ASTM A735 steel is a material standard for medium and high silicon steel plates used in high temperature and high pressure services, especially suitable for manufacturing boilers and pressure vessels. This standard specifies the technical requirements for ASTM A735 steel's chemical composition, mechanical performance requirements, impact testing, hardness, dimensional tolerances, heat treatment requirements, surface quality, detection and control requirements, etc.

ASTM A735 standard is aimed at medium and high silicon steel plates for high temperature and high pressure service. Its chemical composition requirements include:

1. Carbon content: no more than 0.30%. Carbon is the basic element of steel and affects strength and hardness.

2. Manganese content: 0.70-1.60%. Manganese increases the strength and toughness of steel.

3. Silicon content: 0.15-0.60%. Silicon helps improve steel's resistance to wear and corrosion.

4. Phosphorus content: not more than 0.025%. Too much phosphorus can reduce the toughness of steel.

5. Sulfur content: not more than 0.025%. Sulfur affects the workability and brittleness of steel.

6. Molybdenum content: not more than 0.10%. Molybdenum increases the strength and corrosion resistance of steel.

7. Nickel content: not more than 0.40%. Nickel increases the corrosion resistance and strength of steel.

8. Chromium content: not more than 0.35%. Chromium helps improve steel's corrosion resistance.

9. Copper content: not more than 0.25%. Copper increases steel's corrosion resistance.

10. Vanadium content: no more than 0.08%. Vanadium increases the strength and wear resistance of steel.

The control of these chemical compositions can ensure that ASTM A735 steel has the required mechanical properties and durability, and is suitable for manufacturing equipment such as boilers and pressure vessels that work under high temperature and high pressure conditions. These requirements are designed to ensure material reliability, resistance to high temperature and pressure use, and safety. ASTM A735 steel is of great significance for manufacturing equipment and components that need to withstand extreme working conditions.