Sandvik 254 SMO (ESR) (Billets)

Chemical composition

Forms of supply

Sizes and tolerances

Round-cornered square, as well as round billets, are produced in a wide range of sizes according to the following tables. Larger sizes offered on request.

Surface conditions

Square billets

Unground, spot ground or fully ground condition.

Round billets

Peel turned or black condition.

Sizes and tolerances apply to the rolled/forged condition.

Other products

Mostly supplied in non-ESR condition

• Welded tube and pipe
• Seamless tube and pipe
• Fittings and flanges

Mechanical properties

For billets testing is performed on separately solution annealed and quenched test pieces.

The following figures apply to material in the solution annealed condition.

At 20°C (68°F)

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.

Impact strength

Due to its austenitic microstructure, Sandvik 254 SMO/ESR has very good impact strength both at room temperature and at cryogenic temperatures.
Tests have demonstrated that the steel fulfils the requirements (60 J (44 ft-lb) at -196 ^oC (-320 ^oF)) according to the European standards EN 13445-2 (UFPV-2) and EN 10216-5.

At high temperatures

Intermetallic phases are precipitated within the temperature range of 600-1000°C (1110-1830°F). The steel should therefore not be exposed to these temperatures for prolonged periods. Minimum proof strenght properties at high temperatures are based on datasheets seamless tubes and pipe. Since the tubes have thin walls the values should only be used as indicative values for billets.

Physical properties

Density: 8.0 g/cm³, 0.29 lb/in³

1) mean values in temperature ranges (x10⁶)

1) (x10³)

Corrosion resistance

Stress corrosion cracking (SCC)

Ordinary austenitic steels of the AISI 304 and 316 types are prone to stress corrosion cracking in chloride-containing solutions at temperatures exceeding about 60°C (140°F). For austenitic steels, resistance to SCC increases with increasing nickel and molybdenum contents. The tables below give the results of two accelerated tests, showing that Sandvik 254 SMO has very good resistance to SCC.

Stress corrosion cracking tests in boiling 25% NaCL solution, pH=1.5. U-bend specimens.

Intergranular corrosion

Sandvik 254 SMO/ESR has a very low carbon content. This means that there is very little risk of carbide precipitation during heating, for example, when welding. The steel passes the Strauss test (ASTM A262, practice E) even after sensitizing for one hour at 600-1000°C (1110-1830°F).

However, due to the high alloying content of the steel, intermetallic phases can precipitate at the grain boundaries in the temperature range at 600-1000°C (1110-1830°F). These precipitations do not involve any risk of intergranular corrosion in the environments in which the steel is intended to be used. Thus, welding can be carried out without any risk of intergranular corrosion.

Pitting corrosion

The high chromium content and particularly the molybdenum content give Sandvik 254 SMO/ESR excellent resistance to pitting and crevice corrosion.

The high nitrogen content also improves pitting resistance. The results of laboratory determination of the critical pitting temperature (CPT) in 3 % NaCl shows that Sandvik 254 SMO/ESR has a far greater CPT than 904L and it possesses very good resistance in water containing chlorides. Sandvik 254 SMO/ESR is, therefore, a suitable material for use in, for example, seawater.

Crevice corrosion

The weak point of conventional stainless steels is their limited resistance to crevice corrosion. In seawater, for example, there is a considerably greater risk of crevice corrosion under gaskets, deposits or fouling. Tests in natural seawater at 60°C (140°F) have shown that Sandvik 254 SMO/ESR can be exposed for prolonged periods, without suffering crevice corrosion.

For further information regarding corrosion resistance of Sandvik 254 SMO, please see the data sheet Seamless tube and pipe - Sandvik 254 SMO. The data should be considered in the knowledge that it may not be applicable for thick sections, such as forgings.

Hot working

Hot working should be carried out at a material temperature of 950-1200°C (1740-2190°F). Hot working of Sandvik 254 SMO/ESR should be followed by rapid cooling in air or water. Subsequent heat treatment should be carried out in accordance with the recommendations given for heat treatment.

Heat treatment

Billets are delivered in the hot worked condition. The following heat treatment is recommended.

Solution annealing

1150-1200°C (2100-2190°F), followed by quenching in water.

Welding

The weldability of Sandvik 254 SMO/ESR is good. Preheating and post-weld heat treatment are normally not recommended. Suitable methods of fusion welding are manual metal-arc with covered electrodes and gas shielded arc welding, mainly by means of the TIG and MIG/MAG methods.

Since the material is intended for use under severely corrosive conditions, welding must be carried out with care, and followed by thorough cleaning to ensure that the weld metal and the heat affected zone will have as good corrosion properties as possible. Degreasing of the weld area with acetone or alcohol is recommended, in order to avoid porosity and fissuring.

The heat input during welding should not exceed 1.0 kJ/mm, and in multi-pass welding, the interpass temperature should not exceed 100°C (210°F). A stringer bead welding technique should be used.

The welding of fully austenitic steels usually entails a risk of hot cracking in the weld metal, particularly if the weldment is under constraint. However, since Sandvik 254 SMO/ESR has a very high degree of purity, the risk of this type of cracking is greatly reduced. Backing bars and similar devices of copper alloys, however, cannot be used, since copper penetration into the grain boundaries in stainless steel can lead to cracking.

In common with all austenitic stainless steels, Sandvik 254 SMO/ESR has low thermal conductivity and high thermal expansion. For this reason, welding should be carefully planned in advance so that distortion of the welded joint can be minimised. If, despite these precautions, it is believed that residual stresses may impair the function of the weldment, it is recommended that the entire structure is solution annealed. See under Heat treatment.

Sanicro 60 wire and electrodes are recommended as filler metal. This filler metal is overalloyed and produces a weld that has better corrosion properties than the parent metal. Sanicro 60 is also suitable for welding joints between Sandvik 254 SMO/ESR and nickel alloys, other stainless steels or carbon steels.

Machining

Machining Sandvik 254 SMO/ESR, as with other stainless steels, requires an adjustment to tooling data and machining method, in order to achieve satisfactory results. Compared to Sanmac 316/316L, the cutting speed must be reduced by approximately 55-60% when turning Sandvik 254 SMO/ESR with coated, cemented carbide tools. Much the same applies to other operations. Feeds should only be reduced slightly and with care.

Detailed recommendations for the choice of tools and cutting data are provided in the data sheet for Sanmac 316/316L.

Applications

Sandvik 254 SMO is used in the following applications:

• Equipment for handling seawater - for example, heat exchangers, cooling water systems, ballast water systems, firefighting systems etc.
• Equipment in pulp bleaching plants.
• Components in gas cleaning systems.

* 254 SMO is a trademark owned by Outokumpu OY.