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Hot rolled dual-phase steel sheets with high stretch-flangeability and manufacturing method thereof

A hot-rolled dual-phase steel and extended flange technology, which is applied in the field of steel rolling, can solve problems such as cracking, insufficient forming performance of extended flanges, and low fatigue strength, and achieve the effect of reducing costs

Inactive Publication Date: 2012-04-11
SHANDONG IRON & STEEL CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

This new method uses two different materials - one made from pure iron (C) while another consists mostly of silicon carbide or aluminum nitride instead of carbon). By controllably reducing these components without adding extra material like molydenum, this technology can make it more cost-effective than existing methods for producing high-strength steels at lower levels of purity compared to current techniques such as casting.

Problems solved by technology

This patented technical problem addressed by this patents relates to developing high-quality hot rolled steel sheet that can be applied into various industries including auto vehicles while maintaining their structural integrity over longer periods without losing functionality or causing cracks under severe conditions like thermal stress and impact damage from external factors like rainwater.

Method used

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  • Hot rolled dual-phase steel sheets with high stretch-flangeability and manufacturing method thereof
  • Hot rolled dual-phase steel sheets with high stretch-flangeability and manufacturing method thereof
  • Hot rolled dual-phase steel sheets with high stretch-flangeability and manufacturing method thereof

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Experimental program
Comparison scheme
Effect test

Embodiment 1

[0059]The chemical composition of the experimental steel A is shown in Table 1. The initial thickness of the billet is 135 mm, and the thickness of the finished product is 4 mm. The process route is: BOF-CAS-LF-CCM-hot rolling. The billet was heated to 1180°C for 2 hours in a walking heating furnace and then rolled and deformed for 9 passes. The deformation system is shown in Table 2. The rolling process is carried out on a 1700mm ASP hot rolling line. The finished product size is 4*1290mm. After the final rolling, a three-stage cooling mode is adopted. The cooling line is 80m long, and 14 sets of headers are distributed. The coiling temperature is 400-500°C. The cooling process parameters are shown in Table 3. The mechanical properties of the steel plates are listed in Table 4.

[0060] The chemical composition of table 1 embodiment 1 experimental steel A

[0061]

[0062] The rolling schedule of table 2 embodiment 1

[0063]

[0064] The temperature and cooling sys...

Embodiment 2

[0073] The chemical composition of the experimental steel B is shown in Table 5. The initial thickness of the billet is 135 mm, and the thickness of the finished product is 6 mm. The process route is: BOF-CAS-LF-CCM-hot rolling. The billet was heated to 1180°C for 2 hours in a walking heating furnace, and then rolled and deformed for 9 passes (the reduction ratio in the rough rolling stage was 74.1%, and the reduction ratio in the finish rolling stage was 82.8%). The rolling process is carried out on a 1700mm ASP hot rolling line. The finished product size is 6*1290mm. After the final rolling, a three-stage cooling mode is adopted. The cooling line is 80m long, and 14 sets of headers are distributed. The coiling temperature is 400-500°C. The cooling process parameters are shown in Table 6. The mechanical properties of the steel plates are shown in Table 7.

[0074] The chemical composition of table 5 embodiment 2 experimental steel B

[0075]

[0076] Temperature regime ...

Embodiment 3

[0082] Example 3 The chemical composition of the experimental steel C is shown in Table 8. The initial thickness of the billet is 150 mm, and the thickness of the finished product is 10 mm. The process route is: BOF-CAS-LF-CCM-hot rolling. The billet was heated to 1200°C for 2 hours in a walking heating furnace, and then rolled and deformed for 9 passes (the reduction ratio in the rough rolling stage was 73.3%, and the reduction ratio in the finish rolling stage was 75%). The rolling process is carried out on a 1700mm ASP hot rolling line. The finished product size is 10*1290mm. After the final rolling, a three-stage cooling mode is adopted. The cooling line is 80m long, and 14 sets of headers are distributed. The coiling temperature is 400-500°C. The process parameters are shown in Table 9. The mechanical properties of the steel plates are shown in Table 10.

[0083] The chemical composition of table 8 embodiment 3 experimental steel C

[0084]

[0085] Temperature regi...

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Abstract

The invention discloses hot rolled dual-phase steel sheets with high stretch-flangeability and a manufacturing method thereof. The manufacturing method has the following advantages: (1) the contents of C and Si are reduced, Mo is eliminated and defined amount of Cr and P are added, thus substantially lowering the cost and being beneficial to improvement of the surface quality and welding properties of the steel sheets; (2) the continuous casting slabs with medium thickness are adopted, and the walking beam furnace is used as buffer, thus realizing connection of casting machines and rolling machines, which are subjected to confluence and direct hot charging rolling; and high temperature rolling, water cooling+air cooling+water cooling stepped cooling path control technology and medium temperature coiling are adopted, so the sheet shapes are obviously improved, thus improving the stability of the steel sheet properties; and (3) the pearlites are effectively restrained by the advanced thermo mechanical control process and P and Cr microalloying paths, thus promoting generation of soft and hard phase structures of ferrites and bainites (or containing fewer martensites); the crystallite dimensions of the ferrites are 4-10mu m; and the hot rolled dual-phase steel with high stretch-flangeability and tensile strength being not less than 580MPa, stretch rate being not less than 26% and hole-expansion rate being not less than 75% is manufactured.

Description

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Claims

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Application Information

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Owner SHANDONG IRON & STEEL CO LTD
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