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SS 321 Bolts Manufacturer & Exporter in India

Explore SS 321 Bolts Manufacturer & Exporter in India manufactured for demanding industrial applications with reliable strength, corrosion resistance and compliance with international standards.
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-196

Min Temp

870

Max Temp

🌡

870

Suitable for continuous service up to approximately 870°C under typical operating conditions.

⚡

620

Typical tensile strength around 620 MPa depending on product form and heat treatment.

🛡

Very Good

Very Good corrosion resistance in a wide range of industrial environments.

⚖

8

Typical density is approximately 8.0 g/cm³.

Product Overview

What are SS 321 Bolts?

SS 321 bolts are austenitic stainless steel fasteners manufactured from UNS S32100 bar stock, conforming to ASTM A193/A194 and ASTM A276 standards. Alloy 321 is stabilized with titanium (Ti) to prevent intergranular corrosion after welding, making it ideal for high-temperature bolted joints and exhaust systems.

With excellent resistance to oxidation up to 870°C and immunity to carbide precipitation, SS 321 bolts are widely specified for petrochemical, thermal processing, and aerospace applications where standard 304/316 stainless steel bolts would fail due to sensitization or scaling.

Quick Specifications

MaterialStainless Steel 321
UNS NumberS32100
DIN Number1.4541
Material StandardASTM A193 / ASTM A276
Bolt Standard (Metric)DIN 931 / DIN 933 / ISO 4014
Bolt Standard (Inch)ASME B18.2.1
Thread FormISO Metric / UNC / UNF
Diameter RangeM6-M100 / ¼"-4"
Tensile Strength515 MPa (75 ksi) min
Yield Strength205 MPa (30 ksi) min
HardnessMax 223 HB / 95 HRB
? All material certified by NABL-accredited laboratory. PMI and IGC test available on request.

Complete the Fastener Set

Other SS 321 Fastener Products Available from RealBolt

RealBolt also manufactures the complete SS 321 fastener range from certified stainless steel bar stock, including SS 321 Nuts, SS 321 Screws, SS 321 Washers, SS 321 Studs, and SS 321 Threaded Rods. All SS 321 fastener types are produced to ASTM with full EN 10204 MTC 3.1/3.2 documentation.
SS 321 Nuts
SS 321 Screws
SS 321 Washers
SS 321 Studs
SS 321 Threaded Rods

Technical Data

SS 321 Bolts Dimensions, Sizes & Thread Standards

SS 321 Bolts are available in metric M6–M100 and inch ¼″–4″ as standard. Per DIN 931 (partial thread) / DIN 933 (full thread) / ISO 4014. Custom lengths in 5mm increments. Inch dimensions available per ASME B18.2.1. All SS 321 bolts dimensions are verified against applicable DIN, ISO, and ASME

Hex Bolt Dimensions - Metric (DIN 931 / ISO 4014)

Size (M)Pitch (mm)A/F (mm)Head Ht (mm)Min L (mm)Max L (mm)
M61.0104.010200
M81.25135.312250
M101.5176.416300
M121.75197.520400
M162.02410.025500
M202.53012.530600
M243.03615.040600
M303.54618.750800
M364.05522.5601000
M424.56526.0801000
M485.07530.01001200
M565.58535.01201500
M646.09540.01402000
M726.010545.01602000
M806.011550.01802500
M1006.014563.02003000

Dimensional & Material Standards

StandardCoversThread
DIN 931Hex bolts, partial threadMetric
DIN 933Hex bolts, full threadMetric
ISO 4014Hex head screws, partialMetric
ISO 4017Hex head screws, fullMetric
ASME B18.2.1Hex & heavy hex boltsUNC/UNF
ASME B16.5Stud bolts for flangesUNC
MSS SP-75Stud bolts, high-pressureUNC
Material StandardRequirement
ASTM A193Bolt bar/rod - UNS S32100
ASTM A276Forged/rolled bar
ASTM A194Heavy hex nuts
EN 10204 3.1Mill test certificate
EN 10204 3.2TPI-witnessed MTC

Material Chemistry

SS 321 Chemical Composition

SS 321 Bolts are manufactured from an iron-chromium-nickel alloy with chromium (16–26%), nickel (8–28%), and grade-specific molybdenum additions per ASTM and ASTM A193/A194. Chromium content governs the self-healing passive oxide film; molybdenum (2–6%) enhances chloride pitting resistance; and carbon content determines sensitization risk in welded assemblies.

