Sanmac® 4571 Hollow bar

Standards

• ASTM: 316 Ti
• UNS: S31635
• EN Number: 1.4571
• EN Name: X6CrNiMo17-12-2

Product standards

Hollow Bar:

• 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) %

Applications

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

Corrosion resistance

General corrosion

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.

Intergranular corrosion

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 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. SAF™ 2304, Sanmac^® 2205 or SAF™ 2507 have higher resistance to stress corrosion cracking than 4571.

Gas corrosion

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

Straightness +/-1.5mm/m

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.

Heat treatment

Hollow Bar is normally delivered in heat treated condition. If additional 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
1000-1100°C (1830-2010°F), 5-20 minutes, rapid cooling in air or water.

Mechanical properties

At 20°C (68°F)

1 MPa = 1 N/mm²
a)R_p0.2and R_p1.0correspond 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.

Impact strength

Due to its austenitic micro structure, 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 (-320^oF)) 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.

Physical properties

Density: 8.0 g/cm³, 0.29 lb/in³

Welding

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)

MMA/SMAW welding

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)

Machining

saknas