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Is there a steel alloy that is stronger than 1018 and can be welded to A36 plate?
2

Is there a steel alloy that is stronger than 1018 and can be welded to A36 plate?

Is there a steel alloy that is stronger than 1018 and can be welded to A36 plate?

(OP)
Is there a steel alloy that is stronger than 1018 and can be welded to A36 plate?

By stronger, I mean a higher tensile strength.

The material needs to be machined before welding.

The application is a shaft that a hub assembly with bearings bolts on to (similar to a weld-on trailer axle stub shaft).

RE: Is there a steel alloy that is stronger than 1018 and can be welded to A36 plate?

Quote (JST Fab)

Is there a steel alloy that is stronger than 1018 and can be welded to A36 plate?
Almost any steel is stronger than 1018. By which I presume you mean SAE 1018.
Personally I substitute A516-70 for A36 plate wherever possible. It is just as available (i.e., same cost) and will give you a good bump in tensile properties while having excellent weldability.

Quote (JST Fab)

The material needs to be machined before welding.
All carbon steels have good machinability. Since you are welding you should avoid the resulphurized and/or leaded grades, whose only claim to fame is enhanced machinability, but at the expense of everything else.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

RE: Is there a steel alloy that is stronger than 1018 and can be welded to A36 plate?

4130 seems like the obvious choice.

RE: Is there a steel alloy that is stronger than 1018 and can be welded to A36 plate?

Whatever you pick, check carbon equivalency to see if you need to preheat before welding and if post-weld heat treatment is indicated.

RE: Is there a steel alloy that is stronger than 1018 and can be welded to A36 plate?

Planning welding on high-strength steels is more than checking CEq.
But that is indeed a good place to start.
Some others are:
avoidance of cold cracking (directly related to CEq), delamination on the plate, weld geometry/fatigue design, weld process control (eg. spray arc, penetration depth, choice of filler material)...

RE: Is there a steel alloy that is stronger than 1018 and can be welded to A36 plate?

4130 is not such an obvious choice; nobody has said how strong it needs to be;

and

'carbon equivalency' is not a thing

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

RE: Is there a steel alloy that is stronger than 1018 and can be welded to A36 plate?

1030 to 1035 would provide higher tensile properties and easy weldability without preheat or PWHT.

RE: Is there a steel alloy that is stronger than 1018 and can be welded to A36 plate?

And do you really need the whole thing stronger or do you need some areas harder?
Is it just the pin or the plate as well?
How strong do you need it? 50ksi, 70ksi, 200ksi? Give us a clue.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

RE: Is there a steel alloy that is stronger than 1018 and can be welded to A36 plate?

Carbon equivalency is of course a thing, at least according to AWS. It provides a good guideline for pre/post weld heat treatment and if they are needed. Agree with kingnero on the other the other parameters as well.

RE: Is there a steel alloy that is stronger than 1018 and can be welded to A36 plate?

I understand the concept perfectly well, but what is wrong here is the colloquialization (I know, probably not a word) of a technical term. Even google knows it.



Maybe I am being overly touchy here, but most of my days now are spent at war with overpaid semi-literates at giant EPCs. In code space, precision in communication still matters.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

RE: Is there a steel alloy that is stronger than 1018 and can be welded to A36 plate?

(OP)
We are leaning towards 4130 or 8620.

The failure point is where the inner bearing seats. See diagram below. The shaft snaps completely at this point.

Note: when used as directed, the shaft works great. It is when the product is used incorrectly (ie: extreme offset wheel used off road) where there is a failure.

Ideally we would like to avoid heat treating processes. We do not have the equipment for this in house.

The ideal choice would be easy to machine, materials cost not too high, can be mig welded (preferably with ER70s-6 wire using spray arc transfer), no post heat treat, as strong as possible without adding extra cost or complexity to the job (ie: we simply have the machinist switch the material).

RE: Is there a steel alloy that is stronger than 1018 and can be welded to A36 plate?

8620 is a case hardening steel, meaning especially made for heat treatments. For your application,this doesn't seem a logical choice.
Also requires a carefully selected welding process.

Does the failure originates from the radiused step ? If so, can't you make the radius bigger?

RE: Is there a steel alloy that is stronger than 1018 and can be welded to A36 plate?