Chemical Composition per ASTM A276

ElementComposition (%)
Chromium (Cr)17.0-19.0%
Nickel (Ni)9.0-12.0%
Carbon (C)0.08% max
Manganese (Mn)2.00% max
Silicon (Si)0.75% max
Phosphorus (P)0.045% max
Sulfur (S)0.030% max
Titanium (Ti)5xC min, 0.70% max
Iron (Fe)Balance
? All heats verified by NABL-accredited spectrometry. PMI and IGC test available on request.

Why SS 321 Alloy Composition Matters for Bolts

Titanium Stabilization — Prevents Sensitization
Titanium in SS 321 binds carbon, preventing chromium carbide precipitation at grain boundaries during welding or high-temperature service. This ensures bolts retain corrosion resistance after fabrication and in thermal cycling environments.
High Chromium & Nickel — Oxidation Resistance
The 17–19% chromium and 9–12% nickel content provide robust resistance to scaling and oxidation up to 870°C, making SS 321 bolts ideal for exhaust manifolds, furnace doors, and heat exchanger flanges.
Low Carbon — Maintains Ductility
Low carbon content ensures SS 321 bolts remain ductile and tough, even after long-term exposure to elevated temperatures, reducing the risk of brittle failure in critical bolted joints.

Fastener Performance

SS 321 Bolts Mechanical Properties & Torque Reference

The table below lists mechanical properties and torque reference for SS 321 Bolts per ASTM. SS 321 bolts achieve 620 MPa tensile strength, with hardness, yield, and elongation values verified by NABL-accredited testing and reported in the EN 10204 MTC.

Bolt SizeDry (Nm)Lubricated (Nm)Clamp Load (kN)
M12705625
M1617013650
M2034027280
M24590472120
M301200960190
M3621001680275
M4233002640370
M4848003840500
?? Anti-galling: Use molybdenum-based or PTFE anti-seize. Lubricated values assume K=0.16. Avoid dry assembly for large diameter SS 321 bolts to prevent thread galling.

Industry Applications

SS 321 Bolts Applications — Industries & End Uses

SS 321 Bolts from RealBolt are specified across food and dairy, pharmaceutical, marine, chemical processing, and oil and gas where very good corrosion resistance and 620 MPa tensile strength are required for reliable fastener performance. Click each industry below for detailed application examples.
SS 321 bolts are widely used for bolting in refinery heaters, catalytic reformers, and process piping where resistance to polythionic acid stress corrosion and high-temperature scaling is required. ASTM A193 B8T bolts are standard for heater flanges and tube sheets.
Hex bolts and stud bolts for furnace doors, heat exchanger flanges, and radiant tube supports where continuous service up to 870°C is required. SS 321 bolts prevent intergranular attack after repeated thermal cycling.
SS 321 bolts are specified for aircraft exhaust manifolds, turbocharger flanges, and jet engine mounting hardware due to their high-temperature strength and resistance to oxidation and scaling. AMS 5645 and EN 10269 listed.
Used in high-temperature sterilizer closures, autoclave flanges, and process vessel connections where both corrosion resistance and non-sensitization after welding are critical for hygiene and safety.

