Stainless Steel – 400 Series Alloy

Information from Materials Standards for PM Structural Parts, 2024 Edition
published by Metal Powder Industries Federation

Overview

This subsection details PM (Powder Metallurgy) materials made from prealloyed ferritic stainless steel powders. When necessary, carbon content is controlled by adding graphite powder.

Material Characteristics

Density: Utilized as medium to high-density PM materials.
Homogeneity: Achieved using prealloyed powder with normal commercial sintering cycles.
Processing Influence: Processing has a moderate effect on mechanical properties. Optimal soft-magnetic properties are obtained by high-temperature sintering (above 2100 °F or 1150 °C) in a nitrogen-free atmosphere (pure hydrogen or vacuum).
Corrosion Resistance: Generally inferior to 300 series stainless steels when processed under the same conditions.

Applications

The 400 series stainless steels are selected for their magnetic properties or heat-treat response:

SS-409L: Chosen for welded applications.
SS-410L: Selected for soft-magnetic properties and environments requiring minimal corrosion resistance.
SS-410-90HT: Valued for its combination of strength, hardness, and wear resistance. Carbon addition enhances heat-treat response. This alloy is sinter-hardenable and can be further hardened by quenching and tempering, although corrosion resistance and machinability are poor.
SS-430: Offers lower magnetic properties compared to SS-410 but somewhat better corrosion resistance.
SS-434: Similar magnetic properties to SS-430 but with slightly better corrosion resistance.

Microstructure

Ferritic Alloys: SS-409LE, 410L, 430, and 434 alloys are ferritic in the as-sintered condition.
Dual-Phase Alloy: SS-409LNi has a ferritic-martensitic microstructure.
Martensitic Alloy: SS-410-90HT is fully martensitic after cooling from the sintering cycle and can be further hardened, generally tempered for optimal toughness.

Chemical Composition Requirements

The chemical composition for various 400 Series Alloy stainless steels is detailed below:

Material Designation	Fe	Cr	Ni	Mn	Si	S	C	P	Mo	N	Cb (Nb)	Element
SS-409L	Bal.	10.50	—	0.0	0.0	0.00	0.00	0.00	—	0.00	0.30	Minimum
	Bal.	11.75	—	1.0	1.0	0.03	0.03	0.04	—	0.03	0.80	Maximum
SS-409LE (1)	Bal.	10.50	0.0	0.0	0.0	0.00	0.00	0.00	0.00	0.00	0.30	Minimum
	Bal.	13.50	0.5	1.0	1.0	0.03	0.03	0.04	0.30	0.03	0.80	Maximum
SS-409LNi (2)	Bal.	10.50	1.1	0.0	0.0	0.00	0.00	0.00	0.00	0.00	0.30	Minimum
	Bal.	13.50	1.4	1.0	1.0	0.03	0.03	0.04	0.30	0.03	0.80	Maximum
SS-410	Bal.	11.50	—	0.0	0.0	0.00	0.05	0.00	—	0.00	—	Minimum
	Bal.	13.50	—	1.0	1.0	0.03	0.25	0.04	—	0.60	—	Maximum
SS-410L	Bal.	11.50	—	0.0	0.0	0.00	0.00	0.00	—	0.00	—	Minimum
	Bal.	13.50	—	1.0	1.0	0.03	0.03	0.04	—	0.03	—	Maximum
SS-430N2	Bal.	16.00	—	0.0	0.0	0.00	0.00	0.00	—	0.20	—	Minimum
	Bal.	18.00	—	1.0	1.0	0.03	0.08	0.04	—	0.60	—	Maximum
SS-430L	Bal.	16.00	—	0.0	0.0	0.00	0.00	0.00	—	0.00	—	Minimum
	Bal.	18.00	—	1.0	1.0	0.03	0.03	0.04	—	0.03	—	Maximum
SS-434N2	Bal.	16.00	—	0.0	0.0	0.00	0.00	0.00	0.75	0.20	—	Minimum
	Bal.	18.00	—	1.0	1.0	0.03	0.08	0.04	1.25	0.60	—	Maximum
SS-434L	Bal.	16.00	—	0.0	0.0	0.00	0.00	0.00	0.75	0.00	—	Minimum
	Bal.	18.00	—	1.0	1.0	0.03	0.03	0.04	1.25	0.03	—	Maximum
SS-434LCb	Bal.	16.00	—	0.0	0.0	0.00	0.00	0.00	0.75	0.00	0.30	Minimum
	Bal.	18.00	—	1.0	1.0	0.03	0.03	0.04	1.25	0.03	0.80	Maximum

Other Elements: Up to 2.0 wt.% maximum for other minor elements added for specific purposes.

Notes:

LE = L grade, Extended chemical composition.
LNi = Ferritic-martensitic grade.

Selection and Agreement

To ensure optimal properties and cost-effectiveness, it is essential to discuss the part application with the PM parts manufacturer. Both the purchaser and the manufacturer should agree on the following before manufacturing: