Sanmac® 4571 is titanium-stabilized austenitic stainless chromium–nickel–molybdenum steel with improved machinability.
ASTM: 316 Ti
EN Number: 1.4571
EN Name: X6CrNiMo17-12-2
- EN 10216-5*, EN 10294-2, EN 10297-2
- ASTM A312, (ASTM A511)
* The leakage test is deferred to the finished component
Chemical composition (nominal) %
Sanmac® 4571 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
Sandvik Sanmac® 4571 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.
Sandvik Sanmac® 4571 has better resistance to intergranular corrosion than unstabilised steels. The addition of titanium prevents precipitation of chromium carbides in the grain boundaries after prolonged heating in the temperature range 450- 850°C (840-1560°F).
Pitting and crevice corrosion
Resistance to these types of corrosion improves with increasing molybdenum content and Sandvik Sanmac® 4571 with about 2.1% Mo has substantially higher resistance than steels of type AISI 304/304L.
Stress corrosion cracking
Austenitic stainless 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. Such service conditions should therefore be avoided. Conditions when plants are shut down must also be considered as the condensates which are then formed can develop a chloride content that leads to both stress corrosion cracking and pitting.
In applications demanding high resistance to stress corrosion cracking, austenitic- ferritic steels, e.g. Sandvik SAF 2304®, Sanmac® 2205 or SAF 2507® have higher resistance to stress corrosion cracking than 4571.
Sandvik Sanmac® 4571 can be used in:
- Air up to 850°C (1560°F)
- Steam up to 750°C (1380°F)
Creep behavior 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 these steels 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 oxidizing or reducing, i.e. the oxygen content, and whether impurities such as sodium and vanadium are present.
Forms of supply
Hollow bar-Finishes, dimensions and tolerances
Hollow bar Sanmac® 4571 is stocked in a large number of sizes up to 250 mm outside diameter in the solution-annealed and white-pickled condition. See catalogues S-110-ENG, S-029-ENG or S-02909-ENG.
Dimensions are given as outside and inside diameter with guaranteed component sizes after machining for OD<2.5 X OD.
Outside diameter +2 / -0 %, but minimum +1 / -0 mm
Inside diameter +0 / -2 %, but minimum +0 / -1 mm
Better tolerances can be supplied to special order.
Other forms of supply Solid bar and billet
Steel with improved machinability, Sanmac®, is also available in round bar and billet.
Hollow Bar is normally delivered in heat treated condition. If additional heat treatment is needed after further processing the following is recommended.
850-950°C (1560-1740°F), 10-15 minutes, cooling in air.
1000-1100°C (1830-2010°F), 5-20 minutes, rapid cooling in air or water.
At 20°C (68°F)
|Proof strength||Tensile strength||Elong.||Hardness|
|Proof strength||Tensile strength||Elong.||Hardness|
|Rp0.2a c)||Rp1.0a c)||Rmc)||Ab)||A2"||HRB|
1 MPa = 1 N/mm2
a)Rp0.2and Rp1.0correspond to 0.2% offset and 1.0% offset yield strength, respectively.
b) Based on L0= 5.65ÖS0where L0is the original gauge length and S0the original cross-section area.
Due to its austenitic micro structure, Sandvik Sanmac® 4571 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 (-320oF)) according to the European standards prEN 13445-2 (UFPV-2) and prEN 10216-5.
At high temperatures
d) For hollow bar with wall thicknesses greater than 10 mm (0.4 in.) the proof strength values may be slightly lower but still fulfill the requirements according to DIN 17458 and SS 14 23 50.
Density: 8.0 g/cm3, 0.29 lb/in3
|Temperature, °C||W/m °C||Temperature, °F||Btu/ft h °F|
|Temperature, °C||J/kg °C||Temperature, °F||Btu/lb °F|
|Temperature, °C||Per °C||Temperature, °F||Per °F|
|Temperature, °C||MPa||Temperature, °F||ksi|
The weldability of Sanmac® 4571 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.
Since this material is alloyed in such a way to improve its machinability, the amount of surface oxides on the welded beads might be higher compared to that of the standard 316Ti steels. This may lead to arc instability during TIG/GTAW welding, especially welding without filer material. However, the welding behavior of this material is the same as for standard 316Ti steels when welding with filler material.
For Sanmac® 4571, heat input of <1.5 kJ/mm and interpass temperature of <100°C (210°F) are recommended. Preheating and post-weld heat treatment are normally not necessary.
Recommended filler metals
TIG/GTAW or MIG/GMAW welding
ISO 14343 S 19 12 3 Nb / AWS A5.9 ER318 (e.g. Exaton 19.12.3.Nb)
ISO 14343 S 19 12 3 L / AWS A5.9 ER316L (e.g. Exaton 19.12.3.L)
ISO 3581 E 19 12 3 Nb R / AWS A5.4 E318-16
ISO 3581 E 19 12 3 L R / AWS A5.4 E316L-17(e.g. Exaton 19.12.3.LR)