Research and Application of New Generation Controlled Hot-Rolling Technology and Post-rolling Super-cooling Technology



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16 March 18
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Hot rolling – cooling – heat treatment integrated micro-structure control technology is through the heating, rolling, cooling and heat treatment process in the critical process of technological innovation, give full play to fine grain, precipitation, phase transformation of the comprehensive strengthening effect, without adding or less added alloy elements under the premise of improving the comprehensive mechanical properties of steel to meet the different performance requirements of steel.

New generation of controlled rolling technology

The controlled rolling is to combine the metal frictional deformation and the solid phase transition during the hot rolling process, and cut off the heat treatment after rolling. This is a new technology of hot rolling which can both to produce excellent strength and toughness of steel, but also save energy consumption.

Mild Steel Plate​​

The control rolling process is mainly used for low carbon steel containing trace elements which often contains niobium, vanadium, titanium alloys, and the total amount is less than 0.1%. Controlled rolling is the control of rolling parameters, including temperature, deformation, etc., to control the re-crystallization process, to obtain the desired organization and performance. The addition of certain trace elements increases the steel re-crystallization start temperature while lowering the rolling temperature as appropriate. So that can get the effect of multi-pass deformation superimposed and the re-crystallization in the larger strain and lower temperature to make the steel to meet the requirements of the organization and performance.

The new generation of controlled rolling technology has significant advantages in improving rolling permeability, developing fine grain steel on the surface, improving the temperature uniformity of steel plate.

1) improved permeability rolling deformation: The high-intensity cooling between the rolling pass causes the thick layer to produce a large temperature gradient, as the steel plate near the surface temperature is low, deformation resistance is large, in the rolling load conditions, the metal of the rolling surface is more difficult to produce deformation, to promote the deformation to the central penetration.

2) Preparation of fine crystal products on the surface: By controlling the deformation of the austenite, the re-crystallization behavior, the phase transition and the reverse transformation behavior Can greatly refine the surface of the steel plate. The refinement of the surface layer promotes the thickness of the ductile failure zone (shear lip), the crack nucleation work is improved, to improve the crack resistance of the steel plate, This provides strong support for the large container ship high strength steel plate crack arrest development. Rolling with water cooling conditions, the use of low-carbon micro-alloy composition system, in the austenitic temperature deformation – return temperature – austenite re-crystallization process, after 2 cycles of simulation, the austenite re-crystallization rate rose to 94.0%, austenite refinement to 3.3μm; In the austenite phase transformation – return temperature – reverse phase transformation simulation process, obtained toughness transition temperature as low as -160 ℃ high toughness low temperature steel.

3) Temperature uniformity control: Through the head and tail fast shelter, horizontal water crown, the amount of water from the upper and lower pipes and a series of cooling homogenization control technology, to make the whole steel plate rolling process control temperature fluctuations within 12 ℃, thereby effectively protect the tissue properties of the steel sheet temperature and uniformity. Practice shows for the large thickness of the steel for high permeability rolling, increasing the internal deformation of the steel plate permeability, refine the internal organization, improve the internal quality of steel plate.

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Ultracold technology after rolling for steel plate

Using this ultracold technology after rolling for steel plate makes the function of ultra-fast cooling device diversification, with this equipment technology, can achieve accelerated cooling ACC; advanced Ultrafast Cooling UFC; intermediate cooling (IC); segmental cooling; intermittent quenching IDQ; Direct Quenching DQ; Direct quenching carbon distribution (DQ · P) and other functions, Meet the ferrite / pearlite, bainite, bainite / martensite and martensite and other products of the phase change process control needs. Through the on-line quenching process to achieve the following specifications 80mm specifications of various varieties of steel (Q690, Co-Mo steel, FH690, etc.) batch production. And our mill’s 5000mm wide plate production line with this ultra-fast cooling device production of pipeline steel with the thickness range of 10.7-33mm (X65-X90), the maximum width of 4400mm, and completed a thick-gauge large diameter X80 pipeline steel production and gets world’s first certification.

The advanced hot-rolling-cooling-heat-treated integrated tissue-performance control technology is a series of original technological innovations around rolling, cooling and heat treatment processes in hot-rolled steel-making processes. Through the hot-rolled process integration of organizational performance control process, equipment innovation, achieves a comprehensive improvement in the performance of hot-rolled steel materials, reduces the amount of alloying elements, reduces the production cost of steel, and saves resources and energy, reduces emissions play an important role in collaborative innovation.

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Fiona.yu@sinowellmetal.com

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