I think I need a new heat treater

[JNewman]

A few weeks ago I forged 50 scraper/chisels for a customer out of W1, quench and tempered to 50-65 Rc. which is what the customer specified. The chisel is 1" diameter then is a 3/8 thick blade tapering down to a 1/8" thick square edge. In heat treating them myself I had two of them crack near the edge so I had to make one more, I should have made the extras to begin with but this customer will not accept extra parts so I didn't want to sit on the inventory. I had 30 more to make this week so I made 34 of them and decided to take them to my heat treater to avoid the cracked parts and because I have a fair bit of rush work right now and I figured that they could do it cheaper than me anyways. I went to the heat treater this morning to pick up the parts and deliver them to the customer they had cracked SEVEN!!! out of 34. I now have to make more chisels and the job is already late. I questioned the guy at the heat treater trying to figure out what they did differently than I had.

I had used warm water to quench the parts, they had used BRINE!!! he claimed that with W1 using water the hardening would only be .030 deep I can see this in a part a few inches thick but this is only 1/8" thick in the area that has to be hard. Do any of the Metallurgists on here know how deep the hardening would be on a 3/8 thick piece of W1? I think when I heat treat these I am going to re-harden on of the chisels that is cracked on the tip cut it appart at the 3/8 end and see if it is hard. Till now I have been very happy with this heat treater but this experience has me questioning there knowledge.

[Nakedanvil - Grant Sarver]

Well I'm not a metallurgist, but in that cross-section I'd have quenched them in oil and gotten high 50's.

[Mainely,Bob]

Seems to me that your heat treater should have looked closely at the work,known if it was possible to do the work within your specs and once he accepted the work(without cautions)then he`s responsible for the pieces from there on.If there was a glitch in his controller and all the pieces were ruined then what would have happened?
You had already determined the loss ratio thru your own experiments.His job was to reduce that ratio not multiply it times 4.
Just my $.02.

[JNewman]

I had quenched them in water because that is what the drawing called for. I just quenched one of the broken ones in oil and one in water the oil quenched one seems plenty hard. I am tempering them both at 450 for an hour and I am going to mill or zip cut off 1/8" and see how hard they are. Assuming they are hard at depth I think I will take them into the heat treater and get him to throw away the bill. He did cut the bill but I am paying him for his knowledge as well as his equipment.

[Nakedanvil - Grant Sarver]

I hate specifications that dictate the method rather than the result. Results should be all they care about. They want to dictate the method, but then they want you to be responsible for the results. Usually go nearly 1600 for oil, but brine quenching should be done from 1450-1500.

[JNewman]

I checked the hardness on the broken one I quenched in oil from about 1500 after tempering. I ground off a little to remove the decarb. and it came in as between 50 and 55 Rc. I think on the higher end but my hardness tester is a set of Tsubosan files so I cannot be sure. However it is inside specs. I am still going to check the hardness at 1/8" depth and also compare that to a water quenched sample.

[Nakedanvil - Grant Sarver]

Having done a gazillion (or maybe even a bazillion) points and chisel in oil I can attest to their toughness even heated to 1600 and oil quenched - no draw. Lotta 1078 and 1080. I often checked my work by hanging 3/4 of an inch off the edge of the anvil and trying my darnedest to break it off with a 3lb hammer. Amazing stuff, carbon steel.

Oil quench for W-1 is recommended 1550-1600 (Carpenter). I would expect everything back to 3/8 thick to be full hardness.

[JNewman]

I machined 1/8" off the oil quenched sample (Carbide inserts are great) and at that depth it is just as hard as the surface. If the oil one is that hard the water one will definately be as hard. I will quench from slightly higher temperatures next time and quench in oil. Well at least I have learned from this, but I think I will be dropping by the heat treater tomorrow.

