What is 630 stainless steel?

2025-03-19

What is 630 stainless steel:

630 stainless steel is a 17-4 martensitic stainless steel with excellent wear resistance, weldability, and good fabrication properties, although it may lose plasticity at high temperatures. 630 is hardened to achieve optimal mechanical properties, and high strength and hardness are achieved after heat treatment. The heat resistance and wear resistance of 630 and 304 are almost the same, and the difference between 630 and 304 is that the pressure of 304 is around 300MPA, but the pressure of 630 is over 1000MPA. The content of this article will explore the composition, mechanical and physical properties, usage methods, wear resistance, heat treatment capabilities, and considerations for processing and welding of stainless steel 630.

You are learning about 630 and intend to use this stainless steel in your work. The following is important information about 630 that you need to know before you choose them.

What is 630:

630 is a family of martensitic stainless steels made by heat treatment hardening deposition method, which involves heat treatment at high temperature and then rapid cooling to form a hard alloy crystal structure.

The main components of 630 are Crom 17-19%, Niken 3-4%, especially with a high level of Molypden elements added.

Inox 630 has high mechanical properties and corrosion resistance, and is usually produced in the form of coils, plates, axial tubes or accessories such as connectors, flanges, bolts, etc.

Is 630 stainless steel good:

Due to heat treatment and curing, as well as high chromium and nickel content, stainless steel 630 improves high corrosion resistance, even in strong acid or sea salt environments.

In addition to good corrosion resistance, 630 stainless steel also has magnetic properties, weldability and high plasticity. Compared with stainless steel 410 and 416, martensitic stainless steel 630 is overrated in all aspects.

However, compared with ordinary stainless steel widely used in Vietnamese industry, the cost of this stainless steel is relatively high, such as stainless steel 304 or 316. So it is also a very competitive market choice.

Composition of stainless steel 630:

The proportion of Crom and Niken in 630 is high, the same as 304, and these two elements determine the corrosion resistance. However, Molypden is added to 630 which is not present in 304 and this helps prevent excessive corrosion in highly acidic environments.

Chemical composition	630 Stainless Steel
Crom (Cr)	15.5 – 17.5
Mangan (Mn)	0.0 – 1.0
Silic (Si)	0.0 – 1.0
Cacbon (C)	0.0 – 0.7
Phốt pho (P)	0.0 – 0.04
Lưu huỳnh (S)	0.0 – 0.03
Niken (Ni)	3.0 – 5.0
Nb+Ta	0.15 – 0.45

Physical Properties of 630:

Going through the physical properties of 630, we can see that the weight of 1 cubic meter of Inox is 7.750 kg which indicates the strength of this Inox. In addition, you may need to be concerned with pressure index (gpas), thermal expansion (µm/m/°C) and thermal conductivity (J/kg.K).

Physical properties	Value
Density (kg/m3)	7750
Elastic modulus (GPa)	197
Mean co-eff of thermal expansion (µm/m/°C) 0-100°C	10.8
Mean co-eff of thermal expansion (µm/m/°C) 0-315°C	11.6
Mean co-eff of thermal expansion (µm/m/°C) 0-538°C	-
Thermal conductivity (W/m.K) at 100°C	18.4
Thermal conductivity (W/m.K) at 100°C	22.7
Specific heat 0-100°C (J/kg.K)	460
Elec resistivity (nΩ.m)	800

Mechanical properties of inox 630:

The mechanical properties of inox 630 include hardness, corrosion resistance and elasticity. These factors allow engineers to assess whether the load-bearing capacity of inox 630 steel is suitable for their application.

Mechanical properties	Value 1/4 Hard
Tensile strength is aged at 900°F (482°C) (MPa)	1310 min
Tensile strength is aged at 1150°F (621°C) (MPa)	930 min
Yield strength 0.2% proof is aged at 900°F (482°C)	1170 min
Yield strength 0.2% proof is aged at 1150°F (621°C)	724 min
Elongation (% in 50mm) is aged at 900°F (482°C)	10 min
Elongation (% in 50mm) is aged at 1150°F (621°C)	16 min
Hardness rockwell C (HR C) is aged at 900°F (482°C)	40 min
Hardness rockwell C (HR C) is aged at 1150°F (621°C)	28 min
Hardness brinell (HB) is aged at 900°F (482°C)	388 min
Hardness brinell (HB) is aged at 1150°F (621°C)	277 min

Heat resistance:

630 stainless steel has high heat resistance and can withstand temperatures up to 350 degrees Celsius for a short time or 250 degrees Celsius for a long time without affecting its mechanical properties.

However, it should be noted that the heat resistance of 630 stainless steel depends on the initial heat treatment process. Heat treatment increases the hardness of stainless steel but weakens its heat resistance.

Therefore, if 630 stainless steel is used for heat-resistant applications, a reputable 630 stainless steel supplier should be selected. This type of stainless steel must undergo the correct heat treatment process to ensure that hardness and heat resistance are balanced and the system operates safely.

Heat treatment technology:

Heat treatment technology goes through 4 basic stages: heating-cooling-heating-cooling. This process must be checked and evaluated regularly. Because it is an important step in determining the performance of 630 stainless steel.

630 stainless steel is heat treated, heated at 1040°C for 30 minutes to form an austenitic structure, and then cooled to 30°C in air or cooled by oil or water to form a martensitic structure to improve mechanical properties.

Manufacturing:

First, to process stainless steel 630, it must go through basic cleaning, cutting and bending steps to form the initial shape. Next comes the machining steps (milling, turning, welding, chiseling, punching, cutting, hammering, bending).

After the manufacturing process is almost completed, the next step is grinding and polishing to give the stainless steel surface an extremely high aesthetic appearance. In addition, the quality control process during the processing must also be closely monitored.

Welding technology:

The welding of 630 stainless steel is quite complicated, but it can still be welded using conventional methods. In order to obtain good welding results, the welder must have superb skills.

Follow welding techniques such as initial cleaning and setting the appropriate welding current (ampere). For example, stainless steel 630 has a higher content of Cr and Ni, so the welding current should be set lower than other stainless steels to avoid cracking of the weld.

Application of 630 stainless steel:

Due to its excellent properties such as corrosion resistance, high strength and good durability, 630 stainless steel is selected by many units for large-scale industrial applications.

Manufacturing propeller shafts and pump shafts:

These parts must withstand a lot of friction in water environments containing many corrosive substances. Therefore, using 630 stainless steel as the material for propellers and pump shafts will help improve durability.

Engine Parts Manufacturing:

Stainless steel 630 is also one of the best choices for manufacturing engine parts - these parts must be heat-resistant and have good hardness. In addition, there are other more economical options such as stainless steel 304, 316L, 420.

Plastic Mold Processing:

In addition, stainless steel 630 is also used in the plastic industry to make plastic molds due to its high wear resistance and good corrosion resistance.

Valve and Gear Manufacturing: Valve discs, valve shafts or valve gaskets and gears are all parts that must and must bear loads in the transmission system. Therefore, choosing stainless steel 630 is the best choice for this application.

Oil and Gas, Chemical Equipment:

Stainless steel 630 has very high corrosion resistance, even in acidic environments and concentrated chemicals, so it is used in the oil and gas industry, such as marine environments, chemical tanks and oil storage systems.

Gas Turbines:

In addition to being used to manufacture components such as rotors, stators and bearings, 630 stainless steel is also used to manufacture gas turbines - a component that is always subjected to high pressure and high temperature.