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astm a312 tp304 erw or seamless is a titanium stabilized austenitic stainless steel pipe. tp304/ tp304l seamless pipes shall be made by a cold-drawn or hot-rolled process that does not involve welding at any stage of production, while welded pipes shall be made using an automatic welding process with no addition of filler metal during the welding process. the pipe may be furnished with plain or bevel butt welding ends, or threaded ends in accordance with asme b1.20.1.
what is 304 stainless steel?
304l stainless steel, also known as ultra-low carbon stainless steel, is a versatile stainless steel material that is widely used to make equipment and parts that require good comprehensive performance (corrosion resistance and formability).
regarding the stainless steel of this material, let’s first understand 304 or 304l stainless steel.
304l is a variant of 304 stainless steel with lower carbon content and is used where welding is required. the lower carbon content minimizes the precipitation of carbides in the heat-affected zone near the weld, and the precipitation of carbides may cause stainless steel to produce intergranular corrosion (welding erosion) in certain environments.
heat treatment
stainless steel pipes made of austenitic stainless steel astm a312 tp304 or tp304l shall be solution annealed. during annealing, the pipes shall be heated to the temperature no less than 1900°f [1040°c] and soak at the temperature for a period long enough so that all chromium carbides are dissolved. since the chromium carbide dissolves slowly, the highest practical temperature consistent with limited grain growth should be selected. this temperature is in the vicinity of 1095° [2000°f]. complete dissolution of chromium carbides reduces precipitation of intergranular carbides hence improves the resistance to intergranular corrosion. subsequent cooling (quenching) from the annealing temperature must be fast, thus ensuring that dissolved carbides remain in solution.
chemical composition of astm a312 tp304 stainless steel seamless pipes
the chemical composition of grade 304 stainless steel is outlined in the following table
grade | c | mn | si | p | s | cr | mo | ni | n | |
304 | min. | - | - | - | - | - | 18.0 | - | 8.0 | - |
max. | 0.08 | 2.0 | 0.75 | 0.045 | 0.030 | 20.0 | 10.5 | 0.10 | ||
304l | min. | - | - | - | - | - | 18.0 | - | 8.0 | - |
max. | 0.030 | 2.0 | 0.75 | 0.045 | 0.030 | 20.0 | 12.0 | 0.10 | ||
304h | min. | 0.04 | - | - | -0.045 | - | 18.0 | - | 8.0 | - |
max. | 0.10 | 2.0 | 0.75 | 0.030 | 20.0 | 10.5 | ||||
mechanical properties of astm a312 tp304 stainless steel seamless pipes
the mechanical properties of grade 304 stainless steel are displayed in the following table.
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 | ||||
304 | 515 | 205 | 40 | 92 | 201 |
304l | 485 | 170 | 40 | 92 | 201 |
304h | 515 | 205 | 40 | 92 | 201 |
304h also has a requirement for a grain size of astm no 7 or coarser. | |||||
astm a312 tp304 stainless steel pipes physical properties
physical properties of 304 grade stainless steel in the annealed condition
| 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 |
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