Full Transcript:
What’s up guys?!?!?! Michael with Michael Talks Metal back for more martensitic machinations in our 2nd part on Martensitics!!!!
In our video last week we talked about martensitic types that have a maximum carbon content of point 15% and maximum hardness of about 40 Rc. If you did not check out that video .. click here
Higher carbon contents allow us to achieve higher hardness and strength with heat treatment.
Higher Chromium and other added elements can improve corrosion performance and / or mechanical properties.
First up today are several alloy grades that are small modifications of the chemistry we saw in type 410. They have similar applications but are utilized where 410 is not quite satisfactory:
Type 414 at point 15% max carbon and 11.5-13.5% Chromium has Nickel added at 1.25-2.50 % which improves its ability to harden and adds toughness that makes it more useful in the low 40’s Rc hardness range than type 410.
| Grade 414 | MIN | MAX |
|---|---|---|
| Carbon | 0.15 | |
| Chromium | 11.5 | 13.5 |
| Nickel | 1.25 | 2.5 |
The Nickel also improves corrosion performance in some environments. It also improves mechanical properties at modestly higher temperatures as compared to type 410.
Type 431 at point 20 max carbon, 15 to 17 % Chromium and 1.25%-2.50 % Nickel has improved corrosion performance from the higher Chromium as compared to either 414 and 410.
| Grade 431 | MIN | MAX |
|---|---|---|
| Carbon | 0.2 | |
| Chromium | 15 | 17 |
| Nickel | 1.25 | 2.5 |
Type 418 (aka Greek Ascoloy) at point 15 to point 20% carbon, 12 to 14 % Chromium, 1.8 to 2.20 % Nickel, has 2.50 to 3.50 % tungsten for higher strength at elevated temperatures….. above those where 403 and 410 are used. Jet engine or land-based gas turbine applications would be examples.
| Grade 418 Greek Ascoloy | MIN | MAX |
|---|---|---|
| Carbon | 0.15 | 0.2 |
| Chromium | 12 | 14 |
| Nickel | 1.8 | 2.2 |
| Tungsten | 2.5 | 3.5 |
Type 422 at point 20 to point 25 % carbon, 11 to 13 % Chromium, point 5 to 1 % Nickel, point 75 to 1.25 % Molybdenum, point 15 to .30% Vanadium and point 75 to 1.25% Tungsten. Say THAT ten times fast! Also used for the complex requirements at elevated temperatures.
| Grade 422 | MIN | MAX |
|---|---|---|
| Carbon | 0.2 | 0.25 |
| Chromium | 11 | 13 |
| Nickel | 0.5 | 1 |
| Molybdenum | 0.75 | 1.25 |
| Vanadium | 0.15 | 0.3 |
| Tungsten | 0.75 | 1.25 |
Next up is a type that could easily be considered as its own group of alloys since type 420 is very broadly defined as point 15 MINIMUM carbon, 12 to 14% Chromium. First time we have encountered a stainless alloy with carbon specified as minimum. We know how important the carbon content is in martensitic stainless steels so we can expect a wide variation in hardness and strength depending on the carbon content. Hardness can range from the low 30’s to middle 50’s on the Rc scale.
In the most common compositions, the carbon is in the range of point 3 to point 4% carbon. Common applications are in cutlery and plastic molds. There are also free machining grades indicated by the “F” suffix… 420F. ALWAYS be looking for a further specification that defines the material to assure the final product will do what it needs to do in service.
Lastly, we have a group of alloys in the highest range of carbon in the martensitic series ……. the 440’s
Chromium content is 16 to 18% and has three variations with differing carbon content. The higher Chromium content improves corrosion performance over type 420 or 410 and the higher carbon increases the strength and hardness capability.
440A has point 60 to point 75% carbon.
440B has point 75 to point 95% carbon.
440C has point 95 to 1.25% carbon
Hardness from the low 50’s for “A” and mid 50’s for “B” and are commonly used in cutlery and similar applications. 440C is typically used at around 60 Rc and used in valves or bearings and other applications where both corrosion and wear resistance are important.
As usual, we caution viewers that chemical composition can be further restricted by specifications and add important additional requirements. So for the 142nd time…CHECK THE SPECS !!!! TWICE
This is Michael with Michael Talks Metal. Michlin Metals is a full service, value added distributor of all things Martensitic Stainless and more, check the website www.michlinmetals.com for more info. Still here and haven’t subscribed? Click here and help support the channel. Missed last weeks video? Click here. This is Michael with Michael Talks Metal. I will see you next week, same time, same place. 10am YT. I’m out.
