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|Surface:||2B NO.1||Feature:||Corrosion Resistance|
253MA is a grade combining excellent service properties at high temperatures with ease of fabrication. It resists oxidation at temperatures up to 1150°C and can provide superior service to Grade 310 in carbon, nitrogen and sulphur containing atmospheres.
Another proprietary designation covering this grade is 2111HTR.
253MA contains fairly low nickel content, which gives it some advantage in reducing sulphide atmospheres when compared to high nickel alloys and to Grade 310. The inclusion of high silicon, nitrogen and cerium contents gives the steel good oxide stability, high elevated temperature strength and excellent resistance to sigma phase precipitation.
The austenitic structure gives this grade excellent toughness, even down to cryogenic temperatures.
These properties are specified for flat rolled product (plate, sheet and coil) as Grade S30815 in ASTM A240/A240M. Similar but not necessarily identical properties are specified for other products such as pipe and bar in their respective specifications.
Typical compositional ranges for grade 253MA stainless steels are given in table 1.
Table 1. Composition ranges for 253MA grade stainless steel
Typical mechanical properties for grade 253MA stainless steels are given in table 2.
Table 2. Mechanical properties of 253MA grade stainless steel
|Tensile Str (MPa) min||Yield Str 0.2% Proof (MPa) min||Elongation (% in 50mm) min||Hardness|
|Rockwell B (HR B) max||Brinell (HB) max|
Typical physical properties for grade 253MA stainless steels are given in table 3.
Table 3. Physical properties of 253MA grade stainless steel
|Density (kg/m3)||Elastic Modulus (GPa)||Mean Coefficient of Thermal Expansion (mm/m/°C)||Thermal Conductivity (W/m.K)||Specific Heat
|Electrical Resistivity (nW.m)|
|0-100°C||0-600°C||0-1000°C||at 20°C||at 1000°C|
Approximate grade comparisons for 253MA stainless steels are given in table 4.
Table 4. Grade specifications for 253MA grade stainless steel
|UNS No||Old British||Euronorm||
|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 to grade 253MA stainless steels are given in table 5.
Table 5. Possible alternative grades to 253MA grade stainless steel
|Grade||Why it might be chosen instead of 253MA|
|310||Carburising atmospheres require a higher nickel content|
|304H||Lower cost alternative, provided the operating temperature is below about 800°C|
|Nickel Alloys||Carburising atmospheres or temperatures above the 1100 - 1150°C maximum of 253MA.|
Although not designed for aqueous corrosion resistance the high chromium and nitrogen contents give the grade a pitting resistance approximating that of 316. 253MA does however have a high carbon content so is highly susceptible to sensitisation from welding or service exposure.
Oxidation - excellent resistance to air, at temperatures up to 1150°C. At high temperatures the steel quickly forms a thin, highly adherent and elastic oxide. This oxide gives good protection even under cyclic conditions.
Carburisation - Under oxidising conditions this grade can perform well, but alloys with higher nickel content are preferred if the atmosphere is reducing.
Sulphidation - good resistance to sulphur-bearing gases in an oxidising atmosphere, even if only traces of oxygen are present. Reducing gases prevent the protective oxide forming.
253MA has high strength at elevated temperatures so is often used for structural and pressure-containing applications at temperatures above about 500°C and up to about 900°C. Its strength at these temperatures is higher than that of alternatives such as Grade 310.
253MA 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.
Solution Treatment (Annealing) - Heat to 1050-1150°C and cool rapidly. It is recommended that the material be solution treated after 10-20% cold work to achieve maximum creep strength in service.
This grade cannot be hardened by thermal treatment.
Excellent weldability by all standard fusion methods, using matching filler metals. AS 1554.6 pre-qualifies welding of 253MA with Grade 22.12HT rods or electrodes. Grade 309 fillers can be used if lower creep strength can be tolerated. Pure argon shielding gas should be used.
As for other austenitic stainless steels, the machining requires sharp tools, slow speeds and heavy feed. This grade has a low sulphur content
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