High Temp Metals 800-500-2141

AM 350 TECHNICAL DATA

Type Analysis | Description | Corrosion Resistance | Physical Properties | Heat Treatment | Workability | Typical Mechanical Properties

Type Analysis

Element

Min

Max

Carbon

0.07

0.11

Manganese

0.50

1.25

Silicon

--

0.50

Phosphorus

--

0.040

Sulfur

--

0.030

Chromium

16.00

17.00

Nickel

4.00

5.00

Molybdenum

2.50

3.25

Nitrogen

0.07

0.13

Description

Alloy 350 is a chromium-nickel-molybdenum stainless steel which can be hardnened by martensitic transformation and/or precipitation hardening. It has been used for gas turbine compressor components such as blades,discs,rotors,and shafts,and similar parts where high strength was required at room and intermediate temperatures. Depending upon the heat treatment,alloy 350 may have an austenitic structure for best formability,or a martensitic structure with strengths comparable to those of martensitic steels. The alloy normally contains about 5 to 10% delta ferrite. The corrosion resistance of alloy 350 approaches that of the chromium-nickel austenitic stainless steel


Corrosion Resistance

Alloy 350 has corrosion resistance superior to that of other quench-hardenable martensitic stainless steels. It has shown good corrosion resistance in ordinary atmospheres and numerous other mild chemical environments. Material in the double-aged or equalized condition is susceptible to intergranular corrosion because of the precipitation of chromium carbides. When the alloy is hardened by treatments employing sub-zero cooling as in the following paragraph,it is not subject to intergranular attack. The treatment for optinum stress-corrosion resistance of alloy 350 is as follows:
Heat to 1850/1950 °F(1010/1066 °C),cool rapidly to room temperature,sub-zero cool 3 hours at -100 °F(-73 ° C) reheat to 1700/1750 °F(927/954 °C)about 90 minutes per inch(25.4 mm)of thickness,cool rapidly to room tempertature,sub-zero cool 3 hours at -100 °F(-73 °C),then temper 3 hours at 1000 °F(538 °C). For optimum corrosion resistance,surfaces must be free of scale and foreign particles and finished parts should be passivated.


Physical Properties

Specific gravity:
annealed.............................................. 7.92
sub-zero cooled,
tempered 850 °F(454 °C) ................... 7.81
Density:
annealed
lb/cubic in ...........................................0.286
kg/cubic m .......................................... 7810
Melting Range
°F............................................... 2500/2550
°C ..............................................1371/1399

Electrical resistivity
Sub-zero cooled,tempered 850 °F(454 °C)

Test Temperature

Ohm-cir mil/ft

Microhm-mm

°F

°C

80

27

474

788

134

57

485

806

199

93

497

826

370

188

532

884

461

238

549

912

541

282

566

941

729

388

601

999

835

446

618

1027

981

527

647

1075

1162

627

678

1128

1349

732

693

1152

Mean Coefficient of Thermal Expansion
Sub-zero cooled,tempered 850 °F(454 °C)

Test Temperature

10(-6)/°F

10(-6)/°C

68 °F to

20 °C to

212

100

6.3

11.3

572

300

6.8

12.2

752

400

7.0

12.6

932

500

7.2

13.0

1150

620

7.2

13.0

1350

735

6.7

12.1

1500

815

7.0

12.6

1700

925

7.5

13.5

Thermal Conductivity
Sub-zero cooled,tempered 850 °F(454 °C)

Test Temperature

Btu-in/ft²-h-°F

W/m-K

°F

°C

100

38

101

14.5

200

93

106

15.4

300

149

112

16.2

400

204

118

17.0

500

260

124

17.8

600

316

130

18.7

700

371

136

19.6

800

427

140

20.3

900

482

146

21.1

Moduli of elascity (E) and Rigidity (G)

Test Temperature

E

G

°F

°C

ksi x 10(3)

MPa x 10(3)C

ksi x 10(3)

MPa x 10(3)C

80

27

29.4

203

11.3

78

400

204

27.3

188

10.4

72

600

316

25.9

179

9.8

68

700

371

25.2

174

9.6

66

800

427

24.3

168

9.3

64


Heat Treatment

Annealing
Heat to 1850/1950 °F(1010/1066 °C),cool rapidly to room temperature.

Hardening
Alloy 350 can be hardened by either sub-zero cooling and tempering (SCT) or double aging(DA). Sub-zero cooling and tempering will result in higher strength than double aging. "Conditioning" of the alloy by rapid cooling from 1710 °F (932 °C) +/-25 °F is required before the SCT treatment,and is not required, but is recommended before double aging. It is further recommended that following an anneal at 1850/1950 ° F (1010/1066 °C), alloy 350 be cooled to -100 °F (-73 °C) for at least 3 hours before hardening.

Sub-zero cooling
After conditioning at 1710 °F(932 °C) +/-25 °F (rapid cool) for 90 minutes per inch of thickness, alloy 350 is held for a minimum of 3 hours at -100 °F, then tempered at either 850 °F or 1000 °F (454 °C or 538 °C) for a minimum of 3 hours. The 850 °F temper produces the highest strengths and hardnesses,and the 1000 °F temper produces improved toughness and stress corrosion properties.

Double age
Hold for 3 hours at 1350/1400 °F(732/760 °C), air cool to room temperature; heat to 825/875 °F(440/468 ° C), hold for 2-3 hours, air cool.


Workability

Hot working
Alloy 350 is readily hot worked. It is worked from a maximum temperature of 2150 °F(1177 °C). The use of temperature above 2150 °F will cause an increase in the amount of ferrite. Finishing temperature should be in the range of 1700/1800 °F(927/982 °C) to prevent grain coarsening on subsequent heat treatment and promote homogenous precipitation of carbides.

