STAINLESS STEEL MATERIAL GRADE
Stainless steel fasteners are particularly popular in the automotive industry, which involves stainless steel screws in the construction of structural automotive components.
Because automobiles are subject to variable weather conditions and hazardous contaminants like salt in some cases, stainless steel is an excellent fastener composition; it resists weather and salt-induced oxidation. For these and other reasons, stainless steel screws are also used in the electronics manufacturing, medical products, watercraft building and construction industries.
Stainless steel alloys are iron-based metals containing at least 10% chromium and other metals, which provide added corrosion and heat resistance. They do not require a protective coating, and they are able to perform well in a wide range of conditions and temperatures.
Stainless Steel
We are the biggest producers for stainless steel bolts and nuts in India, as our name suggests we are manufacturing big bolts and nuts in stainless steel grades in the under mentioned table.
| Fastener Type | Diameter | Grades | Grades | Grades | Grades |
| Hexagon bolts | M-12 to M-100 | 304 / 304 L | 316 / 316 L | 310 / 310 S | 410 / 431 |
| Hex bolts | M-12 to M-100 | 304 / 304 L | 316 / 316 L | 310 / 310 S | 410 / 431 |
| Hex cap screws | M-12 to M-100 | 304 / 304 L | 316 / 316 L | 310 / 310 S | 410 / 431 |
| Socket head cap screws | M-30 to M-72 | 304 / 304 L | 316 / 316 L | 310 / 310 S | 410 / 431 |
| Hex nuts | M-30 to M-72 | 304 / 304 L | 316 / 316 L | 310 / 310 S | 410 / 431 |
| Hex lock nuts | M-30 to M-72 | 304 / 304 L | 316 / 316 L | 310 / 310 S | 410 / 431 |
| Hex nylock nuts | M-30 to M-64 | 304 / 304 L | 316 / 316 L | 310 / 310 S | 410 / 431 |
| Hex castle nuts | M-12 to M-72 | 304 / 304 L | 316 / 316 L | 310 / 310 S | 410 / 431 |
| Heavy hex nuts | M-12 to M-72 | 304 / 304 L | 316 / 316 L | 310 / 310 S | 410 / 431 |
| Washers | M-12 to M-72 | 304 / 304 L | 316 / 316 L | 310 / 310 S | 410 / 431 |
| Stud bolts | M-12 to M-72 | 304 / 304 L | 316 / 316 L | 310 / 310 S | 410 / 431 |
Comparison chart for international steel grades for stainless steel bolting’s
| Grades | European Number | ASTM grade | UNS | British standard | DIN |
| 304 | 1.4301 | ASTM A 193 Gr B8 | S 30400 | BS 970 | X 5CrNi1810 |
| 304 L | 1.4306 | ASTM A 320 Ge B8 | S 30403 | BS 970 | X 2CrNi1911 |
| 316 | 1.4401 | ASTM A 193 Gr B8M | S 31600 | BS 970 | X 5 CrNiMo 17 13 2 |
| 316 L | 1.4404 | ASTM A 320 Ge B8M | S 31603 | BS 970 | X 2 CrNiMo 17 13 2 |
| 310 | 1.4841 | ASTM A 479 | S 31000 | BS 970 | X 12 CrNi 25 21 |
| 310 S | 1.4845 | S 31008 | BS 970 | X 12 CrNi 25 21 | |
| 410 | 1.4006 | S 41000 | BS 970 | X 10Cr13 | |
| 431 | 1.4057 | S 43100 | BS 970 | X 20CrNi172 | |
| 316S31 | 1.4401 | ASTM A 193 Gr B8M | S 31600 | BS 970 | X 5 CrNiMo 17 12 2 |
Stainless steel can be broken down into three different types: Austenitic, Martensitic and Ferritic.
• Austenitic Stainless Steel
(Between 15%-20% Chromium, Between 5%-19% Nickel) – Austenitic stainless has the highest degree of corrosion resistance of the three types. This type of stainless includes these grades: 302, 303, 304, 304L, 316, 32, 347 and 348. They also have a tensile strength of between 80,000 – 150,000 PSI.
• Martensitic Stainless Steel
(Between 12%-18% Chromium) – Martensitic stainless steel is considered a magnetic steel. It can be heat treated to increase its hardness and is not recommended for welding. This type of stainless includes: 410, 416, 420 and 431. They have a tensile strength of between 180,000 and 250,000 PSI.
• Ferritic Stainless Steel
(Between 15%-18% Chromium) – Ferritic stainless steel has a tensile strength of 65,000 – 87,000 PSI. While it is still corrosion resistant, it is not recommended for areas where corrosion is likely to occur. This material cannot be heat treated. Due to the forming process it is magnetic and not suitable for welding. Ferritic grades of stainless include: 430 and 430F.
