Chemical composition (nominal) %

Forms of supply

Hollow bar-Finishes, dimensions and tolerances
Hollow bar Sanmac 316/316L is stocked in a large number of sizes up to 250 mm outside diameter in the solution-annealed and white-pickled condition.
See catalogue S-110-ENG or S-1492-ENG.

Dimensions are given as outside and inside diameter with guaranteed component sizes after machining.
Outside diameter +2 / -0 %, but minimum +1 / -0 mm
Inside diameter +0 / -2 %, but minimum +0 / -1 mm
Straightness +/-1.5mm/m
Other tolerances can be supplied against special order.

Other forms of supply
Bar
Steel with improved machinability, Sanmac, is also available in bar.

Filler metals for welding
The sizes listed below are Sandvik stock standard. The local stocks carry sizes in common demand on the market. For technical information on the filler metals please refer to brochures S-2361-ENG and S-2362-ENG.

Wire electrodes and filler wire/rods:
Sandvik 19.12.3.L: 0.80, 1.00, 1,20, 1.60, 2.00, 2.40, 3.00, 3.20, 4.00 mm

Covered electrodes
Sandvik 19.12.3.LR: 1.6, 2.0, 2.5, 3.25, 4.0 mm
Sandvik 19.12.3.LB: 2.0, 2.5, 3.25, 4.0, 5.0 mm
Sandvik 19.12.3.LRHD: 2.5, 3.25, 4.0, 5.0 mm

Corrosion resistance

General corrosion

Sandvik Sanmac 316/316L has good resistance to:

• Organic acids at high concentrations and temperatures, with the exception of formic acid and acids with corrosive contaminants
• Inorganic acids, e.g. phosphoric acid, at moderate concentrations and temperatures, and sulphuric acid below 20% at moderate temperatures.
  The steel can also be used in sulphuric acid of concentrations above 90% at low temperature.
• E.g. sulphates, sulphides and sulphites
• Caustic environments

Intergranular corrosion

Sandvik Sanmac 316/316L has a low carbon content and therefore good resistance to intergranular corrosion.

Stress corrosion cracking

Austenitic steels are susceptible to stress corrosion cracking. This may occur at temperatures above about 60°C (140°F) if the steel is subjected to tensile stresses and at the same time comes into contact with certain solutions, particularly those containing chlorides. In applications demanding high resistance to stress corrosion cracking, the austenitic-ferritic steels Sandvik SAF 2304, Sandvik 10RE51 or Sandvik Sanmac 2205 have higher resistance to stress corrosion cracking than 316L.

Pitting and crevice corrosion

Resistance to these types of corrosion improves with increasing molybdenum content. Thus, the molybdenum-alloyed Sandvik Sanmac 316/316L has substantially higher resistance to attack than steels of type AISI 304 and 304L.

Gas corrosion

Sandvik Sanmac 316/316L can be used in:

• Air up to 850°C (1560°F)
• Steam up to 750°C (1380°F)

Creep behaviour should also be taken into account when using the steel in the creep range. In flue gases containing sulphur, the corrosion resistance is reduced. In such environments the steel can be used at temperatures up to 600-750°C (1110-1380°F) depending on service conditions. Factors to consider are whether the atmosphere is oxidising or reducing, i.e. the oxygen content, and whether impurities such as sodium and vanadium are present.

Mechanical properties

For hollow bar with wall thicknesses greater than 10 mm (0.4 in.) the proof strength may fall short of the stated values by about 10 MPa (1.4 ksi).

At 20°C (68°F)

1 MPa = 1N/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 ÖS₀ where L₀ is the original gauge length and S₀  the original cross-section area.
c)NFA 49-317 with min 45% can be fulfilled

Impact strength

Due to its austenitic microstructure, Sandvik Sanmac 316/316L 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

Physical properties

Density: 8.0 g/cm³, 0.29 lb/in³

Heat treatment

Hollow bar is delivered in heat treated condition. If further heat treatment is needed after further processing the following is recommended:

Stress relieving
850-950°C (1560-1740°F), cooling in air.

Solution annealing
1000-1100°C (1830-2010°F), rapid cooling in air or water.

Welding

Suitable welding methods for Sandvik Sanmac 316/316L are manual metal-arc welding (MMA) with covered electrodes and gas-shielded arc welding with the TIG and MIG methods as first choice. Preheating and post-weld heat treatment are normally not necessary.

Due to the fact that this material is alloyed in such a way that it shall have good machinability there can be a higher amount of surface oxides on the weld beads compared to standard 316L steels. This may lead to arc instability during TIG welding, especially at autogenous welding. A correct setting of the welding current is of great importance. However, when filler metal is used, the weldability is the same as for standard 316L steels.

When filler metal is used, Sanmac 316/316L has the same behaviour as standard 316/316L at welding.

Since the material has low thermal conductivity and high thermal expansion, welding must be carried out with a low heat input and with welding plans well thought out in advance so that the deformation of the welded joint can be kept under control. If, despite these precautions, it is foreseen that the residual stresses might impair the function of the weldment, we recommend that the entire structure be stress relieved. See recommendations under "
Recommendations of filler metal:

Machining

Sanmac stands for Sandvik Machinability Concept. In Sanmac materials, machinability has been improved without jeopardising properties such as corrosion resistance and mechanical strength.
The improved machinability is owing to:

• Optimised non-metallic inclusions
• Optimal chemical composition
• Optimised process and production parameters

Detailed recommendations for the choice of tools and cutting data regarding turning, thread cutting, parting/grooving, drilling, milling and sawing are provided in the brochure S-02909-ENG.

The diagram shows the ranges within which data should be chosen in order to obtain a tool life of minimum 10 minutes when machining austenitic Sanmac 316/316L.

The ranges are limited in the event of low feeds because of unacceptable chip breaking. In the case of high cutting speeds, plastic deformation is the most dominant cause of failure. When feed increases and the cutting speed falls, edge frittering (chipping) increases significantly. The diagram is applicable for short cutting times. For long, continuous cuts, the cutting speeds should be reduced somewhat.

The lowest recommended cutting speed is determined by the tendency of the material to stick to the insert (built-up-edge), although the integrity of insert clamping and the stability of the machine are also of great significance.

It is important to conclude which wear mechanism is active, in order to optimise cutting data with the aid of the diagram.

Applications

Sanmac 316/316L is used for a wide range of industrial applications where steels of type ASTM 304/304L have insufficient corrosion resistance. Typical applications are:

• Machined parts for tube and pipe fittings
• Components for valves, pumps, heat exchangers and vessels
• Different tubular shafts in chemical, petrochemical, fertilizer, pulp and paper and power industries as well as in the production of pharmaceuticals, foods and beverages