Alloy Steel from Specialty Steel
Alloy steel combines 1-50% of various elements to enhance properties such as strength, durability, weight ratios, and corrosion resistance. This flexibility makes alloy steel bars and other configurations suitable for a wide range of applications.
When you need the right alloy to fit precise metrics and requirements, Specialty Steel delivers with perfect chemistry for the job.
Popular Alloy Steel Grades
We offer popular grades like 4140 and 4150 alloy steel, known for their high performance:
- 4140 Steel: Contains carbon (0.38-0.43%), manganese (0.75-1.00%), silicon (0.15-0.35%), phosphorus (max 0.035%), sulfur (max 0.040%), chromium (0.80-1.10%), and molybdenum (0.15-0.25%).
- 4150 Steel: Contains carbon (0.48-0.53%), manganese (0.75-1.00%), silicon (0.15-0.35%), phosphorus (max 0.035%), sulfur (max 0.040%), chromium (0.80-1.10%), and molybdenum (0.15-0.25%).
Properties and Applications
Thru-hardening ensures our 4140 and 4150 steel are exceptionally tough and resilient. Both 4140 alloy steel material and 4150 are versatile and reliable for demanding industrial applications.
4140 Alloy Steel Properties
This steel has a hardness rating of approximately 197-237 BHN, providing excellent wear resistance and toughness. It is widely used for its strength and impact resistance.
4140 Applications
- Automotive: Used in crankshafts, steering knuckles, and axle shafts due to its strength and wear resistance.
- Industrial Machinery: Ideal for gears, spindles, and fixtures that require toughness and high fatigue strength.
- Tool and Die Making: Suitable for manufacturing dies, molds, and tooling components.
4150 Alloy Steel Properties
Slightly harder with a typical hardness range of 255-321 BHN, 4150 steel is ideal for high-stress applications requiring superior strength and durability.
4150 Applications
- Firearms: Commonly used in barrels and bolts for its superior hardness and durability.
- Heavy Equipment: Utilized in components like sprockets, drive shafts, and other parts subject to high stress.
- Oil and Gas: Applied in downhole tools and equipment that demand high strength and resistance to fatigue.
| C | Mn | Si | P | S | Cr | Mo |
| .38-.43 | .75-1.00 | .15-.35 | .035 max | .040 Max | .80-1.10 | .15-.25 |
| C | Mn | Si | P | S | Cr | Mo |
| .48-.53 | .75-1.00 | .15-.35 | .035 max | .040 Max | .80-1.10 | .15-.25 |
Product Categories
Specialty Steel stocks AISI 4140 and AISI 4150 steel in a variety of shapes including rounds, squares, and flats, all provided in a hot roll finish.
Our 4140 round bar and 4150 steel are available in heat-treated TGP (Rc 28/34) alloy shafting, ensuring superior performance. Additionally, we offer AISI 4140 steel in squares, flats, and hexagons, making it versatile for various industrial applications.
Ordering and Availability
Specialty Steel carries the largest selection of alloy bar stock in North America in one location. We offer an extensive inventory of hard-to-find sizes and lengths including (10/12 Ft Random Lengths, 20/24 Ft Random Lengths and Custom Cut-To-Length options).
Quality Assurance and Traceability
As an ISO-certified top distributor in high-strength alloys and specialty steel products, we offer proven expertise. As the sole authorized exporter of Associated Steel Corporation products to Canada, Mexico, and overseas, we deliver tailored solutions for diverse industrial needs. Our ISO-certified quality assurance guarantees uncompromised quality and traceability in every steel product we supply.
Frequently Asked Questions
4140 alloy steel is a chromium-molybdenum low-alloy steel known for its exceptional balance of strength, toughness, and hardness. Its controlled chemical composition (including carbon, chromium, molybdenum, and manganese) gives it high tensile strength and superior wear resistance. Because of these traits, it’s commonly used in automotive, aerospace, oil and gas, and heavy machinery components.
4140 offers a unique combination of machinability, strength, and cost-effectiveness. It’s tougher and more hardenable than 4130, yet easier and less expensive to machine than higher-strength alloys like 4340. This makes it a preferred “middle ground” alloy for applications requiring durability without excessive manufacturing costs.
4140 heat treatment unlocks the steel’s full performance potential. When quenched and tempered, 4140 achieves much higher strength and hardness than its annealed form. However, it’s crucial to avoid tempering within the 200°C–400°C range to prevent Martensite Temper Embrittlement (MTE), which can lead to cracking and loss of toughness. Proper post-quench tempering within four hours is also essential to prevent residual stress failures. Learn more about annealing vs. heat treating 4140 alloy steel here!
Hot-rolled (HR) 4140 bars are formed at high temperatures, resulting in a rough surface and liberal tolerances but lower cost—ideal when parts will be extensively machined later. Cold-finished (CF) bars are drawn or polished at room temperature, giving them a smooth finish, tighter tolerances, and higher strength due to strain hardening. CF stock is preferred for precision applications requiring consistent dimensional control.
Quality assurance starts with Material Test Reports (MTRs) that verify chemical composition, mechanical properties, and traceability. Always confirm that the heat number and alloy designation match your purchase order. Partnering with certified ISO and ASTM-compliant suppliers—like Specialty Steel—ensures full traceability, proper documentation, and compliance with industry standards for reliability and performance.
"*" indicates required fields