Alloy structural steel engineering and metallurgical process characteristics

Engineering structural steel is used to manufacture a variety of projects specifically refers to a large class of steel structures, such as the manufacture of bridges, hulls, oil or mine steel, rail, pressure vessels, piping and building steel structure. In steel production, and engineering structural steel accounts for about 90%. Engineering structural steel, including carbon steel and low alloy high strength steel.
Common structural steel works is a low carbon hot rolled or normalized form used, the microstructure is ferrite - pearlite. In order to be able to withstand greater loads and to reduce the weight of the structure, requiring the steel has high strength and good ductility. Therefore, through the ferrite - pearlite steel alloying elements to improve strength and toughness.
Carbon steel, structural steel is the most widely used, the maximum number of. Often rolled into sheets, profiles and generally does not require heat-treated directly. For general construction and engineering.
First, low-alloy high-strength structural steels alloyed
Low alloy high strength steel often use Nb, V, Ti alloying grain refinement. Its role order: Ti, Nb, V. The basic components of low alloy high strength steel manganese content should be considered a low-carbon, slightly higher, and the appropriate use of silicone enhancement.
Structural steel engineering performance requirements:
1) sufficiently high strength, good ductility;
2) the appropriate room temperature impact toughness, sometimes requires appropriate low temperature impact toughness;
3) Good process performance.
Second, structural steel metallurgical process engineering features: controlled rolling and controlled cooling
Controlled rolling mainly consists of three phases:
1) high temperature recrystallization region of deformation;
2) in the immediate vicinity of the low-temperature above Ar3 no recrystallization zone deformation;
3) deformation of austenite and ferrite two-phase region
Billet heating temperature, holding time, open rolling temperature, rolling passes and road deformation of times, finishing temperature and cooling after rolling and other parameters, are extremely important. By controlling various parameters of the rolling process, the formation of the rolling process.
Mainly controlled cooling after coiling phase transition process.