Production method of low-yield-ratio structural steel 280VK

Abstract

The invention discloses a production method of steel 280VK for a low-yield-ratio structure. The steel 280VK for the low-yield-ratio structure comprises the following chemical components in percentage by mass: less than or equal to 0.15% of C; mn < = 2.0%; less than or equal to 0.020% of P; less than or equal to 0.020% of S; n is less than or equal to 0.0080%, and the balance is Fe and inevitable impurities. The invention further discloses a production process and related parameters. The mechanical properties of the low-yield-ratio structural steel 280VK produced by the invention meet the following requirements: the yield strength is 280-380MPa, the yield ratio is less than or equal to 0.78, the ductility is greater than or equal to 28.0%, the quality problems such as cracking or wrinkling caused by strength are not found in use, the performance is proper, and the low-yield-ratio structural steel 280VK can be popularized and used in a large range.

Description

Technical Field

[0001] The invention belongs to the technical field of steel metallurgy and steelmaking technology, and in particular relates to a production method of 280VK structural steel with low yield ratio. Background Art

[0002] Structural steel products often adopt a low-carbon and alloy design to ensure the strength required by users. However, some structural parts have certain requirements for the yield ratio due to their complex deformation. In order to make the product have both strength and plasticity, we try to adopt a low-carbon and high-manganese, alloy element removal design method to develop low-yield ratio structural steel to meet user needs.

[0003] 280VK is a structural steel, and its uses are significantly different from those of enameled steel and low-carbon steel SPCC. The design ideas and angles are different. In order to prevent scale explosion, the design composition of high-strength enameled steel mainly considers hydrogen storage traps and ensures strength; in order to avoid the yield platform and extend the service life, SPCC mainly controls the interstitial atomic content; 280VK normally uses alloy niobium or titanium to ensure product strength. Aiming at the special stamping process requirements of users, the present invention adopts a dealloying design on the basis of the original process, and only controls the carbon and manganese content and cooperates with process regulation to reduce the product yield strength ratio while ensuring product strength. Summary of the invention

[0004] The purpose of the present invention is to provide a production method of 280VK structural steel with low yield ratio. Aiming at the special stamping process requirements of users, on the basis of the original process, a dealloying design is adopted, and the yield ratio of the product is reduced while ensuring the strength of the product by only controlling the carbon and manganese contents and coordinating process regulation.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] The invention discloses a production method of low yield ratio structural steel 280VK, comprising the following processes: steelmaking process-hot rolling process-cold rolling process-continuous annealing process; wherein: the steelmaking process comprises: converter top and bottom combined blowing smelting-LF refining-slab continuous casting; the hot rolling process comprises: billet heating-high pressure water descaling-width setting press-E1R1 roughing mill rolling-E2R2 roughing mill rolling-insulating cover-flying shear-high pressure water descaling-F1-F7 finishing mill rolling-densified laminar cooling-coiling; the cold rolling process comprises: pickling uncoiling-welding-tension straightening-pickling-rinsing-drying-edge trimming-continuous rolling mill cold rolling-coiling; the continuous annealing process comprises: continuous annealing uncoiling-welding-cleaning-entry looper-annealing furnace-exit looper-leveling-loop looper inspection-edge trimming-surface inspection-oiling-coiling-packaging; the invention is characterized in that:

[0007] The tapping temperature of the converter is ≥1640℃ to ensure that the composition and temperature are coordinated. If there is a new tapping port or abnormal turnover ladle, the tapping temperature shall be increased by 10-15℃ on the basis of the upper limit. During the tapping process of the converter, ferroaluminum, ferrosilicon and ferromanganese are added for deoxidation and alloying.

[0008] The LF furnace is used for slagging, deoxidation and desulfurization, and aluminum iron, silicon iron and manganese iron alloy are added to adjust the composition to the target range; calcium treatment is carried out after the LF treatment is completed;

[0009] Slab continuous casting, the superheat control range of the intermediate ladle during the casting process of the casting machine is 25~45℃, and the production casting speed is 1.0~1.8m / min;

[0010] The thickness of the ingot is 230mm, and the hot-rolled thickness is 2.5-5.5mm;

[0011] During the heating of the ingot, the heating temperature is 1200-1250°C, the heating time is 160-240min, the soaking temperature is 1200-1250°C, the soaking time is 25-60min, and the furnace discharge temperature is 1220°C;

[0012] The final rolling temperature of the finishing rolling is ≥860℃, and the coiling temperature is 550-650℃;

[0013] The cooling method is front dispersion cooling;

[0014] The chemical composition of the low yield ratio structural steel 280VK is as follows by mass percentage: C≤0.15%; Mn≤2.0%; P≤0.020%; S≤0.020%; N≤0.0080%, and the rest is Fe and unavoidable impurities.

