The typical chemical composition for this grade is given in the table below, together with composition limits given for the product according to different standards. The required standard will be fully met as specified on the order.

The chemical composition is given as % by mass.

The mechanical properties of the available products in soft annealed condition at room temperature are given in the table below. Moderate strengths can be reached at elevated temperatures (~550 °C / 1022 °F). Temperatures for excessive scaling are close to 850 °C/1562 °F. This product, along with other austenitic corrosion resistant stainless steels, exhibits very high ductility and high elongation to fracture. It is not susceptible to brittle fracture in the solution annealed condition.

¹⁾Elongation according to EN standard:
A₈₀ for thickness below 3 mm.
A for thickness = 3 mm.
Elongation according to ASTM standard A_2” or A₅₀.

Core 301LN/4318 has excellent corrosion resistance in solutions of many halogen-free organic and inorganic compounds over a wide temperature and concentration range. It can withstand many organic and sufficiently diluted mineral acids depending on the temperature of the solution. Core 301LN/4318 may suffer from uniform corrosion in mineral acids and hot strong alkaline solutions.

Due to its high carbon content, Core 301LN/4318 is easily sensitized for intergranular corrosion during heat treatment or welding.

In aqueous solutions containing halogenides, e.g. chlorides or bromides, pitting and crevice corrosion may occur depending on halogenide concentration, temperature, pH-value, concentration of oxidizing compounds, or crevice geometry, if applicable. Due to its relatively high nitrogen content, the resistance of Core 301LN/4318 against pitting and crevice corrosion is nearly on the same level as the basic austenitic CrNi Core 304/4301 and Core 304L/4307. The presence of corrosion inhibiting or accelerating compounds like e.g. transition metal ions or organic compounds may influence the corrosion behavior of Core 301LN/4318.

Core 301LN/4318 is prone to chloride-induced stress corrosion cracking at temperatures over about 50 °C depending on the applied stress and the chloride concentration in the environment. Prior cold deformation of the structure under load increases the risk of stress corrosion cracking.

Core 301LN/4318 can be used for indoor and outdoor applications in rural areas and urban environments where chloride contamination is low. The best material performance is typically reached with the help of adequate design, correct post-weld treatment, and regular cleaning during use (if applicable).

For more information on corrosion resistance, please refer to the Outokumpu Corrosion Handbook or contact the our corrosion experts.

PRE Pitting Resistant Equivalent calculated using the formula: PRE = %Cr + 3.3 x %Mo + 16 x %N
CPT Corrosion Pitting Temperature as measured in the Avesta Cell (ASTM G 150), in a 1M NaCl solution (35,000 ppm or mg/l chloride ions).
CCT Critical Crevice Corrosion Temperature is the critical crevice corrosion temperature which is obtained by laboratory tests according to ASTM G 48 Method F

The physical properties of the available products are given in the table below

Austenitic crystal structure, non-magnetic as soft annealed. Becomes easily magnetic when deformed.

*) Austenitic stainless steel grades may be magnetizable to a certain degree after cold deformation, e.g. in temper rolled condition.

Forming and machining

Work hardening is pronounced due to high work hardening rate and formation of martensite in the range of larger deformations. Formability is good, thus forces needed and the elastic return is bigger compared with carbon steels and even when compared with Core 304/4301. Because of high ductility and work hardening it is recommended to use sharp cutting tools and an effective cooling and adequate feed of tool when machined.

Welding

Core 301LN/4318 has good weldability and is suitable for the full range of conventional welding methods (like MMA, MIG, MAG, TIG, SAW, LBW or RSW), except gas welding. Core 301LN/4318 has about 50% higher thermal expansion and lower heat conductivity compared to carbon steels. This means that larger deformation and higher shrinkage stresses may result from welding.

In thin sections, autogenous welding may be used. To ensure that the weld metal properties (such as strength, corrosion resistance) are equivalent to those of the parent metal, matching or slightly over-alloyed fillers should preferably be used. The recommended welding metal is 19 9 L. Shielding gases should be Ar/He based or contain up to 3% nitrogen to minimize nitrogen drop.

Core 301LN/4318 in the cold stretched condition can be welded in the same way as material in the annealed condition. As the additional strength obtained by temper rolling is lost within the weldment, the strength, including fatigue strength, is also reduced. The use of high heat input may also reduce the strength in the heat-affected zone (HAZ). Since the strength is reduced in the weld area, the location of the welds must be carefully considered at the design stage and the welds must be placed, if possible, in less stressed areas.

Post-weld heat treatment is generally not required. In special cases with high risks of stress corrosion cracking or fatigue, stress relief treatment may be considered.

In order to fully restore the corrosion resistance of the weld seam, the weld discoloration should be removed by pickling and passivation.

More detailed information concerning welding procedures can be obtained from the Outokumpu Welding Handbook, available from our sales offices.

The most commonly used international product standards are given in the table below.