1.4401 (AISI 316) Annealed Stainless Steel Tube

What Is 1.4401

EN 1.4401, designated X5CrNiMo17-12-2 and equivalent to AISI 316, is a molybdenum-alloyed austenitic stainless steel. It offers significantly improved resistance to pitting and crevice corrosion in chloride environments compared with 304, making it one of the most reliable choices for industrial tubing in corrosive service.

Annealing and Its Benefits

Annealing heats the tube to 1050 to 1150 degrees C and rapidly cools it in water or air. This softens the material, relieves internal stresses from forming, and optimizes the microstructure for better ductility and corrosion resistance. Annealed tube has a minimum elongation of 40 percent and hardness up to about 210 HBW, versus 20 to 30 percent elongation and 220 to 250 HBW for unannealed material.

Chemical Composition

Limits are chromium 16.5 to 18.5 percent, nickel 10.0 to 13.0 percent, molybdenum 2.0 to 2.5 percent, carbon 0.07 percent maximum, manganese 2.0 percent, silicon 1.0 percent, phosphorus 0.045 percent, and sulfur 0.015 percent.

Mechanical Properties

In the annealed condition the tube has a minimum tensile strength of 520 MPa, a minimum yield strength of 220 MPa, and a minimum elongation of 40 percent, with hardness up to 90 HRB and density of 8.0 g per cubic centimeter.

Fabrication

Annealed 316 tube welds well, and the reduced internal stress improves weldability, though ER316 filler metal is recommended to maintain corrosion resistance in the weld. The annealed condition also supports bending, flaring, and tube fitting applications without cracking.

Applications

1.4401 annealed tube is used for process piping, heat exchanger tubes, hydraulic and pneumatic lines, instrumentation tubing, and structural components in chemical, marine, food, and pharmaceutical industries where chloride resistance matters.

Frequently Asked Questions

Q: What is 1.4401 equivalent to?

A: AISI 316, UNS S31600, and X5CrNiMo17-12-2.

Q: Why anneal 316 tube?

A: To restore ductility, relieve stress, and maximize corrosion resistance.

Q: What is the tensile strength of annealed 1.4401?

A: 520 MPa minimum.

Q: Can annealed 316 tube be welded?

A: Yes, with ER316 filler metal recommended.

Q: How does it compare with 304 tube?

A: Better chloride resistance and durability because of molybdenum.

Q: What sizes are available?

A: Outer diameters from 6 to 219 mm with walls from 0.5 to 10 mm.

Contact us for 1.4401 annealed tubes with mill certificates, custom sizes, and polished or pickled finishes.