PDA

View Full Version : Hardening Steel



R. McAuley 3014V
09-09-2010, 11:37 PM
When hardening steel gun parts, how do you determine the right instant when to quench the part to obtain maximum hardness? Or is this achieved only through trial and error?

Eggman
09-10-2010, 10:58 AM
I heat it with a standard propane torch, sprinkle Kasenite on the critical surface as it gets real hot, then quench it in water when I see the metal begin to glow red. Takes quite a bit of time before you begin to see this. A metals factory guy (Dave Ferguson) taught me this.

Southron Sr.
09-12-2010, 06:27 PM
First of all, the CASEHARDENING is only a thin layer of carbon on the surface of steel-that layer is what makes the steel "hard."

HOW I HARDENED A FLINTLOCK FRIZZEN:

I wrapped the frizzen in some old leather shoe laces (making sure that they were REAL leather first!) Then I wrapped everything in a tight ball of aluminum foil, about a dozen layers thick. Then I placed the aluminum foil ball containing the part in my fireplace and build a blazing fire on top of it. As it was winter time, I kept adding logs to the fire until I went to bed.

The next morning I sifted thru the ashes and pulled out the aluminum foil ball. The foil fell away and I had a flintlock frizzen that was a dull gray color. When I installed it on my repop St. Etienne, it sparked wonderfully. It was casehardened.

HOW I "COLOR CASEHARDEN" A REPRO LOCKPLATE:

Polish the lockplate. Lay it on a rock and then sprinkle an ample amount of Kasenit on it. Using a propane torch, heat the lockplate to a red color, playing the flame back and forth across the face of the lockplate. Drop red hot lockplate in can of motor oil. It will come out with beautiful "case colors"!

Michael Bodner
09-13-2010, 08:27 AM
Hardening steel is, for us torch and fireplace folks, more art than science. If you have a furnace capable of 1800 degree temperatures (accuratly), you can woek with steel very easily!

But basically, hardening steel is a) bringing the metal to a specific temperature. The cool part of this is that at any particular temperature, the steel will exhibit a particular color. Its getting to understand how to relate the color to a specific temperature range. If it isn't hot enough before quenching, it will be too soft. If its too hard, it will be too brittle. Step b) is to plunge the object into water (or oil) to quickly cool it. This makes the metal hard, but also, brittle. Depending on if it needs some flexability, like a spring, it will need to be tempered, which is basically, reheating it to a much lower temperature than before, and then allowing it to slowly cool. The key word here is slowly.

Use Kasenit allow you to reach higher temperatures than what you can obtain with just a propane (or Mapp) torch. It brings you higher up the temperature/color scale.

Do some Google searches on hardining metal. Look specifically for color/temperature charts. That will get you started.

BTW: The reason a blacksmith shop is often dark, was to allow the Blacksmith to see the glowing metal easier and to distinguish the different subtly colors more easily.

Good luck!!

-Mike

Eggman
09-13-2010, 11:28 AM
I should have clarified that all the hardening I've done was to achieve (or reachieve) surface hardness - like the full cock notch on the tumbler after stoning, or the full cock notch on a revolver hammer, same purpose. Frizzen hardening is an art - have watched it done - the hardening (again still using Kasenit), then the drawing out based on color to eliminate brittleness. Old round ballers have seen many a frizzen snap in two when struck by the flint when not done perfectly. Anyway, can't remember what the frizzen was quenched in but it might have been oil. My friend always used a torch.

Southron Sr.
09-13-2010, 04:03 PM
Now if you want to harden steel absoutely correctly, Brownells sells an electric furnace in their catalog that cost a bit over $500.00 (the last time I checked.)

R. McAuley 3014V
09-13-2010, 09:18 PM
Was just curious what method others were using, and see whether anyone else was using this method:

Magnetic Test for Heat in Hardening Steel

When hardening steel one must know the proper point at which to quench it to obtain the best results. Workmen who do this kind of work regularly, learn to gauge the point of quenching quite accurately, but for the amateur, steel hardening presents many difficulties.

