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UNS S31603 Austenitic Molybdenum Stainless Steel

What is UNS S31603? Grade S31603 is the molybdenum grade defined in the UNS system, which comes after the UNS S30400 in its importance within the austenitic stainless steels. The molybdenum offers S31603 enhanced corrosion resistant properties than UNS Grade S30400, especially more resistance to crevice corrosion and also pitting in chloride atmosphere.

What is ASTM A240 / A240M? UNS S31603 is also identified in the standard as 316L grade. It is an American material standard for standard Specification for Chromium and Chromium-Nickel Stainless Steel Plate, Sheet, and Strip for Pressure Vessels and for General Applications.

Why S31603 called Grade 316L Stainless Steel? When a material grade is specified as stainless steel, it means it has chromium content but this grade has molybdenum in it that makes it different. S31603 is the UNS designation alloy, also referred as 316L alloy in SAE designation and is defined in ASTM A240 standard. 316L is the low carbon version of 316 grade.

Alloy UNS S31603 offers robust and high temperature tensile, creep and stress-rupture strengths, together with outstanding formability and weld-ability. S31603 is the lower carbon version of S31600 and is uninfluenced from sensitization; thus, it is commonly utilized in heavy gauge welded parts.

Available Forms in Market: Following are the available forms of S31603 steels in the global market:

  • Coils and sheets
  • Wires
  • Pipes and tubes
  • Seam welded, cold redrawn and annealed
  • Plates and Round bars
  • Seam welded and cold redrawn forms

Dimensional Characteristics of S31603 Steels: The applicable thickness for this S31603 material as obtained by statistics in the market starts from 0.30 mm to 35 mm defending upon processes (cold rolled or hot rolled). However the width of this material varies and it is available in 660 mm and over. As it is available in different forms, dimensional aspects should be confirmed from suppliers.

The Indicative Chemical Composition of S31603 Steels:  The chemical composition of this grade is indicated as under:

  • Maximum percentage of Carbon (C) is 0.03 percent.
  • Maximum percentage of Manganese (Mn) is 2.0 percent.
  • Maximum percentage of Phosphorous (P) is 0.045 percent.
  • Maximum percentage of Sulphur (S) is 0.03 percent.
  • Minimum percentage of Chromium is 16.0 percent and maximum percentage of Chromium is 18.0 percent.
  • Minimum percentage of Nickel is 0 percent and maximum percentage is 14.0 percent.
  • Maximum percentage of Silicon (Si) is 0.75 percent.
  • Maximum percentage of Molybdenum (Mo) is 3.0 percent and minimum is 2.0 percent.

Remaining is iron (Fe) percentage and with few negligible impurities.

Mechanical Properties of S31603 Steels: Following are some of the mechanical properties of 316L steels:

  • The tensile strength of the 316L alloy steel is expressed in Newton per millimeters and it must be at-least 485 N/mm2 (MPa).
  • The elongation property of S31603 steel varies with the heat treatment process and thickness but it is indicated typically 40%.
  • S31603 can be welded by all fusion and resistance methods. But it is not weld able with oxyacetylene welding methods.
  • The maximum Brinell hardness is indicated around 217.
  • Corrosion resistance is higher than the other known austenitic grades.

Equivalent Material Grades in Other International Standards:

  • Equivalent grade of this type in SAE is 316L
  • In JIS designation, the corresponding material is referred as SUS 316L alloy.
  • In DIN standard, the corresponding material is referred as 1.4404 type steel.
  • In Swedish SS standard, the corresponding material is referred as 2348 type steel.

Applications of S31603 Stainless Steels: Applications are as under

  • Equipment and accessories in lab
  • Equipment and processing utilities in chemical industry
  • Equipment and utilities in food preparation in chloride environments
  • Equipment and processing utilities in textile industry
  • Equipment and processing utilities in pharmaceutical industry
  • Equipment used in pollution control
  • Fittings, and accessories in marine industry
  • Heat exchangers for chloride environment

Suppliers of S31603 Steel: Suppliers are also listed below:

  • Supplier Penn Stainless Steel bearing contact number 215-536-3053.The supplier address is 190 Kelly Road Quakertown, PA 18951
  • Supplier Ulbrich Stainless Steels & Special Metals, Inc. bearing contact number 203-239-4481.The supplier address is 153 Washington Ave. North Haven, CT 06473


Waqas Imam is an Industrial Engineer, Certified Lead Auditor, Material Consultant and Blog Writer.

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