[forgemaster]

Hey Grant

Funny how even though blokes are on different continients, we still all use the same methods to test points and chisels, over the anvil and whale s_it out of it with a hammer, nope did;nt break, into the bin with the others. We normally oil quench from 850 deg C then "flare" the oil left on the tool off with the Oxy when they have cooled down. (after we pull them out of the oil and let them drip for a few minutes)

Phil

[dimenickel]

Hi J

when the edge cracked.. did it look sort of sandy/grainy... or was the break smooth like when you crack a file in two ..
- it may have been some grain growth from high forging temps... and may need some normalization cycles to bring the grain size down and lower some of the stress

watch your heat treating temps.. too high and grain growth will happen quickly with shallow hardening steels..

and make sure to temper properly

was there an alloy spec sheet that came with the W1... as W1 has a very wide carbon/alloy content..


Greg

[JNewman]

They had run at least one maybe 2 normalizing cycles. When I heat treated them I normalized them as well. The grain structure on both my heat treatment and the heat treaters was very small. The surface was very smooth. One thing that was different between the ones I had crack and the ones they had crack, was the cracked surface was blue on the ones they did and gray on the ones I did. So they cracked on them while the steel was still hot while the ones I did cracked after they had cooled.

Forgemaster can you give more information on flaring off the oil? You have also mentioned reheating forge tools to the igniton point of the oil to temper them. How do you keep all the oil from burning off in the forge while reheating them before they get to the flashpoint of the oil?

I quenched the replacement chisels in oil and tempered them to 450F and they seemed hard enough. After this I was talking to a retired smith who worked at the steel mill these are going to he told me that they often just placed these by the bottom of the shop door in the winter and the cold air was enough to harden them.

[ArtWerkz]

I found this online John.
TREATMENT

TEMPERATURE RANGE

COOLING/QUENCHING

NOTES

FORGING

1700-1900° F

In air.

Heat slowly to maximum temperature. Forging should begin as soon as the section is uniformly heated through.

ANNEALING

1400-1450° F

Cool slowly in the furnace at a maximum rate of 50° F per hours..

Protect against surface decarburization by pack-annealing. Hold at temperature for 1 hour.

STRESS RELIEVING

1200-1250° F

Cool slowly in air.

Stress relieve after rough machining

PREHEATING

1200-1250° F



Preheat time in furnace is ¾ Hr. per inch of thickness.

HARDENING

1375-1450° F

In water or in a brine solution.

Small tools or parts may be heated in molten lead or in a salt bath. Soak time is 10 minutes per inch of thickness. Minimum of 30 minutes.

TEMPERING

(See Chart)



Temper immediately after hardening and quenching. Recommended temperature is 350-550° F.

[dimenickel]

Hi J

pending on the carbon level... you have to look at the temp of your normalization....... eg .9 to 1.10% carb would require higher normalization temp.. say about 1600F... to deal with carbides being in the wrong place or just to have all the C in solution..

i use timken W1 and i'll normalize 3 times with a descending temp... then i'll heat to 1450F and hold for 5 to 10min but thickest i deal with 1/4inch.. and a hold for 5min at 1200F for preheat....

generally if you go above .8% carb the heat treat gets more complicated..


if grain was small.....that is good... but it might not deal with grain boundary carbide... which can be trouble

w1 is a shallow hardening steel.. it wouldn't harden much by aircooling... but if it was s7, then the shop door might work.. ( but you could have untempered martensite... ouch )
-I'd do things by the book.. homebrew heat treats are fine for some, but if i'm going to tag my name to something, i'll do it by the book... the asm book if you have

Greg

They had run at least one maybe 2 normalizing cycles. When I heat treated them I normalized them as well. The grain structure on both my heat treatment and the heat treaters was very small. The surface was very smooth. One thing that was different between the ones I had crack and the ones they had crack, was the cracked surface was blue on the ones they did and gray on the ones I did. So they cracked on them while the steel was still hot while the ones I did cracked after they had cooled.

Forgemaster can you give more information on flaring off the oil? You have also mentioned reheating forge tools to the igniton point of the oil to temper them. How do you keep all the oil from burning off in the forge while reheating them before they get to the flashpoint of the oil?

