The 45 steel grade is commonly used in various industries, including:

1. Automotive industry: Components such as shafts, gears, and crankshafts in engines and transmissions.

2. Machinery manufacturing: Parts such as bolts, nuts, and machinery components.

3. Construction industry: Structural components, such as steel beams and columns.

4. Oil and gas industry: Pipes and fittings used for transporting and extracting oil and gas.

5. Manufacturing industry: Various tools, dies, and molds.

6. Aerospace industry: Components used in aircraft structures and engines.

7. Energy industry: Equipment such as turbines and generators.

8. Mining industry: Components used in mining equipment, such as drill bits and crushers.

9. Railway industry: Components for railway tracks, bridges, and locomotives.

These industries rely on the 45 steel grade due to its desirable mechanical properties, high strength, good toughness, and wear resistance. The chemical composition and heat treatment also play a crucial role in determining the suitability of 45 steel grade for specific applications.