While 52100 (AMS 6440) is a popular general-purpose bearing steel, other alloys within the 52100 family, specifically ASTM A485 Grade 1, may perform better depending on your application. A485 Grade 1 has high hardenability, and makes it possible to through-harden larger components than when using 52100.
This post looks at the details of ASTM A485 Grade 1 (a modification of 52100) and when it’s the best option.
Sullivan Steel sells and supports both 52100 and ASTM A485-1.
Composition of ASTM A485 Grade 1
ASTM International specification A485 concerns the “high hardenability modifications of high-carbon bearing quality steel.” The spec covers multiple modified grades, including Grade 1.
SKF Steel (now Ovako) developed Grade 1 by adding chromium, magnesium, and silicon to 52100’s chemical composition. These alterations changed the makeup from 100Cr6 (52100) to 100CrMnSi4-4 (A485 Grade 1).
|
Material Name |
Chemical Composition |
||||||
|
C |
Mn |
Si |
Cr |
Ni (max) |
Cu (max) |
Mo (max) |
|
|
52100 |
0.93-1.05 |
0.25-0.45 |
0.15-0.35 |
1.35-1.60 |
0.25 |
0.30 |
0.10 |
|
A485-1 |
0.90-1.05 |
0.90-1.20 |
0.45-0.75 |
0.90-1.20 |
0.25 |
0.30 |
0.10 |
Let’s look at situations where A485 Grade 1 delivers superior performance.
A485 for Through Hardening Larger Parts
The A485 mod grades were developed mainly to create a series of steels based on hardenability for manufacturing parts with cross sections too large for 52100 to fully through harden.
- Hardness; a material property. The steel’s actual penetration resistance. It is often determined via Rockwell or Brinell testing.
- Hardenability; a measurement. A measure of the steel’s potential for hardness versus depth at specific heat treatment and quench. It is often determined via Jominy end-quench testing.
|
Material Name |
Hardenability |
||||||
|
J1 |
J2 |
J6 |
J10 |
J12 |
J24 |
J32 |
|
|
52100 |
66/63 |
65/63 |
42/36 |
38/32 |
35/30 |
29/23 |
26/19 |
|
A485-1 |
- |
67/64.5 |
66.5/64 |
64/53 |
- |
38.5/32.5 |
35/30 |
Steels, such as A485, with high hardenability are vital to making large high-strength components. For example, consider a point contact bearing (a ball bearing). In this application, the contact between the ball and raceway creates a very high stress at the bearing’s surface AND a high subsurface stress gradient.
As bearing size increases, the steel needs increasing hardenability to avoid deformation, which could happen anywhere between the surface and center of the bearing.
In general:
- 100Cr6 (52100) is the most widely used bearing steel, with a hardenability suited to components with cross sections up to 0.5 inches*.
- 100CrMnSi4-4 (ASTM A485 Grade 1) has increased hardenability for high-strength components with cross sections up to 0.75 inches*.
*In practice, the actual section size hardness depends on the effectiveness of the quench and other heat treatment parameters.
A485 Grade 1 to Prevent Cracking During Quench
For 52100, oil quenching is used to through hardened components with cross sections up to 0.5 inches, and water quenching can be used for larger cross sections. However, water quenching raises the possibility of distortion or cracking.
A485 Grade 1 is designed through hardening sections up to 0.75 inches using an oil quench.
Sullivan’s Final Thoughts
Many factors come into play when it comes to hardening steel—the properties of the grade itself, quenching rate, heat treatment parameters, and more. Understanding the differences between 52100 and ASTM Grade 1 steel is essential to achieving the desired performance for your component.
At Sullivan Steel, our experts support customers at every step of the manufacturing process. Ask us about the benefits of using A485 Grade 1 for your next project.
