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Method of making galvanized or zinc-coated annealed steel sheet by dff conditioning

A technology of zinc coating and steel sheet, applied in manufacturing tools, coating, hot dip plating process, etc., can solve problems such as the cost impact of steel sheet

Active Publication Date: 2012-02-01
ARCELORMITTAL INVESTIGACION Y DESARROLLO SL
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, this has the major drawback that high levels of tensile strength, i.e. around 800 MPa, can only be achieved when the carbon content is increased
However, this has an impact on the cost of the steel sheet

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0070] The steel sheet A is continuously introduced in a straight-fired furnace where it is brought into contact with an atmosphere comprising air and fuel with an air-to-fuel ratio of 0.94, heated from ambient temperature (20°C) to 700°C, so as to form a 0.073 μm thick iron oxide layer. Subsequent and continuous annealing was performed in a radiant tube furnace where it was heated from 700°C to 850°C, then soaked at 850°C for 40 s, and finally cooled to 460°C.

[0071] The atmosphere in the radiant tube furnace contains 4% by volume of hydrogen, the balance being nitrogen and unavoidable impurities. The length of the radiant tube furnace is 60m, the sheet speed is 90m / min, and the gas flow rate is 250Nm 3 / h. Under these conditions, the reduction rate of the iron oxide layer was 0.0024 μm / s. Thus, the reduction of the iron oxide layer continues during the residence time of the sheet in the radiant tube furnace and at the exit of said furnace the iron oxide is completely re...

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PUM

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Abstract

The present invention relates to a method for the preparation of a hot-dip galvanized or zinc-coated annealed steel sheet having a TRIP microstructure, said method comprising the following steps: - providing a steel sheet having a composition by weight ratio: 0.01≤C≤0.22 %, 0.5 0≤Mn≤2.0%, 0.2≤Si≤2.0%, 0.005≤Al≤2.0%, M0≤1.0%, Cr≤1.0%, P≤0.02%, Ti≤0.20%, V≤0.40%, Ni ≤ 1.0%, Nb ≤ 0.20%, the balance of the composition is iron and unavoidable impurities from smelting, - oxidized in a direct flame furnace in which the atmosphere contains air and fuel and the ratio of air to fuel is 0.80-0.95 Steel sheet such that an iron oxide layer with a thickness of 0.05-0.2 μm is formed on the surface of the steel sheet, and inner oxides of Si and / or Mn and / or Al are formed, reduction at 0.001-0.010 μm / s reducing said oxidized steel sheet at a rate so as to achieve reduction of the iron oxide layer, - subjecting said reduced steel sheet to hot-dip galvanizing to form a zinc-coated steel sheet, and - optionally, making The hot-dip coated steel sheet is subjected to an alloying treatment to form a zinc-coated annealed steel sheet.

Description

technical field [0001] The present invention relates to a method of manufacturing hot-dip galvanized or zinc-coated annealed steel sheets having a TRIP microstructure. Background technique [0002] In order to meet the need to lighten the structure of powered land vehicles, it is known to use TRIP steels (the term TRIP stands for Transformation Induced Plasticity), which combine high mechanical strength with the possibility of very high deformation levels. TRIP steels have a microstructure comprising ferrite, retained austenite and optionally martensite and / or bainite, which allows them to achieve tensile strengths of 600-1000 MPa. Such steels are widely used in the production of energy absorbing parts such as structural and safety parts such as longitudinal members and reinforcements. [0003] Steel sheets are usually coated with a zinc-based coating by hot-dip galvanizing before being sent to the car manufacturer in order to improve corrosion resistance. After leaving th...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C23C2/28C23C2/02C23C2/06
CPCC21D9/46C21D9/561C23C2/02C23C2/28C23C2/06C23C2/40C22C1/002Y10T428/12799C22C1/11C23C2/0222C23C2/0038C23C2/0224C23C2/261
Inventor F·贝特朗D·胡恩H·圣德-雷芒德
Owner ARCELORMITTAL INVESTIGACION Y DESARROLLO SL