Microalloy HRB400E steel bar containing chrome and nitrogen and production method thereof

Abstract

The invention discloses a microalloy HRB400E steel bar containing chrome and nitrogen and a production method thereof. By fully utilizing the strengthening effect and the corrosion-proof effect of chrome on the steel bar, solid solution strengthening elements, namely manganese and silicon, are partially substituted, and a microalloy element, namely vanadium or columbium is partially or fully substituted; a cheap nitrogen element is used for performing microalloy treatment on the steel bar, so that the micro nitrogen separating strengthening effect is achieved; by the production method, the HRB400E steel bar can be produced; Rel of the steel bar is 430 to 490MPa, Rm of the steel bar is 570 to 650 MPa, A is 24 to 35 percent, Rm / Rel is 1.30 to 1.40, the cold bending qualified rate is 100 percent, the welding carbon equivalent weight is less than or equal to 0.45, and the comprehensive cost of one ton of the steel bar is 20 to 80 yuan lower than that of one ton the steel bar produced by the conventional method; during aging of three months, the fluctuations of the Rm value and the Rel value are less than 10MPa; the welding performance is excellent; and the steel bar has good corrosion-proof property.

Description

technical field [0001] The invention relates to a micro-alloyed steel bar containing chromium and nitrogen and a production process thereof, in particular to a HRB400E steel bar with micro-alloying treatment containing chromium and nitrogen and a production process thereof. Background technique [0002] At present, there are three types of production processes for HRB400MPa steel bars. One is the carbon-manganese steel system composition design mainly based on 20MnSi, using manganese and silicon-based iron alloys for manganese and silicon alloying, using vanadium-iron or vanadium-nitrogen alloys for vanadium microalloying, or using niobium-iron alloys for niobium Microalloying, the main components of which are controlled between [Mn] 1.2-1.6%, [Si] between 0.40-0.60%, [C] between 0.17-0.25%, and [V] between 0.04-0.12% Between or [Nb] is controlled between 0.03-0.08%, yield strength (Rel) ≥ 400MPa, tensile strength ≥ 550MPa, reduction of area (A) ≥ 16%, mainly relying on car...

AI Technical Summary

Problems solved by technology

However, this method has the following problems: ①Silo-manganese and carbon content are high, and the cost of the alloy increases; ②Element segregation is easy to occur during solidification and cooling; ③High carbon equivalent has poor welding performance, and the content of vanadium or niobium is high. High cost; ④ prone to inconspicuous yield and mixed crystal phenomenon

This method is still in the stage of industrial experimentation and promotion. At the same time, this method has the following disadvantages: ①It is necessary to greatly increase the capacity of the rolling mill, greatly increase equipment investment and renovate the old rolling mill, which will bring a substantial increase in fixed asset investment; ②The steel bars produced cannot use conventional Welding, otherwise the strength of the steel bar will drop significantly due to the growth of the grain in the welding zone; ③The strength-to-yield ratio of the steel bar will decrease, and the shock resistance will decrease

The third category is to control the composition to the lower limit, and rarely use vanadium or niobium. The composition of the alloy can also be greatly reduced by forced cooling through water after rolling. This method is currently used more commonly, but it is different from the national standard in some aspects such as There is a conflict in the organizational structure, which has an adverse effect on the performance of the steel bar. At the same time, there are the following defects: ① Need to increase the water penetration equipment and increase investment; ② The performance of the steel bar fluctuates greatly, and the aging phenomenon is serious; ③ The welding performance is poor; ④ The steel bar is easy to rust and anti-seismic ⑤ The structure of the steel bar surface and the core is inconsistent, and the surface is prone to tempered martensite and tempered sorbite, which exceeds the basic requirements of the national standard that the steel bar structure is ferrite + pearlite