Stainless steel 304,304L,304H

Stainless steel 304 and stainless steel 304L are also known as 1.4301 and 1.4307 respectively. 304 is the most versatile and widely used stainless steel. It is still sometimes referred to by its old name 18/8 which is derived from the nominal composition of 304 being 18% chromium and 8% nickel. 304 stainless steel is an austenitic grade that can be severely deep drawn. This property has resulted in 304 being the dominant grade used in applications like sinks and saucepans. 

304L is the low carbon version of 304. It is used in heavy gauge components for improved weldability.  

304H, a high carbon content variant, is also available for use at high temperatures. 

Chemical Composition

	C	Si	Mn	P	S	Ni	Cr	Mo	N
SUS304	0.08	0.75	2.00	0.045	0.030	8.50-10.50	18.00-20.00	－	0.10
SUS304L	0.030	1.00	2.00	0.045	0.030	9.00-13.00	18.00-20.00	－	－
304H	0.030	0.75	2.00	0.045	0.030	8.00-10.50	18.00-20.00	-	-

Mechanical Properties

Grade	Tensile Strength (MPa) min	Yield Strength 0.2% Proof (MPa) min	Elongation (% in 50 mm) min	Hardness
				Rockwell B (HR B) max	Brinell (HB) max	HV
304	515	205	40	92	201	210
304L	485	170	40	92	201	210
304H	515	205	40	92	201	-

304H also has a requirement for a grain size of ASTM No 7 or coarser.

Physical Properties

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
304/L/H	8000	193	17.2	17.8	18.4	16.2	21.5	500	720

Approximate grade comparisons for 304 stainless steels

Grade	UNS No	Old British		Euronorm		Swedish SS	Japanese JIS
		BS	En	No	Name
304	S30400	304S31	58E	1.4301	X5CrNi18-10	2332	SUS 304
304L	S30403	304S11	-	1.4306	X2CrNi19-11	2352	SUS 304L
304H	S30409	304S51	-	1.4948	X6CrNi18-11	-	-

These comparisons are approximate only. The list is intended as a comparison of functionally similar materials not as a schedule of contractual equivalents. If exact equivalents are needed original specifications must be consulted.

Possible Alternative Grades

Grade	Why it might be chosen instead of 304
301L	A higher work hardening rate grade is required for certain roll formed or stretch formed components.
302HQ	Lower work hardening rate is needed for cold forging of screws, bolts and rivets.
303	Higher machinability needed, and the lower corrosion resistance, formability and weldability are acceptable.
316	Higher resistance to pitting and crevice corrosion is required, in chloride environments
321	Better resistance to temperatures of around 600-900 °C is needed…321 has higher hot strength.
3CR12	A lower cost is required, and the reduced corrosion resistance and resulting discolouration are acceptable.
430	A lower cost is required, and the reduced corrosion resistance and fabrication characteristics are acceptable.