I quenched the replacement chisels in oil and tempered them to 450F and they seemed hard enough. After this I was talking to a retired smith who worked at the steel mill these are going to he told me that they often just placed these by the bottom of the shop door in the winter and the cold air was enough to harden them.

[Nakedanvil - Grant Sarver]

For me "the book" is a starting place or a reference to see if the procedure being used makes sense along side the book. Experience IN USE trumps "the book" every time. The book is dealing with a lump of material of a certain size. Tools, on the other hand, can be of size, shape or use never imagined by the author of the book. The book just adds to my "knowledge base".

You ever break a high carbon steel magnet? Huge crystals. There is no "right" answer for everything. Fine grain makes for a less crack prone tool, but large grains can give a higher ultimate hardness. And taken to the extreme, a single large crystal can be harder and tougher than either. The choice comes down to intended use.

"The book" is a general purpose answer, specific to nothing. It also requires you to make "inferences" based on their test piece compared to your work. They are using a de-carb free .505 diameter ground and polished test piece, are you? Not even good heat treaters duplicate laboratory test conditions.

[Nakedanvil - Grant Sarver]

Hi J


w1 is a shallow hardening steel.. it wouldn't harden much by aircooling... but if it was s7, then the shop door might work.. ( but you could have untempered martensite... ouch )
-I'd do things by the book.. homebrew heat treats are fine for some, but if i'm going to tag my name to something, i'll do it by the book... the asm book if you have

Greg

And yet the customer was happy with the result. Who do you want to satisfy?

[dimenickel]

Hi Nakedanvil

sorry...don't want to step on any toes.. just wanted to help J with his cracking problem.. as he indicated that he was unhappy with the failure rate..

in the end ...both J and customer should be happy..

And yet the customer was happy with the result. Who do you want to satisfy?

[Nakedanvil - Grant Sarver]

Sorry dimenickel. Guess you just got me started on a rant that unleashed here. Not meant for you in particular, just a general view of mine that you uncovered. Sometime things just get triggered by the simplest reference. You just brought up an interesting subject.

Don't worry, my toes are Rc 50! Hope I didn't damage your toes.

OBTW: I was talking about the customer being happy with tools quenched "by the door".

[JNewman]

I don't plan on using the by the door method although that was the method sometimes used by their internal shop despite what the drawing says. I had good results using oil and I think I will continue with this. These chisels are for scraping tar off coke oven charge doors and cleaning carbon deposits out of pipes in the coke ovens. They are definatly a consuamable and in use are often heated way past the draw temperature, when they had their own blacksmith shop they would often straighten them after them being badly bent.

[forgemaster]

They had run at least one maybe 2 normalizing cycles. When I heat treated them I normalized them as well. The grain structure on both my heat treatment and the heat treaters was very small. The surface was very smooth. One thing that was different between the ones I had crack and the ones they had crack, was the cracked surface was blue on the ones they did and gray on the ones I did. So they cracked on them while the steel was still hot while the ones I did cracked after they had cooled.

Forgemaster can you give more information on flaring off the oil? You have also mentioned reheating forge tools to the igniton point of the oil to temper them. How do you keep all the oil from burning off in the forge while reheating them before they get to the flashpoint of the oil?

I quenched the replacement chisels in oil and tempered them to 450F and they seemed hard enough. After this I was talking to a retired smith who worked at the steel mill these are going to he told me that they often just placed these by the bottom of the shop door in the winter and the cold air was enough to harden them.