Below are some of the many bolt grades of stainless steel that we carry.
a ) 18-8 Stainless Steel:
(18% Chrome, 8% Nickel, .08% Maximum Carbon) – 18-8 Stainless refers to 300 series stainless steel. 303 and 304 Stainless are the most commonly listed grades, the standard grade for stainless fasteners. They are corrosion-resistant and durable. They are often used in marine applications in freshwater environments but will not work as effectively in a salt-water environment as 316 stainless. Stainless alloy resists oxidizing and rusting, however it can tarnish over time. Equivalent to metric A2 Stainless Steel.
b ) 305 Stainless Steel:
(17%-19% Chrome, 8%-10% Nickel, .12% Maximum Carbon) – This grade has been developed specifically to improve the cold heading qualities of 18-8. Corrosion resistance and physical qualities are equal to Type 304. 305 stainless steel is most commonly used to make deck screws, which are used to fasten wood or composite boards to the main beams of a deck.
c ) 316 Stainless Steel:
(16%-18% Chrome, 10%-14% Nickel, .08% Maximum Carbon, 2.00% Maximum Molybdenum) – This grade of steel is used and recommended for applications in severe, harsh or marine environments. Its corrosion resistance is greater than 18-8 stainless, which is why we recommend using 316 stainless steel fasteners for salt-water application. It is important to remember that even the salt in the air near a body of salt-water can do damage to dry applications, so 316 is the material of choice. Common applications of 316 stainless fasteners include use on boats, docks, piers, and pools.
d ) 410 Stainless Steel:
(11.5%-13.5% Chrome, .15% Maximum Carbon) – Since this grade of stainless steel can be hardened up to approximately 40 Rockwell C, it is durable in most environments. Harder than 18-8 stainless but with less corrosion resistance, 410 stainless is commonly used to make roofing screws, siding screws and self-
Over the past few years we have manufactured many different kind of stainless steel grades of bolts and nuts, however the above grades mentioned in the table are the main grades which we are manufacturing consistently. With constant improvement in quality we have been able to excel in the manufacturing process for the above steels and their respective grades.
Screws with reduced load bearing capacity due to the head or shaft design that can be subjected to a tensile test are now labeled with the strength class by the supplementary number 0. For example 050, 070, 080, 0100.
The designation of the steel grade (first block) consists of one of the letters:
- A for austenitic steel
- C for martensitic steel
- F for ferritic steel
- D for Duplex steel
Example:
A2-70 indicates: austenitic steel, cold worked, min. 700 N/mm2 tensile strength
A8-100 indicates: austenitic steel, cold worked, min. 1000 N/mm22 tensile strength
C4-70 indicates: martensitic steel, hardened and tempered, min. 700 N/mm2 tensile strength
The designation of the property class consists of two digits representing 1/10 of the tensile strength of the fasteners respectively 1/10 of the proof load of the nuts.
If fastener elements are classified over the hardness, the hardness class is given according to Vickers by 2 digits standing for 1/10 of the minimum hardness value. The letter H refers to the hardness.
Designation example of a minimum hardness 250 HV: A4 25 H, austenitic steel, work hardened
according to ISO 3506
More than 97 % of all fasteners made from stainless steels are produced from this steel composition group. They are characterised by impressive corrosion resistance and excellent mechanical properties.
1) Stabilized against intergranular corrosion through addition of titanium, possibly niobium, tantalum.
2) Sulfur may be replaced by selenum.
3) If the nickel content is below 8 %, the min. manganese content shall be 5 %.
4) There is no min. limit to the copper content, provided that the nickel content is greater than 8 %.
5) If the chromium content is below 17 %, the min. nickel content should be 12 %.
6) For austenitic stainless steels having a max. carbon content of 0,03 %, nitrogen may be present to a max. of 0,22 %.
7) This shall contain titanium ≥ 5 x C up to 0,8 % max. for stabilization and be marked appropriately as specified in this table, or shall contain niobium (columbium) and / or tantalum ≥ 10 x C up to 1 % maximum for stabilization and be marked appropriately as specified in this table.
8) At the discretion of the manufacturer, the carbon content may be higher where required in order to obtain the specified mechanical properties at larger diameters, but shall not exceed 0,12 % for austenitic steels.
