Dura 420/4021
EN 1.4021, ASTM TYPE 420 / UNS S42000

General characteristics

Very popular martensitic grade. Corrosion resistant in water and steam. Low-medium hardness for applications such as cutting utensils, surgical instruments, press plates, brake discs and mechanical parts.

Typical applications

  • Springs
  • Cutting utensils and surgical instruments
  • Press plates
  • Brake discs
  • Mechanical parts
  • Wear resistant applications


Product forms, available sizes and finishes


Product typeFinishesThicknessWidth
Cold rolled coil and sheet2B, Work hardened0,40-4,50≤ 1250
Hot rolled coil and plateHot rolled white2,50-7,00≤ 1250
Chemical composition

The chemical composition is shown in the table below.

The chemical composition is given as % by weight.

TypicalDura 420/40210.2013.0
ASTM A240/A240MTYPE 420 / UNS S42000<0.030<117.0-19.0<0.50<0.030Si:<1 P:<0.040 S:<0.030 Ti Al:<0.15
EN 10088-21.40210.16-0.25<1.5012.0-14.0Si:<1 P:<0.040 S:<0.015
Mechanical properties

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


StandardGradeRp0.2Rp1.0RmElongationImpact strengthRockwellHBHV
Product type: Cold rolled coil and sheet
Typical (thickness 1 mm)Dura 420/402135037558084HRB
Product type: Hot rolled coil and sheet
Typical (thickness 4 mm)Dura 420/40213604055752983
Product type: Hot rolled quarto plate
Typical (thickness 15 mm)Dura 420/402150058065020

1)Elongation according to EN standard:
A80 for thickness below 3 mm.
A for thickness = 3 mm.
Elongation according to ASTM standard A2” or A50.

Corrosion resistance

For more information, see Outokumpu Corrosion Handbook.

Pitting corrosion resistanceCrevice corrosion resistance

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



Physical properties

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


DensityModulus of elasticityThermal exp. at 100 °CThermal conductivityThermal capacityElectrical resistanceMagnetizable


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.


Standards & approvals

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


ASTM A240/A240MTYPE 420 / UNS S42000
EN 10088-21.4021