Materials: Stainless Steel

Features and applications of common stainless steel alloys

Austenitic stainless steel accounts for 85% – 90% of the stainless fasteners. It has the best corrosion resistance of stainless alloys; is non-magnetic before cold working; has low heat conductivity and good strength at higher temperatures; and is not hardenable by heat treatment.

Martensitic stainless steel accounts for about 5% of the stainless fasteners. Its no nickel content and high carbon content mean the lowest corrosion resistance of the stainless alloys and it is magnetic.

Ferritic stainless steel accounts for only a few percent of the stainless fasteners. Its high chromium content helps corrosion resistance, and it is magnetic and cannot be hardened by heat treatment.

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Austenitic Stainless Steel – Principal Design Features & Applications

Alloy

UNS Designation

Principal Design Features

Applications

18-8

Austenitic stainless steels that contain approximately 18% chromium and 8% nickel are often referred to as “18-8″ stainless steel.

The list is endless. Almost every conceivable industry uses 18-8 stainless in some way.

302

S30200

Type 302 is slightly higher carbon version of type 304, most commonly found in strip and wire forms. While still used in a variety of industries, many applications have shifted to types 304 and 304L due to the advances in melting technology, availability, and cost.

Primarily used in the stamping, spinning, and wire forming industry. This alloy is formed into all types of washers, springs, screens, and cables.

303

S30300

Type 303 is one of the most popular of all the free machining stainless steels. It offers good strength, corrosion resistance, and great machineability. It will resist scaling at temperatures up to 1600° F (871° C).

Used in an incredibly wide variety of parts both in screw and general machining industries. Applications include hardware, fasteners, valve parts, nozzles, and trim.

304

S30400

Type 304 is one of the most widely used and oldest of the stainless steels. It possesses an excellent combination of strength, corrosion resistance, and fabricate-ability. It is available in the widest variety of forms and sizes of any stainless steel.

The list is endless. Almost every conceivable industry uses some of this material in some way. Everything from stovetops to ball point pen barrels to flatware to fasteners has been fabricated from this alloy.

304L

S30403

Type 304L is a low carbon version of type 304 stainless. It is used almost interchangeably with type 304 but is preferred for welding operations. It offers a good combination of strength, corrosion resistance, and fabricate-ability.

The list is endless. Almost every conceivable industry uses some of this material in some way. Everything from stovetops to ball point pen barrels to flatware to fasteners has been fabricated from this alloy.

305

S30500

Type 305 has the lowest work and strain hardening rate of all the austenitic stainless steels. It was designed for maximum formability. It combines good strength and corrosion resistance and is readily available in strip and some bar sizes from the mills.

Any application requiring maximum formability such as spun or deep drawn eyelets, barrels, shells, cold headed rivets or screws will work well.

309

S30900

Type 309 is known for good strength and oxidation resistance in continuous service temperatures up to 2000° F (1093° C). It is superior to type 304 stainless in both strength and corrosion resistance.

Oven linings, boiler baffles, fire box sheets, furnace components, and other high temperature containers.

310

S31000

The strength of type 310 is a combination of good strength and corrosion resistance in temperatures up to 2100° F (1149° C). Due to its relatively high chromium and nickel content, it is superior in most environments to types 304 or 309 stainless.

Oven linings, boiler baffles, kilns, lead pots, radiant tubes, annealing covers, saggers, burners, combustion tubes, refractory anchor bolts, fire box sheets, furnace components, and other high temperature containers.

316

S31600

Type 316 has an increased molybdenum content to increase its resistance to corrosion when compared to other 300 series alloys. It will resist scaling at temperatures up to 1600° F (871° C) and maintains good mechanical properties and creep strength at high temperatures.

Widely used in industry, it was initially designed for paper mill machinery. It has been used in marine environments and a wide variety of general industrial components.

316L

S31603

Type 316Lis the low carbon version of type 316 and is often substituted for 316 stainless due to its superior weldability with no appreciable difference in price or properties. It combines good availability in all forms and size ranges with great strength and corrosion resistance.

Components used in marine environments and chemical equipment. Suitable for any application where 316 stainless is used and stronger welds desirable.

317

S31700

Type 317 is a higher chromium, nickel, and molybdenum version of 316 stainless designed principally for increased strength and corrosion resistance.

Textile, pulp paper, and chemical equipment, for corrosion resistance.

321

S32100

The key feature of type 321 stainless is its resistance to intergranular corrosion. It employs titanium as a stabilizing element against chromium carbide formation. This alloy also exhibits strength characteristics superior to those of 304 stainless.

Jet engine parts, furnace heat treated parts, expansion joints, turbo superchargers, oil refiners, exhaust manifolds, and high temperature chemical production equipment.

347

S34700

Similar to type 321 stainless, type 347 uses columbium as a stabilizing element to maximize its principal feature: resistance to intergranular corrosion. It can be used in applications requiring repeated heating in the range of 800° and 1650° F (427° – 899° C).

High temperature gaskets and expansion joints, rocket engine parts, aircraft collector rings, and exhaust manifolds and chemical production equipment.

Martensitic Stainless Steel – Principal Design Features & Applications

Alloy

UNS Designation

Principal Design Features

Applications

410

S41000

Type 410 is the basic martensitic stainless which will attain high mechanical properties after heat treatment. It has good impact strength, corrosion and scaling resistance up to 1200° F (649° C).

Cutlery, steam and gas turbine blades and buckets, bushings, valve components, fasteners, screens, and kitchen utensils.

