CSteel vs Iron?

[nashdude]

Since I get most of my knife steel from old tools or junkyard/metal yard scraps, I could seriously use some tips here. And as I'm scroungin', I really don't have the resources to send the metal off to be tested

Now, I know that you can tell pretty much any iron-based metal by its magnetism. Also, I know you can tell stainless steel from carbon steel by the type of rust that coats it. Stainless is generally dusty, surface rust. Carbon steel is generally a much harder rust---very little dust, a good deal of pitting.

What I'd like to know is if there is any similar way to tell the difference between steel and iron? Is there any backwoods way to tell what metal is what?

[Dave English]

The problem won't be figuring out the difference between iron and steel, pure iron is hard to come by and has become a specialty metal, most of the time your problem will be trying to discovery how much carbon is in your steel. Wrought iron will often fracture if it's worked at too low of a heat and if bent over too much, the surface can crack. Pure iron (today) can be found in generator cores, some types of pipe, water tanks and other special applications. I'll let the others talk about steels.

[LarryM]

nashdude, The best way to identify unknown steel is the use the grinder spark test. I won't go into detail but just spark test steels that you do know the carbon, alloy content of, and compare with unknown steels. There is also pictures available to compare with. This is not an very accurate way to do it but It will give you and idea. You can also just experiment with heat treating different steels. There is a lot of info either on the internet, books to get you started. If you know what the steel was used for in it's previous life that will get you a place to start. Like most of the people will tell you if you are making something special (For Example Knives) use new know steels.

Larry

[nashdude]

nashdude, The best way to identify unknown steel is the use the grinder spark test.

EXCELLENT! Thanks for the tip, Larry---it proved very fruitful. On a Google Search, this is what I found...

A great advantage of this form of test is that it can be carried out on the steel at any point, e.g.. as a billet, an ingot. a bar, a forging, or often a finished piece. The test is carried out on the steel as it stands, and the elaborate drilling of separate samples with the possibility of confusion is eliminated. At the present time, also, the test has great utility, because it enables pieces of undesired metal in a batch of different composition to be picked out quickly and cheaply, and set aside for scrap or salvage, whereas to have to analyse them chemically would constitute a prohibitive charge.

The principle on which the test is based is this: The effect of bringing a piece of steel into contact with the face or cutting edge of a grinding wheel is to force or wrench off tiny fragments of the steel. The wheel runs at a high speed, and the friction is so great that the temperature of these fragments is raised to such a height that they become white hot. This makes them brilliantly visible against a dark background, and their passage through the air as they are flung off has an almost comet-like trajectory, which is termed a " carrier line."

The basis of the test is that different metals give off sparks or particles of incandescent character each having a different trajectory and form. For example, wrought or ingot iron will give off a little bundle of individual lines called a " spark picture." A O.2 per cent. carbon steel will give a line of brighter colour and will throw off a series of fine branches from this line known as " forks," or " primary bursts." These are due to the presence of carbon. It will thus be seen that wrought iron can readily be distinguished from carbon steel by means of the spank given off.

Raising the Temperature. The effect of raising the temperature of a metallic particle to white heat and hurling it through the air at great velocity is to cause any carbon existing in the fragment to combine with oxygen in the atmosphere to form carbon dioxide. The change from solid carbon to gaseous carbon dioxide results in an increase of volume. This increase of volume is withstood to the best of its ability by the particle, and the result is the setting up of an internal stress that ultimately leads to the complete disruption of the particle thus causing the fork or burst responsible for the branching out of the line. This, at all events, is the theory. The greater the percentage of carbon in the steel, the more marked is the branching effect, and this has proved fairly conclusively that carbon is the element causing these forks or bursts.

Examples. A few examples will serve to illustrate these facts:



Fig. 1 shows cast iron, which possesses a dull red, non-explosive spark that thickens towards the end. Fig, 2 shows wrought iron, whose spark is brighter, as indicated, and has a luminous extremity. If any traces of carbon are found in the iron, the extremity may reveal a burst or fork.

Fig. 3 shows mild steel. The thick, luminous iron spark is broken up by the branching due to carbon. Fig. 4 shows a 0.60 per cent. carbon steel spark. The tendencies have virtually vanished, and the carbon branching occurs nearer to the grinding wheel. Fig. 5 shows a high grade tool steel containing carbon. Fig. 6 is high-speed tool steel. An odd carbon spark or two are to be seen, but the rest are modified by the other alloying elements. The sparks are of an orange hue, and vary in brightness as they travel, giving the effect of an interrupted line, while they have a more luminous tip.

Fig. 7 is high manganese steel. In this case the spark is different from that of the carbon spark inasmuch as the explosive particle leaves the luminous line at right-angles. and the sub-division of explosions is also at 90 degrees, as against the 40-50 degrees of the carbon sparks at Fig. 3. Fig. 6 is self-hardering Mushet steel. Here an odd manganese spark is visible, and the relatively high tungsten percentage appears to give discontinuity to the spark. Finally, Fig. 9 is a tungsten magnet steel. Here can be perceived the respective sparks of manganese tungsten and the like.

EDIT: Also found this video on YouTube which demonstrates the above info. YouTube - How to tell the difference between cast iron and steel

Again, thanks for the tip :) Edited January 17, 2009 by nashdude

[Woody]

I have a list of the usual type of steels found in various pieces of junkyard steels, ie. springs, axles etc and I have a chart that shows the compositions of many types of steel if you send me youe email addrese via the private message feature on this forum I will email it to you. It is in MS Word Format

Woody

[matt87]

There is a blueprint on junkyard steels, along the same lines as Woody suggested. IT is important to point out that these are not a guarantee; it's an 'educated guess' based upon past testing of these items and some thought as to what the engineers who designed them required.