Stainless Steel – Grade 347H (UNS S34709)

Topics Covered

Introduction
Chemical Composition
Physical Properties
Mechanical Properties
Other Designations
Fabrication and Heat Treatment
Machinability
Welding
Hot Working
Cold Working
Annealing
Hardening

Introduction

Stainless steels are high-alloy steels which have high corrosion resistance than other steels owing to the presence of large amounts of chromium in the range of 4 to 30%. Stainless steels are classified into martensitic, ferritic and austenitic based on their crystalline structure. In addititon, they form another group known as precipitation-hardened steels, which are a combination of martensitic and austenitic steels.

The following datasheet will provide more details about grade 347H stainless steel, which is slightly tougher than grade 304 steel.

Chemical Composition

The following table shows the chemical composition of grade 347H stainless steel.

Element Content (%)
Iron, Fe 62.83 - 73.64
Chromium, Cr 17 - 20
Nickel, Ni 9 - 13
Manganese, Mn 2
Silicon, Si 1
Niobium, Nb (Columbium, Cb) 0.320 - 1
Carbon, C 0.04 - 0.10
Phosphorous, P 0.040
Sulfur, S 0.030

Physical Properties

The physical properties of grade 347H stainless steel are given in the following table.

Properties Metric Imperial
Density 7.7 – 8.03 g/cm3 0.278 – 0.290 lb/in³

Mechanical Properties

The mechanical properties of grade 347H stainless steel are displayed in the following table.

Properties Metric Imperial
Tensile strength, ultimate 480 MPa 69600 psi
Tensile strength, yield 205 MPa 29700 psi
Rupture strength (@750°C/1380°F, time 100,000 hours) 38 - 39 MPa, 5510 - 5660 psi
Elastic modulus 190 – 210 GPa 27557 – 30458 ksi
Poisson’s ratio 0.27 – 0.30 0.27 – 0.30
Elongation at break 29% 29%
Hardness, Brinell 187 187

Other Designations

Other designations that are equivalent to grade 347H stainless steel include the following:

  • ASTM A182
  • ASTM A213
  • ASTM A240
  • ASTM A249
  • ASTM A271
  • ASTM A312
  • ASTM A336
  • ASTM A376
  • ASTM A403
  • ASTM A430
  • ASTM A479
  • ASTM A813
  • ASTM A814
  • SAE 30347H

Fabrication and Heat Treatment

Machinability

Machining grade 347H stainless steel is slightly tougher than that of grade 304 steel. However, the hardenability of this steel can be minimized by the use of constant positive feeds and slow speeds.

Welding

Grade 347H stainless steel can be welded using most of the resistance and fusion methods. Oxyacetylene welding is not preferred for this steel.

Hot Working

Forging, upsetting and other hot work processes can be performed at 1149 to 1232°C (2100 to 2250°F). The grade 347H steel has to be water quenched and annealed to obtain maximum hardness.

Cold Working

Grade 347H stainless steel can be readily stamped, blanked, spun and drawn as it is quite tough and ductile.

Annealing

Grade 347H stainless steel can be annealed at temperature ranging from 1010 to 1193°C (1850 to 2000°F) and then quenched with water.

Hardening

Grade 347H stainless steel is unresponsive to heat treatment. The hardness and strength of the steel can be increased through cold working.

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