Alleima® 253 MA Tube and pipe, seamless

Standards

• UNS: S30815
• EN Number: 1.4835
• W.Nr.: (1.4893)*/(1.4828 mod.)*
• SS: 2368*

Product standards

• ASTM A213, A312
• EN 10297-2
• SS 14 23 68*

* Obsolete. Replaced by EN.

Approvals

Approved for use in ASME Boiler and Pressure Vessel Code, Section I, III and VIII, Div. 1 (SA-182, SA-213, SA-240, SA-249 SA-312 and SA-479).

Chemical composition (nominal)

Chemical composition (nominal) %

C	Si	Mn	P	S	Cr	Ni	N	Ce*
0.08	1.6	≤0.8	≤0.040	≤0.030	21	11	0.17	0.05

Applications

The high creep strength of Alleima 253 MA, coupled with its excellent oxidation resistance and its good resistance to carburization in constantly carburizing gas, makes it a very suitable material for end uses in which 18/8 steels lack the necessary resistance to oxidation and carburization.

Alleima 253 MA is often preferred instead of stainless chromium steels which have insufficient creep strength and structural stability. Furthermore, Alleima 253 MA can very well take the place of higher alloyed materials such as 25Cr/20Ni steels and Alloy 800H, or even Alloy 600 in certain cases.

Alleima 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

Trademark information: 253 MA is a trademark owned by Outokumpu OY

Corrosion resistance

Air

Alleima 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 (2100^oF) 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 Alleima 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 Alleima 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.

In alternately oxidizing and carburizing atmospheres and carburizing slags, Alleima 253 MA is slightly more prone to carburization than steels of higher chromium and/or nickel content.

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, Alleima 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.

Alleima 253 MA is more resistant than the higher alloyed 25Cr/20Ni steels to combustion gas attacks in cyclic conditions. It has an equivalent resistance, compared to the same grades, in conditions which are virtually isothermal. Alleima 253 MA can also be used in nitrogen-containing atmospheres provided that the gas contains enough oxygen to form a protective oxide layer. In gas shields containing little or no oxygen the resistance of Alleima 253 MA is inferior to that of Alloy 800H and 25Cr/20Ni steels as illustrated in Fig. 6. Thus, the grade is not recommended for use in muffle tubes using cracked ammonia gas.

Figure 6. Testing for 400 h at 825°C (1515°F) in nitrogen containing 43 and 205 ppm O₂ , respectively.

Salt and metal melts

Compared with conventional austenitic stainless steels, Alleima 253 MA has good resistance to cyanide melts and neutral salt melts and also to metal melts, e.g. lead, at high temperatures. Its resistance to metal melts is to a great extent determined by the oxygen content of the melt. As with other alloyed steels, corrosion is greatest at the surface of the metal bath.

Wet corrosion

Alleima 253 MA is not generally used in conditions requiring great resistance to wet corrosion. The steel is, however, slightly more resistant than ASTM TP304 to stress corrosion cracking in chloride bearing aqueous solutions. Its resistance is more or less the same as that of ASTM TP316.

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.

Forms of supply

Seamless tube and pipe in Alleima 253 MA is supplied in dimensions up to 260 mm (10.2 in.) outside diameter in the solution-annealed and white-pickled condition or solution annealed by a bright-annealing process.

Other forms of supply

• Fittings
• Welded tube and pipe
• Strip
• Wire, drawn or ground
• Bar steel
• Plate, sheet and wide strip

Heat treatment

Tubes are delivered in the heat treated condition. If another heat treatment is needed after further processing, the following is recommended:

Stress relieving

850-950°C (1560-1740°F), 10-15 minutes, cooling in air.

Solution annealing

1050-1150°C (1920-2100°F), 5-20 minutes, rapid cooling in air or water.

Mechanical properties

1 MPa = 1 N/mm²

a) R_p0.2 and R_p1.0 correspond to 0.2% offset and 1.0% offset yield strength, respectively.
b) Based on L₀ = 5.65 √S₀ where L₀ is the original gauge length and S₀ the original cross-section area

At high temperatures

Creep strength

The creep and creep rupture strength values correspond to values evaluated by the Swedish Institute for Metals Research for inclusion in the Swedish Standard. The evaluation is based on data submitted by AB Sandvik Materials Technology and Outokumpu Stainless and tests made by the Swedish Institute for Metals Research. The values apply to tube, pipe, sheet, plate and bar steel.

The higher values given in parentheses apply to Alleima seamless tube and pipe only. The basic values have been determined by testing at intervals of 100°C and at 750°C (1380°F), under uniaxial stress and with a constant load. The mean values in the tables below have been evaluated from the test results with the aid of linear regression of the logarithmic relationship between stress and time. This evaluation has also provided the basis of interpolation and extrapolation of temperatures and times.

The temperature above which design calculations are based on creep rupture strength instead of R_p0.2 proof strength, can be read off from Fig. 1. For Alleima 253 MA this temperature is about 550°C (1020°F). Fig. 2 shows the relationship between nominal stress and minimum creep rate, measured during testing under constant load.

Fig. 1. Proof strength Rp0.2 and creep rupture strength at 10 000 and 100 000 h.

Fig. 2 Relationship between nominal stress and minimum creep rate at 600 –1100°C (1110–2010°F).

Physical properties

Density: 7.8 g/cm³, 0.28 lb/in³

Relative magnetic permeability

1.003 (typical value)

1) mean values in temperature ranges (x10^-6)

1) (x10³)

Structural stability

Because Alleima 253 MA contains less chromium, and because of the addition of nitrogen the grade is less prone to sigma phase embrittlement than 25Cr/20Ni steels. See Fig. 7.

Figure 7. Time-Temperature- Transformation (TTT) diagram showing 1% sigma phase formation curves. The figures at the measuring points refer to sigma phase percentages by volume.

Welding

The weldability of Alleima 253MA is good. Suitable methods of fusion welding are manual metal-arc welding (MMA/SMAW) and gas-shielded arc welding, with the TIG/GTAW method as first choice.

In common with all austenitic stainless steels, Alleima 253MA has low thermal conductivity and high thermal expansion. Welding plans should therefore be carefully selected in advance, so that distortions of the welded joint are minimized. If residual stresses are a concern, solution annealing can be performed after welding.

For Alleima 253MA, heat-input of <1.5 kJ/mm and interpass temperature of <150°C (300°F) are recommended.

Recommended filler metals

TIG/GTAW or MIG/GMAW welding

EN ISO 14343-A G 21 10 N / W.no (EN no.) 1.4829

MMA/SMAW welding

EN ISO 3581-A E Z 23 10 N R 12