(OP)
Hi Kingnero,

Yes the failure is in the radius step. Originally it did not have a radius. We added the largest radius possible in that area (that the bearing would allow). Still needs to be stronger.

I think we are leaning more towards 4130.

RE: Is there a steel alloy that is stronger than 1018 and can be welded to A36 plate?

I've had good results using a peening process introducing compressive stresses in the surface, in a similar application.
There are many variants on this process. Might be worth exploring...

RE: Is there a steel alloy that is stronger than 1018 and can be welded to A36 plate?

4130 could be pre-hardened, but the welding will be more demanding. There will be weld pre-heating and PWHT needed.
Any higher strength alloy will be more hardenable and will require similar treatment.
Peening may help, but this will likely require more.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

RE: Is there a steel alloy that is stronger than 1018 and can be welded to A36 plate?

Components fail at the weakest point so the radius adjacent to the bearing seat surface would be the expected point of failure due to higher stresses and geometry. I think it is most likely the shaft fractured under fatigue during service during time as opposed to a one time event that broke it - I mention this because the term "snapped" implies a one-time event, which would really require further investigation. You are on the right track looking for higher strength steel (which also means higher fatigue strength) and looking at actions outlined above including shot peening. Changing the radius may help, but the main factor here is the increase in stress under loading that results from the reduction in shaft diameter at this critical point.

RE: Is there a steel alloy that is stronger than 1018 and can be welded to A36 plate?

Quote (EdStainless)

4130 could be pre-hardened, but the welding will be more demanding.

Welding would destroy the temper at the critical location where fatigue initiates.

Geometry; i.e., stress concentration factor and surface condition (finish, compressive stress) carry more weight than other factors like material strength. Not that strength is unimportant, but high strength is wasted if the design is not good.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

RE: Is there a steel alloy that is stronger than 1018 and can be welded to A36 plate?

First off, have you determined what strength you need? Also, what are the toughness requirements?

If you only need to get up to 85/40 ksi (tensile/yield) you can do that with a modified 1018. A little more Mn and maybe Mo along with a quench and temper can give you those strengths with decent toughness that is easily weldable. We would cast a modified LCC material like this that was welded into the truck of passenger rail cars.

If you need more strength, I like an 8620 material. It is not just a carburizing grade. However, you will need a bit of preheat and probably a draw after welding depending on the toughness that you need in the HAZ. We would use a bit higher carbon grade of 8625 to go from 90/60 ksi up to 120/100 ksi.

4130 seems to be overkill, especially if you plan to weld it with ER70S-6 wire. It is a good way to get good strength without paying for the Ni in 8620. carbon and Cr are cheaper ways to go, however you will have a more difficult time welding it. You will need preheat and a draw after welding.

I think you need to better understand the strength and toughness that is actually required before just swapping out materials.

Bob

RE: Is there a steel alloy that is stronger than 1018 and can be welded to A36 plate?

Hot finished bar or cold finished? ASTM specs or SAE specs?
Either way you don't want to order by chemistry only, you need a spec that has required strength properties (ASTM A663 or SAE J410 for example).
If fatigue is an issue do you need some cleanliness limits? Some NDT requirements?
You should be able to find steels with 70ksi min UTS and C<0.26% (maybe with Mn and or Si higher) that will be plenty weldable.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

RE: Is there a steel alloy that is stronger than 1018 and can be welded to A36 plate?

By inspection I'm kind of surprised that the plate-to-axle weld toes have not shown to be a fatigue problem.
Perhaps the original non-radius was quite sharp indeed.

IN the picture it appears there may also be a joint or seam in the axle ~ .5" to the left of the alleged "failure point".
What's up with that ?
Was the axle portion machined from one piece or was it two pieces welded together, or a sleeve added to form the bearing abutment or ???

RE: Is there a steel alloy that is stronger than 1018 and can be welded to A36 plate?

The choice of a heat treatable alloy steel is probably not the best decision if one is going to weld it and then have no intention of a post weld heat treatment.

I can see the back-room discussion; "Let's pick a stronger steel so it won't break again."
"Why did it break?"
"I don't know."
"Was it fatigue? Did it happen immediately or after several years of use?"
"I don't know, but if we use a stronger steel, it won't happen again. We can order the steel annealed or hardened. The annealed stuff doesn't have the strength the hardened stuff has, so let's order it in the hardened condition!"

