Super Alloy INCOLOY Alloy 27-7MO (UNS S31277)

Topics Covered

Introduction
Chemical Composition
Physical Properties
Mechanical Properties
Other Designations
Fabrication
     Machinability
     Welding
     Forming
     Hot working
     Cold Working
     Annealing
Applications

Introduction

INCOLOY alloys are super alloys that have nickel as the base metal. Apart from nickel, chromium and iron are the other major components of this alloy. Addition of metals such as molybdenum, copper, etc., enhances characteristics such as strength and corrosion resistance.

INCOLOY alloy 27-7MO is an advanced super-austenitic stainless steel containing 7% of molybdenum. When the content of molybdenum is increased the corrosion resistance in many environments is enhanced. The combination of nickel, nitrogen and molybdenum increase the corrosion resistance range to reducing media, pitting, crevice, acids, stress cracking and caustic corrosion. This alloy is also capable of resisting corrosion by sea water and chemicals in the pulp, paper, oil and gas industries. The standard forms in which this alloy is available are plate, sheet, rod, bar, tube and pipe.

This datasheet will look into the chemical composition, properties and applications of INCOLOY 27-7MO.

Chemical Composition

The chemical composition of INCOLOY alloy 27-7MO is given in the following table.

Element Content (%)
Iron, Fe 35.54-46.2
Nickel, Ni 26-28
Chromium, Cr 20.5-23
Molybdenum, Mo 6.5-8
Manganese, Mn ≤3
Others Remainder

Physical Properties

The following table discusses the physical properties of INCOLOY alloy 27-7MO.

Properties Metric Imperial
Density 8.02 gm/cm3 0.290 lb/in3

Mechanical Properties

The mechanical properties of INCOLOY alloy 27-7MO are tabulated below.

Properties Metric Imperial
Tensile strength(annealed) 827 MPa 120 ksi
Yield strength(annealed) 414 MPa 60 ksi
Elongation at Break( in 2 in 50 mm) 50% 50%
Poissons Ratio 0.29 0.29
Modulus of Elasticity 138 GPa 20000 ksi
Hardness, Rockwell B 95 95
Hardness, Vickers (0% cold work) 225 225

Other Designations

Some of the designations used to denote INCOLOY alloy 27-7MO are listed below:

  • UNS N08926
  • ASTM A 479
  • ASTM A240
  • ASTM A 213
  • ASTM A 249
  • ASTM A312
  • ASTM A182
  • ASME SA 182.

Fabrication

Machinability

Machining characteristics of this INCOLOY alloy 27-7MO is on the same lines as that of other austenitic alloys. This alloy is machined under annealed conditions.

Welding

INCOLOY alloy 27-7MO can be welded by gas metal arc welding, gas tungsten arc welding, shielded arc welding, plasma arc welding and submerged metal arc welding. The filler metal and electrodes are usually made of INCONEL alloy.

Forming

This alloy can be formed under hot or cold conditions.

Hot working

INCOLOY alloy 27-7MO can be hot worked at temperature ranges of 980-1150°C (1800-2100°F).

Cold Working

Cold rolling may be done on the alloy after annealing.

Annealing

INCOLOY alloy 27-7MO should be annealed at temperatures greater than 1121-1175°C (2050- 2150°F).

Applications

The INCOLOY alloy 27-7MO is used in the following applications:

  • Pollution control
  • Power, marine and chemical industries
  • Pulp, paper, oil and gas industries.

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