Applications

253 MA has come to be used extensively in the metallurgical, petrochemical and power industries. Typical applications are:

Tubes in waste heat recovery systems in the metallurgical industry, e.g. recuperators

Tubes in heat treatment furnaces, e.g. radiation tubes, thermocouple protection tubes, burner components, furnace rollers

Tubes for injection of pulverized coal in blast furnaces Tubing for fluidized-bed combustion plants

Furnace tubes for mud incineration plants

Tubes for carbon black process gas coolers/air heaters Tubes for the glass and cement industries

Styrene reactor tubes EDC cracking tubes

Convection tubes in ethylene cracking

Air preheater tubes in sulphuric acid gas converters Muffle tubes in continuous wire annealing furnaces

Corrosion resistance

Air

253 MA has very high resistance to oxidation, especially at cyclically varying temperatures. See Figs. 3 and 4. The service temperature in air should not exceed about 1150°C (2100°F).

Isothermal oxidation at 1150°C (2100°F) for 100 h results in a corrosion rate of about 0.3 mm/year (13 mpy), and exposure at the same temperature for 1000 h causes about 0.2 mm/year (9 mpy).

Cyclic oxidation at 1150°C (2100oF) for 5 x 24 h, with cooling to room temperature every 24 hours gives a   corrosion rate of less than 1.1 mm/year (43 mpy), which is only marginally greater than the corrosion rate at 1000°C (1830°F).

Cyclic oxidation testing for 1000 h (15 minutes at the testing temperature and 5 minutes at room temperature,   making a total of 3000 cycles) places heavy demands on the elasticity and adhesive capacity of the oxide. The

test results in Fig. 4 show that the resistance of 253 MA in such difficult conditions is superior to that of both ASTM TP310 and EN 1.4828 (ASTM TP309). The very good properties of this grade in cyclic conditions

have been achieved by adding rare earth metals and silicon.

	Figure 3. Oxidation in air during cyclic testing 5x24 h with cooling to room temperature every 24 h. Comparison of Alleima 253 MA with four other high temperature materials. 1 = EN 1.4828 (ASTM TP309) 2 = ASTM TP446  3 = ASTM TP310 4 = Sandvik 253 MA  5 = Alloy 800 H
	Figure 4. Oxidation in air during 1000 h cyclic exposure. The cycles comprise 15 min. at the testing temperature and 5 min at room temperature. The curves represent averages. Carburizing atmosphere Carburization can occur when a material comes into contact with hot gases with high carbon activity, e.g. hydrocarbons. The degree of carburization depends on the composition of the material and on the carbon and oxygen contents of the gas. Thanks to the relatively high chromium content and the addition of silicon and rare earth metals, a protective oxide is easily formed on the surface of 253 MA material. Carburization resistance is, therefore, good.Fig. 5    shows carburization after 500 h at different temperatures, in a mixture of about 10% methane and about 90% argon containing 0.5% oxygen. As can be seen, Alleima 253 MA is less prone to carburization at high temperatures in these conditions than ASTM TP310 and Alloy 800H.
	Figure 5. Carburization of a cylindrical test piece at 0.5 mm (0.02 in.) distance from the surface after testing for 500 h at different temperatures in about 10% CH4+ about 90% Ar + 0.5% O2. Other gaseous atmospheres In addition to its very good oxidation resistance in air, 253 MA is also highly resistant to other atmospheres. The highly protective oxide layer makes it possible to use this steel at high temperatures in atmospheres containing sulphur and other aggressive compounds.

Bending

Annealing after cold bending is not normally necessary, but this should be reviewed depending on the degree of bending and the operating conditions.

If cold bending has exceeded 10–20%, we recommend solution annealing for tubes that are to be used at  temperatures above about 800°C (1450°F), and when the highest possible creep strength is required in the bent tube.

Hot bending should be carried out at 1100–850°C (2050–1560°F) and should be followed by solution annealing.