What is 304 stainless steel pipe

304 stainless steel pipe is produced according to the United States ASTM standard stainless steel brand. 304 stainless steel pipe is equivalent to China’s 0Cr19Ni9 (0Cr18Ni9) stainless steel pipe.

 

304 stainless steel pipe classification there are many, the first is seamless pipe and straight seam welded steel pipe, the most basic classification is 304 stainless steel pipe and industrial fluid delivery with 304 stainless steel pipe.

 

It is a versatile stainless steel pipe that is widely used to produce equipment and machines that require good overall performance (corrosion resistance and formability). For example: food production equipment, the former chemical equipment, nuclear energy and so on.

 

Grade specifications for 304 grade stainless steel

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

 

Typical Chemical Composition % (max values, unless noted)

Weight %	C	Mn	P	S	Si	Cr	Ni
304	.08	2.00	.045	.030	1.00	18.0-20.0	8.0-11.0

 

Typical Mechanical Properties

Grade	Tensile
	Ultimate/Min		Yield/Min		Elongation/Min
	KSI	MPA	KSI	MPA	%
304	75	515	30	205	35

 

Physical properties of 304 grade stainless steel 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
304/L/H	8000	193	17.2	17.8	18.4	16.2	21.5	500	720

 

304 stainless steel pipe anti-intergranular corrosion performance is good, with excellent corrosion resistance and cold processing, stamping performance, can be used as a heat-resistant stainless steel. At the same time, the steel at -180 ℃under the conditions of its mechanical properties are still good. In the solid solution state of steel plasticity, toughness, cold workability in the oxidizing acid and atmospheric, water and other medium corrosion resistance, therefore, it is the most widely used steel.

 

304 stainless steel pipe tolerances:

NPS Designator	Permissible Variations in Outside Diameter​
	Over In.	Under In.
1/8 to 1-1/2, incl	1/64 (0.015)	1/32 (0.031)
Over 1-1/2 to 4, incl	1/32 (0.031)	1/32 (0.031)
Over 4 to 8, incl	1/16 (0.062)	1/32 (0.031)
Over 8 to 18, incl	3/23 (0.093)	1/32 (0.031)

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Minimum Wall Thickness on Inspection:

   tn * 0.875 = tm
Where:
tn = nominal wall thickness, in. [mm], and
tm= minimum wall thicknesses, in. [mm]

   The wall thickness is inch-pound units is rounded to three decimal places in accordance with the rounding method of Practice E29. The wall thickness in SI units is rounded to one decimal place in accordance with the rounding method of Practice E29.

· This table is a master table covering wall thicknesses available in the purchase of different classifications of pipe, but it is not meant to imply that all the walls listed herein are necessarily obtainable for the applicable product specification.

Nominal Thickness		Minimum Thickness on Inspection		Nominal Thickness		Minimum Thickness on Inspection		Nominal Thickness		Minimum Thickness on Inspection
in.	mm	in	mm	in	mm	in	mm	in	mm	in	mm
0.068	1.7	0.060	1.5	0.294	7.5	0.257	6.5	0.750	19.0	0.658	16.6
0.068	2.2	0.077	2.0	0.300	7.6	0.262	6.7	0.812	20.6	0.710	18.0
0.091	2.3	0.080	2.0	0.307	7.8	0.269	6.8	0.843	21.4	0.736	18.7
0.095	2.4	0.083	2.1	0.308	7.8	0.270	6.9	0.854	21.7	0.756	19.2
0.113	2.9	0.099	2.5	0.312	7.9	0.273	6.9	0.875	22.2	0.766	19.5
0.119	3.0	0.104	2.6	0.318	8.1	0.278	7.1	0.906	23.0	0.783	20.1

 304 stainless steel pipe’s theory weight calculation formula: (diameter – wall thickness) × wall thickness × 0.02491 = weight per meter (kg)

Corrosion Resistance

Excellent in a wide range of atmospheric environments and many corrosive media. Subject to pitting and crevice corrosion in warm chloride environments, and to stress corrosion cracking above about 60°C. Considered resistant to potable water with up to about 200mg/L chlorides at ambient temperatures, reducing to about 150mg/L at 60°C.

Heat Resistance

Good oxidation resistance in intermittent service to 870°C and in continuous service to 925°C. Continuous use of 304 in the 425-860°C range is not recommended if subsequent aqueous corrosion resistance is important. Grade 304L is more resistant to carbide precipitation and can be heated into the above temperature range.

Grade 304H has higher strength at elevated temperatures so is often used for structural and pressure-containing applications at temperatures above about 500°C and up to about 800°C. 304H will become sensitised in the temperature range of 425-860°C; this is not a problem for high temperature applications, but will result in reduced aqueous corrosion resistance.

Heat Treatment

Solution Treatment (Annealing) – Heat to 1010-1120°C and cool rapidly. These grades cannot be hardened by thermal treatment.

Welding

Excellent weldability by all standard fusion methods, both with and without filler metals. AS 1554.6 pre-qualifies welding of 304 with Grade 308 and 304L with 308L rods or electrodes (and with their high silicon equivalents). Heavy welded sections in Grade 304 may require post-weld annealing for maximum corrosion resistance. This is not required for Grade 304L. Grade 321 may also be used as an alternative to 304 if heavy section welding is required and post-weld heat treatment is not possible.

Machining

A “Ugima” improved machinability version of grade 304 is available in bar products. “Ugima” machines significantly better than standard 304 or 304L, giving higher machining rates and lower tool wear in many operations.

Dual Certification

It is common for 304 and 304L to be stocked in “Dual Certified” form, particularly in plate and pipe. These items have chemical and mechanical properties complying with both 304 and 304L specifications. Such dual certified product does not meet 304H specifications and may be unacceptable for high temperature applications.

Applications

Typical applications include:

· Food processing equipment, particularly in beer brewing, milk processing & wine making.

· Kitchen benches, sinks, troughs, equipment and appliances

· Architectural panelling, railings & trim

· Chemical containers, including for transport

· Heat Exchangers

· Woven or welded screens for mining, quarrying & water filtration

· Threaded fasteners

· Springs

Source: wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)​

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