Type
Analysis
|
Element
|
Min
|
Max
|
|
Carbon
|
--
|
0.09
|
|
Manganese
|
--
|
1.00
|
|
Silicon
|
--
|
1.00
|
|
Chromium
|
14.0
|
16.0
|
|
Nickel
|
6.50
|
7.75
|
|
Sulfur
|
--
|
0.04
|
|
Phosphorus
|
--
|
0.04
|
|
Molybdenum
|
2.00
|
3.00
|
|
Aluminum
|
0.75
|
1.50
|
Description
15-7 Mo is a semi-austenitic
precipitation-hardening stainless steel that provides high strength
and hardness, good corrosion resistance, and minimum distortion on
heat treatment. It is easily formed in the annealed condition and
develops an effective balance of properties by simple heat
treatments. For application requiring exceptionally high strength,
cold-reduced 15-7 Mo Stainless Steel in Condition CH 900 is
particularly useful for applications permitting limited ductility and
workability. This alloy is particularly beneficial for a wide range
of applications that include retaining rings, springs, diaphragms,
aircraft bulkheads, welded and brazed honey comb paneling and other
aircraft components requiring high strength at elevated temperatures.
Corrosion Resistance
The general level of corrosion
resistance in Condition TH 1050 and RH 950 is superior to standard
hardenable types of stainless such as Types 410, 420 and 431, but not
quite good as Type 304
Physical
Properties
|
Condition
A
|
Condition
TH
1050
|
Condition
RH
950
|
|
Density, lbs/cu in
(g/cu cm)
|
0.282 (7.804)
|
0.277 (7.685)
|
0.277 (7.680)
|
|
Modulus of
Elasticity, ksi (MPa)
|
--
|
29.0 x 10(3) (200)
|
29.0 x 10(3) (200)
|
|
Thermal
Conductivity
BTU/hr/ft²/in/°F (W/m-K)
70°F
(21°C)
200°F (93°C)
600°F (316°C)
900°F
(482°C)
|
--
--
--
--
|
104
(15.1)
112 (16.2)
136 (19.7)
--
|
104
(15.1)
112 (16.2)
133 (19.2)
150 (21.7)
|
|
Mean Coefficient of
Thermal Expansion
in/in/°F (um/m-K)
70-200°F
(21-93°C)
70-600°F (21-316°C)
70-800°F
(21-427°C)
70-1000°F (21-538°C)
|
8.5 x 10(-5)
(14.4)
8.5 x 10(-5) (15.3)
8.9 x 10(-5) (16.0)
9.4 x
10(-5) (16.9)
|
6.1 x 10(-5)
(11.0)
6.1 x 10(-5) (11.0)
6.3 x 10(-5) (11.3)
6.6 x
10(-5) (11.9)
|
5.0 x 10(-5)
(9.00)
5.6 x 10(-5) (10.1)
5.9 x 10(-5) (10.6)
6.1 x
10(-5) (11.0)
|
Heat Treatment
PH 15-7 Mo Stainless Steel requires
three essential steps in heat treating:
1) austenite conditioning,
2) cooling to transform the austenite to martensite and 3)
precipitation hardening.
The material normally is supplied from
the mill in Condition A. After fabrication, an austenite conditioning
treatment is followed by a transformation treatment to either
Condition T or Condition R100. Then the material is precipitation
hardened to either Condition TH 1050 or Condition RH 950 to develop
fully useable properties.
To obtain the highest mechanical
properties in this alloy, Condition A is transformed to martensite at
the mill by cold reduction to Condition C. After fabrication by the
user, hardening to Condition CH 900 is accomplished with a single low
temperature heat treatment.
Mechanical Properties
|
Property
|
Condition
A
|
Condition
TH
1050
|
Condition
RH
950
|
Condition
C
|
Condition
CH
900
|
|
UTS, ksi (MPa)
0.2%
YS, ksi (MPa)
Elongation % in 2"
Hardness,
Rockwell
|
130 (896)
55
(372)
35
B88
|
210 (1448)
200
(1379)
7
C44
|
240 (1655)
225
(1552)
6
C48
|
220 (1517)
190
(1310)
5
C45
|
265 (1828)
260
(1793)
2
C50
|
Workability
Formability
The material in
Condition A can be formed comparably to Type 301. It work hardens
rapidly and may require intermediate annealing in deep drawing or in
forming intricate parts. Springback is similar to that of Type 301.
This alloy is extremely hard and strong in Condition C, so
fabrication techniques for such material must be used.
Weldability
The
precipitation hardening class of stainless steel is generally
considered to be weldable by the common fusion and resistance
techniques. Special consideration is required to achieve optimum
mechanical properties by considering the best heat-treated conditions
in which to weld, and which heat treatments should follow welding.
This particular alloy is generally considered to have poorer
weldability compared to the most common alloy of this stainless
class, 17-4 PH Stainless Steel. A major difference is the high Al
content of this alloy, which degrades penetration and enhances weld
slag formation during arc welding. Also, the austenite conditioning
and precipitation hardening heat treatments are both required after
welding to achieve high strength levels. When a weld filler is
needed, W P 15-7 Mo or W 17-7 PH is most often specified.
|
