SUS630 stainless steel: mechanical properties，heat treatment

What is sus 630 material?

SUS630 is a high-strength, corrosion-resistant, martensitic precipitation-hardening stainless steel (also known as 17-4 PH) that gets its name from its approximate composition of 17% chromium and 4% nickel, plus copper and niobium. It offers excellent mechanical properties, including high strength and hardness after heat treatment (aging), while maintaining good corrosion resistance similar to Grade 304 stainless steel, making it ideal for aerospace, medical, and general engineering parts like shafts, fasteners, and valves.

 

What is the equivalent materials for SUS630 stainless steel?

SUS630 stainless steel is a precipitation-hardening grade, and its main equivalents are AISI 630, UNS S17400, and EN 1.4542, often known as 17-4PH, offering high strength, hardness, and good corrosion resistance similar to Grade 304. Other common designations include X5CrNiCuNb16-4 (European/ISO) and NAS 630.

Equivalent Grade	Europe (EN)	Japan (JIS)	China (GB)	India (IS)
630 Stainless Steel	1.4542	SUS630	0Cr17Ni4Cu4Nb	X5CrNiCuNb16-4

 

SUS630 Chemical Composition (Typical, wt.%)

Element	Chromium (Cr)	Nickel (Ni)	Copper (Cu)	Niobium (Nb)	Carbon (C)	Manganese (Mn)	Silicon (Si)	Phosphorus (P)	Sulfur (S)
Percentage (%)	15-17.5	3-5	3-5	0.15-0.45	≤0.07	≤1.00	≤1.00	≤0.04	≤0.03

 

SUS630 Mechanical Properties (By Heat Treatment Condition)

Condition	Tensile Strength (MPa)	Yield Strength (MPa)	Hardness	Elongation (%)
Solution Annealed (A)	≥ 930	≥ 725	≤ HRC 28	≥ 10
H900	≥ 1310	≥ 1170	HRC 40–44	≥ 10
H1025	≥ 1070	≥ 1000	HRC 35–38	≥ 12
H1075	≥ 1000	≥ 860	HRC 32–35	≥ 13
H1150	≥ 930	≥ 725	HRC 28–32	≥ 15

 

Physical Properties of SS 630

630 stainless steel (17-4PH) has key physical properties like high density, good thermal conductivity, and electrical resistivity, making it suitable for aerospace components, chemical processing equipment, marine applications, etc. The values below are general and may not apply in all environments, especially extreme temperatures or corrosive conditions.

Property	Metric (SI)	Imperial (US)
Density	7.80 g/cm³	0.282 lb/in³
Melting Point	1400-1440°C	2550-2625°F
Thermal Conductivity	16.3 W/m·K	9.4 BTU/(hr·ft·°F)
Electrical Resistivity	0.8 x 10⁻⁶ Ω·m	31.5 x 10⁻⁶ Ω·in
Specific Heat Capacity	460 J/kg·K	0.11 BTU/lb·°F
Thermal Expansion Coefficient	10.8 x 10⁻⁶ /K (20-100°C)	6.0 x 10⁻⁶ /°F (70-212°F)

 

SUS630 Stainless Steel Corrosion Resistance
Under weakly acidic or neutral conditions, the corrosion resistance of 630 stainless steel is comparable to that of 304 stainless steel. Its high chromium, nickel, and copper content ensures durability and effectively resists stress corrosion cracking, making it suitable for various industries. Its corrosion resistance is further enhanced by processing at higher aging temperatures.

 

SUS630 Stainless Steel Heat Resistance
630 stainless steel exhibits good oxidation resistance below 550°C, effectively resisting corrosion from atmospheric environments, dilute acids, and salts. Heat treatment between 1010°C and 1150°C restores its toughness and strength, making it suitable for high-temperature environments.

 

SUS630 Stainless Steel Weldability
630 stainless steel can be welded using standard welding techniques without preheating. Post-weld heat treatment is recommended to restore the material's mechanical properties. In the solution-treated condition, its machinability is similar to that of 304 stainless steel.

 

SUS630 Stainless Steel Machinability
Despite its high hardness, 630 stainless steel has relatively good machinability, especially in the annealed or unaged condition. It supports turning, milling, and drilling, and excellent machining results can be achieved.

 

Is SUS630 Stainless Steel Magnetic?
Due to its martensitic structure, 630 stainless steel is magnetic in both the annealed and hardened states. Its magnetic response is stronger in the solution-treated state, but the magnetism decreases after aging treatment, making it suitable for applications requiring moderate magnetism.