing steel strip include, by weight percentage: C: 0.99-1.06%, Si: 0.21-0.32%, Mn: 0.26-0.45%, S: 0-0.050%; P: 0-0.015%, Cr: 1.50-1.65%, Al: 0.020-0.045%, O: 0-0.0012%, N: 0-0.0050%, and the balance is Fe and unavoidable impurities.

[0018] Compared with the prior art, the present invention controls the reduction of the continuous casting slab during the rough rolling process of hot rolling to account for more than 70% of the total reduction of the continuous casting slab during the hot rolling process; through the deformation of the large reduction during the rough rolling process, it is ensured that the continuous casting slab can also obtain sufficient deformation in the width direction, reducing the difference in its structure in the width direction and improving the uniformity of the structure; the single-pass reduction rate during the rough rolling process is controlled to 18-40%; the higher single-pass reduction rate during the rough rolling process helps to increase the deformation penetration of the continuous casting slab in the thickness direction, thereby reducing the uneven deformation in the thickness direction, and further improving the uniformity of the structure. The present invention can effectively suppress the precipitation of carbides by setting a high cooling rate (10-20℃ / s) after hot rolling. When the cooling rate is ≥10℃ / s, the precipitation of carbides can be completely suppressed, thereby improving the plastic deformation performance of the wide-width bearing steel strip. Controlling the final cooling temperature to 580-620°C facilitates the formation of pearlite in wide bearing steel strips. This prevents the problem of the wide bearing steel strips transforming into bainite or martensite due to excessively low final cooling temperatures, which in turn increases the strip's strength and makes it less suitable for cold forming applications such as stamping. As can be seen, the wide bearing steel strips produced using the method of the present invention have a more uniform structure, lack network cementite, and exhibit better plastic deformation properties, making them more suitable for cold forming applications such as stamping. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a flow chart of preparing a wide bearing steel strip in an embodiment of the present invention;

[0020] Figure 2 This is the metallographic structure diagram of the wide bearing steel strip finally obtained in Example 1;

[0021] Figure 3 This is the metallographic structure diagram of the wide bearing steel strip finally obtained in Example 2;

[0022] Figure 4 This is the metallographic structure diagram of the wide bearing steel strip finally obtained in Example 3. DETAILED DESCRIPTION

[0023] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0024] It should be noted that, in the absence of conflict, the features in the embodiments of the present invention can be combined with each other. The terms "comprise", "include", "contain", and "have" are non-restrictive, that is, other steps and other ingredients that do not affect the results may be added. The above terms cover the terms "consisting of..." and "essentially consisting of...". Unless otherwise specified, materials, equipment, and reagents are all commercially available. It should be noted that, assuming that the thickness of the continuous casting billet before a certain pass of rolling is M0, and the thickness is reduced to M1 after the pass of rolling, the single pass reduction rate = (M0-M1) / M0, for example, the thickness of the continuous casting billet before the first pass of rough rolling is 100mm, the thickness after the first pass of rough rolling is 80mm, and the thickness after the second pass of rough rolling is 60mm, then the single pass reduction rate of the first pass of rough rolling = (100-80) / 100, and the single pass reduction rate of the second pass of rough rolling = (80-60) / 80.

[0025] like Figure 1 As shown, an embodiment of the present invention provides a method for manufacturing a wide bearing steel strip, comprising:

[0026] Step S1, heating the continuous casting billet that meets the GCr15 steel composition requirements;

[0027] Step S2, performing hot rolling on the continuous casting billet after the heating treatment to obtain an initial steel strip, wherein the hot rolling treatment includes a rough rolling treatment and a finish rolling treatment, and the reduction of the continuous casting billet during the rough rolling treatment accounts for more than 70% of the total reduction of the continuous casting billet during the hot rolling treatment; the rough rolling treatment is performed in multiple passes, and the reduction rate of each pass is 18-40%;

[0028] Step S3: Cool the initial steel strip to the coiling temperature and then coil it to obtain a wide bearing steel strip; wherein the width of the wide bearing steel strip is 1000-1400 mm, the thickness is 3.6-10 mm, the cooling rate is 10-20°C / s, and the coiling temperature is 580-620°C.

