What materials/alloys are used for excavator booms and sticks?

[universalpete]

Hello All,

I am a mechanical designer who is new to the heavy equipment industry. My experience is in camera/lighting systems for the glass industry. I am trying to get up to speed as fast as possible so I don't have to ask so many questions and so that I can add value to my work.

I am looking for help understanding common materials used in various parts of excavators and similar equipment. If anyone could chime in on what alloys they are familiar with for various elements of heavy equipment, or let me know of some resources that they would recommend, that would be awesome.

Thanks!

 

[Nige]

Generally the materials used for structures fall into the category of a welded steel structure with castings as reinforcement in critical areas.

1. The steel plate for fabricated box sections is generally a 290 MPa structural steel to a specification something like ASTM A513/A519/A572.
2. The castings would be generally malleable steel and fully weldable when combined with the steel plate as specified above.

 

[Dualie]

occasionally you will see some crane booms and low beds manufactured with T-1

 

[7379df]

I know this is a pretty old thread but thought i would start here. So if we were going to make repairs on an excavator boom, the above mentioned would be ideal so as to match the original factory metal, correct ? Thanks for any help

 

[John C.]

Most everyone uses 7018 rod or E70T wire to repair excavator booms. There is nothing exotic in that steel.

 

[Tugger2]

50000lb yield plate on most excavator booms , frame components and buckets ive worked on. Qt 400 plate cutting edges and wear bars, 4340 pins induction hardened.

 

[7379df]

Appreciate that guys. Sounds like with 50000lb plate it would be overkill and possibly a good place for a fracture if a guy used 8018 on that type of plate? I will stick to the 7018 or ER70s-6. As far as plate goes in the 50000lb range, which one of these would be most commonly used or easier to purchase ?
ASTM A513/A519/A572.

 

[7379df]

We just found some 3/8" astm 572 at our local steel supplier for a small fee of $38.30 square ft. This should be comparable to the boom steel ?

 

[Tugger2]

Ive alway bought my steel by the lb wheather its plate ,sheetpile,structural steel or pipe. Rule of thumb i keep in mind is 1" plate = 40.84 lbs/sq.ft. divide by 8 = 5.10 lbs/sq ft. X3 = 15.3 for/lbs./sq.ft. your 3/8" PL. Thats 2.50/lb for your 3/8" PL if my math isnt messed up. I have not bought steel for a few months now but that sounds like full retail for a small piece. Im going to call my supplier and get an update on pricing today.
If you can get your hands on a steel suppliers hand book they are very handy as they list a lot of grades ,sizes and structural member specs and weights.They used to give them away,I found one from Carnegie Steel printed in 1910 which is still very handy today.
I would alway ask for the mill certification on the specific steel i was ordering,lots of times ,especially with structural steel the yield strength would come up higher than spec. This was particularly handy when looking for angle iron for boom repair on my American cranes ,the inspector i have dealt for 30 years with would ask for 50000 yield Angle iron for angle boom chords when we were doing a repair.

 

[7379df]

Thank ya Tugger .. Thats some good info. and i like the old school stuff for sure. i will have to look that Carnegie steel book up see if i can find one. I have an old Norton tool room grinding hand book. We do some of our own machining and tool sharpening for our machines. That ole book was printed back in 1947 and is just about handier than pockets on a shirt. Appreciate your time.

 

[Welder Dave]

I'd wouldn't use ER70S-6 solid wire Mig unless it was in spray transfer mode. Penetration/fusion could be suspect. E71-T1 (all position) dual shield flux-core is the closest wire to compare with 7018 stick. Sometimes for additional strength you could use 8018 (8018C3) which has 1% nickel for extra toughness. It is often specified for repairing crane booms unless they are T1. T1 requires 11018 or an equivalent flux-core wire. It is not advisable to use rods such as 11018 on mild steel because it has different properties than the base metal and can crack. Preheat on heavier sections and peening while hot can help relief stress from the welding process.

 

[chidog]

I worked at a place that made grapples, booms and such for excavators. Like Nige mentions above. Mostly A572 was used.

 

[chidog]

We just found some 3/8" astm 572 at our local steel supplier for a small fee of $38.30 square ft. This should be comparable to the boom steel ?

Sure expensive stuff now.

 

[Tugger2]

I have always kept solid wire for doing light gauge materials . Dual shield wire like Lincoln 71 Elite with C o 2 for anything structural on machines. Ive used that wire for QT 100 or QT 400 plate on buckets with no problems.

 

[Welder Dave]

Solid wire is OK for general repairs that aren't subject to stresses like booms and dozer frames are under.

 

[Camshawn]

I have a data book from A J Forsyth (Vancouver BC) that my Dad gave me 30 yrs ago. Cam

 

[7379df]

Roger that guys.. will use either 8018 or the 71. May be easier to just get 8018 although i like my mig. Also Welder Dave on the preheat what do you like to shoot for as far as temps go ? just enough to fry any egg but not too hot...300 - 400 deg ?
Really do appreciate all the info from you guys. Good to know there is still some good ole boys left out there !!

 

[chidog]

The thing about any welding with flux, is the heat needs to be enough to keep it out of the joint.
Very easy to get porosity if you are not an expert at welding.
Does the Cat factory use fluxed welding wire for their welds?
I have never welded mig with flux. But only use mig on small materials not over 1/4 inch thick.
Any thick materials I have always used stick.

 

[John C.]

One would normally only want an expert welding on booms and sticks.

We used both hard wire and dual shield for heavy welding. Hard wire was used a lot for clean metals and high deposition. Dual shield was mainly used for repair welding and a lot of out of position stuff. We used .045 wire with both wire types but only used dual shield for the 1/16" machine. There was a Hobart Handler mig for the small fineness stuff and we only used hard wire. As I recall it had .023 wire in it. The was a roll of inner shield for it but no body touched that stuff. It smelled terrible and coated you nose and throat when using it.

Stick was for the most part used for crane booms or something special when I moved out of the shops. The field trucks kept a ten pound sealed tube of 7018 on the truck all the time.

When I started in the business the only industry using squirt guns was the ship yards. Critical welds were only done with stick and the exotic stuff was in the aircraft industry or for the piping systems on ships. Now it seems everything is done with a squirt gun.

 

[Welder Dave]

Around 300 deg's. is usually fine for preheat but it depends on the material. Done properly flux turns to slag and comes to the top. No different than stick welding but usually very easy to remove. I think someone said back in the day Cat used solid wire but in spray arc mode (flat and horizontal welds only). Dual shield flux-core and sub-arc for larger weldments has pretty much taken over. There is metal-core wire that is kind of a cross between solid wire Mig and dual shield without slag but I don't think it's used for heavy equipment much.