1.Introduction
UNS S31673, also known as Type 316LN stainless steel, is a low-carbon version of Type 316 stainless steel, containing nitrogen for improved mechanical properties. In production processes for Type 316LN stainless steel, the amount of nitrogen added is about 0.1%, resulting in improved mechanical properties and corrosion resistance. As a general-purpose corrosion and heat-resistant stainless steel, UNS S31673 can effectively resist corrosion attacks from reducing and oxidizing agents, and has good stress corrosion cracking resistance and excellent pitting corrosion resistance.
2.Designations
UNS S31673 stainless steel is also known by various other designations. According to EN 10088-1: 2005 standard, Type 316LN stainless steel is referred as X2CrNiMoN17-13-5, and according EN 10088-3: 2005 standard, it is referred as X2CrNiMoN17-13-5. In addition, the average strength and heat resistant tests of UNS S31673 stainless steel are equivalent to Type 316L, AISI 316L and is referred as 1.4429.
3.Composition Range
UNS S31673 is austenitic stainless steel containing molybdenum. According ASTM A240/ASME SA240, the composition range of stainless steel UNS S31673 is given in the following table.
Table 1. Chemical composition of stainless steel UNS S31673
Element Content (%) Iron, Fe Balance Carbon, C 0.030 max Manganese, Mn 2.00 max Silicon, Si 0.75 max Chromium, Cr 16.00 – 18.00 Nickel, Ni 10.00 – 14.00 Nitrogen, N 0.10 – 0.20 Molybdenum, Mo 2.00 – 3.00 Phosphorus, P 0.045 max Sulphur, S 0.030 max
4.Physical Properties
Table 2. Physical properties of stainless steel UNS S31673
Properties Metric Imperial Density 8.0 g/cm³ 0.289 lb/in³
5.Mechanical Properties
Table 3. Mechanical properties of stainless steel UNS S31673
Properties Metric Imperial Tensile strength 520 MPa 75300 psi Yield strength 220 MPa 31900 psi Elongation 40 % 40 % Modulus of elasticity 193 - 200 GPa 28000 - 29000 ksi
6.Temperature Range
The temperature range of UNS S31673 stainless steel is - 425 - 4700 °F (- 255 - 2560 °C).
7.Applications
Due to its improved corrosion and mechanical properties, UNS S31673 is especially suitable for applications in hostile environments, such as marine, offshore, and chemical processing. Typical application of UNS S31673 includes surgical tools, food processing equipment such as steam turbine components, and petrochemical processing equipment such as containers. The low carbon version of Type 316 stainless steel has a higher toughness than Type 304 stainless steel, so UNS S31673 stainless steel is suitable for use in construction and structural components. In addition, UNS S31673 stainless steel is also used for high-temperature springs.
8.Disadvantages
UNS S31673 stainless steel is prone to stress corrosion cracking and its tendency is higher than that of Type 316 stainless steel when chloride ion concentration is greater than 0.01%. Therefore, UNS S31673 is not suitable for chloride environments. In addition, UNS S31673 is not suitable for welding.