You haven't really told us much about the failure. You didn't include any history of the failure or past failures. What was the mode of failure?
You haven't told us what the calculated loads are, the application, etc. What are the details of the welded connection? What are the dimensions? What is the degree of restraint during welding?

Please, please tell me this is for a homemade trailer that will be pulled by a tractor in the field and not intended for highway use.




Best regards - Al

RE: Is there a steel alloy that is stronger than 1018 and can be welded to A36 plate?

The bearing obviously sets the diameter where the shaft is currently failing but the diameter at the weld joint is uncontrolled. Control of the size of the HAZ can limit the softening to the larger diameter where the reduction in strength won't be an issue.

RE: Is there a steel alloy that is stronger than 1018 and can be welded to A36 plate?

Quote (gtaw)

Please, please tell me this is for a homemade trailer that will be pulled by a tractor in the field and not intended for highway use.
Unless highways are heavily potholed in your neck of the woods, pulling a trailer through a field would impart some seriously higher fatigue loads. Just saying!

Quote (TugboatEng)

Control of the size of the HAZ can limit the softening to the larger diameter where the reduction in strength won't be an issue.

Not sure how that works. A smaller HAZ is made by lower heat input and it could end up harder than you would like.

Folks, we are seriously overthinking this. I suggest the OP do some simple benchmarking or even reverse engineer the design from a competitor's part. This configuration has been made millions of times before and the vast majority never fail.
It is not very big, so there is no need to go to a heavily alloyed steel. And in general, follow the K.I.S.S. principle by going to minimum alloy and minimum manufacturing complexity.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

RE: Is there a steel alloy that is stronger than 1018 and can be welded to A36 plate?

I figured if it failed in the back hay lot, fewer people would be endangered.

Best regards - Al

RE: Is there a steel alloy that is stronger than 1018 and can be welded to A36 plate?

Ironic, I'm just trying to say that there are ways to keep the HAZ in the low stress areas through design, not just perform a "cold weld". For example, one could press fit the spindle in the plate and weld only the back side.

RE: Is there a steel alloy that is stronger than 1018 and can be welded to A36 plate?

Did anyone mention ASTM A572-65?
65ksi yield / 80 ksi tensile. Easy to machine, bend... Very weldable (unlike chromoly).
After that, A516.

RE: Is there a steel alloy that is stronger than 1018 and can be welded to A36 plate?

If you get really desperate, you might consider bolting the shaft to the plate. Buy some 4130 tubing heat treated to a medium strength, machine it and bolt it on. A long center bolt would provide a favorable compressive pre-stress.

Disadvantages would be the higher cost (bolting versus welding) and the possibility that the bolt would come loose.

RE: Is there a steel alloy that is stronger than 1018 and can be welded to A36 plate?

Might also consider reducing the shaft diameter between the bearing shoulder and the fillet weld edge. This might reduce the stress concentration at the bearing shoulder fillet.

RE: Is there a steel alloy that is stronger than 1018 and can be welded to A36 plate?

I would be most reluctant to modify the "design" or even change materials before examining the fracture and reviewing a big chunk of reliable history.

Like some Old Time Radio cop (pre Dragnet) said - "my business is facts ma'am. Do you know any?"

===========

One of our suppliers made shafts to drawings of a mature and successful product.
A couple of the shafts broke pretty quickly,

It turned out that the new-ish shop foreman interpreted one of our admittedly under-dimensioned drawings from the (19)60s as having a relatively deep, sharp cornered groove as transition at the end of some threads on the shaft in between the keyed drive end and the high inertial built up rotor.
Basically they machined the thread transition groove to the full depth of a nearby "keyway" for a large tabbed bearing lockwasher, and with amazingly sharp corners.

In our case Maybe obviously, maybe not, the correct "solution" was to add some dimensions to the drawing that had sufficed to create reliable shafts for 2 score years.
NOT to change the material.
Not to even change the shaft "design."

RE: Is there a steel alloy that is stronger than 1018 and can be welded to A36 plate?

Quote (ironic metallurgist)

Folks, we are seriously overthinking this.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

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