Sanmac 304/304L (Hollow bar)

Chemical composition (nominal) %

Forms of supply

Hollow bar- Finishes, dimensions and tolerances

Hollow bar in Sanmac 304L is stocked in various sizes in the solution annealed and white-pickled condition. See catalogues S-110-ENG or S-02909-ENG.

Dimensions are given as outside and inside diameters with guaranteed component sizes after machining, see catalogues.

Outside diameter tolerance is +2/-0%, but minimum +1/-0mm
Inside diameter tolerance is +0/-2%, but minimum +0/-1mm
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 metal 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.

Welding electrodes and filler wire/rods

Sandvik 19.9.L: 1.60, 2.00, 2.40, 3.00, 3.20 and 4.00 mm
Sandvik 19.9.LSi: 0.80, 1.00, 1.20 and 1.60 mm

Covered electrodes

Sandvik 19.9.LR: 1.60, 2.00, 2.50, 3.25, 4.00 and 5.00 mm
Sandvik 19.9.LB: 2.50, 3.25, 4.00 and 5.00 mm
Sandvik 19.9.LRHD: 3.25, 4.00 and 5.00 mm

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.

Impact strength

Due to its austenitic microstructure, Sandvik Sanmac 304/304L 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: 7.9 g/cm³, 0.29 lb/in³

Corrosion resistance

General corrosion

Sandvik Sanmac 304/304L has good resistance to:

• Organic acids at moderate temperatures, with the exception of formic acid
• Sulphates, sulphides and sulphites
• Caustic solutions at moderate temperatures
• Oxidising acids like nitric acid

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 SAF 2205 have higher resistance to stress corrosion cracking than 304L.

Intergranular corrosion

Sandvik Sanmac 304/304L has a low carbon content and therefore good resistance to intergranular corrosion.

Pitting and crevice corrosion

The steel may be sensitive to pitting and crevice corrosion even in solutions of relatively low chloride content. Molybdenum-alloyed steels have better resistance and the resistance improves with increasing molybdenum content.

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 304/304L 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 304L 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 304L steels.

When filler metal is used, Sanmac 304/304L has the same behaviour as standard 304/304L 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 "Heat treatment".

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 materials (304/304L, 316/316L).

Figure 1. Machining chart Sandvik Sanmac 304L and 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 304/304L is used for a wide range of industrial applications. Typical examples are: Machined parts for tube and pipe fittings, valves, components for 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.