Heat treating A36 steel

[Steelforbrains]

My company is constructing large cylinders (6 to 8 ft in diameter and 35 to 40 ft long, built in 5 ft sections) for the sorting of aggregate. These drums are constructed of 3/8" A36 plate rolled into cylinders. On each end there built up welded sections (made of 3/4" plate) for the cylinder to roll on. We are having some problems with the welds cracking around these end sections. I suspect that there are significant residual stresses from the cold rolling and welding of the steel. I have suggested stress relieving the end sections. Will that affect the strength of the material? We would also like to case harden the face that the drum rolls on. Does anyone have any suggestions for the best method to do this for A36 steel?

Can anyone suggest a good comprehensive book covering metallurgy (including material selection) and heat treatment? I am not a metallurgist so nothing too in depth. Oh, and all of that for around $100.

Thanks in advance...

 

[swall]

Not quite clear about your configuration. Are the 3/4" thick end pieces also ring rolled or are they built up discs? Which welds are cracking? Is the seam of the rolled 3/8" section welded?

 

[Steelforbrains]

Swall,
The end section is a 5 ft long by 6 ft diameter cylinder of A36 steel. Near the end of this cylinder there are two 3/4"x5" flat bars rolled the hard way (on edge) that are fillet welded to the cylinder. Sitting on top of those two rings is a 3/4"x10" flat bar rolled the easy way. The 3/4"x10" flat bar is welded to the two 3/4"x5" flat bars via a fillet weld on each side. When the cylinder rotates it rides on the outside face of the 3/4"x10" plate. The fillet welds between the 10" plate and the 5" plates are cracking. The welds between the 3/4"x5" plates and the 3/8" cylinder are fine though. I suspect that there is a large amount of stress in those welds do to the cold forming of the plates and due to the welding.
We want to harden the outside face of the 3/4"x10" plate. Clear as mud?

 

[CoryPad]

The learning material you need is Metallurgy for the Non-Metallurgist, available from ASM International as a book, video, traditional classroom class, and online class:

http://www.asminternational.org/Tem...=Ecommerce/ProductDisplay.cfm&ProductID=11068

http://www.asminternational.org/Content/NavigationMenu/Training/OnlineTraining/OnlineTraining.htm

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[metengr]

We are having some problems with the welds cracking around these end sections. I suspect that there are significant residual stresses from the cold rolling and welding of the steel.

What is the weld joint configuration on the end of the rolled and seam welded cylinder? Normally, 3/8" thick A 36 does not need a post weld heat treatment. A 36 material is very weldable. However, I suspect that you may not have used preheat during welding. Can you come back with some additional information on the welding details?

 

[unclesyd]

One of the names for you fabrication is a "tire". A similar component is used on rotary kilns and dryers.
Most of these tires are cast and attached to the drum by bolts. They can be a one or multiple piece component.

More than likely what you are seeing is failure from fatigue as the tire turns on the support rollers. The stresses are normally from two directions, one is wave that travels on the face of the tire and the other from a slight movement in fore and aft longitudinal direction. I would first look at the face wave problem.

You could be lucky if for some reason you don't have enough weld metal holding the face plate wall plates.

As mentioned above can you comeback with more details:

What size are your support rollers?
Is there a slant to drum?
How are you driving the drum?

 

[Steelforbrains]

Unclesyd,
It sounds like you know exactly what I am talking about. I am looking at using a forged tire and bolting that to my cylinder. The forged tire adds a considerable amount of money to the project, but probably not as much as flying guys out to repair welds. I do suspect that the biggest problem was insufficient welding but I would like to make the design a little more robust for the future.

Let me answer your questions:
-There was no preheat used and only partial penetration joints were made.
-The support rollers are currently 18" diameter by 6" face width, 1018 cold drawn steel. It is estimated that the maximum load on one wheel is around 28,000 lbs
I am having a difficult time determining the stress, due to the contact between the tire and the support wheel since it is difficult to determine the contact area between the two.
-The drum is slanted 5 degrees
-We are driving the drum with a chain drive. We are currently using a 30 HP motor, the cylinder speed is around 10 rpm. The drive is mounted to the side of the cylinder so that the chain is pulling down on mainly one support wheel (the wheel with the the 28,000 lb reaction force).

We may need to think about using a better grade of steel for the tire but I am worried about causing more welding issues. What I would really like to know is what people's opinions are of stress relieving and hardening A36 steel.

 

[metengr]

Steelforbrains;
I can provide an opinion regarding your last statement;

What I would really like to know is what people's opinions are of stress relieving and hardening A36 steel.

Based on the added information from unclesyd and your follow-up posts, I don't believe stress relief is going to prevent cracks in service – this points to more of a design problem. I believe you need to modify the current design to avoid these low cycle fatigue cracks in service.

One option might be to do away with the two smaller fillet welded support rings under the 3/4" X 10" wide fillet welded ring and simply go with a one piece solid ring installed directly over the carbon steel cylinder. In lieu of hardfacing the wear surface, you can select a low alloy steel (4140) for the one piece ring that can be surface hardened using an induction process and afterwards can be installed directly on the main cylinder using an interference fit versus fillet welding.

 

[Steelforbrains]

I have looked into getting a solid ring forged and machined from 4340, but it was kind of pricey. As a side question... The ring forging company quoted a rough machined surface finish of 500 RMS. I am having a hard time finding a reference to let me know how smooth a 500 RMS finish is, any suggestions?

How does the 4140 compare in price/performance to 4340?

I do like the idea of the one piece ring but I don't think that I will be able to hold tight enough tolerances for an interference fit. I don't want to weld a chunk of alloy steel that size to my cylinder, but that is not totally out of the question. We have kicked around the idea of rolling two pieces of angle leg out then bolting them to the cylinder and then bolting the tire to the angles by either drilling and tapping the tire or through bolting. Any other ideas on how to maount this solid tire?

 

[CoryPad]

4140 has no nickel, so it will be cheaper than 4340. 4140 is limited in the allowable section size that can be hardened via martensitic transformation, which is why 4340 is used for larger parts.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[Steelforbrains]

Can anyone recommend that a grade of steel that is
1) Hardenable
2) "Easily" welded to A36 steel
3) Is available in 1"x8" flat bar stock

 

[swall]

For the hardening, you might consider flame hardening. This would be a natural for the configuration of this product, since you can rotate it. This could be done on site or you could set it up to rotate it while still in the shop. These flame hardening heads are basically glorified torches that put out a tremendous amount of heat in a controlled pattern. Any steel with a carbon content around .50 or higher would work, but will require precautions for welding, namely pre-heat. I would try to find 1050,1060 4150, or 5160 in the bar size you need.

 

[unclesyd]

You might want to give these people a call concerning the use of Astrally-V Plate or Bar. They have a lot experience using this material in mining and quarrying industry.

http://www.astralloy.com/products/av/astralloy-v.asp?page=plate