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Tempered martensitic steel having low yield ratio and excellent uniform elongation, and manufacturing method therefor

A technology of tempering martensitic and martensitic steel, which is applied in the direction of manufacturing tools, furnace types, heat treatment furnaces, etc., can solve the problems of unsatisfactory toughness, reduction of yield strength and tensile strength, and halving the effect of addition, etc., to achieve Reduced weight and increased service life, excellent balance, and low yield ratio

Active Publication Date: 2019-08-06
浦项股份有限公司
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

As a plan to improve the strength, the limited composition of the existing boron-containing heat-treated steel, that is, after fixing Mn at 0.5-1.5% and Cr at 0.1-0.3% and performing heat treatment, increase the strength in consideration of the strength. When the C content is increased, the quenching strength increases in proportion to the content of C, Mn, etc., but when heat treatment is performed at a temperature range of 500 to 550°C in a conventional method in order to impart toughness and ductility, the yield strength and tensile strength will decrease. Significantly reduced, so the effect of adding C, Mn, etc. will be halved, and the expectation that the toughness will increase proportionally with the increase in strength cannot be met.

Method used

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  • Tempered martensitic steel having low yield ratio and excellent uniform elongation, and manufacturing method therefor
  • Tempered martensitic steel having low yield ratio and excellent uniform elongation, and manufacturing method therefor
  • Tempered martensitic steel having low yield ratio and excellent uniform elongation, and manufacturing method therefor

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0113] Steels having the composition shown in Table 1 below were prepared. The steel is in the temperature range of 1200±20°C. After heating the slab with the composition shown in the following table 1 for 180 minutes to carry out homogenization treatment, rough rolling and finish rolling are carried out, and then at 650°C A hot-rolled steel sheet having a thickness of 3.00 mm produced by coiling at a high temperature. Yield strength (YS), tensile strength (TS), and elongation (El) of the hot-rolled steel sheets were measured and recorded in Table 2 below.

[0114] The hot-rolled steel sheet was pickled and heated to a temperature of 930° C. for 6 minutes, and then cooled at a cooling rate of 30° C. / sec to the cooling termination temperature described in Table 2 below. When the cooling termination temperature is 20°C, it is indicated as "-", and there is no additional holding time. When the cooling termination temperature exceeds 20°C, keep it for 15 minutes and then air-coo...

Embodiment 2

[0131] Steels having the composition shown in Table 3 below were prepared. The steel is in the temperature range of 1200±20°C. The slab with the composition shown in the following Table 3 is heated for 180 minutes to perform homogenization treatment, and then rough rolling and finish rolling are carried out, and then recorded in Table 4 A hot-rolled steel sheet with a thickness of 3.0 mm produced by winding at a winding temperature in . Yield strength (YS), tensile strength (TS), and elongation (El) of the hot-rolled steel sheets were measured and reported in Table 4 below.

[0132] The hot-rolled steel sheet was pickled and heated to a temperature of 930° C. for 6 minutes, and then cooled to the cooling termination temperature described in Table 4 below at a cooling rate of 30° C. / sec. When the cooling termination temperature is 20°C, it is indicated as "-", and there is no additional holding time. When the cooling termination temperature exceeds 20°C, keep it for 15 minute...

Embodiment 3

[0148] Steels having the composition shown in Table 5 below were prepared. The steel is in the temperature range of 1200±20°C, and the slab with the composition shown in the following table 5 is heated for 180 minutes to perform homogenization treatment, and then rough rolling and finish rolling are carried out, and then recorded in table 6 A hot-rolled steel sheet with a thickness of 3.0 mm produced by winding at a winding temperature in . Yield strength (YS), tensile strength (TS), and elongation (El) of the hot-rolled steel sheets were measured and reported in Table 6 below. At the same time, it is designed that steel type 1 has a tempering strength of 1800MPa, steel 2 has a tempering strength of 1500MPa, steel 3 and steels 5-19 have a tempering strength of 2000MPa, and the tensile strength level depends on the cooling termination temperature after quenching Therefore, when each did not reach the above strength, it was marked as a comparative example as shown in Table 6. ...

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Abstract

One aspect of the present invention relates to a tempered martensitic steel having a low yield ratio and an excellent uniform elongation, the tempered martensitic steel: comprising, by wt%, 0.2-0.6% of C, 0.01-2.2% of Si, 0.5-3.0% of Mn, 0.015% or less of P, 0.005% or less of S, 0.01-0.1% of Al, 0.01-0.1% of Ti, 0.05-0.5% of Cr, 0.0005-0.005% of B, 0.05-0.5% of Mo, 0.01% or less of N, and the balance of Fe and inevitable impurities; having a yield ratio of 0.4-0.6; having a product (TS*U-El), of a tensile strength and a uniform elongation, of 10,000 MPa% or more; and having a microstructure containing, by an area fraction, 90% or more of martensite, 5% or less of ferrite and the balance of bainite.

Description

technical field [0001] The present invention relates to a tempered martensitic steel having a low yield ratio and excellent uniform elongation and a method for producing the same. Background technique [0002] Recently, with the strengthening of safety regulations for protecting vehicle occupants or fuel efficiency regulations for protecting the global environment, attention has been paid to improving the rigidity of vehicles and reducing the weight of vehicles. For example, stabilizer bars (Stabilizer bars) and tubular torsion beams (Tubular torsions beam axle) of the vehicle chassis are components that support the weight of the vehicle body and are continuously subjected to fatigue loads during driving. The use of high-strength components is expanding to simultaneously Ensure rigidity and longevity. [0003] The fatigue life of steel sheets used for vehicle components is closely related to the increase in tensile strength and elongation. The manufacturing method of high-...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C38/28C22C38/32C22C38/22C22C38/38C22C38/34C21D1/18C21D8/02
CPCC21D6/002C21D6/004C21D6/005C21D6/008C21D8/0205C21D8/0226C21D8/0236C21D2211/008C22C38/22C22C38/24C22C38/28C22C38/32C22C38/34C22C38/38C22C38/42C22C38/44C22C38/50C22C38/54C21D1/18C21D8/0263C21D2211/005C21D8/0247C21D9/46C21D2211/002C22C38/001C22C38/002C22C38/02C22C38/04C22C38/06
Inventor 赵悦来成焕球裵成范
Owner 浦项股份有限公司