Super Austenitic Stainless Steel (904L)

Overview

904L stainless steel is a highly alloyed, low-carbon austenitic stainless steel. It offers excellent corrosion resistance in dilute sulfuric acid and is designed for harsh corrosive environments. With high chromium and nickel content, along with added copper, it resists acids, chloride crevice corrosion, and stress corrosion cracking. Pitting and cracking are minimal, and its pitting resistance surpasses other steel grades. The material features good machinability and weldability, making it suitable for pressure vessels.

Brand Names

Chinese brand: 00Cr20Ni25Mo4.5Cu

German brand: 1.4539

American brand: N08904

European standard: 904L

Chemical Composition (%)

Carbon (C): ≤0.03

Silicon (Si): ≤1.00

Manganese (Mn): ≤2.00

Phosphorus (P): ≤0.035

Sulfur (S): ≤0.03

Nickel (Ni): 23.0-25.0

Chromium (Cr): 18.0-20.0

Molybdenum (Mo): 3.0-4.0

Copper (Cu): 4.0-5.0

Performance Characteristics

Tensile Strength (Rm): 490 N/mm²

Yield Strength (Rp0.2): 216 N/mm²

Elongation (A5): 35%

Density: 8.24 g/cm³

Applications

Petrochemical Equipment: Reactors and storage systems

Sulfuric Acid Equipment: Heat exchangers

Flue Gas Desulfurization: Absorption tower components, scrubbers, and fans

Seawater Systems: Heat exchangers and desalination equipment

Industrial Equipment: Papermaking, chemical, pharmaceutical, and food processing machinery

Household Items: Tableware, cabinets, water heaters, and bathtubs

Other Uses: Auto parts, medical equipment, building materials, and ship components

Welding Guidelines

Various welding methods can be used, including manual arc welding and inert gas shielded welding.

Welding materials should match the composition of the base material with higher molybdenum content.

Preheating is generally unnecessary, but in cold environments, joints can be warmed to avoid moisture condensation.

Local temperatures should remain below 100°C to prevent carbon buildup and intergranular corrosion.

Small line energy and continuous, fast welding rates are recommended.

Post-weld heat treatment is rarely required; if needed, heat to 1100-1150°C and cool rapidly.

Machining Guidelines

904L has machining properties similar to other austenitic stainless steels.

Carbide tools with positive rake angles should be used to minimize hardening.

Use sulfurized or chlorinated oils as coolants to reduce tool sticking.

Avoid slow cutting speeds and feeds to prevent work hardening.

Production Process

904L stainless steel plates are cold-rolled to achieve high performance. Applications vary across industries, including food processing, kitchen utensils, and electronics. When working with thinner strips, optimizing cold working performance is critical. Analyzing rolling and annealing processes helps improve product quality and meet specific field requirements.

Summary

904L stainless steel is a versatile, corrosion-resistant material widely used in industrial, household, and marine applications. Its excellent machinability, weldability, and resistance to harsh environments make it a reliable choice for various fields.