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SS 347 / 347H Bolts Manufacturer & Exporter in India

Explore SS 347 / 347H 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 347 / 347H Bolts?

SS 347 / 347H bolts are austenitic stainless steel fasteners manufactured from stabilized grades UNS S34700 and UNS S34709, conforming to ASTM A193/A194 and ASTM A276 standards. Alloy 347 is stabilized with columbium (niobium) to prevent intergranular corrosion after welding, while 347H features a higher carbon content for enhanced high-temperature strength and creep resistance.

These bolts are widely specified for bolted joints in heat exchangers, pressure vessels, and piping systems operating in the 425-900°C range, where standard 304/316 stainless steels are prone to carbide precipitation and sensitization. SS 347 / 347H bolts are ideal for petrochemical, refinery, and power generation applications requiring reliable performance under cyclic thermal loads.

Quick Specifications

MaterialStainless Steel 347 / 347H
UNS NumberS34700 / S34709
DIN Number1.4550 / 1.4961
Material StandardASTM A276 / ASTM A193
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
? All material certified by NABL-accredited laboratory. PMI and IGC test reports available on request.

Complete the Fastener Set

Other SS 347 / 347H Fastener Products Available from RealBolt

RealBolt also manufactures the complete SS 347 / 347H fastener range — SS 347 / 347H Nuts, SS 347 / 347H Screws, SS 347 / 347H Washers, SS 347 / 347H Studs, SS 347 / 347H Threaded Rods — from certified bar stock per ASTM with full EN 10204 MTC 3.1/3.2 documentation and fast Mumbai dispatch.
SS 347 / 347H Nuts
SS 347 / 347H Screws
SS 347 / 347H Washers
SS 347 / 347H Studs
SS 347 / 347H Threaded Rods

Technical Data

SS 347 / 347H Bolts Dimensions, Sizes & Thread Standards

SS 347 / 347H 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 347 / 347H bolts dimensions conform to applicable DIN, ISO, and ASME B18 standards.

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 A276Bar/rod - UNS S34700/S34709
ASTM A193Bolting for high temp/pressure
ASTM A194Heavy hex nuts
EN 10204 3.1Mill test certificate
EN 10204 3.2TPI-witnessed MTC

Material Chemistry

SS 347 / 347H Chemical Composition

SS 347 / 347H 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/A193

Element347 (%)347H (%)
Chromium (Cr)17.0-19.017.0-19.0
Nickel (Ni)9.0-13.09.0-13.0
Carbon (C)0.08 max0.04-0.10
Manganese (Mn)2.00 max2.00 max
Silicon (Si)1.00 max1.00 max
Phosphorus (P)0.045 max0.045 max
Sulfur (S)0.030 max0.030 max
Niobium (Nb)10xC-1.010xC-1.0
Iron (Fe)BalanceBalance
? All heats verified by NABL-accredited spectrometry. PMI and IGC test reports available on request.

Why SS 347 / 347H Alloy Composition Matters for Bolts

Nb Stabilization — Intergranular Corrosion Resistance
Niobium (columbium) stabilizes SS 347 / 347H, preventing chromium carbide precipitation at grain boundaries during welding or high-temperature service. This ensures bolts retain corrosion resistance even after repeated thermal cycling.
347H — High Carbon for Elevated Temperatures
The higher carbon content in 347H increases creep strength and stress rupture resistance, making these bolts suitable for continuous service above 500°C, such as in superheater and reheater connections.
Austenitic Structure — Ductility & Toughness
The austenitic matrix provides excellent ductility and impact toughness, even at cryogenic temperatures, ensuring reliable performance in demanding bolted joints.

Fastener Performance

SS 347 / 347H Bolts Mechanical Properties & Torque Reference

The table below lists mechanical properties and torque reference for SS 347 / 347H Bolts per ASTM. SS 347 / 347H 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
M1617013652
M2034027282
M24590472118
M301200960190
M3621001680275
M4233002640370
M4848003840490
?? Anti-galling: Use molybdenum-based or PTFE anti-seize. Lubricated values assume K=0.16. Avoid copper-based anti-seize for high-temperature service.

Industry Applications

SS 347 / 347H Bolts Applications — Industries & End Uses

SS 347 / 347H 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 347 / 347H bolts are widely used for heat exchanger channel covers, reactor closures, and piping flanges in catalytic reformers, hydrocrackers, and hydrogenation units where resistance to polythionic acid and high-temperature corrosion is critical.
Bolts for superheater header connections, reheater tube sheets, and HRSG ductwork in coal-fired and combined cycle power plants, where thermal cycling and creep resistance above 500°C are required.
Flange bolts and stud bolts for pressure vessels, agitator assemblies, and process piping in nitric acid, urea, and fertilizer plants, where resistance to intergranular attack and stress corrosion cracking is essential.
SS 347 / 347H bolts are specified for jet engine exhaust systems, afterburner flanges, and furnace hardware due to their oxidation resistance and mechanical stability at elevated temperatures.

SS 347 / 347H Bolts Standards & International Certifications

SS 347 / 347H 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 LabMTC 3.1 / 3.2

Buy SS 347 / 347H Bolts from India's Leading Manufacturer — Get a Competitive Quote Today

Partner with RealBolt — India’s leading manufacturer of certified SS 347 / 347H 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 347 / 347H Bolts — Frequently Asked Questions

Browse expert answers to common questions about SS 347 / 347H 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 347 / 347H bolts selection and pricing.
SS 347 / 347H bolts are available to DIN 931 (hex bolts, partial thread), DIN 933 (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 applications. Custom thread forms (BSW, BSF, Whitworth) can be manufactured on request.
For SS 347 / 347H bolts, use a molybdenum-based or PTFE anti-seize compound (such as Molykote 1000 or Loctite LB 8008). This prevents galling and seizing during assembly, especially at elevated temperatures. Avoid copper-based anti-seize for high-temperature or corrosive service.
Yes – SS 347 / 347H bolts are specifically designed for high-temperature applications up to 900°C. The niobium stabilization and, in 347H, higher carbon content, provide excellent resistance to creep, oxidation, and intergranular corrosion in continuous and cyclic thermal environments.
There is no formal MOQ for standard sizes (M12-M36) available ex-stock. Custom sizes or non-standard threads typically require a 10 kg minimum. Flange stud bolt sets are supplied per set with no minimum. Quantity discounts apply 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