| HRB500 hot-rolled ribbed steel bar has the characters of high strength, good toughness and good shock resistance. To achieve the same strength, the dosage of steel bars will save a lot (28% to HRB335, 14% to HRB400). HRB500 steel bar is a kind of high efficiency material, a large number of ore, coke, water, and electricity will be retrenched if HRB335 steel bars is replaced. Also, environment will be benefited from using HRB500. Nowadays, the steel bars of 400Mpa were widely used instead of 335Mpa overseas. Well, the opposite situation to china, where HRB335 were mainly used in the construction of architecture. VN micro alloyed steel can satisfy the standard of GB1499-1998 on the mechanical property of HRB500. To research and develop the production process of HRB500 is of great significance to the national economy.In the process of small converter and tandem rolling, the HRB500 were successfully developed with VN alloy.The cost of the steel bars reduced 616RMB per ton.The effect and existence shape of vanadium& nitrogen were analyzed in this paper, the influence of chemical composition, micro-structure, the way of smelting and rolling to HRB500 were discussed. Then, the regression equation of main chemical composition (containingC, Mn, V) to the mechanical property was figured out by regression analysis. In the end, the production processes of HRB500 were given.The experimental results show that: the average content of vanadium& nitrogen is 0.08%, 0.0096% by adding VN alloys 1.1 Kg per ton. The average yield strength and tensile strength reaches 546Mpa and 701Mpa. The specific elongation is 20%, σ_b/σ_s equals 1.28. The performance of cold bending and reverse bending are up to grade. All the figures above were higher than the national standard. The yield strength increases 200Mpa by VN alloy. The effect of precipitation hardening of vanadium was engendered by nitrogen. It is proved that VN alloy is the efficient way of micro alloying. |
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