Stainless Steel 403 Forgings

Chemical Analysis
C Carbon
0.15 max
Mn Manganese
1.00 max
P Phosphorus
0.040 max
S Sulfur
0.030 max
Si Silicon
0.50 max
Cr Chromium
11.50 – 13.00

General Characteristics of Stainless Steel 403

Type 403 stainless is a martensitic alloy, very similar to stainless type 410, with the exception of a slightly lower maximum silicon content and a slightly lower maximum chromium content. Good levels of strength, toughness and ductility may be obtained with this alloy.

Applications of Stainless 403

This alloy may be used for steam turbine buckets, blades, bucket covers, gas turbine compressor blades, nuclear reactor control rod mechanisms, forged valves, fasteners, shafting, pump parts and machine parts

Forging Stainless 403

This alloy may be readily forged, headed or upset. It requires more blows or a heavier hammer than does mild steel. It should be heated uniformly to 2000/2200ºF (1095/1205ºC), depending upon the degree of deformation, then forged and air cooled. Large forgings should be furnace cooled or cooled in dry lime. This grade should not be forged below 1650ºF (900ºC)./p>

Heat Treatment

Annealing

Parts should be heated uniformly to 1200/1400ºF (650/760ºC) and air cooled. Optimum machinability is obtained by a lowering of the annealing temperature to give a slightly higher hardness. For maximum softness heat to 1500/1650ºF (815/900ºC) and slow furnace cool to give approximately 155 BHN. Maximum softness may be required for subsequent cold forming, for cold heading for instance.

Hardening

Heat to 1750/1850ºF (955/1010ºC), soak and quench in oil or air cool.

Tempering

Temper at temperatures appropriate to produce desired mechanical properties. Soak for at least one hour, longer for larger sections, and air cool.

If this alloy is tempered in the range 750/1050ºF (400/565ºC) there will be a decrease in impact strength and in corrosion resistance – depending upon the media. If tempering in this range is necessary to obtain the desired strength and ductility values, it may be that in many cases the reduced impact strength is not a problem and that the corrosion resistance is only slightly reduced.

Machinability

In its softest condition, type 403 stainless is tough and chips build up on tools. Better finishes are obtained in the cold drawn or heat-treated condition. If higher mechanical properties are required, the material can be machined up to Rc 35.

Weldability

Type 403 may be satisfactorily welded. Parts should be preheated at 350/400ºF (180/205ºC) to prevent cracking, particularly in heavy sections. Since the alloy is air hardening, parts should be annealed immediately after welding.

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