F593 Alloy Groups
| Alloy Group | Alloy Designation | Alloy Type |
|---|---|---|
| 1 | 303, 304, 304L, 305, 384, XM1, 18-9LW, 302HQ, 303Se | Austenitic |
| 2 | 316, 316L | Austenitic |
| 3 | 321, 347 | Austenitic |
| 4 | 430, 430F | Ferritic |
| 5 | 410, 416, 416Se | Martensitic |
| 6 | 431 | Martensitic |
| 7 | 630 (17-4) | Precipitation Hardening |
F593 Mechanical Properties / Condition
| Alloy Group | Condition | Marking | Diameter Range | Tensile, ksi | Yield, ksi min | Rockwell Hardness |
|---|---|---|---|---|---|---|
| 1 | AF | F593A | 1/4 to 1-1/2 | 65 to 85 | 20 | B85 max |
| A | F593B | 1/4 to 1-1/2 | 75 to 100 | 30 | B65 to 95 | |
| CW1 | F593C | 1/4 to 5/8 | 100 to 150 | 65 | B95 to C32 | |
| CW2 | F593D | 3/4 to 1-1/2 | 85 to 140 | 45 | B80 to C32 | |
| 2 | AF | F593E | 1/4 to 1-1/2 | 65 to 85 | 20 | B85 max |
| A | F593F | 1/4 to 1-1/2 | 75 to 100 | 30 | B65 to 95 | |
| CW1 | F593G | 1/4 to 5/8 | 100 to 150 | 65 | B95 to C32 | |
| CW2 | F593H | 3/4 to 1-1/2 | 85 to 140 | 45 | B80 to C32 |
F593 Chemical Requirements
| Element, max except as shown | Alloy Group 1, Type 304 | Alloy Group 2, Type 316 |
|---|---|---|
| Carbon | 0.08% | 0.08% |
| Manganese | 2.00% | 2.00% |
| Phosphorus | 0.045% | 0.045% |
| Sulfur | 0.030% | 0.030% |
| Silicon | 1.00% | 1.00% |
| Chromium | 18.0 to 20.0% | 16.0 to 18.0% |
| Nickel | 8.0 to 10.5% | 10.0 to 14.0% |
| Copper | 1.00% | |
| Molybdenum | 2.00 to 3.00% |
F594 Alloy Groups
| Alloy Group | Alloy Designation | Alloy Type |
|---|---|---|
| 1 | 303, 304, 304L, 305, 384, XM1, 18-9LW, 302HQ, 303Se | Austenitic |
| 2 | 316, 316L | Austenitic |
| 3 | 321, 347 | Austenitic |
| 4 | 430, 430F | Ferritic |
| 5 | 410, 416, 416Se | Martensitic |
| 6 | 431 | Martensitic |
| 7 | 630 (17-4) | Precipitation Hardening |
F594 Mechanical Properties / Condition
| Alloy Group | Condition | Marking | Diameter Range | Proof Stress, Hex Nuts, ksi | Proof Stress, Heavy Hex Nuts, ksi | Rockwell Hardness |
|---|---|---|---|---|---|---|
| 1 | AF | F594A | 1/4 to 1-1/2 | 70 | 76 | B85 max |
| A | F594B | 1/4 to 1-1/2 | 75 | 81 | B65 to 95 | |
| CW1 | F594C | 1/4 to 5/8 | 100 | 108 | B95 to C32 | |
| CW2 | F594D | 3/4 to 1-1/2 | 85 | 92 | B80 to C32 | |
| 2 | AF | F594E | 1/4 to 1-1/2 | 70 | 76 | B85 max |
| A | F594F | 1/4 to 1-1/2 | 75 | 81 | B65 to 95 | |
| CW1 | F594G | 1/4 to 5/8 | 100 | 108 | B95 to C32 | |
| CW2 | F594H | 3/4 to 1-1/2 | 85 | 92 | B80 to C32 |
F594 Chemical Requirements
| Element, max except as shown | Alloy Group 1, Type 304 | Alloy Group 2, Type 316 |
|---|---|---|
| Carbon | 0.08% | 0.08% |
| Manganese | 2.00% | 2.00% |
| Phosphorus | 0.045% | 0.045% |
| Sulfur | 0.030% | 0.030% |
| Silicon | 1.00% | 1.00% |
| Chromium | 18.0 to 20.0% | 16.0 to 18.0% |
| Nickel | 8.0 to 10.5% | 10.0 to 14.0% |
| Copper | 1.00% | |
| Molybdenum | 2.00 to 3.00% |
Stainless Steel & Stainless Steel Fasteners
Chemical, Physical and Mechanical Properties
Stainless steel describes a family of steels highly resistant to tarnishing and rusting that contain at least two
separate elements alloyed together. In its most basic form, chromium is added to ordinary steel in order to become
corrosion resistant. The mechanical properties of stainless steel (eg strength, ductility), and how well the alloy
withstands corrosion depends entirely on which elements were alloyed together and their relative proportions.
Corrosion Resistance
The corrosion resistance of stainless steel is derived from chromium. Chromium has a strong affinity for oxygen and
when added to steel in sufficient quantity (minimum 11%), it will form a microscopic film of chromium oxide on the
surface of the alloy. The film is only about 0.01 microns thick but prevents further surface corrosion as well as any
corrosion from spreading into the metal’s internal structure. This chromium oxide film is nonreactive with other
materials and does not promote further oxidation of adjacent chromium. It is also bonded solidly to the surface of
the alloy and in the event of surface damage (eg scratching), the newly exposed chromium will react immediately
with oxygen in the air to renew the protective chromium oxide film.
