Metal alloys are being used in many different industrial applications. One such alloy is AISI 4145, a chromium-molybdenum steel that is frequently used in the energy industry to make pump shafts, drilling tools, and other heavy equipment parts. For the purpose of creating strong and long-lasting engineering components, it is essential to comprehend its qualities, composition, and machining features. Everything you need to know about AISI 4145, including its applications and recommended heat treatment methods, will be covered in this blog post.
- AISI 4145: What is it?
A low to medium carbon steel with a chromium-molybdenum alloy content, AISI 4145 is extensively utilized in the oil and gas sector. Its primary alloying components are typically 0.30% Carbon, 0.40% Manganese, 0.20% Silicon, 0.15% Chromium, and 0.15% Molybdenum; minor amounts of additional elements including vanadium and nickel are also present. This grade of steel is a great option for a variety of applications where strength and fatigue resistance are crucial, such as drill collars, downhole tools, sucker rods, etc. because it has good strength, toughness properties when heat treated, and superior ductility when compared to other grades of similar composition.
- ASIA 4145 Formulation
With 0.45% carbon, 0.75% manganese, 1.00% chromium, 0.20% molybdenum, and 0.15% vanadium, AISI 4145 is a low-alloy steel grade. Strength and toughness are two examples of the mechanical and physical qualities that the alloying elements improve. The alloy can also be quenched and tempered to increase its hardness and wear resistance thanks to its carefully balanced composition.
| Element | Content (%) |
| Iron, Fe | 96.795-97.72 |
| Chromium, Cr | 0.800-1.10 |
| Manganese, Mn | 0.750-1.00 |
| Carbon, C | 0.430-0.480 |
| Molybdenum, Mo | 0.150-0.250 |
| Silicon, Si | 0.150-0.300 |
| Sulfur, S | ≤ 0.0400 |
| Phosphorous, P | ≤ 0.0350 |
- Mechanical Properties of AISI 4145
As a low-alloy steel grade, AISI 4145 has outstanding strength, toughness, and wear resistance. AISI 4145 has a minimum yield strength of 89 KSI and an ultimate tensile strength that varies from 125 to 140 KSI based on the heat treatment parameters. The alloy is a great option for producing important parts like heavy-duty shafts and drill collars because of its exceptional toughness and fatigue resistance.
| Properties | Metric | Imperial |
| Bulk modulus (typical for steels) | 140 GPa | 20300 ksi |
| Shear modulus (typical for steels) | 80.0 GPa | 11600 ksi |
| Elastic modulus | 190-210 Gpa | 27557-30458 ksi |
| Poisson’s ratio | 0.27-0.30 | 0.27-0.30 |
| Hardness, Brinell | 208 | 208 |
| Hardness, Knoop (converted from Brinell hardness) | 230 | 230 |
| Hardness, Rockwell B (converted from Brinell hardness) | 94 | 94 |
| Hardness, Rockwell C (converted from Brinell hardness, value below normal HRC range, for comparison purposes only) | 15 | 15 |
| Hardness, Vickers (converted from Brinell hardness) | 218 | 218 |
| Machinability (annealed and cold drawn, based on 100 machinability for AISI 1212 steel) | 60 | 60 |
- Physical Properties of AISI 4145
The density and melting point of AISI 4145 are 7.85 g/cm3 and 1424°C (2580°F), respectively. Its thermal conductivity is 42.6 W/mK and its coefficient of thermal expansion is 11.2 µm/mK. The alloy is a great option for high-temperature applications since its physical characteristics hold true throughout a wide temperature range.
| Properties | Metric | Imperial |
| Density | 7.85 g/cm3 | 0.284 lb/in³ |
- AISI 4145 Equivalents
| ASTM A29 | ASTM A322 | ASTM A331 | ASTM A519 | ASTMA711 |
| ASTM A752 | ASTM A829 | SAE J1397 | SAE J404 | SAE J412 |
| ASTM A505 | SAE J770 | MIL SPEC MIL-S-16974 |
- AISI 4145 Applications
Numerous heavy-duty and high-stress applications make use of AISI 4145. It is employed in the energy industry to make pump shafts, drilling equipment, and other parts needed for exploration and production. It is also widely used in the aerospace and defense industries for the production of shafts, gears, and other essential parts. Because of its superior strength and resistance to corrosion, it is the perfect material for components exposed to seawater, such as marine motor shafts and other offshore uses.
- AISI 4145 Thermal Processing
AISI 4145’s mechanical and physical characteristics can be changed by undergoing a variety of heat treatment procedures. Quenching and tempering, which entails heating the steel to 927°C (1700°F) and quickly cooling it in a quenching media like water, oil, or air, is the most used heat treatment method for AISI 4145. After that, the steel is tempered to improve its mechanical qualities.
- Machining according to AISI 4145
With the appropriate tools and methods, it is possible to effectively machine AISI 4145, a steel machine with a moderate degree of difficulty. Because of the alloy’s moderate hardness and toughness, high cutting pressures, minimal chip loads, and sharp cutting tools are all required to prevent premature failure and tool wear. Using cutting fluids will help keep your tools from overheating and extend their lifespan.