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High-yield-ratio high-strength cold-rolled steel sheet excellent in hole expandability and manufacturing method thereof

A technology of cold-rolled steel sheet and manufacturing method, applied in the field of high-yield ratio type high-strength cold-rolled steel sheet and its manufacturing, can solve the problems of dents, poor weldability, etc. Effect

Active Publication Date: 2018-04-06
浦项股份有限公司
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

However, the steel sheet produced by the technique of Patent Document 2 may have poor weldability due to excessive addition of carbon, and may cause dents in the furnace due to excessive addition of silicon.

Method used

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  • High-yield-ratio high-strength cold-rolled steel sheet excellent in hole expandability and manufacturing method thereof
  • High-yield-ratio high-strength cold-rolled steel sheet excellent in hole expandability and manufacturing method thereof
  • High-yield-ratio high-strength cold-rolled steel sheet excellent in hole expandability and manufacturing method thereof

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Embodiment

[0074] Vacuum melting was performed on the slab with the composition in Table 1 below, reheating was carried out at a heating temperature of 1200° C. for one hour in a heating furnace, and then hot rolling and coiling were carried out according to the conditions in Table 2 below. Next, the coiled hot-rolled steel sheet was pickled and cold-rolled at a reduction ratio of 45%, thereby obtaining a cold-rolled steel sheet, and then subjected to continuous annealing, primary cooling, and secondary cooling according to the conditions in Table 2 below. Thereafter, overaging treatment was performed for 300 seconds at the secondary cooling termination temperature. At this time, the primary cooling rate was constant at 2°C / sec, the primary cooling termination temperature was constant at 650°C, and the secondary cooling rate was constant at 15°C / sec.

[0075] Next, the phase fraction, size and hardness of the microstructure of each produced cold-rolled steel sheet were measured, and the ...

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Abstract

The invention discloses a high strength cold rolled steel sheet having high yield ratio and excellent hole expansibility and a method for manufacturing the same. The cold rolled steel sheet includes, by weight, 0.035-0.07% of C, less than 0.3% and greater than 0% of Si, 2.0-3.5% of Mn, 0.3-1.2% of Cr, 0.03-0.08% of Ti, 0.01-0.05% of Nb, 0.01-0.10% of Sol.Al, 0.0010-0.0050% of B, and the balance Fe and unavoidable impurities. In microstructure, the cold rolled steel sheet includes 90 area% of martensite, wherein the average grain diameter of the martensite is less than 3 [mu]m; the martensite includes tempered martensite and lath martensite; the average grain diameter of the lath martensite is less than 1 [mu]m; the area fraction of the lath martensite with the average grain diameter less than 1 [mu]m is less than 5%; and precipitate with the diameter less than 10 nm and 150 / [mu]m2 is included.

Description

technical field [0001] The present invention relates to a high-yield-ratio high-strength cold-rolled steel plate excellent in hole expandability and a manufacturing method thereof. ), a high-yield-ratio high-strength cold-rolled steel sheet excellent in hole expandability for automotive structural parts such as ), and a method for producing the same. Background technique [0002] In recent years, with the strengthening of various environmental regulations and energy regulatory mechanisms, high-strength steel sheets for automobiles are required to improve fuel efficiency and durability of automobiles. In particular, with the spread of automobile impact safety regulations, high-strength steel sheets are widely used for structural parts such as members, seat rails, and pillars in order to improve the impact resistance of the vehicle body. Use a steel plate. This high-strength steel plate is designed to absorb the impact energy of a car, and is therefore characterized by a ste...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C22C38/38C21D8/02
CPCC21D8/02C22C38/38
Inventor 韩成豪徐昌孝
Owner 浦项股份有限公司
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