A very simple method by which anyone who wants to harden a few tools may obtain as good results as a professional mechanic, though, perhaps, it will take him a little more time, is by the use of a magnet. The temperature at which steel should be quenched to secure the maximum hardness is just above the point where the carbon in the steel changes from the free to the combined state. Curiously enough, at this same point steel becomes non-magnetic, and by taking advantage of this fact one can harden steel almost perfectly. The ordinary horseshoe magnet is not sensitive enough to show this change, but the balanced magnet illustrated the point is clearly indicated.

Tool steel is preferable for the magnet, but any steel that will harden can be used. A piece of saw steel, or even an old file ground smooth, can be used. Anneal it and then saw and file to shape shown in Fig. 1, and drill a 3/16-inch hole for the pivot, being careful to get the hole perpendicular to the faces. Balance the magnet on a small nail placed through the hole. If it does not balance, take some metal off from the heavier end until it hangs exactly horizontal. If possible, grind the faces parallel and finish it all over. Harden by heating it to a medium red and then quench in water. The metal should be polished, as it movements may then be seen much better in the dim light of the forge. Magnetize the steel by touching it to one of the field poles of a running motor or generator, or wind several hundred turns of fine wire around it, and pass a direct current through the coil thus formed. Only a moderate degree of magnetization is necessary.

Make the support of brass, ½ inch square. Round up one end and square the other as shown in Fig. 2. Drill holes with 5/32-inch drill and then cut the slot. Tap the holes for a machine screw and ream or drill out the hole on one side of the slot to 3/16-inch. Make a headless screw of 3/16-inch brass rod, as shown in Fig. 3, setting a thread on one end and slotting the other with a hacksaw. Leave it a little more than ½-inch long, so that if can be filed up flush with the hanger with in place. Assemble these three parts as shown in Fig. 4 and see that the magnet is free to swing easily through it entire arc.

A piece of 3/16-inch iron rod, 18-inches long, is used for a handle. Threads are cut one end so that it can be screwed into the upper part of the hanger. An old file handle is driven onto the other end of the rod.

The work is heated to a dull red and the point A of the magnet, held by the handle, is applied to the heated part. If a chisel is to be hardened, it must, of course, be tested near the cutting edge where it is to be the hardest. If the magnet sticks to the work, heat a little more and try again. When the work gets to a medium red, it will be found that there is no attraction for the magnet. This means that the hardening point has been reached and passed a little, so the work should immediately be plunged into brine, water or oil, according to the degree of hardness required. If the steel is chipped a little, it will be found to have a very fine grain and is therefore very hard. This method, while not speedy, will produce good results, if care is taken to watch the actions of the magnet.

[Popular Mechanics Magazine, Vol. 18, No. 4 (October 1912), “Shop Notes,” pp602-03.]

http://i267.photobucket.com/albums/ii305/rmac1023/Fig1.jpg

http://i267.photobucket.com/albums/ii305/rmac1023/Fig4.jpg

John Wells 3rd US
10-26-2010, 08:06 PM
Kit Ravenshear was a fantastic gunsmith for antique firearms. His pamphlets are a goldmine of techniques and ideas on recreation, repair, and restoration of classic weapons. Here's a link to his homepage, I guess maintained by his widow or daughter. the pamphlets are still available. There's a good one on metal treatment. Dixie, Dixon's, and others have them.

http://www.kitravenshear.com/

firelock
10-27-2010, 10:00 PM
When in doubt about what alloy of steel you are working with, heat to cherry red , quench in oil. Test with a old file ,if hard the file will skate not cut. If the part is not hard then reheat and quench in brine. Brine is a more violent quench and can crack steels meant to be oil quenched. Then you need to polish the part and temper by heating the part till it comes to a particular color. Home heat treatment is almost as much art as science. Trial and error is as good a teacher as any as long as you quench in oil first. If oil does not work then quench in brine. Make sure you heat the steel to the non magnetic point pluss a bit brighter color. If the part still does not harden then it must be case hardened using casenite or pack hardening with leather scraps,bonemeal and ground charcoal. Quench in oil. Ther's more to it than this three cent overview but it is easily learned from a veriety of sources.

