Microalloy HRB500E steel bar containing chrome and nitrogen and production method thereof

Abstract

The invention discloses a microalloy HRB500E 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 HRB500E steel bar can be produced; Rel of the steel bar is 520 to 580MPa, Rm of the steel bar is 640 to 730 MPa, A is 22 to 32 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 0.50, and the comprehensive cost of one ton of steel bar is 40-100 yuan lower than that of one ton of the steel bar produced by the conventional method; during aging of three months, the fluctuation values of the Rm value and the Rel value are less than 10MPa; and the steel bar has excellent welding performance and good corrosion-proof property.

Description

technical field [0001] The invention relates to a chromium-nitrogen micro-alloyed steel bar and a production process thereof, in particular to a HRB500E steel bar with chromium and nitrogen micro-alloying treatment and a production process thereof. Background technique [0002] At present, there are three types of production processes for HRB500MPa 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, and using niobium-iron alloys for niobium microalloying. Alloying, its main components control [Mn] between 1.3-1.6%, [Si] between 0.45-0.80%, [C] between 0.17-0.25%, [V] between 0.08-0.12% Sometimes [Nb] is controlled between 0.05-0.12%, or vanadium + niobium composite alloying is used. Yield strength (Rel) ≥ 500MPa, tensile strength (Rm) ≥ 630MPa, reduction of area (A) ≥ 16%, m...

AI Technical Summary

Problems solved by technology

However, this method has the following problems: ① high silicon-manganese and carbon content, high carbon equivalent, poor welding performance, and high alloy cost; ② element segregation is easy to occur during solidification and cooling; ③ high vanadium or niobium content, On the one hand, a large amount of precious resources are consumed, and on the other hand, the cost of the alloy is high; ④ Yield is not obvious and mixed crystals are prone to occur

The disadvantages of this method are: ①It is necessary to greatly increase the capacity of the rolling mill or to build a new rolling production line, which requires a huge investment, and the existing equipment cannot be used; The strength is greatly reduced; ③The production of HRB500 by this method is still in the stage of industrial exploration and experimentation, the technology is immature, there are many uncontrollable factors, and the product quality is unstable

The third category is to control the composition to the lower limit, and rarely use vanadium or niobium, and the composition of the alloy can be greatly reduced by forced cooling through water after rolling. This method is only in the stage of industrial testing, and has the following obvious defects: ① Need Increase water-piercing equipment and increase investment; ②The performance of steel bars fluctuates greatly, the aging phenomenon is serious, and the stability of product quality is extremely poor; The HRB500 steel bar produced by this method is not accepted; ④The surface and core structure of the steel bar are 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