Cr-V vs Cr-Mo

[sensei_]

Hey guys,

I was sorting out some tools from a local garage sale lately, and would like to get some advise from the wise guys in here.

Is it true that:

Cr-V = Not for impact wrenches
Cr-Mo = Suitable for impact wrenches

The reason for wanting to clear this one up is because I have noticed that all my impact sockets bear the Cr-Mo marking and are usually black in color. However the chrome finished sockets are usually Cr-V and are not suitable for impact wrench use as they will shatter.

However, I have noticed that I have a Cr-Mo that is shiny from a japanese company "minimax", and this got me thinking, could i use this extension bar marked Cr-Mo with an impact wrench?

 

[metaleltr]

Well I have a set of Cr-V impact sockets from Menards. Cr-Mo is stronger though.

 

[Snapped-off]

Cr-Mo isn't exactly stronger, it's softer so it will wear as it's impacted. Cr-V is very hard, which makes it brittle, hence why the can shatter and also wear out your impact over time.

 

[tkonetzke]

Snapped off is right, cr-v is harder(read more liked to shatter or crack) although my 6 year old hf cr-v impacts are all going strong yet, even with the last two years of being spun by a SO mg725. So make of it what you will

 

[Engineer61]

Cr-Mo is 4xxx alloy grade steel, and Cr-V is 6xxx alloy grade steel, but without knowing which exact steel alloy it is (4150, 4340, 6150, 6118 etc) it's hard to fairly compare one to another. Look up Molybdenum or Vanadium and you'll find that they both are added to steel as "grain refiners" that keep the metal crystals smaller and more even in size.

 

[Steinmetz]

Cr-Mo alloys have greater impact resistance (toughness) than Cr-V alloys.

 

[sensei_]

Cheers for the input! chemistry was never my strong point (in high school, and even today )

but at least now i know what cr-v and cr-mo is, and their purposes.