Besides chromium, another important element often added to stainless steel to increase corrosion resistance is
molybdenum. Molybdenum becomes far more important than chromium to further enhance corrosion resistance in
stainless steel once the amount of chromium in the alloy exceeds 18%.
Strength and workability
Nickel is added to stabilize the austenitic structure of stainless steel making the alloy more workable and improve
ductility. Manganese is added to partially replace nickel in order to stabilize the austenitic structure. Similar to nickel,
molybdenum improves the workability of the alloy, and also increases yield and tensile strengths in concentrations
above 2%. The addition of sulfur and selenium to the austenitic grades of stainless steel improves machining of the
alloy. The addition of carbon and nitrogen directly impact the strength of stainless steel. Nitrogen added to these
alloys improves the mechanical properties of low carbon grades of austenitic stainless steels. Other elements like
aluminum, titanium and/or columbium can be added to stainless steel to increase the mechanical properties of
stainless steel. They also help to increase the strength of the alloy while retaining corrosion resistant properties.
Grades
Many different grades of stainless steel are available. Each contains varying ratios of steel to chromium in addition
to varying amounts of other elements such as nickel, molybdenum and manganese. Each specific grade of stainless
steel has its own unique chemical, mechanical and physical property profile making it ideal for specific applications.
To compare corrosion resistances of common stainless steel grades see table 1.
Table 1 Corrosion Resistance Comparison Among Common Stainless Steels
Grade UNS No Mild Atmospheric
and fresh water
Atmospheric Chemical
Industrial Marine Mild Oxidizing Reducing
201 (S20100) x x x x x
202 (S20200) x x x x x
205 (S20500) x x x x x
301 (S30100) x x x x x
302 (S30200) x x x x x
302B (S30215) x x x x x
303 (S30300) x x x
303 Se (S30323) x x x x
304 (S30400) x x x x x
304L (S30403) x x x x x
304N (S30451) x x x x x
305 (S30500) x x x x x
308 (S30800) x x x x x
309 (S30900) x x x x x
309S (S30908) x x x x x
310 (S31000) x x x x x
310S (S31008) x x x x x
314 (S31400) x x x x x
316 (S31600) x x x x x x
316F (S31620) x x x x x x
316L (S31603) x x x x x x
316N (S31651) x x x x x x
317 (S31700) x x x x x x
317L (S31703) x x x x x
321 (S32100) x x x x x
329 (S32900) x x x x x x
330 (N08330) x x x x x x
347 (S34700) x x x x x
348 (S34800) x x x x x
384 (S38400) x x x x x
403 (S40300) x x
405 (S40500) x x
409 (S40900) x x
410 (S41000) x x
414 (S41400) x x
Table 1 cont.
Grade UNS No Mild Atmospheric
and fresh water
Atmospheric Chemical
Industrial Marine Mild Oxidizing Reducing
416 (S41600) x
416 Se (S41623) x
420 (S42000) x
420F (S42020) x
422 (S42200) x
429 (S42900) x x x x
430 (S43000) x x x x
430F (S43020) x x x
430F Se (S43023) x x x
431 (S43100) x x x x
434 (S43400) x x x x x
436 (S43600) x x x x x
440A (S44002) x x
440B (S44003) x
440C (S44004) x
442 (S44200) x x x x
446 (S44600) x x x x x
(S13800) x x x x
(S15500) x x x x x
(S17400) x x x x x
(S17700) x x x x x
The many grades of stainless steel can be further sub-classified into one of five distinct metallurgical “families” or
classifications:
1) Austenitic
2) Ferritic
3) Martensitic
4) Precipitation hardening
5) Duplex
Each familiy defines the metallurgical composition of the alloys within each classification, and in turn, reflects
differences in property profiles (corrosion resistance, durability, workability) and potential uses.
Austenitic Grade Stainless Steels
Austenitic stainless steels are chromium-nickel-manganese or chromium-nickel containing alloys identified by the
200 and 300 series, respectively. The 300 series stainless steels are the most widely used of all stainless steels.
The austenitic stainless steels, because of their high chromium and nickel content, are highly corrosion resistant,
nonmagnetic, workable and are hardened by cold working. For chemical and physical properties of austenitic
stainless steels see table 2.
Basic properties
• excellent corrosion resistance
• excellent for welding
• excellent formability, fabricability and ductility
• excellent cleaning and hygiene characteristics
• good high and excellent low temperature properties
• non magnetic
• hardened by cold work only
Straight Grades
The straight grades of austenitic stainless steel contain a maximum of .08% carbon, with no minimum carbon
requirement as long as the material meets the physical requirements of the specific grade.
“L” Grades
The “L” grades are typically used in welding for optimal corrosion resistance. The “L” after a stainless steel grade
indicates low carbon (eg 304L). The carbon is kept to .03% or under to minimize carbide precipitation. Carbon in
steel precipitates out when heated to temperatures between 800oF to 1600
oF and then combines with the chromium.
