Sep 17 2012
Topics Covered
IntroductionChemical CompositionPhysical PropertiesMechanical PropertiesThermal PropertiesOther DesignationsFabrication and Heat Treatment Machinability Forming Welding Heat Treatment Cold Working Annealing Tempering HardeningApplications
Introduction
Carbon steels have a composition with carbon as the significant alloying element. They may contain 0.4% of silicon and 1.2% of manganese. Molybdenum, chromium, nickel, copper, and aluminium are also present in small quantities. AISI 1118 carbon steel is a free machining steel. It is added with sulfur in order to improve its machining characteristics.
The following datasheet gives an overview of AISI 1118 carbon steel.
Chemical Composition
The following table shows the chemical composition of AISI 1118 carbon steel.
| Element |
Content (%) |
| Iron, Fe |
98.03 - 98.48 |
| Manganese, Mn |
1.30 - 1.60 |
| Carbon, C |
0.14 - 0.20 |
| Sulfur, S |
0.080 - 0.13 |
| Phosphorous, P |
≤ 0.040 |
Physical Properties
The physical properties of AISI 1118 carbon steel are tabulated below.
| Properties |
Metric |
Imperial |
| Density |
7.85 g/cm3 |
0.284 lb/in³ |
| Melting point |
1449°C |
2640°F |
Mechanical Properties
The mechanical properties of AISI 1118 carbon steel are outlined in the following table.
| Properties |
Metric |
Imperial |
| Tensile strength |
525 MPa |
76100 psi |
| Yield strength |
315 MPa |
45700 psi |
| Bulk modulus (typical for steel) |
140 GPa |
20300 ksi |
| Shear modulus (typical for steel) |
80.0 GPa |
11600 ksi |
| Elastic modulus |
190-210 GPa |
27557-30458 ksi |
| Poisson's ratio |
0.27-0.30 |
0.27-0.30 |
| Elongation at break (in 50 mm) |
32% |
32% |
| Reduction of area |
70% |
70% |
| Hardness, Brinell |
149 |
149 |
| Hardness, Knoop (converted from Brinell hardness) |
169 |
169 |
| Hardness, Rockwell B (converted from Brinell hardness) |
80 |
80 |
| Hardness, Vickers (converted from Brinell hardness) |
155 |
155 |
Thermal Properties
The thermal properties of AISI 1118 carbon steel are given in the following table.
| Properties |
Metric |
Imperial |
| Thermal conductivity (typical steel) |
49.8 W/mK |
346 BTU in/hr.ft.°F |
Other Designations
Other designations that are equivalent to AISI 1118 carbon steel include:
- ASTM A29
- ASTM A510
- ASTM A576
- SAE J1397
- SAE J403
- SAE J412
- ASTM A107
- ASTM A108
- FED QQ-S-637 (1118)
- SAE J414
Fabrication and Heat Treatment
Machinability
The machinability rate of AISI 1118 carbon steel is 85.
Forming
AISI 1118 carbon steel can be formed using conventional techniques.
Welding
AISI 1118 carbon steel has good welding property. It is recommended that free machining steels should not be welded because gases produced from the sulfur content can result in unsound welds.
Heat Treatment
AISI 1118 carbon steel can be heat treated at 844°C (1550°F) followed by quenching in water and tempering.
Cold Working
AISI 1118 carbon steel is limited to clod working. It is recommended that severe cold working process such as swaging or cold heading are not performed because the steel can be crumbled due to the presence of sulfur.
Annealing
AISI 1118 carbon steel is annealed at 872°C (1600°F) following by slowly cooling in the furnace. Stress relief annealing process can also be performed at 538°C (1000°F).
Tempering
AISI 1118 carbon steel can be tempered at 315 to 538°C (600 to 1000°F)
Hardening
AISI 1118 carbon steel can be hardened by cold working, or heat treatment and quenching.
Applications
AISI 1118 carbon steel can be mainly used in free machining stock such as fasteners and screws.