[0015] Furthermore, the cold-rolled thickness is 0.6-2.5 mm.

[0016] Furthermore, in the continuous annealing process, the annealing heating temperature is 750-850° C., the annealing soaking temperature is 760-840° C., and the leveling mill elongation is 1.0-1.8%.

[0017] Furthermore, the yield strength of the produced structural steel 280VK is 280-380MPa.

[0018] Furthermore, the yield strength ratio of the produced structural steel 280VK is ≤0.78.

[0019] Furthermore, the structural steel 280VK produced has been used by users and no quality problems such as cracking or wrinkling due to strength reasons have been found.

[0020] Compared with the prior art, the beneficial technical effects of the present invention are:

[0021] The mechanical properties of low yield strength ratio structural steel 280VK meet the following requirements: yield strength: 280-380MPa, yield strength ratio ≤0.78, elongation ≥28.0%; the actual performance is even better.

[0022] The present invention is designed according to the needs of users. Since the product is used for stamping automobile parts, it requires a certain strength support and a certain deformation ability. Figure 4 As can be seen from the data in Table 8, the strength of the 280VK designed in the present invention is significantly higher than that of ordinary low-carbon steel. However, compared with the 280VK normally required by the market, the yield strength range is reduced and controlled within a fluctuation range of 100 MPa, which is conducive to stable use by customers. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present invention will be further described below in conjunction with the accompanying drawings.

[0024] Figure 1 The yield strength performance range of the steel strip 280VK obtained in the example.

[0025] Figure 2 This is the elongation performance range of the steel strip 280VK obtained in the example.

[0026] Figure 3 This is the yield strength ratio performance range of the steel strip 280VK obtained in the example.

[0027] Figure 4 Comparison of yield strength performance before and after optimization. DETAILED DESCRIPTION

[0028] Aiming at the actual demand for complex formed structural parts in China, the present invention provides a production method of special steel for low yield ratio structural parts that meets the user's stamping process by adopting new component design and metallurgical process parameters.

[0029] The production method specifically includes the following steps: steelmaking step - hot rolling step - cold rolling step - continuous annealing step; wherein:

[0030] The steelmaking process includes: converter top and bottom combined blowing smelting - LF refining - slab continuous casting - slow cooling;

[0031] The tapping temperature of the converter is ≥1640℃ to ensure that the composition and temperature are coordinated. If there is a new tapping port or abnormal turnover ladle, the tapping temperature will be increased by 10-15℃ on the basis of the upper limit. During the tapping process of the converter, aluminum iron, silicon iron, manganese iron, etc. are added for deoxidation and alloying.

[0032] The LF furnace slags, deoxidizes and desulfurizes, and adds alloys such as ferroaluminum, ferrosilicon, and ferromanganese to adjust the composition to the target range. After the LF treatment, calcium treatment is performed;

[0033] In the slab continuous casting, the superheat degree of the intermediate ladle is controlled within the range of 25 to 45° C. during the casting process of the casting machine, and the production casting speed is 1.0 to 1.8 m / min.

[0034] The thickness of the above-mentioned ingot is 230mm, and the hot-rolled thickness is: 2.5-5.5mm;

[0035] The hot rolling process includes: heating of the ingot - high-pressure water descaling - fixed width press - E1R1 roughing mill rolling - E2R2 roughing mill rolling - insulation cover - flying shear - high-pressure water descaling - F1-F7 finishing mill rolling - dense laminar cooling - coiling; this process uses a walking heating furnace to heat the ingot (heating process see Table 1), rough rolling uses double-frame R1 and R2 reciprocating rolling, finishing rolling uses F1-F7 continuous rolling process, and the cooling method is front dispersed cooling method. The specific hot rolling process is shown in Table 2.

[0036] Table 1: Billet heating system

[0037]

[0038]

[0039] Table 2: Rolling process

[0040]

[0041] The cold rolling process includes: pickling uncoiling - welding - straightening - pickling - rinsing - drying - trimming - continuous rolling mill cold rolling - coiling;

[0042] The continuous annealing process includes: continuous annealing uncoiling - welding - cleaning - entrance looper - annealing furnace - exit looper - leveling - looper inspection - edge trimming - surface inspection - oiling - coiling;

[0043] The specific process system of the continuous annealing process is shown in Table 3.

[0044] Table 3: Annealing process

[0045]

[0046] The present invention is described in detail below through specific examples. The examples are only intended to help understand the present invention but are not intended to limit the present invention.