This interferes with chromium’s ability to protect the steel and results in corrosion adjacent to the grain boundaries.
By reducing the amount of carbon precipitation, corrosion is reduced.
“H” Grades
The “H” grades contain a minimum of .04% carbon and a maximum of .10% carbon and have the letter “H” following
the alloy number. The “H” grades are most typically used when the alloy is to be exposed to extreme temperatures
as the higher carbon content in the alloy improves the strength of the metal under those conditions
Ferritic Grade Stainless Steels
Stainless Steels of the ferritic family, have low carbon (.08 to .20%), high chromium but no nickel, and identified by
the 400 series numbers. As such they do not harden by heat treatment. They are all magnetic, resist corrosion and
oxidation, and are highly resistant to stress induced cracking. They can be cold worked and softened by annealing.
They are highly resistant to atmospheric oxidation and strong oxidizing solutions. As a group, they are more
corrosion resistant than the martensitic grades, but inferior to the austenitic grades. They are typically used for
decorative trim, sinks, and automotive applications, particularly exhaust systems. For chemical and physical
properties of ferritic stainless steels see tables 3 & 4.
Basic properties
• moderate to good corrosion resistance increasing with chromium content
• not hardened by heat treatment
• always used in the annealed condition
• magnetic
• poor welding properties
• formability not as good as austenitics
Ferritic Stainless Steels
Table 3 Chemical Analysis % (Max. Unless otherwise noted)
Type Cr Ni C Mn P S Si Mo Other
405 11.50/14.50 0.60 0.08 1.00 0.040 0.030 1.00 0.10/0.30 Al
409 10.50/11.75 0.50 0.08 1.00 0.045 0.045 1.00 6x C/0.75 Ti
429 14.00/16.00 0.75 0.12 1.00 0.040 0.030 1.00
430 16.00/18.00 0.75 0.12 1.00 0.040 0.030 1.00
430F 16.00/18.00 0.12 1.25 0.060 0.015 (min) 1.00 0.60
430F Se 16.00/18.00 0.12 1.25 0.060 0.060 1.00 0.15 Se (min)
434 16.00/18.00 0.12 1.00 0.040 0.030 1.00 0.75/1.25
436 16.00/18.00 0.12 1.00 0.040 0.030 1.00 0.75/1.25
442 18.00/23.00 0.60 0.20 1.00 0.040 0.030 1.00
446 23.00/27.00 0.75 0.20 1.50 0.040 0.030 1.00 0.25 N
Ferritic Stainless Steels
Table 4 Mechanical Properties (Annealed Sheet Unless otherwise noted)
Type Tensile Strength Yield Strength
(0.2% offset)
Elongation in
2” (50.80mm)
%
Hardness
(Rockwell)
Product Form
Ksi MPa Ksi MPa
405 65 448 40 276 25 B75
409 65 448 35 241 25 B75
429 70 483 40 276 30 B80 Plate
430 75 517 50 345 25 B85
430F 95 655 85 586 10 B92
430F Se 95 655 85 586 10 B92 Wire
434 77 531 53 365 23 B83
436 77 531 53 365 23 B83
442 80 552 45 310 20 B90 Bar
446 80 552 50 345 20 B83
Martensitic Grade Stainless Steels
.
The martensitic grades are straight chromium steels containing no nickel. They are a group of stainless alloys that
are corrosion resistant, hardened by heat treating and are magnetic. They are suited for applications that require
corrosion resistance, hardness, strength, and wear resistance (resist atmospheric oxidation, mildly corrosive
chemicals and wet or dry corrosion, such as in steam and gas turbine parts, bearings and cutlery). For chemical
properties of martensitic stainless steels see tables 5 & 6.
