Stainless steel 1.4021 is a martensitic machining bar with machinability improved with the addition of Sulphur. The Sulphur also lowers weldability, corrosion resistance, and formability to below that of its non-free machining equivalent Grade 410.
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Martensitic stainless steels are designed for high hardness, and other properties are compromised to an extent. Their functional operating temperature range is restricted by their loss of ductility at sub-zero temperatures, and loss of strength by over-tempering at high temperatures.
Alloy designations of 1.4021 is similar, but it may not be a direct equivalent to: 420, UNS42000, 1.4021, 1.4024, 1.4028, 1.4029, 1.4030, and 1.4034. It is supplied in the form of a bar.
Corrosion resistance is lower than the common austenitic grades. It offers resistance to fresh water, dry atmospheres, and mild alkalies and acids; however, the resistant is lower than equivalent non-free-machining grades. High Sulphur content free machining grades - such as 416 - are not suitable for chloride exposure or in marine condition.
Maximum corrosion resistance can be achieved in the hardened condition with a smooth surface finish. The steel has a fair heat resistance to scaling in intermittent service up to 760°C, and up to 675°C in continuous service. It is not recommended for use in temperatures exceeding the relevant tempering temperature.
||0.16 - 0.25
||12.00 - 14.00
||0.0 - 1.50
||0.0 - 1.00
||0.0 - 0.04
||0.0 - 0.03
||10.3 x 10-6/K
|Modulus of Elasticity
||0.55 x 10-6 Ω.m
|Bar - Up to 160mm Dia/Thickness
||500 - 600 MPa
||700 - 950 MPa
||12 - 13%
Fabrication must be carried out by methods that allow for poor weldability, as well as for a final harden and temper heat treatment.
Cold working – It is not recommended, It is only suitable for minor deformation. Cracking will occur due to severe deformation.
Hot working - Hot working processes should be carried out after uniform heating to 2100-2250°F (1149-1232°C). Hot working below 1700°F (927°C) could result in cracking.
Machinability - Grade 420 offers very good machinability, the highest of any of the commonly available stainless steels. It is achieved best in sub-critical annealed condition.
Weldability - Grade 420 has poor weldability. It can be pre-heated to 150-320°C and post-heated at 610-760°C. Grade 420 coated welding rods can be used for high strength joints, where a post-weld hardening and tempering heat treatment can be carried out. If parts need to used in the "as welded" condition, a ductile joint can be made using Grade 309 filler rod or electrodes.
The main areas of applications include:
- Automatic screw machined parts
- Valve parts
- Pump shafts
- Motor shafts
- Bolts and nuts
- Shear blades
- Cutlery blades
- Surgical Instruments
- Washing machine parts
This information has been sourced, reviewed and adapted from materials provided by Aalco - Ferrous and Non-Ferrous Metals Stockist.
For more information on this source, please visit Aalco - Ferrous and Non-Ferrous Metals Stockist.