General Stainless Steel Information

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Stainless Metals & Alloys is a leading distributor of Stainless Steels, operating from several locations nationwide. We have extensive experience in providing ongoing maintenance support to major corporations, supplying large scale projects, and of course catering to the day to day requirements of Ireland’s stainless steel fabricators.

Major end-use industries include:
Dairy
Pulp and Paper
Architectural / Construction
Water Treatment
Wine & Beverage
Catering Equipment
Meat & Food Processing
Petrochemical Industries
Automotive Industry
Tanker Manufacturers
Biotech Industries

Our extensive range includes the following products, with 304 and 316 Austenitic grades available ex stock while more exotic grades & products are offered on an indent basis.

Flat products, such as stainless steel coil, sheet and plate
Bars in round, square, flat, angle and channel
Square & rectangular tube
Schedule pipe and fittings
Hygienic tube and fittings
Architectural balustrades & fittings
Mesh & perforated sheet
Pipe and tube valves
Coloured, patterned and textured, architectural stainless steel sheet
Fasteners
Tig stainless steel welding wires
Protective films

We also stock a comprehensive range of sundry items.

STAINLESS STEEL FINISHES

Common finishes held in stock are No.1, 2B, BA, No.4, however other finishes can be sourced.

Finishes

No.1 Hot rolled, annealed and pickled. Generally used where smoothness of finish is not a design consideration.

2D A cold rolled finish obtained from a final annealing and pickling, or a final light cold roll pass on dull rollers, which may be polished after fabrication.

2B A smooth finish for general applications. A brighter finish than 2D.

BA (Bright Annealed) A reflective surface obtained from bright annealing after cold rolling. Used for deep drawing products such as sinks, tubs etc. Sheets can be polished on 1 or 2 sides.

No.4 A ‘brushed or satin’ finish obtained from mechanical polishing with 120-240 grit. Used in dairy and kitchen equipment. Meets international 3A Hygiene Standards.

No.8 A mirror finish for high reflectiveness. Can be used as mirrors or reflectors.

HL (Hairline) A finish obtained by mechanical polishing with 120-320 grit.

CF (Cold Formed) A smooth flat reflective finish.

BP (Buff Polished) Mechanically polished tube using 220-240 grit.

AW (As Welded) Receives no further treatment after forming and welding.

Special Notes

Although every endeavour has been made to have all the correct detail, we suggest product specification be confirmed with your representative when placing orders.

Items identified as ‘stocked items’ are defined as goods normally held in stock, and are subject to prior sales.

Terms of trade are supplied at the time of opening a trading account and are available upon request. A copy of this appears on the reverse of all invoices issued. A minimum charge may apply.

All weights and dimensions provided are theoretical. Mill tolerances will affect actual weights (+/). Weights are based on a density of stainless being 8000 kgs/m³.

TYPES OF STAINLESS STEELS

Stainless steel is a name given to a group of steel alloys that contain more than 10.5% chromium. Chromium has a high affinity for oxygen and forms a stable oxide film on the surface of stainless steel.

The film is called the “passive oxide layer” and forms instantaneously in ordinary atmospheres. The film is self healing and rebuilds when it has been removed. It is this film that gives stainless steel its corrosion resistance.

AUSTENITIC GRADES
When nickel (Ni) is added to stainless steel in sufficient quantities, the crystal structure is changed from ferrite to austenite, hence the term austenitic stainless steel. The basic composition of austenitic stainless steel is 18% chromium (Cr) and 8% nickel (Ni). This is called 304 grade, sometimes referred to as 18/8 or 18/10. If additional corrosion resistance is required 2% molybdenum (Mo) is added to form grade 316.

Descriptions and General Uses

200 Series (Indent Only)
The 200-series is a technically valid family of stainless steels, but, like all stainless steel grades, they have their limitations. Because the 200-series grades are austenitic, they are not magnetic and are therefore very difficult to distinguish from the widely used 300-series grades. Most growth in 200-series use over recent years has been in low-nickel and therefore low-chromium versions which have less corrosion resistance than 304. The end result has been corrosion failures in some applications.

302 (Indent Only)
This grade is the original general purpose 18/8 stainless steel (18% chromium, 8% nickel). It has good corrosion resistance combined with good physical properties – it has excellent ductility and welding properties. Non-magnetic when annealed and becomes slightly magnetic when cold worked.

303 (Indent Only)
Especially developed for machining – specially where it involves extensive machining in automatic screw machines. Sulphur or selenium is added to give excellent free machining and non seizing properties. As sulphur or selenium is added corrosion resistance is lower than T304. T303 is not recommended for welding. Non-magnetic when annealed but becomes slightly magnetic when cold worked.

