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Steel sheet for hot press forming having excellent heat treatment and impact property, hot press parts made of it and the method for manufacturing thereof

A technology of hot-rolled steel sheets and steel sheets, which is applied in the field of hot-formed steel sheets, can solve problems such as difficulty in controlling the concentration of the coating solution, and achieve the effects of increased yield strength, reduced weight, and excellent corrosion resistance

Inactive Publication Date: 2008-12-03
POHANG IRON & STEEL CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, adding Cr to form a coating film increases the surface viscosity of the coating solution, and makes it difficult to control the concentration of the coating solution at a constant level, causing the problem that conventional coating operations cannot be performed at high speed.

Method used

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  • Steel sheet for hot press forming having excellent heat treatment and impact property, hot press parts made of it and the method for manufacturing thereof
  • Steel sheet for hot press forming having excellent heat treatment and impact property, hot press parts made of it and the method for manufacturing thereof
  • Steel sheet for hot press forming having excellent heat treatment and impact property, hot press parts made of it and the method for manufacturing thereof

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0097] First, steel slabs having the compositions shown in Table 1 were manufactured. The steel slab is reheated at 1,150-1,250°C for 1 hour, hot rolled and coiled. Hot rolling is done at 850-950°C and coiling is done at 650°C. The parts of the hot-rolled steel sheets were pickled and cold-rolled at a reduction ratio of 50%, to manufacture cold-rolled steel sheets.

[0098] Hot-rolled and cold-rolled steel sheets are galvanized in the following manner. The steel plate was annealed at 800°C, slowly cooled to 650°C at a rate of 3°C / s, cooled to 550°C at a rate of 7°C / s, and continuously annealed at an overaging temperature of 460°C. Then, the annealed steel sheet was hot-dip galvanized for 5 seconds to manufacture a hot-dip galvanized steel sheet.

[0099] On the other hand, the hot-rolled steel sheet and the cold-rolled steel sheet were coated with aluminum in the following manner. The cold-rolled steel sheet is degreased, pretreated, preheated in a non-oxidizing furnace at...

Embodiment 2

[0113] First, steel slabs having the compositions shown in Table 4 were produced. The steel slabs are dissolved under vacuum, heated in a furnace at a temperature of 1,150-1,250°C for an additional hour, and hot-rolled and coiled. Hot rolling is done at 850-950°C and coiling is done at 650°C. Hot-rolled steel sheets are pickled and cold-rolled at a reduction ratio of 50%. The cold-rolled steel sheet is annealed at 800°C and continuously annealed at an overaging temperature of 400°C.

[0114] Then, the annealed steel sheet is heated to 460°C, hot-dip galvanized for 5 seconds, alloyed at 500°C for 10 seconds to alloy the coating, and cooled to room temperature to produce an alloyed hot-dip galvanized steel sheet. Then, the coated steel sheet was heated to each temperature shown in Table 5 at a speed of 10° C. / sec, further heated in this temperature range for 5 minutes, transferred to a mold, and processed in the mold. Immediately after finishing the processing, the finished s...

Embodiment 3

[0126] First, steel slabs having the compositions shown in Table 6 were produced. The steel slabs are dissolved under vacuum, heated in a furnace at a temperature of 1,150-1,250°C for an additional hour, and hot-rolled and coiled. Hot rolling is done at 850-950°C and coiling is done at 650°C. Hot-rolled steel sheets are pickled and cold-rolled at a reduction ratio of 50%. The cold-rolled steel sheet is annealed at 800°C and continuously annealed at an overaging temperature of 400°C.

[0127] This cold-rolled steel sheet was coated with Al in the following manner. The cold-rolled steel sheet is degreased, pretreated, preheated in a non-oxidizing heating furnace at 700°C, and heat-treated in a reducing atmosphere of nitrogen and hydrogen. At this time, heat treatment is performed at a temperature of up to 820°C. The steel plate after the heat treatment was cooled and immersed in the coating solution at 680°C. The coating solution contained 8.5% Si, 2.4% Fe and the balance A...

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Abstract

Disclosed is a steel sheet that exhibits an ultra-high strength after hot press forming followed by rapid cooling, and an enhanced yield strength after painting. The steel sheet has a composition comprising 0.1% to 0.5% by weight of C, 0.01% to 1.0% by weight of Si, 0.5% to 4.0% by weight of Mn, 0.1 % by weight or less of P, 0.03% by weight or less of S, 0.1 % by weight of soluble Al, 0.01% to 0.1% by weight of N, 0.3% by weight or less of W, and the balance Fe and other inevitable impurities. Further disclosed are a hot-pressed part made of the steel sheet and a method for manufacturing the hot-pressed part. The hot-pressed part achieves a high increment in yield strength after heat treatment for painting while ensuring an ultra-high tensile strength. Furthermore, the hot-pressed part exhibits superior adhesion to a coatinglayer, good surface appearance and improved corrosion resistance after painting.

Description

technical field [0001] The present invention relates to a steel sheet for hot press forming, which is mainly used in the manufacture of structural parts and reinforcements for vehicle bodies, to a method for manufacturing the steel sheet, to hot press parts manufactured from the steel sheet and to manufacturing hot press method of pressing parts. More specifically, the present invention relates to a steel sheet for hot press forming having ultra-high strength after hot press forming and improved yield strength after painting, and to a method for manufacturing the steel sheet, a hot press made of the steel sheet Pressed parts and methods of making hot pressed parts. Background technique [0002] In recent years, regulations related to the life and safety of car occupants have become stricter. Under such circumstances, at present, researchers are actively undertaking studies for reducing the weight of a vehicle body and developing a high-strength steel plate for a light-weig...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C38/04C22C38/00
CPCC21D8/0205C21D8/0221C22C38/02C22C38/04C22C38/06C22C38/42C22C38/44C22C38/48C22C38/50C22C38/58
Inventor 吴振根裴大喆金成柱陈光根李在隆朴永俊
Owner POHANG IRON & STEEL CO LTD
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