1018 Steel- Heat Treatment 1

[mtnz]

Hi guys!

We are case-hardening 1018 steels here at work (0.003"-0.005" Deep). I was just curious what would be the HRC value when we test those parts within 0.003-0.005" with Vickers? We are finding them 30-35HRC lately. Do you guys think they are soft? What would be the min-max HRC value for those 1018 steel parts?

Thanks for helping!

 

Only your technical requirement can say if it is too soft. If these results are lower than previous it may indicate your case hardening process has drifted out of control. But first you need to be certain you are inspecting correctly.
Conversion to Rockwell scales using ASTM E140 is very dicey when using low Vickers indentation loads, especially at high hardness.
Knoop hardness might be more appropriate for a very shallow case such as this; for guidance read the applicable ASTM standards including the extensive commentary.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[mrfailure]

30 - 35 HRC does sound low, unless that is what you are specifying for your case. I think hardness values above 50 HRC would more typically be expected on case hardening. Most of my clients specify a minimum case hardness and/or effective case depth.

As for scale, I disagree about Vickers: you can use it, especially for this purpose, provided your indentation meets requirements in ASTM E384 for not being too close to the edge. I often use it when the customer specifies in Vickers scale. Personally, I find it more reflective of actual Rockwell hardness but Ironic is right that you can stack Knoop indentations closer together which can be important in developing a profile especially in SAE J423 testing.

 

[blacksmith37]

Too thin a case for anything but superficial hardness ( 15N ) or maybe 10kg Vickers. And ,unless the parts are thin ( like < 1/8 ") you do not have enough hardenability in 1018 to get high hardness. What quench from what temperature ? For example ,no problem making 15N 90 in 8620 with 0.006 case in a 1/8 thick part ( case carbon = 1 % at the surface).

 

[AidanMc]

Have you evaluated the parts for carbon content at the surface? This could help determine if the hardness your seeing is due to carburizing being ineffective or slack quenching.

Regarding the hardness scale, I assume your measuring micro-Vickers on a cross section. This has been properly polished, right? What weight are you using, we typically use 500g but I've also used 300g for indentations close to a surface.