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Junkyard Steels :

Using recycled steel or steels of unknown pedigree

What steel is it?

This is a very common question on anvilfire and the answer is almost always the same.

YOU are now the metallurgist and YOU must make the determination.

Almost every blacksmith starts out using scrap steel. They use railroad spikes, auto springs and rebar to make all kinds of things. Then there comes a time when they want to know about hardening and tempering the steel they have been using and want to know if it is good for tools or knives. There is NO easy answer.

There are lists of "Junkyard Steels" posted on many web sites. We have one of the popular ones here in graphical format. There are many problems with this kind of list. Manufacturers change material for many reasons including price and availability and do not need to notify anyone. Manufacturers also consider many things including specific alloys a proprietary or trade secret. Manufacturers may use one steel on one product (or model) and another on a similar product and change either during a production run. It is THEIR decision. There is no way to tell.

One of the popular lists referred to is the SAE steel list from MACHINERY'S HANDBOOK This was a suggested list compiled in the 1940's and has changed little since. Many people using this list make the mistake of finding ONE recommended steel (say for springs) and assuming all springs are that steel. In fact the list has many steels recommended for springs if you go through the entire list, not just one or two. Machinery's lists recommends SAE 4140-50 for axels and shafts while modern manufacturers most commonly use SAE 1040 except for a few high performance applications.

There are literally tens of thousands of steel alloys in daily use. Many are so similar that only a very careful chemical analysis can tell the difference. Others are vastly different and their applications and heat treatments are also vastly different.

All you can do is test the specific sample (lots of trial and error), apply it as you best see fit and then test the next piece because you cannot assume any two similar pieces of Junkyard steel are the same.

If a product is important too you then buy new steel of a known composition.

Testing

Magnet Test
The first test that needs to be applied to an unknown metal is a simple magnet test. Is it magnetic? There are many alloys that LOOK like steel that are either stainless or non-ferrous (Monel, Nickle silver, Zirconium). A magnet is a good start. Note that some stainless steels are magnetic and that the non-magnetic varieties can become magnetic by work hardening. Try comparing your magnet to a known piece of steel about the same size. If the mystery metal is weakly magnetic then it may be a stainless.

Wrought Iron
If it is old soft material you may want to test for being wrought. Click link for specifics.

Spark Test
This is a common shop test that can be very handy. Note that it has some faults. In general the higher the carbon the more branches the sparks. Low carbon steel has long sparks with few branches and high carbon steel has positively fuzzy looking sparks. Alloys effect the spark and the best way to tell is with some comparison samples of known alloys.

Faults are primarily that different types of grinding wheels and speeds greatly affect the appearance of the spark. A hand held angle grinder makes a different spark than a bench grinder with fine wheel and that spark is different than one from a small high speed grinder like a Dremel tool. For this reason it is always a good idea to have some comparison samples of known steels. If you do all your testing on the same grinder in low light you can get pretty good at identifying varieties of steel. But using different grinders in different lighting conditions can often be fruitless.

Also be aware that a wheel that is loaded with a different steel may make sparks from the contaminate as much as the test sample. If possible dress the wheel with a diamond or carburundum dressing stick.

See spark test chart from Metals For Engineering Craftsmen

Hardenability
Heat a sample to just over non-magnetic and let cool in free air or gentle breeze. Test the hardness with a file. If the piece is very hard then it is probably a high carbon tool steel above 100 points carbon.

If it didn't air harden, heat a sample to just over non-magnetic and then quench in oil. Test the hardness with a file. A high hardenability steel will oil quench and be hard enough to resist a file used with anything less than very high pressure. Temper the piece to a straw and test again. Temper the piece to a medium blue (560°F) and test again. Try to bend the sample. At a blue most steels will be springy and will not break. However, tool steels over 100 points carbon may still be brittle and my break.

If the test piece did not harden then heat and quench in water. Test as above.

Note that even "mild" steel will harden if heated to an orange (400°F above non-magnetic) and quenched in cold water. However, it will temper soft at a blue or 560°F.

See out Heat Treating FAQ for more details.

If you have a hardness tester you can narrow the specs on the steel somewhat.

