Stainless Steel - Grade 15-7 (UNS S15700)

Topics Covered

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

Introduction

Stainless steels are high-alloy steels which have high corrosion resistance when compared to other steels due to the presence of large amounts of chromium. They contain about 4-30% of chromium. Based on their crystalline structure, they are further divided into ferritic, austenitic, and martensitic steels. Another group of stainless steels are known as precipitation-hardened steels. They are the combination of martensitic and austenitic steels.

Grade 15-7 stainless steel is a semi-austenitic precipitation hardening stainless steel. It has high strength and moderate corrosion resistance. The following datasheet gives an overview of grade 15-7 stainless steel.

Chemical Composition

The following table shows the chemical composition of grade 15-7 stainless steel.

Element Content (%)
Iron, Fe 74.9
Chromium, Cr 15
Nickel, Ni 7
Molybdenum, Mo 2
Aluminum, Al 1.1

Physical Properties

The physical properties of grade 15-7 stainless steel are given in the following table.

Properties Metric Imperial
Density 7.81 g/cm3 0.282 lb/in³

Mechanical Properties

The mechanical properties of grade 15-7 stainless steel are displayed in the following table.

Properties Metric Imperial
Tensile strength 900 MPa 131000 psi
Yield strength (@ strain 0.200%) 380 MPa 55100 psi
Elastic modulus 190-210 GPa 27557-30458 ksi
Poisson's ratio 0.27-0.30 0.27-0.30
Elongation at break 30% 30%
Hardness, Rockwell B (converted from Brinell hardness) 88 88

Thermal Properties

The following table outlines the thermal properties of grade 15-7 stainless steel.

Properties Metric
Imperial
Thermal expansion (@21-93ºC/199ºF)
9 µm/mºC 5 µin/in°F
Thermal conductivity (@21ºC/70ºF)
15.1 W/mK 105 BTU in/hr.ft².°F

Other Designations

Other designations that are equivalent to grade 15-7 stainless steel include:

  • AMS 5520
  • AMS 5657
  • ASTM A564 (632)
  • ASTM A579 (632)
  • ASTM A693 (632)
  • ASTM A705 (632)
  • DIN 1.4532
  • DIN 1.4574
  • MIL S-8955
  • AMS 5812
  • AMS 5813

Fabrication and Heat Treatment

Machinability

Grade 15-7 stainless steel has good machinability in the hardened condition.

Welding

Grade 15-7 stainless steel can be welded using common arc and resistance methods. Inert gas shielding is avoided in order to prevent oxidation of aluminum.

Heat Treatment

Solution treated material is cold worked which results in condition C material. The condition C material is heated at 482°C (900°F) for 1 h followed by cooling.

Solution treated material is heated at 955°C (1750°F) for 10 min in A1750 condition followed. In R100 condition, it is cooled at -73°C (-100°F) for 8 h with in 1 h of treating to A1750 condition. It is again heated at 510°C (950°F) for 1 h in the RH 950 condition. After fabrication, it is heated at 760°C (1400°F) for 90 min in the condition T. It is again cooled at 13°C (55°F) for 0.5 h with in 60 min. It is heated at 565°C (1050°F) for 90 min in TH1050 condition followed by cooling in air.

Hot Working

Grade 15-7 stainless steel has good hot working capacity. This process should be followed by annealing in order to respond heat treatment.

Cold Working

Grade 15-7 stainless steel is limited to cold working.

Annealing

Grade 15-7 stainless steel is annealed at 1038°C (1900°F) followed by cooling rapidly.

Applications

Grade 15-7 stainless steel is used in the following applications:

  • Diaphragms
  • Welded and brazed honeycomb panels
  • Retaining rings
  • Aircraft bulkheads
  • Springs
  • Other applications requiring high strength at elevated temperatures


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