[ Wiki ]Stainless Steel - Grade 430 (UNS S43000)

Chemical Formula

Fe, <0.12% C, 16-18% Cr, <0.75% Ni, <1.0% Mn, <1.0% Si, <0.040% P, <0.030% S

Introduction

Stainless steel grade 430 is a non-hardenable steel containing straight chromium, and belongs to the ferritic group of steels. This steel is known for its good corrosion resistance and formability, coupled with practical mechanical properties. It can be used in certain chemical applications due to its resistance to nitric acid.
Grade 430F stainless steel is usually provided in bar form to be used in automatic screw machines.
Grade 434 has similar properties as grade 430, although it is a molybdenum-bearing version. The molybdenum content enhances its corrosion resistance.

Key Properties

The following sections will provide the key properties of grade 430 stainless steels coil, sheet and plate - covered under ASTM A240/A240M.

Composition

The chemical compositions of various elements of grade 430 stainless steels are tabulated below.

Table 1 – Chemical compositions of grade 430 stainless steels

GradeN		C	Mn	Si	P	S	Cr	Mo	Ni	N
430	min. max.	- 0.12	- 1	- 1	- 0.04	- 0.030	16 18	-	- 0.50	-
430F	min. max.	- 0.12	- 1.25	- 1	- 0.06	0.15 -	16 18	-	-	-

Mechanical Properties

The mechanical properties for grade 430 stainless steels are listed in the table below.

Table 2 - Mechanical properties of grade 430 stainless steels

Grade	Tensile Strength (MPa) min	Yield Strength 0.2% Proof (MPa) min	Elongation (% in 50mm) min	Hardness
				Rockwell B (HR B) max	Brinell (HB) max
430	483	310	22	85	183
430F	552 typical	379 typical	25 typical	-	262

Physical Properties

The following table outlines the physical properties of grade 430 stainless steels.

Table 3 - Physical properties of grade 430 stainless steels in the annealed condition

Grade	Density (kg/m3)	Elastic Modulus (GPa)	Mean Coefficient of Thermal Expansion (μm/m/°C)			Thermal Conductivity (W/m.K)		Specific Heat 0-100°C (J/kg.K)	Electrical Resistivity (nΩ.m)
			0-100°C	0-315°C	0-538°C	at 100°C	at 500°C
430	7750	200	10.4	11.0	11.4	26.1	26.3	460	600
430F	7750	200	10.4	11.0	11.4	26.1	26.3	460	600

Grade Specification Comparison

A comparison of grade specifications for 430 stainless steels is given in the following table.

Table 4 - Grade specifications for 430 stainless steels

Grade	UNS No	Old British		Euronorm		Swedish SS	Japanese JIS
		BS	En	No	Name
430	S43000	430S17	60	1.4016	X8Cr17	2320	SUS 430
430F	S43020	-	-	1.4104	X12CrMoS17	2383	SUS 430F

Possible Alternative Grades

Suitable alternative grades that can be chosen instead of grade 430 stainless steelgrades that can be chosen instead of grade 430 stainless steel are listed in the table below.

Table 5 - Possible alternatives to grade 430 stainless steel

Grade	Reasons for choosing 430
430F	Higher machinability than 430 is needed in bar product, and reduced corrosion resistance is acceptable
434	Better pitting resistance is required
304	Slightly higher corrosion resistance is needed, together with greatly improved ability to be welded and cold formed
316	Much better corrosion resistance is needed, coupled with greatly improved ability to be welded and cold formed
3CR12	Lower corrosion resistance is acceptable in a cost-critical application

Corrosion Resistance

All ferritic grades, such as stainless steel grade 430, have excellent stress corrosion cracking resistance. Grade 430 has good corrosion resistance to numerous substances, such as certain organic acids and nitric acid. The corrosion resistance is maximized in well-polished or buffed condition. Its pitting and crevice corrosion resistance is quite similar to that of grade 304. 430F is a high-sulfur free machining grade, and therefore the resistance to pitting and crevice corrosion is comparatively lesser than those grades that are non-free machining. 

Heat Resistance

Stainless steel grade 430 is capable of resisting oxidation up to 870°C (1598°F) in intermittent usage, and up to 815°C (1499°F) in continuous usage. At room temperature, it has the tendency to become brittle, especially when it has been heated for a long time in the 400-600°C (752-1112°F) range. This issue can be overcome with annealing.

Heat Treatment

Solution annealing can be performed by heating stainless steel grade 430 to 815 - 845°C (1499-1553°F). Then it has to be slow furnace cooled to 600°C (1112°F) and followed by air-cooling in a quick manner - as slow cooling between 540 and 400°C (1004 and 752°F) tends to cause embrittlement.

For sub-critical annealing, heating should be performed to 760-815°C (1400-1499°F), followed by air-cooling or water quenching.

This stainless steel cannot be hardened by thermal treatment.

Welding

To perform any welding, stainless steel grade 430 has to be pre-heated at 150-200°C (302-392°F). In case of embrittlement in the welded metal, the particular area can be post-weld annealed at 790-815°C (1454-1499°F); however grain refinement will not happen.

It is recommended that grade 430, 308L, 309 or 310 filler rod should be used based on the application. 

Machining

The machinability of stainless steel grade 430 is a lot easier than standard austenitic steels such as grade 304 - but there is a chance for galling. Lightly drawn bars are easier to machine than bars in the annealed condition. Grade 430F is easy to machine.

Fabrication

Stainless steel grade 430 has a low work hardening rate which enables easy bending and forming. The low ductility rate, however, makes it difficult to perform very rigorous operations. It is possible for grade 430 wire to handle rigorous cold heading. Sub-critical intermediate annealing may be required for extreme cold working. 

Applications

The following are the applications for stainless steel grade 430:

• Dish washer linings
• Refrigerator cabinet panels
• Element supports and fasteners
• Stove trim rings and chimney liners
• Automotive trim and lashing wires

The key application of grade 430F is in repeatedly used machined parts.