Tensile Test
If you have a tensile tester and machinery to make test coupons with you can further refine what you know about your mystery steel. Small tensile testers are ocassionally found used. Most are for testing weld samples but can be applied to other testing if you understand the principles. These devices have a pair of clamps and a hydraulic cylinder with gauge. A sample is made with a known cross section and radii blending out to the clamping pads. The cylinder is pumped up until it tears the sample in two. For detailed information on the steel you need to add a dial indicator and graph the amount of stretch until the steel yields.

This will tell you many of the steel's properties but still does not identify it as to alloy content. This kind of testing is probably most suited to smiths making Damascus commercialy that want to quantify its characteristics. However, for this purpose you are best off the give a sample to a metallurgical laboratory and pay them to do professional tests.

Selected Posts

I Have been told that vehicle trunks and hoods have been a higher carbon steel since about 1985. My grinder says a probable yes. Do any of you fellows know what steels they use or how to find out? I want to make some finger gauntlets. Thanks for the expertise,
- Oliver Shank - Sunday, 12/21/03

Oliver,
I worked for Ford Mo. Co. for 35 years, the last 17 years as a metal finisher on hoods and doors. In the 80's a new type of steel for surface panels was introduced that was harder to work with (lots of split corners), harder to dent and harder to repair. The only name I recall being used to refer to the new-thinner steel was bake hard! We were never told the composition. It has about the same properties as being case hardened.
Jerry - Tuesday, 12/23/03 02:04:06 EST
Steel for Cars: I can say a little about steel for springs - in the early 80's I worked for J&L Steel as a bar product research metallurgist. One of the things we were trying was development of microalloyed steel (relatively low carbon, doped with columbium (Nb) and nitrogen + I don't remember what else). The goal was to replace SAE 5160 for car springs, the advantage was that required properties would be reached by controlled cooling from the hot forming/forging operation thus eliminating the additional quench and temper required for 5160.

I got laid off in a force reduction when the steel mills went kaput in Pittsburgh, but I've seen an announcement in the last year or two in Metals Progress announcing the commercial realization of such a product, only about 20 years after I was playing with it. Hope the information is of some general use to all.
- Gavainh - Tuesday, 12/23/03 13:07:38 EST
Bake Hardening Alloys: These alloys are considered microalloys in that they have much less total alloy content than a regular alloy steel like 4140/5160. These alloys don't have a great deal of carbon, as the harden not from queching, but during the "tempering" of the paint bake cycle. I can't tell you the names or compositions, but I do remember hearing about them in school. They are probably not good for tools/knives ect., but they are very good for dent resistant applications.
Patrick Nowak (metallurgist) - Tuesday, 12/23/03 13:09:17 EST
On auto steels:
I read a lot about LAHS(low alloy high strength) steels for structuals, but had not heard about the spring replacement alloy. My current employer, forges axles. Conventional wisdom was that axles were 4141. Nope, not in 15 years, I'm told. Axles below 13/8" OD forging stock are 1050, and 1541H above in all the spec's I've seen. 1541H heat treats deep fast, and will quench crack on a dare. Use oil to quench and temper carefully.
- ptree - Tuesday, 12/23/03 16:25:21 EST
Microalloys and Bake Hardening: These are the kinds of things the junkyard steel user needs to know and avoid. The so called conventional wisdom that most auto springs are 5160 was just shot to pieces and the replacement is NOT a blacksmith friendly steel. On the other hand the bake hardening steel may be perfect for the armourer BUT the exact type and heat treatment MUST be known. . .
- guru - Tuesday, 12/23/03 16:10:30 EST

Recycling Ball Pien Hammers:
I've got an excess of ball pein hammers and no cross pein. Is it an easy task to convert my ball pein hammers and what sort of heat treatment will they need?
- Bob G. - Wednesday, 12/24/03 23:23:26 EST


Bob, It is no harder than reworking any tool steel item and is commonly done. You have to work it above an orange and below a yellow.

Typically the round face should also be reworked rectangular so that it has somewhat straight edges to work with. But this is a matter of preference. The flat face DOES need to be crowned and radiused more than is typical of a ball pien. Most are too flat for forging. After hardening and tempering the trick to making a truely useful metalworking hammer is how you grind the faces.

The only trick to reworking a tool steel item is that it IS an unknown steel. Various manufacturers used different steels for hammers and they will act differently to heat treatment. However, at least you DO know it is a tool steel. I would recommend an oil quench for safety. See our FAQs on Junkyard steels and Heat Treating.
- guru - Thursday, 12/25/03 00:00:05 EST

Guru,
At the company I worked at previously, as we diversified, the forge shop branched out form valve and fitting forgings into some job shop work. One of the jobs done was the forging of good quality commercial hammers. Sledge and cross piens, from a pound to 8 or 12#. All of these hammers were C1050, made in 4 blows on a mechanical press, and hot trimmed. They were heat treated prior to shipment.