[0047] Example

[0048] 1. According to the above steelmaking process requirements, the actual slab chemical composition (mass percentage) is shown in Table 4 below.

[0049] Table 4: Chemical composition (%)

[0050]

[0051]

[0052] 2. According to the above hot rolling process requirements, the hot rolling thickness is 2.5-5.5mm, and the actual process is shown in Table 5.

[0053] Table 5: Rolling process

[0054]

[0055] 3. According to the above annealing process requirements, the cold rolling thickness is 0.6-2.5mm, and the actual process is shown in Table 6.

[0056] Table 6: Annealing process

[0057]

[0058] 4. The mechanical properties of the steel strip products obtained through the above process are shown in Table 7. The test method refers to GB / T228.1. Figure 1 As shown, the mechanical properties range of steel 280VK is shown. Figure 1 It can be seen from the curve that the mechanical properties produced by the above process meet the user's requirements.

[0059] Table 7: Mechanical properties

[0060]

[0061] In summary, the steel strip products obtained by the process have been used by users and no quality problems such as cracking or wrinkling caused by strength reasons have been found. The performance is suitable and can be promoted and used on a large scale.

[0062] The comparison of different steel grades is shown in Table 8 below:

[0063] Table 8

[0064]

[0065] The comparison results of yield strength of different steel grades are shown in Figure 4 .

[0066] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for producing low yield ratio structural steel 280VK, comprising the following steps: Steelmaking process - hot rolling process - cold rolling process - continuous annealing process; among which: The steelmaking process includes: converter top and bottom combined blowing smelting - LF refining - slab continuous casting; the hot rolling process includes: billet heating - high-pressure water descaling - fixed width press - E1R1 roughing mill rolling - E2R2 roughing mill rolling - insulation cover - flying shear - high-pressure water descaling - F1-F7 finishing mill rolling - encrypted laminar cooling - coiling; the cold rolling process includes: pickling uncoiling - welding - straightening - pickling - rinsing - drying - trimming - continuous rolling mill cold rolling - coiling; the continuous annealing process includes: continuous annealing uncoiling - welding - cleaning - inlet looper - annealing furnace - outlet looper - leveling - looper inspection - trimming - surface inspection - oiling - coiling - packaging; the characteristics are: The tapping temperature of the converter is ≥1640℃ to ensure that the composition and temperature are coordinated. If there is a new tapping port or abnormal turnover ladle, the tapping temperature shall be increased by 10-15℃ on the basis of the upper limit. During the tapping process of the converter, ferroaluminum, ferrosilicon and ferromanganese are added for deoxidation and alloying. The LF furnace is used for slagging, deoxidation and desulfurization, and aluminum iron, silicon iron and manganese iron alloy are added to adjust the composition to the target range; calcium treatment is carried out after the LF treatment is completed; Slab continuous casting, the superheat control range of the intermediate ladle during the casting process of the casting machine is 25~45℃, and the production casting speed is 1.0~1.8m / min; The thickness of the ingot is 230mm, and the hot-rolled thickness is 2.5-5.5mm; The heating temperature of the ingot is 1200-1250℃, the heating time is 160-240min, the soaking temperature is 1200-1250℃, the soaking time is 25-60min, and the target temperature out of the furnace is 1220℃; The final rolling temperature of the finishing rolling is ≥860℃, and the coiling temperature is 550-650℃; The cooling method is front dispersion cooling; The chemical composition of the low yield ratio structural steel 280VK is as follows by mass percentage: C≤0.15%; Mn≤2.0%; P≤0.020%; S≤0.020%; N≤0.0080%, and the rest is Fe and unavoidable impurities.

2. The method for producing low yield ratio structural steel 280VK according to claim 1, characterized in that: The cold rolled thickness is 0.6-2.5mm.

3. The method for producing low yield ratio structural steel 280VK according to claim 1, characterized in that: In the continuous annealing process, the annealing heating temperature is 750-850°C, the annealing soaking temperature is 760-840°C, and the leveling machine elongation is 1.0-1.8%.

4. The method for producing low yield ratio structural steel 280VK according to claim 1, characterized in that: The yield strength of the produced structural steel 280VK is 280-380MPa.

5. The method for producing low yield ratio structural steel 280VK according to claim 1, characterized in that: The yield strength ratio of the produced structural steel 280VK is ≤0.

78.

6. The method for producing low yield ratio structural steel 280VK according to claim 1, characterized in that: The structural steel 280VK produced has been used by users and no quality problems such as cracking or wrinkling due to strength reasons have been found.

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