630 stainless steel is a high-strength, high-corrosion-resistant stainless steel alloy, also known as 17-4PH stainless steel, which is a martensitic stainless steel that is precipitation hardened to achieve excellent mechanical properties. It is composed of elements such as iron, chromium, nickel and copper, of which 17 means that it contains 17% chromium and 4 means that it contains 4% nickel. One of the main advantages of this stainless steel is that it can be machined and age hardened in solution treated conditions to obtain high strength. It is often used in aerospace, petrochemical, automobile manufacturing, marine engineering and medical equipment and other fields.

Chemical composition of 630 stainless steel



chemical composition



















630 stainless steel mechanical properties



mechanical properties





1000-1300  (MPa)

800-1100 MPa

10% and 15%

40-45 HRC

Physical properties of 630 stainless steel



physical properties



Mean Co-eff of Thermal Expansion (µm/m/°C)


Specific Heat 0-100°C

Elec Resistivity




At 100°C

At 500°C









Heat resistance of 630 stainless steel

Stainless steel has certain heat resistance, but its specific heat resistance depends on the grade and composition of the stainless steel material used.

Generally speaking, common stainless steel materials such as 304 stainless steel and 316 stainless steel have better heat resistance at high temperatures. They can withstand temperatures up to around 870°C at normal temperatures and higher temperatures at lower temperatures.

In addition to the grade and composition of the material, there are other factors that also affect the heat resistance of stainless steel. For example, the processing, heat treatment and service conditions of stainless steel may affect its heat resistance.

In general, 630 stainless steel (17-4PH) also has certain heat resistance and can be used in high temperature environments, but the specific heat resistance performance needs to be tested and evaluated according to the use conditions and requirements.

Corrosion resistance of 630 stainless steel

630 stainless steel, also called 17-4PH stainless steel, is a stainless steel material with good oxidation resistance.

The corrosion resistance of 630 stainless steel is mainly reflected in the following aspects:

High-strength corrosion resistance: 630 stainless steel has high tensile strength and yield strength, and belongs to the high-strength category in stainless steel. Even under high temperature and high pressure, 630 stainless steel can still maintain good corrosion resistance.

Oxidation and corrosion resistance: 630 stainless steel has good oxidation resistance and can form a dense and stable oxide film in the air to effectively prevent further oxidation and corrosion of metals.

Acid resistance: 630 stainless steel has good resistance to common acid solutions, such as sulfuric acid, hydrochloric acid, nitric acid, etc., and can be used in acidic environments for a long time without corrosion.

Alkali resistance: 630 stainless steel also has good resistance to alkali solutions of general concentration, such as sodium hydroxide, potassium hydroxide, etc., and is not easy to corrode.

It should be noted that although 630 stainless steel has good corrosion resistance, corrosion may still occur in some special corrosive media (such as chloride ions, high-concentration sulfuric acid, etc.). Therefore, prolonged exposure of 630 grade to temperatures of 370 to 480°C should be avoided to prevent loss of toughness at ambient temperatures. These grades should not be used at temperatures above the age hardening temperature to avoid reducing the hardness and mechanical properties of the metal.

Heat Treatment of 630 Stainless Steel

630 stainless steel is an austenitic stainless steel with high strength and excellent corrosion resistance. It can be heat treated to improve its mechanical properties and corrosion resistance.

Common heat treatment methods include solution treatment and quenching treatment.

Solution treated, grade 630 stainless steel heated at 1040°C for 0.5 hours then air cooled to 30°C. A small portion of these grades can be oil quenched. 630 stainless steel after solution treatment is often used in hydrogen sulfide corrosion resistant environment.

Quenching treatment, that is, rapid cooling after solid solution treatment, so that stainless steel can quickly form a martensitic structure and improve its hardness and strength. Quenched 630 stainless steel is often used in applications requiring high strength and wear resistance.

Hardening — Grade 630 stainless steel is age hardened at low temperatures to achieve the desired mechanical properties. During this process, surface discoloration occurs with subsequent shrinkage of 0.10% for H1150 and 0.05% for H900.

Welding of 630 stainless steel

Welding of stainless steel is performed using Type 630 stainless steel welding consumables. According to different welding methods and requirements, techniques such as plasma welding, TIG welding or MIG welding can be used for welding. Welding 630 stainless steel does not require preheating, but care needs to be taken when designing and welding high-strength steels to prevent weld stress.

Machinability of 630 stainless steel

630 stainless steel and 304 stainless steel have similar processing rates, and they can both be machined in the solution treated state.

Application of 630 stainless steel

Stainless steel 630 is a high-strength, corrosion-resistant stainless steel that is widely used in the following fields:

  1. Aerospace field: used to manufacture aircraft and spacecraft parts, such as engine parts, missile parts, satellite parts, etc.
  2. Chemical industry: used to manufacture chemical equipment, such as pipelines, containers, reactors, etc. 630 stainless steel has good corrosion resistance and can resist the corrosion of many kinds of chemicals.
  3. Marine engineering field: used to manufacture marine platforms, marine pipelines, marine bridges and other facilities. 630 stainless steel has excellent seawater corrosion resistance and can be used for a long time in harsh marine environments.
  4. Automobile industry: used in the manufacture of auto parts, such as engine parts, chassis parts, exhaust systems, etc. The high strength and tensile properties of 630 stainless steel can meet the requirements of the automotive industry for parts.
  5. Medical equipment field: for the manufacture of surgical instruments, implants, etc. 630 stainless steel has excellent biocompatibility and corrosion resistance, and is suitable for medical devices.

All in all, 630 stainless steel has the advantages of high strength and corrosion resistance, and is widely used in aerospace, chemical industry, marine engineering, automobile industry and medical equipment and other fields.