1. Medium carbon steel: The representative steels are 3, 35, 4 and 45, but also ML3, ML35, ML4 and ML45, which have relatively stable room temperature performance and are used for small and medium-sized structural parts, fasteners, transmission shafts and gears.

2. Manganese steel: representing steel grades 4Mn2 and 5Mn2. It has overheating sensitivity, high-temperature tempering brittleness, easy cracking after water quenching, and higher hardenability than carbon steel.

3. Silicon-manganese steel: representing steel grades 35SiMn and 42SiMn. High fatigue strength, decarburization and overheating sensitivity and temper brittleness. It is used to manufacture gears, shafts, rotating shafts, connecting rods, worms, etc. with medium and high load but little impact, and can also manufacture fasteners below 4℃.

4. boron steel: representing steel grades 4B, 45B, 5BA and ML35B. The hardenability is high, and the comprehensive mechanical properties are higher than those of carbon steel, which is equivalent to 4Cr. It is used to manufacture parts and fasteners with small cross-sectional dimensions.

5. Mn-B steel: representing steel grade 4MnB. Hardenability slightly higher than 4Cr, high strength, toughness and low temperature impact toughness, temper brittleness. 4MnB is often used to replace 4Cr to manufacture large-section parts and 4CrNi to manufacture small parts. 45MnB instead of 4Cr and 45Cr；; 45Mn2B replaces 45Cr and partially replaces 4CrNi and 45CrNi as important shafts, and there is also ML35MnB used in fastener production.

6. Mn-V-B steel: representing steel grades 2MnVB, 4MnVB,. The quenching and tempering properties and hardenability are better than 4Cr, and it has a small tendency to overheat and temper brittleness. It is often used to replace 4Cr, 45Cr, 38CrSi, 42CrMo and 4CrNi to manufacture important quenched and tempered parts, and it also uses ML2MnVB for small and medium-sized bolts below grade 1.9.

7. Mn-W-B steel: 4MnWB. Good low temperature impact performance, no temper brittleness. It is equivalent to 35CrMo and 4CrNi, and is used to manufacture parts below 7mm.

8. Si-Mn-Mo-W steel: representing steel grade 35SiMn2MoW. It has high hardenability, calculated by 5% martensite, the water quenching diameter is 18 and the oil quenching diameter is 1; The tendency of quenching cracking and tempering brittleness is small; It has high strength and toughness. It can replace 35CrNiMoA and 4CrNiMo to manufacture shafts, connecting rods and bolts with large cross section and heavy load.

9. Si-Mn-Mo-W-V steel: the representative steel grade is 37SiMn2MoWVA. Water quenching diameter 1, oil quenching diameter 7; Good tempering stability, low-temperature impact toughness, higher high-temperature strength and less tempering brittleness, and it is used to manufacture large-section shaft parts.

1. chromium steel: represented by 4Cr and ML4Cr. Good hardenability, water quenching 28-6mm, oil quenching 15-4 mm. High comprehensive mechanical properties, good low-temperature impact toughness, low notch sensitivity and temper brittleness. Used for manufacturing shafts, connecting rods, gears and bolts.

11. Chrome silicon steel: it represents steel grade 38CrSi. The hardenability is better than 4Cr, the strength and low temperature impact are higher, the tempering stability is better, and the tendency of tempering brittleness is greater. It is often used to manufacture 3-4mm shafts, bolts and gears with small modulus.

12. Cr-Mo steel: representing steel grades 3CrMoA, 42CrMo, ML3CrMo and ML42CrMo. Quenching in water for 3-55mm, and quenching in oil for 15-4 mm; High room temperature mechanical properties, high high temperature strength and good low temperature impact; No temper brittleness. Used for manufacturing parts with large cross section, bolts and gears with high load, flanges and bolts below 5℃; Conduits and fasteners below 4℃. The hardenability of 42CrMo is higher than that of 3CrMoA, and it is used to manufacture parts with higher strength and larger cross section.

13. Cr-Mn-Mo steel: representing steel grade of 4CrMnMo. The diameter of oil quenching is 8mm, which has high comprehensive mechanical properties and good tempering stability. It is used to manufacture heavy-duty gears and shaft parts with large cross section.

14. Mn-Mo-V steel: the representative steel grade is 3Mn2MoWA. It has good hardenability: water quenching reaches 15mm, and the core structure is upper and lower bainite plus a small amount of martensite; Oil quenching 7mm, more than 95% martensite in the center; Good low temperature impact toughness, low notch sensitivity and high fatigue strength. Used to manufacture important parts below 8 mm.

15. Cr-Mn-Si steel: representing steel grade 3CrMnSiA. Water quenching 4~6mm(95% martensite) and oil quenching 25~4mm. High strength, high impact toughness and temper brittleness. Used for manufacturing high-pressure blower blades, valve plates, clutch friction plates, shafts and gears.

16. Cr-Ni steel: representing steel grades 4CrNi and 45CrNi. Water quenching is 4mm, and oil quenching is 15 ~ 25 mm; Good comprehensive mechanical properties, good low-temperature impact toughness, and little tendency to temper brittleness. 3CrNi3A has high hardenability, good comprehensive mechanical properties, white spot sensitivity and temper brittleness. It is used to manufacture crankshafts, connecting rods, gears, shafts and bolts with large cross sections.

17. Cr-Ni-Mo steel: representing steel grade 4CrNiMoA. It has excellent comprehensive mechanical properties, high impact toughness at low temperature, low notch sensitivity and no temper brittleness. It is used to manufacture large crankshafts, shafts, connecting rods, gears, bolts and other parts with large stress and complex shapes.

18. Cr-Ni-Mo-V steel: representing steel grade 45CrNiMoVA. High strength, good tempering stability, oil quenching up to 6mm(95% martensite). It is used to manufacture elastic shafts and torsion shafts of heavy-duty vehicles under vibration load.