Question for the Metalurgists

[azchrisf]

I just happened to be looking around at who makes what and came across some images that got me curious --

Apparently Infar makes the Carlysle wrenches (and possibly Milwaukee on a custom die - the jaws are the same). Something I noticed in their catalog is that the wrench forgings hot off the press have a TON of scale on them (http://www.infar.com.tw/e-catalog/mobile/index.html#p=68) in their photo - yet in Snapon's video (

), when the wrenches drop off the forge into the collection bin, there is no scale whatsoever.

This was interesting to me. Is this something to do with the quality of the steel used, the temperature the forgings are being carried out, or the type of steel, or all of the above?

Just curious if you metallurgists could clue me in a little.

 

[ddawg16]

You have my curiosity as well.....subscribed

 

[Ole Slewfoot]

http://www.infar.com.tw/e-catalog/mobile/index.html#p=104
Cant answer that, but that catalog does have a cool visualizer for W, M, and SAE socket sizes.

 

[MShaw]

Since you see the Snap on wrenches up close for the first time when they come off the conveyor after the flash has been sheared the subsequent operation after forging may have spalled off some of the scale.

 

[Wyoming09]

Interesting video featuring Snap-On wrenches:

 

[DenisG]

I'm not an authority, but from what I know scale is a problem that engineers have to address when forging steel. Here's one reference that's a description of the problem and an attempt to address it:
https://www.researchgate.net/profil...756473858@1442286783030/download/lubrodal.pdf

 

[Maui]

When the Snap-On wrenches are dropped into the collection bucket off of the forge they are still hot, so it is more difficult to visually tell how much scale is actually present on the surface. And as MShaw pointed out, the first close-up you get of these wrenches in the video is after they go through at least one subsequent operation (and possibly more). Scale is unavoidable unless the bars are heated in a vacuum furnace. And yes, I am a metallurgist.

Maui

 

[scubadoober]

Since you see the Snap on wrenches up close for the first time when they come off the conveyor after the flash has been sheared the subsequent operation after forging may have spalled off some of the scale.

Bingo, there is a step in the video you are not seeing. Scale is an iron oxide layer plain and simple. If steel is rolled or forged hot scale will occur period. The scale is still there, but all of the flake is knocked off. There is still aoxide layer on the wrenches you are seeing just very thin and uniform. That is where the grayish/blue color is coming from. Check out the below videos, and if you start questioning the steel used we might have a problem.

 

[azchrisf]

Bingo, there is a step in the video you are not seeing. Scale is an iron oxide layer plain and simple. If steel is rolled or forged hot scale will occur period. The scale is still there, but all of the flake is knocked off. There is still aoxide layer on the wrenches you are seeing just very thin and uniform. That is where the grayish/blue color is coming from. Check out the below videos, and if you start questioning the steel used we might have a problem.

You two are correct - the devil is in the details. The 1st video therein lies the key - the trim operation pounded the scale right off (or at least most of it)

I know Snapon uses 4140 for just about everything - some have said it's virgin 4140 and no recycled content in it.
But the wrenches in the Infar catalog still have shitloads of scale even after the trim operation - and a very rusty scale too. Can you explain this?

 

[Alava]

Hello,

Stahlwille and Hazet trims the wrench when is cold,
But all the taiwanese brands I know trims right after the forging. Thats why you can see all the oxidation there, because is trimmed and because then is sand blasted off.

One note: Stahlwille video seems very cool with a guy forging alone... But the reality is different (4:00)

Snap-on shows you what he wants, even in their videos, and stahlwille also. They are companies and they want to be shown as perfect brands of perfect material, but I would like to see a Snap-on bin of forgings before all the subsequent process, you can see in the snap-on video this scale all around the place but not in the wrench... Who tells you that is not another process being made there? Ah... That is not shown... Strange...