Super Alloy Sanicro 31HT (UNS N08811)

Topics Covered

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

Introduction

Sanicro 31HT alloy is an austenitic nickel-iron-chromium alloy that exhibits very good resistance to combustion gases, carburization, nitrogen absorption and oxidation. In addition, the alloy has high creep strength and good weldability and structural stability at high temperatures.

The alloy can be used at elevated temperatures of up to 1100°C (2010°F). When used at temperatures above 700°C (1290°F), the ductility of the alloy can be improved.

The following section will provide an overview of Sanicro 31HT alloy.

Chemical Composition

The chemical composition of Sanicro 31HT alloy is outlined in the following table.

Element Content (%)
Iron, Fe 46.7
Nickel, Ni 30.5
Chromium, Cr 20.5
Silicon, Si 0.6
Manganese, Mn 0.6
Aluminum, Al 0.5
Titanium, Ti 0.5
Carbon, C 0.07
Phosphorous, P ≤0.015
Sulfur, S ≤0.010

Physical Properties

The following table shows the physical properties of Sanicro 31HT alloy.

Properties Metric Imperial
Density 7.90 g/cm3 0.285 lb/in3

Mechanical Properties

The mechanical properties of Sanciro 31HT alloy are displayed in the following table.

Properties Metric Imperial
Tensile strength 500-700 MPa 72500-102000 psi
Yield strength ≥170 MPa ≥24700 psi
Elongation at break ≥35% ≥35%
Rockwell B hardness ≤90 ≤90

Thermal Properties

The thermal properties of Sanicro 31HT alloy are given in the following table.

Properties Metric Imperial
Thermal expansion co-efficient (@30-100°C/86-212°F) 15 µm/m°C 8.33 µin/in°F
Thermal conductivity (@20°C/68°F) 12 W/mK 83.3 BTU.in/hrft².°F

Fabrication and Heat Treatment

Machinability

Conventional machining techniques that are used for machining iron-based alloys can be used.

Forming

Sanicro 31HT alloy has excellent ductility, and can be readily formed by all conventional techniques.

Welding

The alloy can be welded using commonly used welding techniques such as gas-tungsten arc welding, shielded metal-arc welding, gas metal-arc welding and submerged-arc welding.

Forging

Sanicro 31HT alloy can be forged at 1010 to 1204°C (1850 to 2200°F) for 15 min and then air cooled.

Hot Working

The alloy can be hot worked at temperatures ranging from 871 to 1204°C (1600 to 2200°F).

Cold Working

Cold working may be performed using standard tooling.

Annealing

The alloy can be annealed to (2100°F) and air cooled.

Hardening

The alloy can be hardened only be cold working.

Other Designations

Other designations that are equivalent to Sanicro 31HT alloy include the following:

  • DIN 1.4959
  • DIN 1.4876
  • ASTM B407
  • ASTM B408
  • ASTM B409

Applications

The following are the list of applications of Sanicro 31HT alloy:

  • Heaters
  • Gas turbine components
  • Chemical process equipment
  • Fixtures
  • Heat exchangers

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