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06Cr25Ni20 (equal to US grade 310S / UNS S31008) is a high-chromium nickel austenitic stainless steel. It has good resistance to high-temperature oxidation, high-temperature strength, and corrosion resistance. It is widely used to make radiant tubes, furnace rollers, muffle tanks, and other furnace parts in industrial heating furnaces. This product is supplied as forged plate and delivered after solution heat treatment. It is specially designed for the tough working conditions of built-in heating furnace tubes.
This product is made strictly according to the JB/T 6398-2018 standard — Heavy stainless acid resistant steel and heat resistant steel forgings — Technical specification. This standard has strict rules on melting (vacuum refining), forging ratio (main section forging ratio ≥ 3), and heat treatment temperature control (deviation ≤ ±10°C). These rules make sure the forging is dense inside and has no defects.
Element | C | Si | Mn | P | S | Cr | Ni |
Value | ≤0.08 | ≤1.50 | ≤2.00 | ≤0.030 | ≤0.020 | 24.00~26.00 | 19.00~22.00 |
The residual Cu content in the steel is no more than 0.20%. The ratio of high Cr (24-26%) to high Ni (19-22%) is the core basis for the material's resistance to high-temperature oxidation.
Standard | Grade |
GB/T 20878 | 06Cr25Ni20 |
ASTM | 310S / UNS S31008 |
ASME | SA-240 310S |
JIS | SUS 310S |
EN | 1.4841 / X8CrNiSi25-21 |
Item | Value |
yield strength Rp0.2 (MPa) | ≥205 |
tensile strength Rm (MPa) | ≥520 |
elongation A (%) | ≥40 |
reduction of area Z (%) | ≥50 |
Hardness HBW | ≤187 |
High-temperature performance
Continuous operating temperature: 1000℃ - 1100℃, up to 1200℃ for short periods
Melting point range: 1398℃ - 1454℃
High-temperature tensile performance reference (in the 600 - 1000℃ range): Yield strength decreases from 180 MPa to 40 MPa, tensile strength decreases from 450 MPa to 50 MPa
Q1: Why is this forged plate good for built-in heating furnace tubes?
A: 06Cr25Ni20 can form a dense Cr₂O₃ oxide film in high-temperature oxidizing conditions. This film stops oxygen atoms from going into the steel. It can work continuously at up to 1100°C. Its austenitic structure does not change at high temperatures, so its properties stay stable. The low carbon content (≤0.08%) reduces the risk of chromium carbide forming at grain boundaries, which helps improve thermal fatigue resistance and resistance to intergranular corrosion. That is why it is a good material for radiant tubes, furnace rollers, muffle tanks, and similar parts.
Q2: What international standards apply to this product?
A: This product is made according to JB/T 6398-2018. The related international standards are:
ASTM A965/A965M – Specification for Austenitic Stainless Steel Forgings for Pressure and High-Temperature Parts (includes grades like 310H)
ASTM A745/A745M – Standard Practice for Ultrasonic Examination of Austenitic Steel Forgings
ASTM A388/A388M – Standard Practice for Ultrasonic Examination of Heavy Steel Forgings
Q3: How is non-destructive testing (NDT) done?
A: According to JB/T 6398-2018 sections 5.5 and 6.4, the ultrasonic test for austenitic stainless steel forgings is done by a method agreed between the supplier and the buyer. In international markets, people often follow ASTM A745/A745M using straight-beam and angle-beam pulse-echo ultrasonic testing. They can also use ASTM A388/A388M.
Q4: What is the delivery condition of the forged plate?
A: The standard delivery condition is solution heat treatment (see JB/T 6398-2018 section 4.3.1). This means heating the steel to 1040~1180°C and then cooling it quickly. This gives a uniform single-phase austenitic structure and ensures the best high-temperature performance.
Q5: What are the hardness uniformity requirements?
A: According to JB/T 6398-2018 section 3.5, the surface hardness uniformity on the same forging should be ≤30 HBW, and on the same batch of forgings it should be ≤40 HBW.