I will add here that I assume you are using quenching oil, if you are doing comercial work you should be using proper quenching oil not old motor oil.
To flare oil off tools like points and chisels we normally use the oxy set up on a stand, we have another stand just in front of it and a bit below that we can rest the tool on to get under the oxy flame, (using a cutting torch here), Have the flame set fairly soft and just run the chisel up and down and around under the flame, don't concentrate on the edge to much it will heat up the quickest, put more attention into the back of the tool to about 2" back from the edge. Move the tool back and forth until all the oil is burnt off and there is no more flashes of flame. To flare larger tools in a forge fire we used to bury say a piece of 2" plate in the forge get that hot, turn the blast off then sit the tool we wanted to temper onto the plate, turn it over periodically to allow it to heat evenly, watch till you see the oil begin to flicker to flame. We also used to do coil spring the same way using a large piece of pipe buried horizontally in the fire with the ends open, place the spring inside it, carefully turn it to get an even heat, as well as move it back and forth, till the oil catches fire. Zip boom your spring is tempered, take it out and stick it on the floor.
Motor oil usually has combustibles in it which makes it more susceptable to ignition.
I can normally teach a kid to put a point or chisel on a tool in a day or two, teaching them how to heat treat them sucessfully takes a little more time, effort and tears on my behalf.

Phil

[JNewman]

Thanks for the info, I have been breaking fewer hammer tools since I started using the flashing oil technique. I have been heating them back up in the gas forge with the burners turned off and pulling them out and splashing a little more oil back on, but I will try using a heavy block. I am using quench oil I bought 40 liters of it a few years ago.

[forgemaster]

Heating up till the oil flashes in a furnace turned off is good, thats the way we used to do hammer tools before we got a tempering furnace. the slower it happens the better,as it gives the heat time to penetrate in more. You can also use the greasy stick if you want to go for a higher temperature, say to 480 - 520 deg C, oil flashes at about 350 deg C I think.

Phil

[bigfootnampa]

Heating up till the oil flashes in a furnace turned off is good, thats the way we used to do hammer tools before we got a tempering furnace. the slower it happens the better,as it gives the heat time to penetrate in more. You can also use the greasy stick if you want to go for a higher temperature, say to 480 - 520 deg C, oil flashes at about 350 deg C I think.

Phil

Phil;

Speaking of your greasy stick method, I have been using it to check temp for hot-setting tangs into handles and find it quite helpful. Thanks for sharing it with me! I use an oxy-propane torch and heat the tangs fairly quickly just until the stick begins to slide... so staying to the lower end of the greasy stick temps and then holding the tool with heavy tongs at the base of the tang, I tap the (previously step drilled) handle against the anvil and the weight of the tool and the tongs drives the tang into the handle. The heat allows the wood around the tang to compress and cooks the resins making them a sort of natural ferrule cement. Thus the tool is captured in a VERY durable way. The compression strengthens the tong socket. I have had such success with this method that I use it for tools that have heavy withdrawal forces (like scorps or drawknives) with absolute confidence. You may note that this system of handle setting has the side benefit of automatically drawing temper in the tang to eliminate any brittleness there (though I mostly heat treat in such a way as to leave this area only slightly hardened anyway). I used to have a little trouble judging the temps and would occasionally misjudge and get the tang halfway in and have to scramble to remove it so that I could reheat it... this greasy stick method eliminates those problems. I've also been using the oil-flash tempering on some of my tools and knives and it is very fast and seems to be doing a good job where I have used it. So THANKS Phil for sharing your knowledge!

[Sam Salvati]

Are you heating these parts in a forge, kiln, salts?

[Frank Turley]

Nakedanvil has been around the block, so I would pay attention.

I'm a smith, not a metallurgist. I read years ago that W1 was a shallow hardening steel. I can't find the source, but the reference stated that W1 below 5/8" thick will harden all the way through. If over 5/8" quenching will produce a "case-core effect." You'll get a hard case and a tough core. The word 'case' is used here, but it has NOTHING to do with case hardening (carburizing). On the 5/8" and larger, the size of the material slows down the rate of heat abstraction, which is the reason for the shallow hardening effect.

An old Bethlehem booklet stated that when quenching W1, oil can be used on thin sections. The booklet did not define 'thin.' I would reckon that 1/8" or less as with a chisel or knife, is 'thin.'

http://www.turleyforge.com Granddaddy of Blacksmith Schools

[forgemaster]

Thamks guys for the feedback, it's nice to know that I'm not here divulging the tricks of the trade with no-one paying any attention.
Anything I can do to assist I'm happy to help.

Cheers
Phil