Basic properties
• moderate corrosion resistance
• hardened by heat treatment (high strength and hardness levels obtainable)
• poor welding properties
• magnetic
Martensitic Stainless Steels
Table 5 Chemical Analysis % (Max. Unless otherwise noted)
Type Cr Ni C Mn P S Si Mo Other
403 11.50/13.00 0.15 1.00 0.040 0.030 0.50
410 11.50/13.50 0.15 1.00 0.040 0.030 1.00
414 11.50/13.50 1.25/2.50 0.15 1.00 0.040 0.030 1.00
416 12.00/14.00 0.15 1.25 0.060 0.015 (min) 1.00 0.60*
416 Se 12.00/14.00 0.15 1.25 0.060 0.060 1.00 0.15 Se (min)
420 12.00/14.00 0.12 1.20 0.040 0.030 1.00
420 F 12.00/14.00 0.15 (min) 1.25 0.060 0.015 (min) 1.00 0.60*
422 11.00/13.00 0.15 (min) 1.00 0.025 0.025 0.75 0.75/1.25 0.15/0.30 V
431 15.00/17.00 0.50/1.00 0.20/0.25 1.00 0.040 0.030 1.00 0.75/1.25 W
440 A 16.00/18.00 0.60/0.75 1.00 0.040 0.030 1.00 0.75
440 B 16.00/18.00 0.75/0.95 1.00 0.040 0.030 1.00 0.75
440C 16.00/18.00 1.25/2.50 0.95/1.20 1.00 0.040 0.030 1.00 0.75
Martensitic Stainless Steels
Table 6 Mechanical Properties (Annealed Sheet Unless otherwise noted)
Type Tensile Strength Yield Strength
(0.2% offset)
Elongation in
2” (50.80mm)
%
Hardness
(Rockwell)
Product
Form
Ksi MPa Ksi MPa
403 70 483 45 310 25 B80
410 70 483 45 310 25 B80
414 120 827 105 724 15 B98
416 75 517 40 276 30 B82 Bar
416 Se 75 517 40 276 30 B82 Bar
420 95 655 50 345 25 B92 Bar
420 F 95 655 55 379 22 220 (Brinell) Bar
422 145 1000 125 862 18 320 (Brinell) Bar
431 80125 862 95 655 20 C24 Bar
440 A 105 724 60 414 20 B95 Bar
440 B 107 738 62 427 18 B96 Bar
440C 110 738 65 448 14 B97 Bar
Precipitation Hardening Stainless Steels
Precipitation Hardening stainless steels can be hardened by a combination of a low-temperature aging treatment
and cold working. They are identified by UNS numbers (e.g. Type S17400), but often referred to by proprietary trade
names (eg 17-4PH). Precipitation hardening stainless steels are particularly useful because uniform hardening can
be obtained without a high-temperature treatment that can result in distortion and scaling. For chemical and physical
properties of precipitation hardening stainless steels see tables 7 & 8.
Basic properties
• moderate to good corrosion resistance
• very high strength
• good welding properties
• magnetic
Precipitation Hardening Stainless Steels
Table 7 Chemical Analysis % (Max. Unless otherwise noted)
Type Cr Ni C Mn P S Si Mo Other
S13800 12.25/13.25 7.50/8.50 0.05 0.10 0.010 0.008 0.10 2.00/2.50 0.90/1.35 Al/0.01 N
S15500 14.00/15.50 3.50/5.50 0.07 1.00 0.040 0.030 1.00 2.50/4.50 Cu
0.15/0.45 Cb + Ta
S17400 15.50/17.50 3,005.00 0.07 1.00 0.040 0.030 1.00 3.00/5.00 Cu
0.15/0.45 Cb + Ta
S17700 16.00/18.00 6.50/7.75 0.09 1.00 0.040 0.040) 0.040 0.75/1.50 Al
Precipitation Hardening Stainless Steels
Table 8 Mechanical Properties (Annealed Sheet Unless otherwise noted)
Type Tensile Strength Yield Strength
(0.2% offset)
Elongation in
2” (50.80mm)
%
Hardness
(Rockwell)
Ksi MPa Ksi MPa
S13800 160 1103 120 827 17 C33
S15500 160 1103 145 1000 15 C35
S17400 160 1103 145 1000 15 C35
S17700 130 896 40 276 10 B90
Duplex Grade Stainless Steels
DUPLEX stainless steels are characterized by their 50% austenitic 50% ferritic structures, containing relatively high chromium
(between 18 and 28%) and moderate amounts of nickel (between 4.5 and 8%). The nickel content is insufficient to
generate a fully austenitic structure and the resulting combination of ferritic and austenitic structures is called duplex.
Most duplex steels contain molybdenum in a range of 2.5 – 4% which allow these materials to offer the corrosion
resistance for the austenitic grades of material while providing good design properties. For chemical and physical properties
of duplex stainless steels see tables 9, 10 & 11.
Basic properties
• high resistance to stress corrosion cracking
• increased resistance to chloride ion attack
• higher tensile and yield strength than austenitic and ferritic steels
• good welding properties and formability
• work hardened
• magnetic
Duplex Stainless Steels
Table 9 Chemical analysis %
Grade UNS No Typical Compositions (%)
C Mn Si P S Cr Mo Ni N Cu
2205
UR52N+
S31803/S32205
S32520/S32550
0-0.03
0.03max
2.00
1.50
1.00
0.80
0-0.03
0.035
0-0.03
0.035
21-23
34-36
2.5-3.5
3.0-5.0
4.5-6.5
5.5-8
0.08-0.2
0.2-0.35
.5-3
Duplex Stainless Steels
Table 10 Mechanical Properties
Grade Tensile Strength (MPa) Proof Stress 0.2% (MPa) Elongation A5 (%)
2205 620 450 25
UR52N+ 770 550 25
Duplex Stainless Steels
Table 11 Physical Properties
Common Name Density
(g.cm3
)
Modulus of Elasticity
(GPa)
Electrical Resistivity
(Ω.m)
Thermal Conductivity
(W/m.K)
Thermal Expansion
(m/m.K)
2205
UR52N+
7.805
7.81
200
205
0.085×10-6
0.085×10-6
19 at 100°C
17 at 100°C
13.7×10-6
to 100°C
13.5×10-6
to 200°C
Stainless Steel Fasteners
The two primary methods for producing fasteners; machining and cold heading still apply in the fabrication of
stainless steel fasteners.