[0029] Compared with the prior art, the present invention controls the reduction of the continuous casting slab during the rough rolling process of hot rolling to account for more than 70% of the total reduction of the continuous casting slab during the hot rolling process; through the deformation of the large reduction during the rough rolling process, it is ensured that the continuous casting slab can also be fully deformed in the width direction, reducing the difference in its structure in the width direction and improving the uniformity of the structure; the single-pass reduction rate during the rough rolling process is controlled to 18-40%; the higher single-pass reduction rate during the rough rolling process helps to increase the deformation penetration of the continuous casting slab in the thickness direction, thereby reducing the uneven deformation in the thickness direction, and further improving the uniformity of the structure. The present invention effectively suppresses the precipitation of carbides by setting a high cooling rate after hot rolling (10-20℃ / s, the upper limit of the cooling rate is affected by the online cooling equipment and can generally be controlled at around 20℃ / s). When the cooling rate is ≥10℃ / s, the precipitation of carbides can be completely suppressed, thereby improving the plastic deformation performance of the wide bearing steel strip. Controlling the final cooling temperature to 580-620°C facilitates the formation of pearlite in wide bearing steel strips. This prevents the problem of the wide bearing steel strips transforming into bainite or martensite due to excessively low final cooling temperatures, which in turn increases the strip's strength and makes it less suitable for cold forming applications such as stamping. As can be seen, the wide bearing steel strips produced using the method of the present invention have a more uniform structure, lack network cementite, and exhibit better plastic deformation properties, making them more suitable for cold forming applications such as stamping.

[0030] In an embodiment of the present invention, preferably, in step S2, the starting rolling temperature of the rough rolling process is 1110-1170° C., and the finishing rolling temperature is 1060-1080° C. The rough rolling process is performed in six passes, wherein the first three passes have a single pass reduction of 18-21%, and the last three passes have a single pass reduction of 30-40%.

[0031] In an embodiment of the present invention, in step S2, the start rolling temperature of the finishing rolling process is 1000-1050°C, and the final rolling temperature is 830-870°C. The finishing rolling process involves seven passes of finishing rolling, wherein the reduction ratio for each of the first four passes is 25-43%, and the reduction ratio for each of the last three passes is 10-20%, decreasing sequentially from the first to the last. The total reduction ratio for the last three passes is 45-50%, and the reduction ratio for the seventh pass is 10-11%. In an embodiment of the present invention, the higher reduction ratio for each of the first four passes is set to reduce structural unevenness caused by partial recrystallization of the prior austenite, particularly in the widthwise direction. The reduction ratio for each of the first four passes is gradually reduced to improve plate shape. The total reduction ratio for the last three passes is controlled to accumulate sufficient structural defects and phase transformation driving force to facilitate grain refinement.

[0032] In an embodiment of the present invention, in step S1, the heat treatment temperature is 1110-1170°C, the duration is 160-200 minutes, and the soaking time is 30-40 minutes. Setting the heat treatment temperature to 1110-1170°C ensures that the alloying elements are dissolved in the austenite while also preventing the original austenite from growing. Controlling the soaking time to 30-40 minutes ensures uniform temperature of the ingot and also prevents coarsening of the austenite.

[0033] In an embodiment of the present invention, the method for manufacturing a wide bearing steel strip further includes: slowly cooling the wide bearing steel strip obtained in step S3 to 400-500°C, with the slow cooling rate being less than 1°C / s. This is because within the temperature range of 580-620°C, the bearing steel structure undergoes partial pearlite transformation; the remaining austenite can still undergo pearlite transformation at a relatively low cooling rate (1°C / s); if the cooling rate is further increased (>1°C / s), the remaining austenite will undergo bainite or martensite transformation, which is not conducive to improving the plastic deformation properties of the steel strip.

[0034] The present invention also provides a wide-width bearing steel strip, which is manufactured according to the manufacturing method of the wide-width bearing steel strip as described above.

[0035] In an embodiment of the present invention, the components of the wide bearing steel strip include, by weight percentage: C: 0.99-1.06%, Si: 0.21-0.32%, Mn: 0.26-0.45%, S: 0-0.050%; P: 0-0.015%, Cr: 1.50-1.65%, Al: 0.020-0.045%, O: 0-0.0012%, N: 0-0.0050%, and the remainder is Fe and unavoidable impurities.

[0036] The present invention will be further described below with reference to specific examples. It should be understood that these examples are only intended to illustrate the present invention and are not intended to limit the scope of the present invention.

[0037] Example 1

[0038] 1.1. A continuous casting billet having a width of 1400 mm and a thickness of 230 mm was subjected to a heat treatment at a temperature of 1110° C. for 200 min, with a soaking time of 40 min. The components of the continuous casting billet, calculated by weight percentage, included the following: C: 1.0%, Si: 0.26%, Mn: 0.35%, S: 0.025%; P: 0.013%, Cr: 1.58%, Al: 0.032%, O: 0.0010%, N: 0.0025%, with the balance being Fe and unavoidable impurities.