304
The most widely used stainless steel with the best all round performance. Its carbon content is lower and its corrosion after welding resistance is higher than T302. It is less susceptible to intergranular corrosion after welding. Non magnetic but slightly magnetic when cold worked.

304L
A low carbon stainless steel with general corrosion resistance like T304, but with superior resistance to intergranular corrosion following welding or stress relieving. Highly recommended for parts which are fabricated by welding and which cannot be annealed. Generally limited to temperatures up to 426℃. The physical properties and thermal treatments of T304L are similar but not identical to T304. Non-magnetic when annealed but slightly magnetic when cold worked.

310S (Indent Only)
310S has been developed for high temperature service where high creep strength is required. Maximum service temperature is around 1100℃ but it is not recommended for applications of prolonged service as it may become brittle. Non-magnetic when annealed or cold worked.

316
Also known a marine grade stainless steel. T316 has 2-3% molybdenum which improves corrosion resistance. T316 has superior corrosion resistance to other austenitic steels when exposed to many types of chemical corrodents as well as marine environments. T316 also has applications in the chemical, textile and paper industries. It has better strength and creep resistance at high temperatures than T304 and greater work hardening properties. Non-magnetic but slightly magnetic when cold worked.

316L
Has lower carbon than T316, with corrosion resistance similar to T316 but superior resistance to intergranular corrosion following welding or stress relieving. It is recommended for parts which cannot be subsequently annealed. Service temperatures up to 426℃. The physical properties and thermal treatments of type 316L are similar but not identical to type 316. Non-magnetic when annealed but slightly magnetic when cold worked.

321 (Indent Only)
Basically 302 (basic 18/8) stabilised by the addition of titanium to five times the carbon content. This prevents intergranular corrosion and offers scale resistance at higher temperatures up to 850℃. Corrosion resistance is lower than 304. Not recommended for bright/mirror polishing. Non-magnetic when annealed but slightly magnetic when cold worked.

904L (Indent Only)
High resistance to general corrosion, eg sulphuric and acetic acids, crevice corrosion, stress corrosion, pitting in chlorine bearing solutions. Good weldability.

MARTENSITIC GRADES
This grade contains 12%-18% chromium and 0.08%-1.00% carbon. The high carbon content allows the stainless steel to respond well to heat treatment to give various mechanical strengths such as hardness. However the carbon is detrimental when welding and care must be taken.

Descriptions and General Uses

409 (Indent Only)
Type 409 is general purpose construction stainless steel. Primarily intended for automotive exhaust systems and in other applications where appearance is secondary to mechanical and corrosion resistance.

410 (Indent Only)
Type 410 is general purpose corrosion and heat resisting martensitic stainless steel. It has good corrosion resistance and can be easily forged and machined. It is not suitable under severe corrosion environments. It is magnetic in all conditions and its main use is for stainless steel cutlery.

420 (Indent Only)
Type 420 has a higher carbon content than 410 to increase hardness to a maximum of approximately 500 brinell. It has optimum corrosion resisting qualities in the hardened and tempered conditions. Type 420 is magnetic in all conditions.

431 (Indent Only)
Type 431 is a nickel bearing martensitic stainless steel designed for heat treatment to the highest mechanical properties. Its corrosion resistance is superior to that of type 410 and 430. It is magnetic in all conditions.

FERRITIC GRADES
These are nickel free. They have varying chromium content of 12%-22%, but a lower carbon content than the martensitic grades.

The increased chromium increases corrosion resistance at elevated temperatures, however the lack of mechanical properties due to the fact that it cannot be heat treated limits its application.

Descriptions and General Uses

430
Type 430 is a corrosion and heat resisting stainless steel with superior corrosion and heat resistance compared to type 410. Type 430 is non hardenable and possesses only mild cold working properties due to the high chromium content. Its weldability is excellent and does not require subsequent annealing. It is magnetic in all conditions and its common uses include builders hardware, domestic appliances (dryers, dishwashers) and automotive trim.

DUPLEX STAINLESS STEEL
Duplex stainless steels have a structure of approximately equal amounts of ferrite and austenitic and therefore may be referred to as ferritic-austenitic stainless steel.

The chromium varies from 18%-28% and a nickel content of 4.5% to 8% is insufficient to develop a fully austenitic crystal structure. Most grades contain molybdenum in the 2.5%-4%, plus a small nitrogen addition which enables both strength and pitting resistance. Common uses include applications such as heat exchanger panels and tubes, tanks and vessels where high chloride concentrations are present, eg sea water cooling, desalination, food pickling plants and aggressive marine waters.

NICKEL AS A PRICE DRIVER
Understanding how nickel affects the price of stainless steel can be relayed as follows;

T304 has approximately 8% nickel (so 1000 kg of S/S has 80kg of nickel)
T316 has approximately 10% nickel (so 1000 kg of S/S has 100kg of nickel)