MACHINING is common for very large diameters and for small production runs. However machining disrupts the
structural integrity of the alloy particularly in the head-to-shank area causing a reduction in load-carrying capability
as well as fatigue resistance.
COLD HEADING a common and economical method of forming wire into various types of standard and specialty
bolts, screws, nails and rivets, particularly for large production runs. Cold heading also cold works the alloy resulting
in significant increases in strength for the 300 Series austenitic steels.
Following heading, the blank is ready for secondary processes like threading. This is achieved typically by either
cutting or rolling. The best quality highest-strength thread is achieved by thread rolling because it is considered a
form of cold working and thus increases yield and tensile strength of the austenitic family of alloys.
TENSILE STRENGTH ultimately determines how much load the fastener can carry before failure. Yield strength is a
measure of the resistance to deformation under load, both of which can be increased by either cold working or heat
treating see Table 12
Table 12
MECHANICAL PROPERTIES OF STAINLESS STEEL BOLTS, SCREWS, STUDS AND NUTS (per ASTM F593-91)
BOLTS, SCREWS AND STUDS NUTS
FULL SIZE BOLTS,
SCREWS, STUDS
MACHINED TEST SPECIMENS OF
BOLTS, SCREWS, STUDS
GRADE DESCRIPTION
YIELD2
STRENGTH
min ksi
TENSILE
STRENGT
H
min ksi
YIELD2
STRENGTH
min ksi
TENSILE
STRENGTH
min ksi
ELONGATION3
% Min
HARDNESS
ROCKWELL
Min
PROOF
LOAD
STRESS
ksi
HARDNESS
ROCKWELL
Min
303
304
Austenitic
Soln annealed 30 75 30 75 20 B75 75 B75
304
305
316
384
XM7
Austenitic
Cold Worked 50 90 45 85 20 B85 90 B85
304
305
316
Austenitic
Strain Hardened
-> 5/8” 100
5/8” -> 1” 70
1” -> 1-1/2” 50
125
105
90
90
65
45
115
100
85
16 C25
125
105
90
C20
410
416
Martensitic
Hardened and
Tempered*
95 125 95 125 20 C22 125 C22
410
416
Martensitic
Hardened and
Tempered**
135 180 135 180 12 C36 180 C36
430 Ferritic 40 70 40 70 20 B75 70 B75
- hardened and tempered at 1100oF min.
** hardened and tempered at 525oF± 50oF
SHEAR STRENGTH – Shear is resistance to lateral forces perpendicular to the axis of the material. It is defined as the load required to cause rupture, divided by the cross sectional area in square inches of the part along the rupture plane. Acceptable shear stresses for stainless steel bolts are given in Table 13. Table 13 Permitted Shear Stress of Stainless Steel Bolts Type Finish Condition & Specification Dia (in.) Min. Tensile Requirement Shear Stress (ksi) 0.2% Yield Strength (ksi) Tensile Strength (ksi) No Threads in Shear Plane Threads in Shear Plane 302 304 316 Hot Finished Condition A (Annealed) in ASTM A276-71 Class 1 (solution treated) in ASTM A193-71 all 30 75 15 10.5 302 304 316 Cold Finished Condition A (Annealed) in ASTM A276-71
Table 14 Maximum Torque for Stainless Steel Bolts
BOLT SIZE 304 316 BOLT SIZE 304 316
2-56 2.5 2.6 7⁄16″-14 376 393
2-64 3 3.2 7⁄16″-20 400 418
3-48 3.9 4 1⁄2″-13 517 542
3-56 4.4 4.6 1⁄2″-20 541 565
4-40 5.2 5.5 9⁄16″-12 682 713
4-48 6.6 6.9 9⁄16″-18 752 787
5-40 7.7 8.1 5⁄8″-11 1110 1160
5-44 9.4 9.8 5⁄8″-18 1244 1301
6-32 9.6 10.1 3⁄4″-10 1530 1582
6-40 12.1 12.7 3⁄4″-16 1490 1558
8-32 19.8 20.7 7⁄8″-9 2328 2430
8-36 22 23 7⁄8″-14 2318 2420
10-24 22.8 23.8 1″-8 3440 3595
10-32 31.7 33.1 1″-14 3110 3250
1⁄4″-20 75.2 78.8 11⁄8″-7 413 432
1⁄4″-28 94 99 11⁄8″-12 390 408
5⁄16″-18 132 138 11⁄4″-7 523 546
5⁄16″-24 142 147 11⁄4″-12 480 504
3⁄8″-16 236 247 11⁄2″-6 888 930
3⁄8″-24 259 271 11⁄2″-12 703 732
Stainless steel is used primarily for long lasting applications, due to its corrosion-resistant nature and durability. Scratching or burring the metal will not create surface rust as the corrosion resistance exists within the metal itself. Stainless is a soft metal due to the low carbon content, therefore most stainless steel bolts are cold-formed and not heat treated or thru-hardened. Cold forming and threading cause stainless bolts to become slightly magnetic, some fasteners will be more magnetic than others depending on size and how quick the cold forming process is. Stainless fasteners are typically a clean silver color, which also makes them common in finishing and decorative applications. Stainless Steel should never be used with aluminum, galvanic corrosion is likely to occur.
