The chemical composition is shown in the table below.

The chemical composition is given as % by weight.

The mechanical properties of the available products are given in the table below.

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.

For more information, see Outokumpu Corrosion Handbook.

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

Data according to EN 10088, EN 10095 or typical values.

Welding
The microstructure of 4021 comprises tempered martensite and some carbide.The steel is normally not considered to be weldable, but if thinner gauges are occasionally welded, the use of low-hydrogen methods (MAG or TIG) is to be preferred to avoid cold cracking. Any electrodes used must be of the basic type. The martensitic steels must be preheated to temperatures above MS typically (250-400ºC). The interpass temperature should be in the same range. The heat input should not be too high or too low (0.5-1.5 kJ/mm).
Austenitic fillers are most commonly used. This avoids the post weld heat treatment that is necessary when compositionally matched filler is used.Much depends on the composition of the steel and the degree of restraint used. When there is no preheating, post weld heat treatment is necessary. However, it may be possible to weld very thin gauges without preheating.

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