Quality carbon structural steel
This steel is characterized by reduced content of impurities, carbon, silicon and manganese comparing to commercial grades.
Quality carbon structural steel is delivered in the form of forgings and rolled stock for further heat treatment, it shows low hardenability and usually used for production of welded structures and machine parts that work under mechanical load.
Alloy structural steel
This is the most numerous group of steel grades. They are characterized by low carbon content (up to 0.6%) and comparatively low content of alloying elements (up to 7-8%).
The following three groups can be singled out:
low-alloy steel, where alloying element content is up to 2.5%;
- medium alloy steel with 2.5-6.0% of alloying elements;
high-alloy steel with over 6.0% of alloying element content.
Low-alloy steel is used for metal constructions (this is manganese steel, silico-manganese steel, vanadium-manganese steel, chromium-silicon-manganese steel, chromium-silicon-nickel steel with copper) and for reinforcement of ferroconcrete constructions (silico-manganese steel with zirconium, and silicon steel). Low-alloy steels show higher toughness, decreased sensitivity to ageing, good weldability; they can be easily machined or cold worked.
Nickel containing steels work as parts under impact loads.
High-strength alloy steels serve in transport and basic engineering industry, automotive industry for production of heavy-loaded parts under impact loads, as well as for machine parts, gears, tubing, steelworks.
The majority of alloy steels is subjected to soft annealing to facilitate cutting or simple cold treatment by pressure. Softening is carried out at 700-800°C for the most of these grades.
Flakes are the main defect inherent to these steels that occur during large section rolling.
Steel grades 18-25X2H4M(B)A, 30X2H2BÔ, 30X2H2BA, 20XH4ÔA at the temperature over Ac1 are liable to quenching even when subsequent cooling is very slow. In this case, steel softening is obtained by triple heat treatment at the temperature of 650-680°C maximum.
The product range of various alloy structural steel grades is:
shafts, spindles, gear-wheels and other parts that shall have enhanced hardness, wear resistance and toughness, as well as those which work under impact loads;
friction disks, shafts, gear-wheels, bearing bushes, cranks and other parts requiring enhanced toughness and wear resistance;
axles, flanges, fingers, forks, parts of welded structures that work under alternating loads;
gear-wheels, shafts, fastening parts working at the temperature of up to 450-500°C;
rods, excavating machine shafts, worm shafts and other parts working at the temperature of up to 400°C.
Springs and membranes made of spring steel are very important parts of different machines. In many cases, spring steels shall have not only high elasticity property, but also corrosion resistance and shall be non-magnetized.
Spring steels of general application
The steel shall have high resistance to low plastic deformation (high elasticity) and high toughness. Besides, in spring production carbon steel grades 65-85 are widely used. These steels are subjected to special heat treatment (i.e. patenting) to obtain high elasticity properties and toughness. After cold plastic deformation the steel gains high elasticity and toughness properties. Except patenting these steels can be subjected to quenching with short-term tempering, electric tempering or normalizing with further cold deformation. All spring steels are liable to decarburization.
Spring steels of general application
Springs that serve in aggressive medium (e.g. vapour, sea water, tropic climate) are made of stainless steel.