416

S41600

Type 416 was the first free machining stainless steel. It is a heat treatable chromium steel with excellent machineability and non-galling characteristics. The alloy is magnetic in all conditions.

A wide variety of screw machine parts including nuts, screws, gears and pinions, valve trim, shafts, and axles.

420

S42000

Type 420 is a general purpose heat treatable chromium steel which is a popular cutlery grade.

Dental and surgical instruments, cutlery, pump shafts, plastic molds and dies, steel balls, and various hand tools.

Ferritic Stainless Steel – Principal Design Features & Applications

Alloy

UNS Designation

Principal Design Features

Applications

405

S40500

Type 405 is a 12% chromium steel designed to be used in the as-welded condition. Unlike other 12% chromium steels, it is not subject to a great deal of hardening through air cooling from high temperatures.

Commonly used for annealing boxes, steam nozzles, quenching racks, partitions, and other fabrications that cannot be annealed after welding.

430

S43000

Type 430 is a basic ferritic, non-heat treatable stainless steel. Its strengths are in ductility, formability, good corrosion and oxidation resistance, thermal conductivity, and finish quality.

Appliance, automotive, and architectural trim, vaults, heat exchangers, scientific apparatus, and vending machine components.

Austenitic Stainless Steel – Chemical Properties

Alloy

UNS Designation

C (max)

Mn (max)

P (max) S (max) Si Cr Ni Cu Other Elements

18-8

0.08%

2%

0.2% 0.03-15% 1% 17-20% 8-13% 0-4%

302

S30200

0.15%

2%

0.045% 0.03% 1% 17-19% 8-10%

303

S30300

0.15%

2%

0.02% 0.15%min 1% 17-19% 8-10%

304

S30400

0.08%

2%

0.45% 0.03% 1% 18-20% 8-10.5% 1%

304L

S30403

0.03%

2%

0.045% 0.03% 1% 18-20% 8-12% 1%

305

S30500

0.12%

2%

0.045% 0.03% 1% 17-19% 10.5-13% 1%

309

S30900

0.20%

2%

0.045% 0.03% 1% 22-24% 12-15%

310

S31000

0.25%

2%

0.045% 0.035% 1% 24-26% 19-22%

316

S31600

0.08%

2%

0.045% 0.03% 1% 16-18% 10-14% 2-3%

316L

S31603

0.03%

2%

0.045% 0.03% 1% 16-18% 10-14% 2-3%

317

S31700

0.08%

2%

0.045% 0.03% 1% 18-20% 11-15% 3-4%

321

S32100

0.08%

2%

0.045% 0.03% 1% 17-19% 9-12% Titanium
5 X Carbon

347

S34700

0.08%

2%

0.045% 0.03% 1% 17-19% 9-13% Columbian
Tantalum
10 X Carbon

Martensitic Stainless Steel Chemical Properties

Alloy UNS
Designation
C
(max)
M
(max)
P
(max)
S
(max)
Si Cr Ni Cu Other
Elements
410 S41000 0.15% 1% 0.04% 0.03% 1% 11.5-13.5%
416 S41600 0.15% 1.25% 0.06% 0.15%min 1% 12-14%
420 S42000 0.15%min 1% 0.04% 0.03% 1% 12-14%

Ferritic Stainless Steel Chemical Properties

Alloy UNS
Designation
C
(max)
Mn
(max)
P
(max)
S
(max)
Si Cr Ni Cu Other
Elements
405 S40500 0.08% 1% 0.04% 0.03% 1% 11.5-14.5% 1-3%
Aluminum
430 S43000 0.12% 1% 0.04% 0.03% 1% 16-18%

 

Austenitic Stainless Steel – Mechanical Properties

Tensile and yield will increase sharply in austenitic stainless steel fasteners made by cold forming, but may decrease in fasteners made by machining.

Alloy UNS
Designation
Tensile (ksi) Yield (ksi) Approximate Rockwell Hardness
18-8 80-150 40 min B85-95
302 S30200 70-125 40 min B85-95
303 S30300 90-125 40 min B85-95
304 S30400 85-150 40 min B85-95
304L S30403 Slightly lower than alloy 304 due to low carbon content Slightly lower than alloy 304 due to low carbon content Slightly lower than alloy 304 due to low carbon content
305 S30500 80-140 40 min B85-95
309 S30900 100-120 40 min B85-95
310 S31000 100-120 60-80 B85-95
316 S31600 85-140 40 min B85-95
316L S31603 Slightly lower than alloy 316 due to low carbon content Slightly lower than alloy 316 due to low carbon content Slightly lower than alloy 316 due to low carbon content
317 S31700 100-120 60-80 B85-95
321 S32100 100-120 60-80 B85-95
347 S34700 100-120 60-80 B85-95

Martensitic Stainless Steel – Mechanical Properties

Tensile and yield will increase sharply in martensitic stainless steel fasteners made by heat treating.

Alloy UNS
Designation
Tensile (ksi) Yield (ksi) Approximate
Rockwell Hardness
410 S41000 180 heat treated 150 heat treated C34
416 S41600 180 heat treated 150 heat treated C34-45
420 S42000 250 heat treated 200 heat treated C45

Ferritic Stainless Steel – Mechanical Properties

Alloy UNS
Designation
Tensile
(ksi)
Yield
(ksi)
Approximate
Rockwell Hardness
405 S40500 70-75 40-45 B65-75
430 S43000 70-75 40-45 B65-75