Needless to say I managed to obtain several in every size and shape. most needed the heat treat. All needed finishing. I have made several custom styles including a couple of angle piens. As you noted the crowning is the trickiest part, with several I did needing several grinds to get them to forge and feel right.

The C1050 is, I believe about standard for American made production hammers. Several cheap Chinese made junkers I played around with were of different stuff! One forged about like cast iron, another like aluminum. I now have several Chinese types, dead soft, with textured balls for lite texture work, but found them to be to unreliable for real work.

ptree - Thursday, 12/25/03 08:41:09 EST

A friend of mine dresses stone masons hammers for a number of companies. Often the tools are good quality imported tools from Europe. Many of these appear to be alloy steels as they forge different and heat treat different. Ptree is probably right about American made hammers, but remember that many American companies are now having their brand of tools made over seas. Assume nothing.

-guru

Rail Road Steels
A standard text, Metallurgy, by Carl G. Johnson and William R. Weeks, American Technical Society, Chicago, 4th edition, 13th printing 1957, says track and wheel steel is low to high carbon, .60 to .70 % (pp. 223, 225). But things have changed a lot since 1957, so maybe RR steel has, too.

Miles Undercut, acting provost, Cracked Anvil Center for Analysis (Cracked's still locked up in there, working on, he says through the intercom, his riveting machine, with Chaz, Swarf and Yummi) - Tuesday, 10/09/01

Old rail road rails -- Someone gave me a neat little book called "Railroad Construction." It gives specs for rails as of 1921.

For Bessemer rails: Carbon is .40 - .50% for rails 70-84# per yard.
It's .45-.55 for 85# and over.

For open hearth rails:
.53-.68 carbon for rails 70-84#
.62-.77 carbon for 85-110#
.67-.82 for 111# and over.

Manganese is .80 - 1.10% for all Bessemer rails and .60-.90% for open hearth.

Mike B - Tuesday, 11/11/03 19:31:21 EST

RR spikes: HC RR spikes are 30 to 40 points of carbon. They make better letter openers than knives. Non-HC spikes were about 20 points of carbon. I have been told that NON-HC spikes haven't been made since the 70's. All current spikes are HC, but there are variations. If there is an additional "C" on the head, it means copper has been added to the alloy. I've seen the "S" code also, but I don't remember what it stands for. As for finding them, I just take a walk along some railroad tracks and pick up cast offs. A good time is after they do track maintenance.
- Rob Fertner - Monday, 12/09/02

General Recomendations

Springs of all types are usualy medium to high carbon steel except for stainless (work hardened) and bronze springs. Automobile leaf and coil springs are both good for making tools and knives. Many manufacturers and spring shops use 5160 for springs but not all. 5160 was a favored steel in the 1980's and was used for many things. Don't forget that sway bars are also springs and that small springs like valve and clutch springs are handy for all kinds of uses including as springs! Round springs like coil springs are actualy better for making things like swords because the cross section is much closer to reality and round flattens to diamond easier than flat forged to diamond.

Truck and Auto Axels have been a favorite for making hardies and hammers as they are one of the largest pieces of forged steel on an automobile. Note that the flange on some axels is the perfect shape for a mushroom stake with a little work. The splined end has been used for texturing. Listed as SAE 4140 in many junkyard steel lists our industry experts claim most are SAE 1050 and 1541H.

Old Tools: Recycling old tools into new things is one of your best choices. Pry bars and big old cold chisles are good tool steel (often 5160 and 1095). Big bandsaw blades are said to be L-6 but all Junkyard steel caveats apply. Blacksmiths commonly rework commercial punches, chisels and hammers.

Common Sense, Knowledge and Experience are key elements in using Junkyard steels. Study steels and heat treating before making assumptions then proceed as if the steel you are working is a complete unknown, it probably IS.

AND even though we are deluged in a bewildering variety of steels today, they are all better than the variable grade steels available 100 to 150 years ago and no more mysterious.

References and Links


Copyright © 2004 Jock Dempsey, www.anvilfire.com

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