Twisted steel for 785 MPa-level high-strength prestressed structure and preparation method of twisted steel

A technology of prestressed structure and threaded steel bar, which is applied in the field of metal material processing, can solve the problems of rapid change in hardness gradient, ferrite network structure in the core tissue, unstable product performance, etc., and achieve slow change in hardness gradient and reticular Significant effect of reduction of ferrite structure and grain refinement

Active Publication Date: 2015-01-21
WUKUN STEEL
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  • Description
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  • Application Information

AI Technical Summary

Problems solved by technology

Micro-alloying + controlled cooling technology for the production of finished-rolled rebar. Due to the fact that there is no unified composition and process requirements in China, the hardness gradient of domestic finished-rolled rebar products changes rapidly, and the core tissue is prone to ferrite network structure, which leads to product damage. Unstable performance

Method used

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  • Twisted steel for 785 MPa-level high-strength prestressed structure and preparation method of twisted steel
  • Twisted steel for 785 MPa-level high-strength prestressed structure and preparation method of twisted steel
  • Twisted steel for 785 MPa-level high-strength prestressed structure and preparation method of twisted steel

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preparation example Construction

[0017] The preparation method of the 785MPa level high-strength prestressed structure threaded steel bar of the present invention comprises steel billet preparation, rolling, post-processing steps, specifically comprises:

[0018] A. Billet preparation:

[0019] 1) Converter smelting of molten iron: the chemical composition C 3.8~4.8wt%, Si 0.25~0.80wt%, Mn 0.25~0.60wt%, P 0.080~0.150wt%, S≤0.025wt%, the rest is Fe and unavoidable The molten iron with impurities, chemical composition C 0.15~0.30wt%, Si 0.20~0.65wt%, Mn 1.10~1.70wt%, P 0.020~0.045wt%, S 0.020~0.045wt%, the rest is Fe and unavoidable Steel scrap and chemical composition of impurities C 3.2~3.8 wt%, Si 0.30~0.60 wt%, Mn 0.30~0.60 wt%, P 0.060~0.090wt%, S 0.020~0.035wt%, the rest is Fe and unavoidable The pig iron with impurities is added to the LD converter for top-bottom combined blowing, and lime, dolomite and magnesite balls are added to make slag. The amount of lime added is 30~40kg / t steel, and the amount o...

Embodiment 1

[0045] A, molten iron converter smelting: molten iron (chemical composition C 3.8wt%, Si 0.30wt%, Mn 0.25wt%, P 0.100wt%, S≤0.018wt%, the rest is Fe and unavoidable impurities), steel scrap (chemical composition C 0.15wt%, Si 0.20wt%, Mn 1.10wt%, P 0.020wt%, S 0.020wt%, the rest is Fe and unavoidable impurities) and pig iron (chemical composition C 3.2wt%, Si 0.35 wt%, Mn 0.30 wt%, P 0.050wt%, S 0.020wt%, and the rest are Fe and unavoidable impurities) into the LD converter for conventional top-bottom compound blowing, adding conventional lime, dolomite, Magnesite ball slagging, the addition of lime is 30kg / t steel, the addition of dolomite is 15kg / t steel, the addition of magnesite balls is 4.0kg / t steel, the carbon content of the control end point is ≥0.10wt%, and the tapping temperature is 1610°C; before tapping, add active lime (activity degree ≥ 300ml) to the bottom of the ladle for slag washing, the amount of lime added is 2.0kg / t steel, the tapping process adopts the wh...

Embodiment 2

[0058] A, molten iron converter smelting: molten iron (chemical composition C 4.3wt%, Si 0.50wt%, Mn0.40wt%, P 0.110wt%, S0.020wt%, the rest are Fe and unavoidable impurities), steel scrap ( Chemical composition C 0.22wt%, Si 0.41wt%, Mn 1.40wt%, P0.032wt%, S 0.030wt%, the rest is Fe and unavoidable impurities) and pig iron (chemical composition C 3.5 wt%, Si 0.50 wt%, Mn 0.45wt%, P 0.075wt%, S 0.027wt%, and the rest are Fe and unavoidable impurities) into the LD converter for conventional top-bottom compound blowing, adding conventional lime, dolomite, diamond Magnesium ball slagging, the addition of lime is 35kg / t of steel, the addition of dolomite is 17.5kg / t of steel, the addition of magnesite balls is 5.0kg / t of steel, the carbon content of the control end point is 0.14wt%, and the tapping temperature is 1620 ℃; Before tapping, add active lime (activity degree ≥ 300ml) to the bottom of the ladle for slag washing. The amount of lime added is 2.0kg / t steel. The tapping proc...

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Abstract

The invention discloses a twisted steel for a 785 MPa-level high-strength prestressed structure and a preparation method of the twisted steel. The twisted steel comprises following constituents in percentage by weight: 0.50-0.55% of C, 0.80-1.10% of Si, 1.00-1.30% of Mn, 0.060-0.12% of V, 0.60-0.95% of Cr, 0.0015-0.0040% of B, 0.010-0.025% of S, 0.010-0.025% of P, and the balance of Fe and unavoidable impurities. The preparation method comprises steps of billet preparation, rolling and after treatment. In the preparation process, when vanadium is utilized to conduct microalloying and reinforcement, the alloying element B is appropriately added to improve the steel hardenability, and the addition of the microalloying reinforcing elements is lowered. As the controlled rolling technology is combined and the cooling technology is applied, the grain refinement of steel structure is obvious, the net-like ferritic structure at the core of the steel is lowered, the steel strength is increased, the hardness gradient change is slow, and the stability of the precision rolled twisted steel is improved. The processed steel is stable in technologic and mechanical performances, and good in prestress relaxation performance.

Description

technical field [0001] The invention belongs to the technical field of metal material processing, and in particular relates to a threaded steel bar for 785MPa high-strength prestressed structures and a preparation method thereof. Background technique [0002] High-strength finish-rolled threaded steel bars for prestressed structures are referred to as finish-rolled threaded steel bars for short. It has the advantages of high strength, convenient and reliable connection, tensioning, and anchoring. It does not need cold drawing and welding during construction, and the construction is simple. Widely used in continuous beams and large frame structures of large-scale water conservancy, industrial and civil buildings, large and medium-span bridges for highways and railways, prestressed concrete structures such as nuclear power plants, and geotechnical anchorage projects. [0003] The traditional production process of finished rolled rebar usually adopts rolling + off-line heat tre...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C38/32C22C33/04
CPCC22C33/04C22C38/02C22C38/04C22C38/12C22C38/18C22C38/32
Inventor 高勇张瑜王洁
Owner WUKUN STEEL
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