Cooling welded connection

[The Haymaker]

Ahhhh,..just before you go,... I have a brief comment someone might correct me on if appropriate?

Not welding but "hot metal related" : I was told years ago by a welder, that when sharpening my mower blades on a grind stone,...(and they certainly do get pretty hot),...he said to dunk 'em immediately in the water bucket to harden the metal.

He told me it takes more heat than a grinder to "harden" metals effectively, but that for a mower blade,...you should dunk it anyway for all the hardness it may acquire.

IF,...that statement is true, (and I tend to believe my welder), then it would indicate that "quick-water-cooling" tends to harden the metal. I have watched him cool welds and often in stages so it doesn't get brittle.

Any comments guys,..or gals?

CHEERS!
. . tug

I dunk my blades, but it is for the opposite reason. I want to keep them from getting hot. Make a couple passes, dunk, make a few more. If you blue the edge of the blade, you've softened it.

 

[20 20]

I was told years ago by a welder, that when sharpening my mower blades on a grind stone,...(and they certainly do get pretty hot),...he said to dunk 'em immediately in the water bucket to harden the metal.

I dunk mine while sharpening so they don't get over heated.

He told me it takes more heat than a grinder to "harden" metals effectively, but that for a mower blade,...you should dunk it anyway for all the hardness it may acquire.

I'd agree it would take a bit of grinding to make the metal hot enough for the hardening process. With that said the old way to harden steel was by using water. heat it, watch for the color change, and dunk as needed.

IF,...that statement is true, (and I tend to believe my welder), then it would indicate that "quick-water-cooling" tends to harden the metal. I have watched him cool welds and often in stages so it doesn't get brittle.

Any comments guys,..or gals?

CHEERS!
. . tug

This is exactly why most of us that weld have said DON'T dunk

 

[20 20]

If you blue the edge of the blade, you've softened it.

I want to baby my grass and don't believe in violence so a softer blade would be more nicer

That's why I don't use a weedeater I don't believe in whip's

Okay I'll stop for now.

 

[JB4310]

If you blue the edge of the blade, you've softened it.

Same as with drill bits. That's why most grinders have a water troth.

Anyone know a simple way to reharden drill bits?
Is it as simple as getting them red hot and quenching in water?

JB.

 

[czechsonofagun]

Same as with drill bits. That's why most grinders have a water troth.

Anyone know a simple way to reharden drill bits?
Is it as simple as getting them red hot and quenching in water?

JB.

I done it with center punch and a screwdriver.

 

[20 20]

Same as with drill bits. That's why most grinders have a water troth.

Anyone know a simple way to reharden drill bits?
Is it as simple as getting them red hot and quenching in water?

JB.

Did it years ago with water, I don't believe you have to get them red hot. Just get them hot enough for the blueish color to start{then dunk}. Don't qoute me on this because it has been many years sense I've done it. Hopefully someone else can give better directions????

 

[Renze]

If you dunk in oil, you can surface harden it: The hot steel will absorb carbon from the oil, which gets contained in the steel molecules, which gives it its hardness.
When you heat it again, the carbon may get burned, softening the steel again.
It doesnt work as good with all steels though.

 

[20 20]

Renze; if I'm not mistaking oil dunk is prefered?

 

[killdozerd11]

Renze; if I'm not mistaking oil dunk is prefered?

It depends on the make up of the steel
some are air hardening some water hardening some oil
You can buy tool steel un hardened and machine it to spec then harden it

You have to heat to the proper temp you can get tempillac pens the ink mark they leave behind melts at a certain specified temp (For small stuff)
they also make a pill type that you can set on the metal

Then there is case o nite for doing small stuff you heat to red then dip in the case o nite and let cool (For CASE hardening)

if you grind on something till it turns blue you went to far

 

[20 20]

thanks Killdozerd11

 

[The Haymaker]

I want to baby my grass and don't believe in violence so a softer blade would be more nicer

That's why I don't use a weedeater I don't believe in whip's

Okay I'll stop for now.

Don't give the PETA granola munchers any ideas!

E

 

[tthopskin@yahoo.ca]

Extreme differential cooling can crack, or strain the metal and make later cracking more likely. It is more of an issue when thick and thin are joined. When I need it quick I use a spray directed to favor cooling as uniform as possible down to a reasonable temp - then dunk to cool to touch.
larry

 

[AlbertaDan]

This is just a question I have. I seen some people to cool down welded piece by dumping it in water to be able to work on it sooner.
I always feel it should cool down on it's own.


What do you think?

Where i work (as a pipeline builder) we do a lot of welding. All of our welding is cooled slowly. when metal cools too quickly it can shock the material cauing microscopic cracks. Over time and use these cracks get bigger. Eventually leading to a failure of the weld.


Do you want to be on the machine when your FEL fails while loading something? Or how would you feel if a failure ended up hurting a family member? The few extra minutes may save a lot of grief later on.

 

[AlbertaDan]

Same as with drill bits. That's why most grinders have a water troth.

Anyone know a simple way to reharden drill bits?
Is it as simple as getting them red hot and quenching in water?

JB.

If you heat them up to red then dunk in oil to quikly cool you will harden them. But this process also makes them brittle.

Then you have to temper them so they wont break the first time you use them. This is done by heating to a specific temp then SLOWLY cooling.

**Note** all those neat colors when you heat steel represent a different temperature---light brown being coolest and bright blue being the hottest before turning red then orange.