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mrmikey
06-08-2011, 08:05 PM
Got a job at work making 12 shafts/blade mount for grader powered brush cutter. the company that makes the unit, Roanoke, is supposidly out of business hense the need for making the mount.
According to the analysis of the one mount we had left, the shaft is a 4150 type of steel and from appearances that is welded to a regular steel mount for the blades, whole thing weighs mabe 60-70 lbs so it's not super heavy.
My question, anyone have any suggestions for the pre/post heat and any other info. From what I've been able to find out it's a cr/moly steel, preheat is 350°F, post dunno, rods are E90XX or E100XX. We are getting info from out local steel supplier but I was trying to get a preliminary idea of whats involved......Mike

A_DAB_will_do
06-09-2011, 09:47 AM
Mike,

Your pre heat sounds correct, unless the thickness of the mount dictates an even higher pre-heat.

Make certain you select a low hydrogen filler metal. I'd use a filler with a strength of 110KSI; something like E11018 for a stick electrode, or wire with similar chemistry and properties.

4150 is a Chrom-Moly steel with 0.050% carbon; which is a signficant amount of carbon.

Found this online for some basic information about 4150:

http://www.matweb.com/search/datasheet.aspx?matguid=100dc677f93643d288f8d7de39b e8f84&ckck=1

and this:

http://www.peerlesssteel.com/productlist/alloysteel/

"AISI 4150 (Mod. RS) CT Annealed Alloy Bars

A modified and resulphurized chemistry of this medium carbon alloy grade provides deeper hardenability and the addition of sulphur along with Calcium Treatment results in improved machinability for many larger part sections.

AISI 4150 CT QTSR Heat Treated Alloy Bars
A modified chemistry of 4150 steel that is Quenched and Tempered to a brinnel hardness of 262 to 311. Furthermore, this product is Stress Relieved to reduce distortion during machining and may be used for many parts without further heat treatment, providing good hardness penetration, toughness and strength. The addition of calcium produces dramatic improvements in machinability and tool life, when used with carbide or high speed tooling."

I strongly urge you to make certain that the 4150 you use is not one of these resulphurized 'free machining' grades. You'll have serious issues with hot-cracking welding 4150 alloys with increased levels of sulphur.

I wouldn't worry too much about post weld heat treatment. Just pack everthing in insulating material and allow it to cool slowly to room temperature after welding.

Given the mechanical properties of 4150, you might want to find a stronger HSLA steel to make the mounts out of. A T1 steel like A514:

http://www.matweb.com/search/DataSheet.aspx?MatGUID=13c258301b6640f98e7cdf4b3ad 66dfe

Would be a good match for properties. But you could choose something lower in strength, but still better than A36, if cost is an issue. Normal A36 steel plate has 25% of the strength found in 4150, and you may have cracking problems due to the large mis-match in strength if you use A36 type material for the mounts.

cowski
06-09-2011, 10:10 AM
if you do not get it right ,it will break right next to the weld.i bought a big john deere 3 bladed cutter .i broke all 3 of the blade holders real fast.the replacements have run many years with no trouble.i think their bar stock was heat treated .during the welding process they made it brittle.it looked almost like cast does when it broke. sorry i can not help with the set up ,

mrmikey
06-09-2011, 09:52 PM
Thanks for the info guys.
ADWD, what you were saying sounds pretty much along my lines of thought as for pre/post heating. Good links, thanks
Cowski, thats my concern, breaking next to the welds. The cutter head does some severe vibrating at times when a piece of the blade breaks out, hard to see rocks buried in brush.
The powers that be were under the impression that 'it's just a big piece of round bar welded to a piece of flat, so what's the big deal" . Seriously, you're working with a possable 15lb blade flying thru heaven knows what.
If/when they ever get the procedure I'll post it here......Mike

Matt_Maguire
06-10-2011, 07:02 AM
I have a couple of thoughts here mrmkey, first I assume you are working from sample and working for the owner of the machinery. I also assume this is the blade mount shaft (rotating assy) itself, and you don't have and can't get prints and original shop routings from the manufacturer.

Made in fair quantities 1060 or 4150 makes sense but both would have a complete heat treat after welding (properties will be above 120ksi yeild). 4130 could be done and stress relieved, 4320, 8620 or 9310 could be done with pre-heat only and slow cool.

4150 and 1060 have high CE numbers (carbon equivalent), and need high pre-heats for welding. After welding they would be held at an elevated temp until placing in heat treat for either normalizing or austenitizing and quench, then temper.

My choice for the plate to attach the blade would be 1030, 1045 or 4130 and not mild steel. HSLA materials like T-1 will not develop the strength needed with simple heat treat after welding.

(edit) I should have asked if you know the type of bearings used (this can be used to make some guesses, some bearing setups need/use shaft strength and some add to shaft strength).

Good Luck
Matt

mrmikey
06-10-2011, 09:15 PM
Hey Matt,

.....first I assume you are working from sample....
correct, only one in existance to my knowledge

....working for the owner of the machinery......
you'd be correct again

After welding they would be held at an elevated temp until placing in heat treat for either normalizing or austenitizing and quench, then temper.
Not disputing your sugestion in the least, but, and it's not a good indication I know, it looks as if there's been minimal if any post heating done after welding. The cross bar doesn't show any signs of heat other than welding generated.
Crap, I meant to take a pic today and I forgot, I'll try and remember Monday but that's two days away. (good memory but short )

I should have asked if you know the type of bearings used
I don't off hand but I think it's just a tapererd roller bearing 3" dia.? or so, runs on a race not the shaft if that's what you were thinking. It must be the more I think about it as the driven end uses a fine thread with a lock collar for setting the preload....Mike

Matt_Maguire
06-12-2011, 08:45 AM
Hey Matt,

I'll try and remember Monday but that's two days away. (good memory but short )


I don't off hand but I think it's just a tapererd roller bearing 3" dia.? or so, runs on a race not the shaft if that's what you were thinking. It must be the more I think about it as the driven end uses a fine thread with a lock collar for setting the preload....Mike

Cool, pics are always fun, and if it shows failure because of fretting & upsetting under a bearing race then 4150 is little better than 1026-1030 in the long run.

