Preparation method of high-toughness Q345 grade hot-rolled equal angle steel for iron tower

Abstract

The invention discloses a preparation method of high-toughness Q345 grade hot-rolled equal angle steel for an iron tower. The method comprises the following steps: 1) smelting a billet: preparing the billet by adopting converter or electric furnace smelting, external refining and protective casting, wherein the carbon equivalent is not more than 0.42%; 2) rolling the billet: rolling the billet according to the sequence of elongation pass, slitting pass and finishing pass, wherein the total compression ratio is not less than 5 and the mean coefficient of elongation of the finishing pass is not less than 1.12; 3) controlling the finishing rolling temperature, wherein the finishing rolling temperature is 930-880 DEG C; 4) cooling with a cooling bed, wherein when the steel temperature is more than 400 DEG C, natural cooling and auxiliary air cooling or fog cooling are adopted; when the steel temperature is less than 400 DEG C, spray cooling is adopted; 5) entering a conventional subsequent procedure and finally preparing the high-toughness Q345 grade hot-rolled equal angle steel for the iron tower. The impact toughness of the angle steel at low temperature is improved while ensuring that the angle steel has sufficient strength by adopting the preparation method.

Description

technical field [0001] The invention relates to a toughening (especially low-temperature toughness) technology of Q345 grade hot-rolled equilateral angle steel for iron towers, in particular to a preparation process for high-toughness Q345 grade hot-rolled equilateral angle steel for iron towers. Background technique [0002] In recent years, my country's power grid construction has made great progress, especially the construction level and development speed of UHV transmission lines are at the forefront of the world. In transmission towers, hot-rolled equilateral angle steel is the most widely used. [0003] According to the different S and P content of steel and impact test requirements, Chinese standards divide structural steel into different quality grades (see Table 1, Table 2). At present, Q235B and Q345B hot-rolled equilateral angle steels are the most widely used in my country, and the product quality of B-grade quality angle steels is relatively stable, but they on...

AI Technical Summary

Problems solved by technology

According to my country's power grid planning, UHV transmission lines will be built in Northeast my country, North China, and Northwest China. These areas have low winter temperatures and require impact toughness guarantees at lower temperatures (-30°C). Currently, there are only a few steel mills in my country It is able to produce C-level angle steels, and D and E-level angle steels currently do not have the production capacity in China, which brings hidden dangers to the long-term safe operation of transmission towers in cold regions.

Images