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Cook

4140 and 6150

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Hi all,

 

Has anyone used these typs of stell before? And if so how are they for making a blade out ofthese typs of steel 4140 and 6150. I did look them up and I'm finding a lot of differnt things on them,so can anybody help me out?

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4140 is not a real good choice. The upper range of hardness is mid 50's, good for axes and hammers, not so much for blades.

 

6150 is a spring steel and if memory serves is pretty much like 5160, which a lot of folks here use as a knife steel.

 

Geoff

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I snagged several feet of leaf spring bolts (2') which are 6150 and as Geoff mentioned it's very similar to 5160 in forging and heat treating. Finding mid-carbon steel in round bar can be challenging. It's great stuff for hawks, hatchets and hammers.

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4140 is not a real good choice. The upper range of hardness is mid 50's, good for axes and hammers, not so much for blades.

 

6150 is a spring steel and if memory serves is pretty much like 5160, which a lot of folks here use as a knife steel.

 

Geoff

@Geoff Keyes

Thank you,I just picked up a piece of 4140(10 Lbs)2x2x6 for a hammer I'm going to try and make in the summer,thanks for the information on both steels,I also just found out I have some machine blads that are M4 steel :)

Edited by Cook

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I snagged several feet of leaf spring bolts (2') which are 6150 and as Geoff mentioned it's very similar to 5160 in forging and heat treating. Finding mid-carbon steel in round bar can be challenging. It's great stuff for hawks, hatchets and hammers.

 

@ B Finnigan

The scrap yeard up the street from me has a lot of 6150,in all size's,I think they sell it for like $1.00 a pound,but they charge a $10 cut fee if you don't bging you own saw.

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AISI 6150 alloy

0.48 - 0.53 Carbon

0.80 - 1.10 Chromium

0.15 Min. Vanadium

 

AISI 6150 is a fine grained, highly abrasion resistant carbon-chromium alloy steel. Very good shock resistance and toughness are also key properties of this alloy in the heat treated condition.

 

6150 is reputed to be even tougher than 5160. It has about 10 points less Carbon and the addition of a bit of Vanadium, otherwise it is the same as 5160. Under the hammer it is stiffer than 5160 and it can suffer from micro cracking if worked too cold. However, it doesn't really hurt this stuff to run it up to a welding heat and work it while it is more ductile. Hardening is where people run into trouble, it doesn't harden unless you soak it awhile at austenitizing temperature. Most alloys you can get to temperature, quench, and everything is good. With this stuff you need to get to temperature, soak 5-10 minutes, and then quench. The Vanadium seems to slow down the transformation to austenite and if you don't let it soak it often fails to harden or hardens incompletely. As noted, wear resistance is greater than 5160 and you will notice your belts get dull faster and that it takes more of them to grind this alloy - in relation to other simple steels that is!

 

~Bruce~

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Love it. Another instance where the tried and true rules on heat treating, in this case no soak for hypoeutictoid other than to heat it all the way through, meet an exception to the rule.

 

Doug

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Just to repeat what others have said... I've used 6150 to make hammer heads. It is quite tough stuff to forge by hand if you're using large sections of it (in my case 2.5"x2.5"). And yeah the soak is important on the HT for it.

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@Bruce and anyone els,

What is " austenitizing temperatureing " exactly? I read some place about using sand to slowly cool it before putting it in oil,am I on the right track???

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Austinization temperature is the temperature that a steel alloy will change from a body centered cube to a face centered cube. The reason that it's important is that this conversion is necessary to dissolve enough carbon into the iron matrix of the steel to allow for hardening later. There are other heat treating options that depend on this change too. That temperature, depending on the alloy will be around 1400-1450°.

 

As far as the sand bit you are mixing up two different heat treating operations. The slow cooling in sand or other insulating material from the austinized state is refered to a annealing. This will make the steel softer and more machinable. It can also cause some problems with carbide growth so I usually don't recommend it. Just allowing the steel to cool slowly in air is usually good enough for grinding and drilling. Cooling in air, as long as we are not talking about an air quenching steel, is known as normalization which can be also be used to reduce grain size.

 

To harden steel by quenching requires, first of all, that the alloy have enough carbon in it to trap in the iron matrix and stress the atomic bonds between the iron atoms in the crystals. Then it must be cooled quickly enough that these carbon molecules cannot escape the iron crystals before the crystals change phase. Tempering is where some of that carbon is allowed to escape to decrease the stress on the bonds and reduce the hardness. The exact temperatures for this and the hardness that can be obtained vary with the exact alloy.

 

Doug

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Cook, here's somewhere you can get some information on heat treating basics. Go to KnifeDogs.com Forum > Knife Makers Area > Heat Treating Forum on KnifeDogs > the sticky at the top of the page: Heat Treating Tool Box. Copy it and read. This will give the a sketch of what we are talking about with heat treatment and it's about the best out there and it's free. The author, Kevin Cashin, isn't a metallurgist but he is a professional knife maker who has studied the subject and is able to do a lot of his own testing. I think that it will help you a lot to understand what's going on.

 

Doug

Edited by Doug Lester

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Austinization temperature is the temperature that a steel alloy will change from a body centered cube to a face centered cube. The reason that it's important is that this conversion is necessary to dissolve enough carbon into the iron matrix of the steel to allow for hardening later. There are other heat treating options that depend on this change too. That temperature, depending on the alloy will be around 1400-1450°.

 

As far as the sand bit you are mixing up two different heat treating operations. The slow cooling in sand or other insulating material from the austinized state is refered to a annealing. This will make the steel softer and more machinable. It can also cause some problems with carbide growth so I usually don't recommend it. Just allowing the steel to cool slowly in air is usually good enough for grinding and drilling. Cooling in air, as long as we are not talking about an air quenching steel, is known as normalization which can be also be used to reduce grain size.

 

To harden steel by quenching requires, first of all, that the alloy have enough carbon in it to trap in the iron matrix and stress the atomic bonds between the iron atoms in the crystals. Then it must be cooled quickly enough that these carbon molecules cannot escape the iron crystals before the crystals change phase. Tempering is where some of that carbon is allowed to escape to decrease the stress on the bonds and reduce the hardness. The exact temperatures for this and the hardness that can be obtained vary with the exact alloy.

 

Doug

@Doug,Thanks a lot that explanes a lot,a big help :)

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Cook, here's somewhere you can get some information on heat treating basics. Go to KnifeDogs.com Forum > Knife Makers Area > Heat Treating Forum on KnifeDogs > the sticky at the top of the page: Heat Treating Tool Box. Copy it and read. This will give the a sketch of what we are talking about with heat treatment and it's about the best out there and it's free. The author, Kevin Cashin, isn't a metallurgist but he is a professional knife maker who has studied the subject and is able to do a lot of his own testing. I think that it will help you a lot to understand what's going on.

 

Doug

@Doug,This is what I all put in my folder,Basics Of Heat Treating; Building Our Toolbox Normalizing

Annealing

Hardening Part 1

Hardening Part 2

Tempering

Chemistry considerations in heat treating operations

 

:):)

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