Cold working
In the annealed condition, alloy 350 is essentially austenitic and has forming characteristics similar to those of the AISI 300 series stainless steels. It has a higher rate of work hardening and cold forming will cause martensite formation in proportion to the amount of deformation. If capacity is limited or deformation is severe, heating the material to 300 °F(149 °C) or above will minimize work hardening. In the hardened condition, alloy 350 has sufficient ductility for limited forming or straightening operations .

Machining
Succesfully maching alloy 350 requires the same pratices used for other stainless steels, such as rigid tool and work suports, slower speeds, positive cuts, absence of dwelling or glazing, and adequate coolant. In the annealed condition, the alloy is soft and gummy and has a high work-hardening rate. Machining alloy 350 in the annealed condition is consequently not recommended. Best machinability is obtained in the equalized and overtempered condition. Finishing operations may be performed in this condition if proper allowances are made for growth during subsequent hardening treatments. If extreme dimensional accuracy is necessary, finish machining should be done in the hardened condition.
Following are typical feeds and speeds for equalized and overtempered alloy 350:

High Speed Tools

Turning-
Cut-Off
And
Forming

Cut-Off
Tool
Width

1/16"

SFPM
IPR

45
.001

1/8"

SFPM
IPR

45
.001

1/4"

SFPM
IPR

45
.0015

1/2"

SFPM
IPR

45
.0015

Form
Tool
Width

1"

SFPM
IPR

45
.001

1-1/2"

SFPM
IPR

45
.001

Drilling

Drill
Dia.

1/4"

SFPM
IPR

50
.004

3/4"

SFPM
IPR

50
.008

Reaming

Under 1/2"

SFPM
IPR

60
.003

Over 1/2"

SFPM
IPR

60
.008

Die Threading

T.P.I

3-7½

SFPM

5-12

8-15

SFPM

8-15

Over 16

SFPM

10-20

Tapping

SFPM

25

Milling-
End Peripheral

Depth of
Cut .050"e;

SFPM
IPR

85
.001-.004

Broaching

SFPM

10

Chip Load in./tooth

.002

When using carbide tools, surface speed feet/minute (sfpm) can be increased
between 2 and 3 times over the high-speed suggestions. Feed can be increased
between 50 and 100%.
Figures used for all metal removal operations covered are average. On certain
work, the nature of the part may require adjustment of speeds and feeds. Each
job has to be developed for best production results with optimum tool life.
Speeds or feeds should be increased or decreased in small steps.

Welding
Alloy 350 can be satisfactorily welded by the shielded fusion and resistance welding processes. Oxyacetylene welding is not recommended, since carbon pickup in the weld may occur. When a filler metal is required, a machining analysis should be used to provide welds with properties approximately the same as the base metal. When designing the weld joint , care should be exercised to avoid stress concentrators, such as shrap corners, threads,and partial-penetration welds. When high weld strength is not needed, a standard austenitic stainless filler, such as E/ER308, should be considered. Preheating is not required to prevent cracking. If possible, the weldment should be annealed after welding to provide the optimum combination of strength, ductility, and corrosion resistance. The alloy must be treated at 1710 °F(932 °C) before hardening by sub-zero cooling and tempering.


Typical Mechanical Properties

Typical Room Temperature Mechanical Properties


Treatment


0.2%
Yield
Strength


Ultimate
Tensile
Strength

%
Elongation
in 2"

%
Reduction
of Area


Rockwell
Hardness

ksi

MPa

ksi

MPa

SCT 850 °F

162

1117

198

1365

15

49

C 48

SCT 1000 °F

150

1034

163

1124

22

53

C 38

Double Aged

142

979

171

1179

12

--

C 40

Annealed

60

414

160

1103

30

--

B 95

Typical Elevated Temperature Tensile Properties
Sub-zero cooled, tempered 850 °F(454 °C)

Test
Temperature

0.2% Yield
Strength

Ultimate
Tensile
Strength

%
Elongation
in 2"

°F

°C

ksi

MPa

ksi

MPa

80

27

170

1172

203

1400

13

400

204

141

972

188

1296

9

600

316

136

938

189

1303

7

700

371

128

883

190

1310

8

800

427

125

862

186

1282

10

900

482

111

765

166

1145

9

1000

538

85

586

106

731

16

Typical Stress Rupture Strength
Sub-zero cooled, tempered

Test
Temperature

Tempering
Temperature

Stress for Rupture in

°F

°C

°F

°C

10 hours

100 hours

1000 hours

ksi

MPa

ksi

MPa

ksi

MPa

800

427

850

454

188

1296

186

1282

183

1262

--

--

1000

538

132

910

130

896

127

876

900

482

850

454

140

965

118

814

95

655

--

--

1000

538

110

758

103

710

98

676

Typical Room Temperature Tensile Properties After Exposure to
Elevated Temperature Under Stress

Sub-zero cooled, tempered 850 °F(454 °C)

Exposure

0.2%
Yield
Strength

Ultimate
Tensile
Strength

%
ELongation
in 2"

°F

°C

ksi

MPa

hours

ksi

MPa

ksi

MPa

Room

--

--

--

158

1089

201

1386

12

600

316

60

414

1000

162

1117

198

1365

14

--

--

90

621

1000

177

1220

202

1393

13

--

--

140

965

1000

201

1386

204

1407

12

700

371

60

414

1000

169

1165

204

1407

11

--

--

90

621

1000

180

1241

206

1420

11

--

--

150

1034

1000

227

1565

228

1572

5

800

427

60

414

1000

190

1310

220

1517

7

--

--

90

621

1000

192

1324

214

1476

8

--

--

130

896

1000

212

1462

220

1517

5*

*Broke outside gage marks

AM 350 - Current Inventory Stock