[0039] 1.2. Dephosphorizing the continuous casting slab after heat treatment and then performing hot rolling treatment to obtain an initial steel strip, wherein the hot rolling treatment includes rough rolling treatment and finish rolling treatment, the starting rolling temperature of the rough rolling treatment is 1110° C., the finishing rolling temperature is 1069° C., and 6 rough rolling passes are performed during the rough rolling process, and the single pass reduction rates of rough rolling passes 1 to 6 are 20.75% (reduction of 47.725 mm), 19.67% (reduction of 35.859 mm), 18.78% (reduction of 27.490 mm), 30.15% (reduction of 35.851 mm), 30.25% (reduction of 25.130 mm) and 3 7.33% (reduction of 21.630mm); the starting rolling temperature of the finishing rolling process is 1025°C, the final rolling temperature is 870°C, and 7 passes of finishing rolling are performed during the finishing rolling process. The single pass reduction rates of the finishing rolling passes 1 to 7 are 37.84% (reduction of 13.741mm), 33.51% (reduction of 7.408mm), 30.09% (reduction of 4.405mm), 24.69% (reduction of 2.546mm), 18.64% (reduction of 1.416mm), 15.63% (reduction of 0.940mm), and 10.73% (reduction of 0.532mm).

[0040] 1.3. Cool the initial steel strip to a coiling temperature and then coil it to obtain a wide bearing steel strip; wherein the thickness of the wide bearing steel strip is 4.5 mm, the cooling rate is 15°C / s, and the coiling temperature is 620°C.

[0041] 1.4. Slowly cool the obtained wide bearing steel strip to 450° C. at a slow cooling rate of 0.5° C. / s.

[0042] Example 2

[0043] 2.1. A continuous casting billet having a width of 1250 mm and a thickness of 230 mm was subjected to a heat treatment at a temperature of 1140° C. for 180 min, with a soaking time of 35 min. The components of the continuous casting billet, calculated by weight percentage, included the following: C: 1.0%, Si: 0.26%, Mn: 0.35%, S: 0.025%; P: 0.013%, Cr: 1.58%, Al: 0.032%, O: 0.0010%, N: 0.0025%, with the balance being Fe and unavoidable impurities.

[0044] 2.2. The continuous casting slab subjected to the heat treatment is dephosphorized and then subjected to hot rolling to obtain an initial steel strip, wherein the hot rolling treatment includes a rough rolling treatment and a finish rolling treatment, the start rolling temperature of the rough rolling treatment is 1140° C., the finish rolling temperature is 1072° C., and 6 rough rolling passes are performed during the rough rolling treatment, and the single pass reduction rates of the rough rolling passes 1 to 6 are 20.75% (reduction of 47.724 mm), 19.67% (reduction of 35.856 mm), 18.77% (reduction of 27.487 mm), 30.14% (reduction of 35.852 mm), 30.17% (reduction of 25.068 mm), and 3 7.17% (reduction of 21.566mm); the starting rolling temperature of the finishing rolling process is 1025°C, the final rolling temperature is 870°C, and 7 finishing rolling passes are performed during the finishing rolling process. The single-pass reduction rates of the finishing rolling passes 1 to 7 are 38.79% (reduction of 14.138mm), 35.55% (reduction of 7.650mm), 32.18% (reduction of 4.425mm), 26.57% (reduction of 2.508mm), 19.93% (reduction of 1.377mm), 16.58% (reduction of 0.897mm), and 11.91% (reduction of 0.529mm).

[0045] 2.3. Cool the initial steel strip to a coiling temperature and then coil it to obtain a wide bearing steel strip; wherein the wide bearing steel strip has a thickness of 4.0 mm, the cooling rate is 18°C / s, and the coiling temperature is 600°C.

[0046] 2.4. Slowly cool the obtained wide bearing steel strip to 420° C. at a slow cooling rate of 0.8° C. / s.

[0047] Example 3

[0048] 3.1. A continuous casting billet having a width of 1000 mm and a thickness of 230 mm was subjected to a heat treatment at a temperature of 1170° C. for 160 min, with a soaking time of 30 min. The components of the continuous casting billet, calculated by weight percentage, included the following: C: 1.0%, Si: 0.26%, Mn: 0.35%, S: 0.025%; P: 0.013%, Cr: 1.58%, Al: 0.032%, O: 0.0010%, N: 0.0025%, with the balance being Fe and unavoidable impurities.

[0049] 3.2. The continuous casting slab subjected to heat treatment is dephosphorized and then subjected to hot rolling treatment to obtain an initial steel strip, wherein the hot rolling treatment includes a rough rolling treatment and a finish rolling treatment, the start rolling temperature of the rough rolling treatment is 1170° C., the finish rolling temperature is 1078° C., and 6 rough rolling passes are performed during the rough rolling process, and the single pass reduction rates of the rough rolling passes 1 to 6 are 20.74% (reduction of 47.698 mm), 19.65% (reduction of 35.820 mm), 18.74% (reduction of 27.447 mm), 30.29% (reduction of 36.051 mm), 30.62% (reduction of 25.412 mm) and 3 9.15% (reduction of 22.541mm); the starting rolling temperature of the finishing rolling process is 1025°C, the final rolling temperature is 870°C, and 7 finishing rolling passes are performed during the finishing rolling process. The single-pass reduction rates of the finishing rolling passes 1 to 7 are 42.82% (reduction of 15.002mm), 37.79% (reduction of 7.856mm), 33.33% (reduction of 4.260mm), 27.96% (reduction of 2.393mm), 20.85% (reduction of 1.280mm), 17.43% (reduction of 0.826mm), and 11.38% (reduction of 0.444mm).

