Grades

Grade
3031.4305303 stainless steel is the most common “free-machining” grade using sulphur to produce sulphides allowing easier chip-breaking during machining. Basically it is 304 with sulphur.

This grade combines the following characteristics:

Fair pitting corrosion resistance but significantly lower than 304.
Improved machinability compared to 304. Machinability index 60% improvement compared to 304
Poor weldability
Higher leaching rates of Cr and Ni than normal austenitic stainless steels

303 stainless steel is a basic stainless steel where high productivity is required. Normally, austenitic stainless steels like 304 are difficult to machine. The high work hardening rate of austenitic stainless steels produces greater tool wear and a tendency to produce “stringy” chips during machining. The situation is made worse by the lower thermal conductivity and higher thermal expansion of these steels.

Applications which illustrate these features include:

Threaded fasteners, shafts, valve bodies, precision measurement devices, pneumatic manifolds.
304/304L1.4301/1.4307304 stainless steel is probably the most common grade in the stainless steel market as a whole.

This grade combines the following characteristics:

Good corrosion resistance
Good weldability
Excellent ductility giving stretch formability in pressings
Hygienic surfaces
Work hardening for spring properties
Ease of manufacture at the steel mill

This combination of properties leads to the grade being used for a wide range of applications including:

Sinks, pots and pans, catering surfaces, architectural cladding, handrails, food processing, water treatment, pressure vessels, transport containers, surgical instruments, building support products, refrigeration equipment, watch cases, automotive trim, street furniture, anaerobic digestion, chemical plant, sanitary ware.
316/316L1.4401/1.4404316 stainless steel is the most common grade which highlights the benefits of molybdenum (Mo).

Mo enhances the corrosion resistance of stainless steel even in relatively small amounts.

In environments where 304 is found to be inadequate, 316 is the natural first grade to be considered. Typical environments where 316 is used are high chloride (saline, coastal), heavy urban, acidic, high temperature solutions. Like all austenitic stainless steels, 316 has good welding and forming characteristics.

Typical applications which demonstrate the improved corrosion resistance of 316 include:

Pharmaceutical plant, chemical processing, offshore oil and gas platform topside equipment, architectural applications in urban and coastal conditions, food processing, water treatment, pressure vessels, transport containers, swimming pool fittings and fixtures, marine structures, yacht fittings, laboratory equipment, heat exchangers.
3211.4541The stabilised austenitic 321 stainless steel is similar to 304 stainless steel but with Ti or Nb to improve intergranular corrosion resistance. It also has superior high temperature mechanical properties compared to 304/304L.

This grade combines the following characteristics:

Similar pitting corrosion resistance to 304L
Intergranular corrosion resistance equal to 304L
Improved high temperature 0.2% proof strength compared to 304L. 20% higher at 100°C, 45% higher at 550°C
Improved creep strength compared to 304L
Weldability equal to 304L
Difficult to achieve good polished finish due to carbides in the microstructure

Applications include:

Heat exchangers, gas boilers, aerospace, exhaust systems, process plant, element tubing, power generation, rocket engine parts.
4101.4006410 stainless steel are general-purpose martensitic stainless steels. However, the corrosion resistance of grade 410 steels can be further enhanced by a series of heat treatment processes.

This grade combines the following characteristics:

Containing 11.5% chromium, which provide good corrosion resistance properties
Controlled balance of mechanical properties by hardening and tempering
Magnetic

Applications include:

Bolts, screws, bushings and nuts, petroleum fractionating structures, shafts, pumps and valves, mine ladder rungs, gas turbines.
4161.4005416 stainless steel is the most common “free-machining” martensitic grade using sulphur to produce sulphides allowing easier chip-breaking during machining.

This grade combines the following characteristics:

Basic corrosion resistance lower than grade 410 due to sulphur
Moderate strength and toughness
Excellent machinability index approximately 90 compared to 100 for free cutting mild steel

416 stainless steel is the preferred free machining grade where higher strength than 303 is required. It is essentially grade 410 with sulphur for free machining. It is ideal for high throughput, intricate components.

Applications include:

Shafts, axles, gears, valves, fasteners, golf club heads, sensors, precision machined components, gun barrels, washing machine parts, dowel pins, clamps, collars.
4201.4021420 stainless steel is a hardenable stainless steel used for its basic corrosion resistance, high strength and wear resistance.

This grade combines the following characteristics:

Basic corrosion resistance
High hardness and strength
Controlled balance of mechanical properties by hardening and tempering
High wear resistance
Cost effectiveness due to low chromium content and absence of nickel
Magnetic
Thermal expansion comparable to carbon steel
Not easy to weld

Typical applications include:

Cutlery blades, solids handling, surgical instruments, plastic moulding, drive shafts, bearings, gears, springs, conveying equipment, cargo handling, tools, seaweed driers.

420 is a great choice for basic corrosion resistance, good strength and wear resistance.
4311.4057431 stainless steel is the “all round” engineering martensitic stainless steel, combining fair corrosion resistance with good strength and impact toughness.

This grade combines the following characteristics:

Fair corrosion resistance (better than 420)
High hardness and strength
Wear resistance
Controlled balance of mechanical properties by hardening and tempering
Improved toughness compared to 420 due to lower carbon and nickel addition
Magnetic
Not easy to weld

431 stainless steel has one of the best combinations of corrosion resistance, high strength and good impact toughness of all the stainless steels.

This accounts for its popularity in a wide range of engineering applications which include:

Drive shafts, propeller shafts, bearings, gears, hydraulic rams, valve stems, actuators, satellite parts, conveyor drive systems, hi-fi equipment stands, packaging machinery, crane pins, seat dampers for boats, mixing blades, golf clubs.

431 offers a cost-effective solution in many challenging engineering applications
316 Ti1.4571The stabilised austenitic 316Ti stainless steel is similar to 316 but with Ti to improve intergranular corrosion resistance. It also has superior high temperature mechanical properties compared to 316/316L.

This grades combines the following characteristics:

Similar pitting corrosion resistance to 316L
Intergranular corrosion resistance equal to 316L
Improved high temperature 0.2% proof strength compared to 316L. 11% higher at 100°C, 30% higher at 550°C
Improved creep strength compared to 316L
Weldability equal to 316L
Difficult to achieve good polished finish due to Ti carbides in the microstructure

Applications which illustrate these features include:

Heat exchangers, process plant, power generation, aerospace.
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