My steel yard has volumes of 4150 tool steel in a usable size.

I typically use spring steel or 4140 for making top & bottom tools, tongs, and hammers.

My question is, can I exchange 4140 for 4150? If so, what is the difference in the two metals. I'm guessing 4150 has more carbon and would require a higher temp range for tempering. Am I right? Can it be cooled the same?

Thanks!

look at the spec sheet. I doubt there is a lot of temperature differance, but you will have better conversion to martinsite at 50 points of carbon.

Those specs may even overlap as the carbon content usually has some slop in it.

I just checked the ASM heat treaters guide for you, the carbon content is the only chemical difference. Quenching temp is 1555 vs 1570 for 4140 and hardness is slightly harder for the same tempering temperature.

I just checked the ASM heat treaters guide for you, the carbon content is the only chemical difference. Quenching temp is 1555 vs 1570 for 4140 and hardness is slightly harder for the same tempering temperature.

So basically, if I'm making something out of 4140 and I go to a light straw temper, then when using 4150 I should use a heavy straw temper. Thanks for checking the specs! I don't have any charts here.

Are there good charts online somewhere?

As I recall my copy of the ASM Heattreating Guide (Vol 2 of the set?) runs to several thousand fairly large pages...

How big are the chunks in the scrap yard? Square or round?

 Treat 4150 the same as 4140 and don't worry about it

The first 2 numbers are the carbon content in points so both have 41 points or .41% carbon. The other two numbers tell about other ingredients. I started to say alloying metals but since carbon is not a metal that would be incorrect, although I see quite often carbon being referred to as an alloying element.

 

 

This information is mixed up,  the carbon is the last set of numbers, the first set is the alloy blend.

The first 2 numbers are the carbon content in points so both have 41 points or .41% carbon. The other two numbers tell about other ingredients. I started to say alloying metals but since carbon is not a metal that would be incorrect, although I see quite often carbon being referred to as an alloying element.

This is incorrect The second 2 numbers relate to the carbon content.  41 refers to a Nickel Chromium alloy. 

 Look up the specs!! Each separate spec lists RANGES of allowable alloy content - including carbon.  Though, admittedly, in this instance only the carbon ranges change. 38 to 43 points for the one and 48 to 53 points for the other.

I'm sorry. I have been incorrect about the first two numbers, such as, 41 indicating the amount of carbon and John Newman was correct that the first two numbers have to do with the alloying metals. The last numbers are carbon content such as 52100 has 100 points or 1% carbon.

So my last post should have read:

Yes, all designations are within a range. The numbers shown, such as 4140 the 40 is the median of the range, or 52100, 100 is a median, not an exact figure.

Can you imagine the cost of steel if manufactures had to have all mixtures exact, especially considering that most all modern steels are made from scrap.

You can buy *exact* alloys and they do cost an arm and a leg and a few other things too (and even they have a range just a much reduced one!)

Yes there is a range like there are in ALL specifications. And yes the final digit can indicate some other alloying elements BUT I challenge you to tell me ANY AISI alloy that the final 2 digits (or 3 in the case of 52100) are not between the upper and lower limits of the alloy.  USUALLY they are ROUGHLY in the middle of the upper and lower limits but some of the lower carbon alloys only have a  maximum carbon allowed.  

 

The AISI system may not be perfect but if I see the 2 final numbers in an alloy I have an idea of how much carbon it has. 

And I challenge you, Sir, to demonstrate that the last two digits specify ONLY carbon content. Start with the plain carbon steels.

I did not say that they do not indicate other alloying elements.  But they do indicate carbon content.  Not EXACT carbon content but they do give you an idea of the carbon content.   I know 1090 is close to 90 points of carbon 9260 is close to 60 points  and 4140 is close to 40 points.  If  you want to know the exact chemistry of any  bar you have to read the Mill test report or pay to have testing done.

We are in agreement. Thank you for your clarification.

How big are the chunks in the scrap yard? Square or round?

 

2.1875-inch (3/16) round about 2 feet long. It's not a scrap yard. It's a wholesale steel yard that gets shipments from who knows where, of what is considered "scrap." Mostly scrap just means that they don't know the grade of steel. I've bought 8-foot pieces of 2x4 channel, and 12-foot pieces of square and round stock, in perfectly good shape from their "scrap" section. What they classify as scrap currently runs 25 cents per pound.

 

They have a very small section of known steel that they still classify as scrap, because it is in small pieces. It usually runs 40 cents per pound. They may have as much as 10 feet of 4150, 2.1875-inch round stock right now. I've also bought 5-foot bars of 2-inch square 4140 for $25.00 a stick. The carbon steel supply there is very limited, and very splotchy, but you can get a good deal if you keep an eye out.