Chemical composition (nominal) %

Forms of supply

Seamless tube and pipe in Sandvik 1C356 is supplied in dimensions up to 120 mm (4.72 in.) outside diameter in the annealed condition, but are also available white-pickled after annealing.

Mechanical properties

1 MPa = 1 N/mm²

1) R_p0.2 and R_p1.0 correspond to 0.2% offset and 1.0% offset yield strength, respectively.
2) Based on L₀ = 5.65 √S₀, where L₀ is the original gauge length and S₀ the original cross-section area.
3) Hot finished products do not generally fulfill the min Rm requirement (500 MPa, 73 ksi) according to SEW 470.

Creep strength (approx. values)

Since Sandvik 1C356 has very large creep-rupture elongation, often more than 100%, and little resistance to creep, it is necessary to allow for considerable creep deformation long before rupture occurs. At normal service temperatures, i.e. over 700°C (1290°F), even the mass of the tubes can cause stresses leading to extensive deformations.

Careful attention must, therefore, be given to the way in which the tubes are supported. Sandvik 1C356, in common with other ferritic chromium steels, is less tough than austenitic stainless steels in the as-delivered condition.

Physical properties

Density: 7.7 g/cm³, 0.28 lb/in³

1) Mean values in temperature ranges x10^-6

1) x 10³

Corrosion resistance

Air

Sandvik 1C356 is highly resistant to oxidation, both at constant and at cyclically varying temperatures. The service temperature in air should not exceed about 1000°C (1830°F).

Isothermal oxidation at 1000°C (1830°F) results in a metal loss of about 10µm/1000h.

Hot corrosion / sulphidation

Owing to its combined aluminium, silicon and chromium content and the absence of nickel, Sandvik 1C356 has very good resistance in sulphidising gases and salts.

Structural stability

Temperatures of about 400–550°C (750–1020°F) should be avoided for even short periods of time, whether the steel is in service or merely being held at that temperature, since severe embrittlement, known as 475 deg. embrittlement, can take place. This is noticeable after the tubes have cooled to room temperature. However, the steel can be restored to its original condition by short term heating at a temperature above 600°C (1110°F).

Embrittlement can also occur as a result of sigma phase formation after prolonged service at 550-750°C (1020-1380°F), but it is less pronunced compared with 24–27 % chromium steels such as ASTM TP 446-1 (EN no. 1.4749), and high chromium-aluminium steels, such as EN no. 1.4762. The sigma phase can be redissolved after heat treatment above 900°C (1650°F).

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

800–850°C (1470–1560°F) 10-30 minutes, rapid cooling in air.

Annealing

800–860°C (1470–1580°F), 5-60 minutes, rapid cooling in air.

Hot working

1100–800°C (2010–1470°F).

Welding

Suitable fusion-welding methods are manual metal-arc welding with covered electrodes or gas-shielded arc welding, preferably using the TIG and MIG methods.

The welding zone should be preheated to 200–300°C (390–570°F). No post-weld heat treatment is necessary, where Sandvik 1C356 is used in structures that operate for prolonged periods at high temperature. For other structures and where heat treatment is considered appropriate, due to design considerations, annealing as described above is recommended.

In cases where there is risk of cracking due to inherent welding stresses, the wire electrodes Sandvik 29.9, Sandvik 25.20.C and Sanicro 72 can be used.

For manual metal-arc welding, the covered electrodes Sandvik 29.9.R, Sandvik 25.20.B and Sanicro 71 are recommended.

When using nickel alloy wire electrode Sanicro 72 and covered electrode Sanicro 71, however, allowance must be made for lower corrosion resistance in a reducing, sulphurous atmosphere.

Also, when using the austenitic stainless steel wire electrode Sandvik 25.20.C and the covered electrode Sandvik 25.20.B, the higher thermal expansion for these austenitic stainless steel electrodes must be considered.

Bending

Sandvik 1C356 tubes can be bent hot or cold. Annealing is not normally necessary after cold bending.

Hot-worked tubes should preferably be bent hot, but they can be bent cold, if the bending radii is greater than 5 times the diameter.

Hot bending is carried out at 900–800°C (1650–1470°F), followed by subsequent cooling in air.

Applications

Sandvik 1C356 should be chosen mainly for service in slightly sulphidizing gases where austenitic stainless steel with low contents of alloying elements may suffer corrosion. Typical applications for Sandvik 1C356 are:

• Recuperators in the metallurgical and allied industries
• Thermocouple protection tubes
• Injection nozzles