[0050] 3.3. Cool the initial steel strip to a coiling temperature and then coil it to obtain a wide bearing steel strip; wherein the wide bearing steel strip has a thickness of 3.5 mm, a cooling rate of 20°C / s, and a coiling temperature of 580°C.

[0051] 3.4. Slowly cool the obtained wide bearing steel strip to 500° C. at a slow cooling rate of 0.6° C. / s.

[0052] Experimental example

[0053] The metallographic structure analysis of the wide bearing steel strip finally obtained in Examples 1-3 is shown in the following table. Figure 2-4 ,from Figure 2-4 It can be seen that the microstructure of the wide bearing steel strips finally obtained in Examples 1-3 is ferrite and carbides, with no network cementite. Mechanical property testing of the wide bearing steel strips finally obtained in Examples 1-3 was performed, and the results are shown in Table 1. It can be seen that the mechanical properties of the wide bearing steel strips finally obtained in Examples 1-3 are suitable for cold forming processes such as stamping. It should be noted that the terms "left," "center," and "right" in Table 1 refer to the left, center, and right regions, respectively, of the wide bearing steel strips in the width direction.

[0054] Table 1

[0055]

[0056] In addition, it should be noted that, although the present invention is disclosed as above, the scope of protection of the present invention is not limited thereto. Those skilled in the art may make various changes and modifications without departing from the spirit and scope of the present invention, and these changes and modifications will fall within the scope of protection of the present invention.

Claims

1. A method for manufacturing a wide bearing steel strip, characterized in that: include: Step S1, heating the continuous casting billet that meets the GCr15 steel composition requirements; Step S2, performing hot rolling on the continuous casting slab that has undergone the heating treatment to obtain an initial steel strip; wherein the hot rolling treatment includes a rough rolling treatment and a finishing rolling treatment, and the reduction of the continuous casting slab during the rough rolling treatment accounts for more than 70% of the total reduction of the continuous casting slab during the hot rolling treatment; the rough rolling treatment is performed in multiple passes, and the reduction rate of each pass is 18-40%; the finishing rolling treatment is performed in seven passes, wherein the reduction rate of each pass of the first four finishing rolling passes is 25-43%, and the reduction rate of each pass of the last three finishing rolling passes is 10-20%, and the reduction rate decreases from the front to the back, and the total reduction rate of the last three finishing rolling passes is 45-50%, and the reduction rate of each pass of the seventh finishing rolling pass is 10-11%; Step S3, cooling the initial steel strip to a coiling temperature and then coiling it to obtain a wide bearing steel strip; wherein the wide bearing steel strip has a width of 1000-1400 mm and a thickness of 3.6-10 mm, the cooling rate is 10-20°C / s, and the coiling temperature is 580-620°C; Step S4: slowly cooling the wide bearing steel strip obtained in step S3 to 400-500° C., with the slow cooling rate being less than 1° C. / s.

2. The method for manufacturing a wide bearing steel strip according to claim 1, characterized in that: In the step S2, six rough rolling passes are performed during the rough rolling process, wherein the reduction ratio of each of the first three rough rolling passes is 18-21%, and the reduction ratio of each of the last three rough rolling passes is 30-40%.

3. The method for manufacturing a wide bearing steel strip according to claim 1, characterized in that: In the step S2, the starting rolling temperature of the rough rolling process is 1110-1170°C, and the finishing rolling temperature is 1060-1080°C.

4. The method for manufacturing a wide bearing steel strip according to claim 1, wherein: In the step S2, the start rolling temperature of the finishing rolling process is 1000-1050°C, and the final rolling temperature is 830-870°C.

5. The method for manufacturing a wide bearing steel strip according to claim 1, characterized in that: In the step S1, the temperature of the heating treatment is 1110-1170° C., the time is 160-200 min, and the soaking time is 30-40 min.

6. A wide bearing steel belt, characterized in that: It is made according to the manufacturing method of the wide bearing steel strip according to any one of claims 1-5.

7. The wide bearing steel strip according to claim 6, characterized in that: Measured by weight percentage, the components of the wide bearing steel strip include: C: 0.99-1.06%, Si: 0.21-0.32%, Mn: 0.26-0.45%, S: 0-0.050%; P: 0-0.015%, Cr: 1.50-1.65%, Al: 0.020-0.045%, O: 0-0.0012%, N: 0-0.0050%, and the balance is Fe and unavoidable impurities.

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