If it has bearing nuts then the shaft is stiffened by the assembly no matter which type of bearing is used. And yes I was wondering about needle or rollers using the shaft for the inner race.

Matt

mrmikey
06-13-2011, 04:27 PM
I remembered to take some pics.
In the bottom pic you can see the two small holes where we drilled to get material to get tested.
The cutter crossbar bolts (two bolts) into the slot made by the two pieces of flatbar on either side in the bottom pic. The blades are held onto the cutter cross bar in by one bolt in each and are allowed to pivot should they hit something (sure they will, something with that mass turning ain't gonna swing like a lawn mower blade) . I think each blade weighs in around 10 lbs or so, I would have grabbed a pic but there was no one in the stockroom when I went by.
In the top pic you can see the bearing areas as well as the threads and the spline for the drive motor thats coupled with a chain coupling together.
The pump that runs this rig is powered by a 3208 cat running a tandem 30 and 12 gallon pump at 2200psi. it carries 100 gallons of hydrauic fluid and 45 gallons of fuel on board. We made 5 of this units, self powered as the origonal setup from Roanoke was powered by the grader engine and there wasn't enough power and the grader engine had to be run too fast which made the machine too fast, hard on clutches. It hangs under the grader frame where the turntable usually is. I would have taken a pic of the setup but there was none around......Mike

Matt_Maguire
06-14-2011, 10:37 AM
Alrighty then, I like the note left on the sample mrmikey! :)

It appears from the nice pics that little if any pre heat was used on that top weld (I'm guessing there is another weld around the spud in the bottom plate)...

You got confirmation on the 4150 (chrome & moly are easy to sort, it's the .5 carbon I'm still choking on). IMHO the designer has a much larger pair than I got! In any case if I were to weld it I would be looking at E80-1Ni or 2Ni which gives a 90ksi weld with very high charpy impact numbers. This would avoid a strength overmatch to one or both of the parts with really good toughness.

AISI 4150 conforms to spec with carbon from .47 to .55 (pretty high to dangerous CE). If you can test the shaft for hardness you can guess the heat treat condition and strength of the material.

Fully annealed 4150 tests around 212 Brinell or about 100ksi tensile (Rockwell "C" hardness would be less than 21 and unreliable). Normalized 4150 in a 3-4" section will test around 295 Brinell or about 140ksi tensile (Rockwell "C" would be around 31 and is a reliable test). If the 4150 is harder than 320 Brinell or 34 Rockwell "C" the danger from any welding goes up really fast as these numbers indicate a heat treated and tempered condition (it is never wise to fool with any steel in tempered to higher strength condition, as it's already being asked to do more than it wants to).

The boxed construction of the blade mount looks OK to me, so I'm wondering how these things fail? I can see possible failure from the bearing fretting near the seal area on the bottom, getting loose and breaking at the radius there. The splines don't appear to be induction hardened so fretting or upsetting there could be a problem (so could hitting something hard). What kind of bearing nut is used, (1) large split nut with capscrews on the face or (2) smaller "AN" type nuts with a locking ring and keyway in the shaft? Locknut back off could be a problem from impact torque twisting the shaft. :eek:

I'm interested in this project! :cool2:

Matt

weldbead
06-14-2011, 12:09 PM
[QUOTE=A_DAB_will_do;518716]Mike,



4150 is a Chrom-Moly steel with 0.050% carbon; which is a signficant amount of carbon.

i thought this would be an very low amount of carbon..isnt low carbon steel:about the same?

mrmikey
06-14-2011, 02:40 PM
Alrighty then, I like the note left on the sample mrmikey!
LOL, not my note but my sentiments exactly.

It appears from the nice pics that little if any pre heat was used on that top weld (I'm guessing there is another weld around the spud in the bottom plate)...
Dunno, if there is it's inside before it's assembled

....so I'm wondering how these things fail?
Vibration and constant beating rocks etc. tears the shaft up. The bearing area is the usual area, the holes beating out for the crossbar when they work loose and bending when it gets wrapped up around a cable.

The splines don't appear to be induction hardened so fretting or upsetting there could be a problem
Agreed, no sign of hardening at all. Believe it or not the splines usually don't go, they wear out obviously but not to the point of failure.

What kind of bearing nut is used
Not sure of the correct name, it's 3/8" thick or so with slots cut around the perimeter for a lock plate.
The way this place works, it'll be a moth of sundays before we find out, more than likely when the sample is gone :mad:......Mike

A_DAB_will_do
06-28-2011, 09:12 AM
Hopefully I'm not ressurrecting a dead topic...But I just noticed your posting weldbead.

0.050% carbon would be low carbon. I fat-fingered the keyboard while I was typing that reply. It should be 0.50% Carbon. My mistake...


[QUOTE=A_DAB_will_do;518716]Mike,



4150 is a Chrom-Moly steel with 0.050% carbon; which is a signficant amount of carbon.

i thought this would be an very low amount of carbon..isnt low carbon steel:about the same?

A_DAB_will_do
06-28-2011, 09:39 AM
I am curious to see how this repair turned out and how the welding wasd done...