Sep 26 2012
Topics Covered
Introduction
Chemical Composition
Physical Properties
Mechanical Properties
Thermal Properties
Other Designations
Fabrication and Heat Treatment
Tempering
Annealing
Cold Working
Welding
Machinability
Hot Working
Hardening
Applications
Introduction
Stainless steels are high-alloy steels with good corrosion
resistance because of large amounts of chromium present in them. About
10% of chromium is present in most stainless steels.
Stainless steels are available in three different groups based on
their crystalline structure. These groups include martensitic,
austenitic and ferritic. The combination of martensitic and ferritic
steels forms a fourth group of stainless steels known as
precipitation-hardened steels.
Grade 440B stainless steel is a high carbon martensitic stainless
steel containing good strength, moderate corrosion resistance and
ability to obtain and maintain wear resistance and excellent resistance.
The following datasheet provides an overview of grade 440B stainless
steel.
Chemical Composition
The chemical composition of grade 440B stainless steel is outlined
in the following table.
| Element |
Content
(%) |
| Iron, Fe |
80 |
| Chromium, Cr |
16.0-18.0 |
| Manganese, Mn |
1.0 |
| Silicon, Si |
1.0 |
| Carbon, C |
0.75-0.95 |
| Molybdenum, Mo |
0.75 |
| Phosphorous, P |
0.040 |
| Sulfur, S |
0.030 |
Physical Properties
The following table shows the physical properties of grade 440B
stainless steel.
| Properties |
Metric |
Imperial |
| Density |
7.74 g/cm3 |
0.280 lb/in³ |
| Melting point |
1482°C |
2700°F |
Mechanical Properties
The mechanical properties of grade 440B stainless steel are
displayed in the following table.
| Properties |
Metric |
Imperial |
| Elastic modulus |
190-210 GPa |
27557-30458 ksi |
| Poisson's ratio |
0.27-0.30 |
0.27-0.30 |
Thermal Properties
The thermal properties of grade 440B stainless steel are given in
the following table.
| Properties |
Metric |
Imperial |
| Thermal conductivity (for stainless
410A0) |
24.2 W/mK |
168 BTU in/hr.ft².°F |
Other Designations
Equivalent materials to grade 440B stainless steel are given in the
table below.
| AISI 440B |
ASTM A276 |
ASTM A314 |
ASTM A473 |
| DIN 1.4112 |
QQ S763 |
FED QQ-S-763 |
MIL SPEC MIL-S-862 |
| SAE J405 (51440B) |
SAE 51440B |
ASTM A580 |
Fabrication and Heat Treatment
Tempering
Grade 440B stainless steel is tempered at 148°C (300°F) to obtain
maximum properties and the maximum hardness that can be obtained is RC
58.
Annealing
Grade 440B stainless steel is annealed at 843-871°C (1550-1600°F)
and then cooled very slowly in a furnace.
Cold Working
Grade 440B stainless steel can be slightly cold worked by common
cold working methods.
Welding
Welding is not generally recommended for grade 440B stainless steel
as it tends to harden in air. If this steel grade is welded the
recommended temperature is 260°C (500°F) and for the post weld
treatment the recommended temperature is 732-760°C (1350-1400°F). The
post weld treatment should take place for 6 h and then the material
should be cooled slowly in a furnace to avoid cracking. Similar high
heat inputs and filler metal should be used during operations.
Machinability
Grade 440B stainless steel is best machined in the annealed
condition. Chip breakers are used to handle tough, stringy chips of
grade 440B stainless steel. Ceramic or carbide tooling is best suited
for this grade 440B stainless steel.
Hot Working
Hot working for grade 440B stainless steel takes place by
pre-heating the steel to 760°C (1400°F) which is then followed by
slowly increasing the temperature range to 1038-1204°C (1900-2200°F).
After the hot working process, the material is then cooled slowly at
room temperature followed by complete annealing.
Hardening
Grade 440B stainless steel is heated at 760°C (1400°F), soaked at
1010°C (1850°F) and finally cooled in oil or air.
Applications
Grade 440B stainless steel is used in measuring instruments, gage
blocks, cutlery, knives, dies, molds, ball bearings and valve
components.