Stainless steel will not rust due to scratching due to the thin layer of chromium creating an invisible protective layer. This thin layer will rebuild itself in the presence of oxygen. Note: If you are not in an oxygen rich environment the material will take longer to rebuild or not rebuild at all. This will leave it open to possible corrosion. Stainless steel can be broken down into three different types: Austenitic, Martensitic and Ferritic.
- Austenitic Stainless Steel(Between 15%-20% Chromium, Between 5%-19% Nickel) – Austenitic stainless has the highest degree of corrosion resistance of the three types. This type of stainless includes these grades: 302, 303, 304, 304L, 316, 32, 347 and 348. They also have a tensile strength of between 80,000 – 150,000 PSI.
- Martensitic Stainless Steel(Between 12%-18% Chromium) – Martensitic stainless steel is considered a magnetic steel. It can be heat treated to increase its hardness and is not recommended for welding. This type of stainless includes: 410, 416, 420 and 431. They have a tensile strength of between 180,000 and 250,000 PSI.
- Ferritic Stainless Steel(Between 15%-18% Chromium) – Ferritic stainless steel has a tensile strength of 65,000 – 87,000 PSI. While it is still corrosion resistant, it is not recommended for areas where corrosion is likely to occur. This material cannot be heat treated. Due to the forming process it is magnetic and not suitable for welding. Ferritic grades of stainless include: 430 and 430F.
- 18-8 Stainless Steel:(18% Chrome, 8% Nickel, .08% Maximum Carbon) – 18-8 Stainless refers to 300 series stainless steel. 303 and 304 Stainless are the most commonly listed grades, the standard grade for stainless fasteners. They are corrosion-resistant and durable. They are often used in marine applications in freshwater environments but will not work as effectively in a salt-water environment as 316 stainless. Stainless alloy resists oxidizing and rusting, however it can tarnish over time. Equivalent to metric A2 Stainless Steel.
- 305 Stainless Steel:(17%-19% Chrome, 8%-10% Nickel, .12% Maximum Carbon) – This grade has been developed specifically to improve the cold heading qualities of 18-8. Corrosion resistance and physical qualities are equal to Type 304. 305 stainless steel is most commonly used to make deck screws, which are used to fasten wood or composite boards to the main beams of a deck.
- 316 Stainless Steel:(16%-18% Chrome, 10%-14% Nickel, .08% Maximum Carbon, 2.00% Maximum Molybdenum) – This grade of steel is used and recommended for applications in severe, harsh or marine environments. Its corrosion resistance is greater than 18-8 stainless, which is why we recommend using 316 stainless steel fasteners for salt-water application. It is important to remember that even the salt in the air near a body of salt-water can do damage to dry applications, so 316 is the material of choice. Common applications of 316 stainless fasteners include use on boats, docks, piers, and pools.
- 410 Stainless Steel:(11.5%-13.5% Chrome, .15% Maximum Carbon) – Since this grade of stainless steel can be hardened up to approximately 40 Rockwell C, it is durable in most environments. Harder than 18-8 stainless but with less corrosion resistance, 410 stainless is commonly used to make roofing screws, siding screws and self-tapping (or self-drilling) screws, because it is a harder material than the metal being fastened in these types of applications.
Inspection & Approval Certificates : C/W Certificate (Calibration Works Certificate) EN 10204 3.1 / DIN 50049 3.1 / ISO 10474 3.1 Mill Test Certificate,
ISI Mark, BIS Certified, NACE HIC TM-0284 / NACE MR-0103 / NACE MR-0175 / ISO 15166, CE Marked, European Pressure Equipment Directive
PED-2014/68/EU, AD-2000-WO, ASME Boiler & Pressure Vessel Code Section-II Part A Edition 2019, API 6A (American Petroleum Institute),
with EN 10204 3.2 Certificate duly Certified & Approved by IBR (Indian Boiler Regulations), LR Class (Lloyd’s Register), GL (Germanischer Lloyd),
BV (Bureau Veritas), DNV (Det Norske Veritas), ABS Class (American Bureau of Shipping), SGS, TUV, RINA, IR Class (Indian Register of Shipping),
NORSOK Approved Standard M-630, M-650 Rev.3
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Regards,
CONTACT PERSON :
MUKESH SHAH
Director
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