John Wells 3rd US
10-28-2010, 06:55 AM
When drawing temper, the heat has to be applied VERY slowly, as the polished part moves through the color changes rather quickly. There's a product called Tempi-lac which is like a paint that is applied to the part if you're uncertain about this. available in several temperature ranges, it essentially melts at the temp desired for the part being tempered. I think Brownell's used to carry it, no doubt other sources as well.

R. McAuley 3014V
10-28-2010, 07:53 AM
I introduced this topic upon account of discovering the 1912 article on magnetic testing for hardening steel since most of the lock parts that skirmishers may occasion to harden are made of steel* rather than iron. At this past National, upon coming off the firing line I discovered that the firing pin carrier of my Spencer centerfire breechblock was shattered into three pieces. It was the drop-in breechblock sold by S&S Firearms, and was presumably hardened by them or their supplier. I took the breechblock by S&S's sutler store to see if they could remove the inner broken off portion, which with some effort finally came out, and I replaced the part with a new one (for $35), but S&S said how they had never seen this occur with this part. Of course, there is no expressed warranty on any of their products, but this issue could perhaps have been avoided had the part been properly hardened, and then tempered to reduce its brittleness.

*see link below for thread regarding the types of steel used in making firearms at Springfield and Harpers Ferry Armories:
viewtopic.php?f=32&t=14163&start=15 (http://n-ssa.org/phpBB3/viewtopic.php?f=32&t=14163&start=15)

DAVE FRANCE
10-28-2010, 09:38 PM
Heat treating steel is a well understood science for those who are educated in that area.

I had an original Enfield tumbler break in a rifle I had. I took another to the metallurgical department for the company I worked for. We guessed what metal it was (low carbon steel with case hardening) and they got it up to the temperature given in a book for that material, cooled it (I don't think it was quenched), heated it up to the tempering temperature from the book, let the temperature drop at the rate the book said, and it was better than new when it was made in the 19th century.

When you don't have the exact information you need, and equipment to heat to an exact temperature, etc.....
It is risky. A famous example is the low number 1903 springfields. They knew what material the receivers were, but they could not control temperatures accurately, and some ended up being too hard and brittle. Part of what was done to stop the problem was to add alloys to the steel that prevented the brittleness. Some of the alloys added to steel are to keep it from cracking when heat-treated.

Companies that do a lot of heat treating use the cheapest steel they can that will work reliably. Screws ( think bolts ) are made of materials that are picked for the final hardness and material properties desired. The highest grades for critical fasteners ( think connecting rod bolts and cylinder head bolts) are made to a material spec that includes what stress range the screw has to yield at and what load that will be. That means the bolt can be tightened by computer controlled equipment in the assembly of an engine, and the clamp load range will be a very low range and at a very high level for the size bolt used. So these fasteners are made to a hardness of RC 34 to RC 39. It can be a real serious problem if it goes above RC 40. It is likely to fail in fatique.

Connecting rods used to be forged steel. Later they were mostly cast nodular iron (like many bullet molds) and now they are mostly powdered metal (also called sintered steel). These have been around since the 80s. They are steel but made in dies from a steel powder, then compressed in dies under heavy loads, and finally heated and heat treated. ( I may have the details wrong.) Then the rod is cracked along a groove created in the dies for that purpose. And when the rods are connected to the crank, bolts are used to hold the two halves together.

There is a national standard for screws because of the accidents that occurred with poor quality fasteners that did not meet the standards they were supposed to be made to. Think of aircraft engines falling off, suspended overhead structures that people walk on, seat belt anchor bolts, etc. Making fasteners that are supposed to meet high level strength levels, and if they don't can land people in prison. (I think the airliner that crashed years ago lost an engine - it fell off - was because of the way it was assembled - the fasteners were not defective.)

I am not sure, but I think worrying about grain flow in highly stressed metal parts is no longer important.
Connecting rods don't have a grain now. And crankshaft can be made of a steel billet, with no grain at all. In fact I think some (maybe all) cranks used in the V-12 fighter engines were made from billets (not forged).

I know this is off the subject but it is connected with steel. Was this interesting to anybody?

David

Did you know that explosive bolts are used to separated the stages on missles, etc. and are used by the Army. You put a current across the leads and it explodes.