SS 321 Bolts Standards & International Certifications

SS 321 Bolts from RealBolt Engineering Industries are manufactured to internationally recognised fastener dimensional standards covering thread form, tolerances, strength grades, and quality requirements. Every batch ships with EN 10204 MTC 3.1/3.2, IS 12427 compliance, ISO 3506 material certification, NACE MR0175, and PMI (XRF) reports — available on request for all orders.
Standards
DIN 931 DIN 933 DIN 960 DIN 961 ISO 4014 ISO 4017 ISO 8676 ISO 8765 ASME B18.2.1 EN ISO 4014 EN ISO 4017 BS EN ISO 4014 BS EN ISO 4017 IS 1363 IS 1364 IS 12427 SAE J429 UNI 5737 UNI 5739 CSN 021101 CSN 021103 PN 82101 PN 82105
Certifications
ISO 9001:2015PED 2014/68/EUNABL LabEN 10204 3.1 / 3.2

Buy SS 321 Bolts from India's Leading Manufacturer — Get a Competitive Quote Today

Partner with RealBolt — India’s leading manufacturer of certified SS 321 Bolts — for competitive pricing, EN 10204 MTC 3.1/3.2 documentation, and fast Mumbai dispatch. Standard sizes are ex-stock; custom dimensions accepted with 2–3 week lead time. Request your quote today.
022-6743-7972
+91 90226 36025
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Answers for Buyers

SS 321 Bolts — Frequently Asked Questions

Browse expert answers to common questions about SS 321 Bolts from RealBolt — covering ASTM A193/A194 grades, chloride resistance, temperature limits, sensitization, sizes, and MTC documentation. Contact our technical team directly for project-specific guidance on SS 321 bolts selection and pricing.
SS 321 bolts are available to DIN 931 (metric partial thread), DIN 933 (metric full thread), ISO 4014/4017, and ASME B18.2.1 (inch hex and heavy hex). Stud bolts are supplied per ASME B16.5 and MSS SP-75 for flange connections. Custom thread forms (BSW, BSF, Whitworth) can be manufactured on request with short lead times.
Use molybdenum-based or PTFE anti-seize compound (such as Molykote 1000 or Loctite LB 8008) on SS 321 bolts to prevent galling and seizing. Apply to both threads and nut bearing surfaces. Avoid copper-based anti-seize in chloride-rich or high-temperature environments.
Yes – SS 321 bolts are specifically designed for high-temperature service up to 870°C, with titanium stabilization preventing intergranular corrosion after welding or thermal cycling. They are the preferred choice for exhaust manifolds, furnace doors, and heat exchanger flanges.
No MOQ for standard sizes (M8-M36) available ex-stock – single pieces can be supplied for urgent maintenance. Custom sizes or non-standard threads typically require a 10 kg minimum. Bulk price breaks at 50, 200, and 500 pieces.

Industrial Cities We Serve:

  • Ahmedabad
  • Aurangabad
  • Bengaluru
  • Chennai
  • Coimbatore
  • Faridabad
  • Gandhidham
  • Greater Noida
  • Gurugram
  • Hazira
  • Hosur
  • Hyderabad
  • Jamnagar
  • Jamshedpur
  • Ludhiana
  • Mumbai
  • Mundra
  • Mysuru
  • Nagpur
  • Nashik
  • Navi Mumbai
  • Noida
  • Pune
  • Rajkot
  • Sanand
  • Surat
  • Thane
  • Tiruppur
  • Vadodara
  • Visakhapatnam

Countries We Export To:

  • US
  • Canada
  • Mexico
  • Germany
  • UK
  • France
  • Italy
  • Spain
  • Netherlands
  • Belgium
  • Poland
  • Sweden
  • Norway
  • Denmark
  • Turkey
  • UAE
  • Saudi Arabia
  • Qatar
  • Oman
  • Kuwait
  • Bahrain
  • South Africa
  • Egypt
  • Nigeria
  • Australia
  • New Zealand
  • Singapore
  • Malaysia
  • Indonesia
  • Thailand
  • Vietnam
  • South Korea
  • Japan
  • Brazil