Hey Walter what type of steel is used to make the pins on Track-hoes and Bull Dozers? Primarily the bucket and blade pivots.

We used S-7 on one a while back and it bent instead of breaking but we liked to have never got it out.

Merry Christmas, Louis

years ago we used a piece of t-3 for a pin in an excavator bucket and it worked quite well for a long time. I don't think that it is what the factory uses but it worked.

You can try 8620 and case harden it. You might also find that 4140HT will work fine as is, no additional heat treat necessary. S7 is great for plastic injection molds that must deal with thermal shock and abrasiveness. I have heard it is good for knives too. Pins for dozers....well looks like you already have your answer. I think I would lean heavily towards the 4140HT and maybe away from the 8620 altogether.

Just my opinions as a machinist and tool maker.

Andy

I remember that from school - steel capable of martenzit transformation induced by plastic deformation. In plain English it will harden in the deformed areas. But first I don't remember the number of the steel and it would be in Czech Technical system anyway

Czech_made, you're thinking of Hadfield steel, a high Manganese steel . But it's used for bucket grousers [teeth] so that when the surface is worn off the underlying steel immediately hardens .Very tough ,not machinable.

Remember that the pins should break before the bucket or dozer does !!4140 would be a good choice .IIRC I made some for a friend of 4140 .

[QUOTE]Originally posted by mete:
Czech_made, you're thinking of Hadfield steel, a high Manganese steel . But it's used for bucket grousers [teeth] so that when the surface is worn off the underlying steel immediately hardens .Very tough ,not machinable.

Is hadfield steel the same as "English Steel"? Different lingo for different parts of the country.

quote:

Very tough ,not machinable.

By conventional means. Try using ceramics!! Super abrasive machining centers are working pre hardened materials upto and above 62Rc!

Sorry to get off topic.

Make sure if using 4140 that you are not using the annealed condition. It will be way too soft. Barstock usually comes pre-heat treated and is around 42-48Rc. Any harder and you sacrifice flexibility and the ease of machining by conventional methods.

Andy

I guess I should have mentioned that I don't have a way to heat treat.
The S-7 worked fine for the Dozer pins but a bushing was left out of the bucket and allowed too much play so it bent instead of just dealing with shear pressures.

Thanks Guys, Louis

41X0 pin and a soft steel bushing ..
turn a bushing out of something cheap .. might go ahead an turn a couple .. and a 4140 or 30 or 50, it doesn't matter, pin... that way, if anything go wrong, you drive the pin out THEN then bushing, and it all comes apart easier

the bushing takes the deformation and the pin takes the shear ... soft and hard.

Andy's right.. annealed is soft, under 20rc, prehard is around 45 ... EITHER can be worked over with a 4.5" grinder

'English steel' sounds like a rather nebulous term. It's certainly not hadfield's. Hadfield steel is non machinable and it's uses are very specific.

"English steel" was a term used to refer to the plate steel used in tin balers car crushers and other equipment that gets a lot of steel on steel wear. The description of hadfield steel sounds like what was called English steel.

Thanks jeffeosso! God Bless, Louis

quote:

I guess I should have mentioned that I don't have a way to heat treat

Do you have an acetelyne torch with a rosebud and a bucket of used motor oil? If so I can tell you how to simply treat your 4140,4150,4340, or 4350. DON'T WASTE YOUR TIME OR MONEY WITH 4130!

Andy

Hey Andy, I do have a torch and rosebud. Don't have an oven. I would appreciate any comments and tips too. Merry Christmas, Louis

quote:

Originally posted by mete:
Czech_made, you're thinking of Hadfield steel, a high Manganese steel . But it's used for bucket grousers [teeth] so that when the surface is worn off the underlying steel immediately hardens .Very tough ,not machinable.

Remember that the pins should break before the bucket or dozer does !!4140 would be a good choice .IIRC I made some for a friend of 4140 .

You are right and I was wrong, thanks for the info.

To heat treat 4140/4150 or the 43 series you will need a bucket big enough to submerge the part completely. Holding the part with very long tongs or some device that you can easily manuever heat with the rosebud until it is a dull orange. Notice I said dull! You do not want a bright orange or yellow as this is way too hot. The temp you are looking for is about 1500-1600*F. When dull orange, plunge the part into the oil and swirl it around. There will be flames at first...get the part submerged quickly and the flames will go away. Swirl around until you can hold the part in your bare palm. Dry it off and clean any scale with 320 emory or scotch brite. Now comes the more critical part. You will need a seperate bucket of whatever soluble oil coolant(this is a water and oil mixture that will provide rapid cooling) your machinist uses when making this pin. Holding the pin again in the tongs heat it until the surface takes on a straw color and very quickly plunge it into the coolant mixture. You will now have a pin that should withstand some pretty severe abuse. I like 4140. 4150, 4340, or even 4350 will work great for this application. These steels are actually considered tool steels due to high carbon content and ability to be hardened and drawn and have a multitude of uses.


Andy

I was afraid of that! It is going to be hard to hold a 2.5" X 24" pin and heat it evenly. I may have to use untempered 4140. Thanks Guys, Merry Christmas, Louis

you might try A1 - it air tempers

A2 is a good steel but you gotta get it a lot hotter and may need dual tempering to get it soft enough.

Clamp a vise-grip onto a frame of some sort and hold the pin in the vise-grip by the end.
Heat with the torch from the bottom in long strokes to "push" the heat into the rest of the pin. When it is at temperature/color release vise-grip and pin falls into bucket of oil. Repeat procedure for drawing with coolant and not quite so hot pin.

There is always a way. Sometimes ya' gotta get creative.