Weld inspection 1

[tmoritz]

I am writing specifications for a new hydraulic piston stem for a single action cylinder. The stem will be fabricated from 17-4PH H1150 stainless steel which has twice the tensile yield strength as the original copper-nickel alloy. The stem is 3" in diameter except for a 4.75" diameter knuckle at one end for a mechancial coupling. The hydraulic cylinder will generate approximately 90,000 lbs force when the cylinder is retracting, the only direction the rod is under hydraulic loading. The rod is approximately 20-feet long. My original thought was to machine the stem from 5" diameter round stock but stock length is random 12 feet and to get a 20-foot length requires purchasing a special mill run, about twice as much material as I need.

Now my thought is to butt weld 3.25 inch or larger round stock to a short segment of 5" round stock, solution anneal and heat treat the weld effected zone, then machine to final dimension. My questions for this venue are: what non-destructive examination methods could be used for quality control on the weld? Which is the best and why?

Thanks in advance,

Tom Moritz
Mechanical Engineer
US Bureau of Reclamation

 

[metengr]

My questions for this venue are: what non-destructive examination methods could be used for quality control on the weld? Which is the best and why?

Reply; The welding of 17-4PH requires the use of E/ER630 filler metal (essentially 17-4 PH composition) to assure similar properties and behavior as the base metal (a complete re-heat treatment and aging process) or you can evaluate an 1150-M heat treatment, as an alternative. How familar are you with welding this material?

The nondestructive testing I would recommend is ultrasonic examination. The reason is you want a full volumetric examination for this type of butt weld joint. I would also suggest you blend grind the outer surface of the weld toes to eliminate any stress risers.

 

[unclesyd]

I would not weld the shaft as you can purchase preheat treated 17/4 up to 36'. The material is as about as straight as you will need. The material is used for boat shafts, though my use was for both boats and agitator shafts up to 30 foot long.
I purchased a lot of this material from Wester Branch Metals. Their server seems to be down.

http://www.aquamet.com/

Very good data.

http://www.gpcprop.com/PDF Files/aqualoy.pdf

anecdot:
When the pulled the plug on the big Armco mill in Balimore I was talk to them about 8 17/4 shafts 30' long tapered from 8" to 4". The has just installed the largest rotary forge in the US at the time.

 

[unclesyd]

Forgot to add, if you could contact AK Steel and see who got the Rotary Forge. It would be no problem to upset what ever type end you need.

 

[unclesyd]

The Western Branch Metals site is backup and the mention rotary forging, so they maybe able to provide you with an shaft with an upset end.

Their approach on materials is to supply the shafting in A-19 and A-22 due to pitting problems with A-17 in stagnant water conditions on boats that sit idle for extended periods of time. In your case there is no such problem so the A-17 is OK.

http://www.wbmetals.com/

 

[tmoritz]

metengr,

I do not have any prior experience with welding 17-4PH. My thoughts were if you weld with E/ER630 filler metal you will alter the material properties in the HAZ and therefore still need to heat treat the HAZ to regain the toughness.

Thanks again for the info,



Tom Moritz
Mechanical Engineer
US Bureau of Reclamation

 

[tmoritz]

unclesyd,

I like your idea of upsetting the end of a shaft vs. welding. I will look into that option.

Regards,


Tom Moritz
Mechanical Engineer
US Bureau of Reclamation

 

[arunmrao]

tmoritz,
unclesyd's idea is a good one followed by taper machining and finally the option of welding two pieces. With the last option you introduce many variables which need to be constantly evaluated in terms of reliability and performance guarantee.

While the other two options though appear to be expensive on a first look will provide you much needed sllep at night.

 

[unclesyd]

I just looked at both sites and the available length is above 30' with a good finish and straightened.
We routinely purchased 16' shafts with a TIR of 0.002". The diametrical tolerance was within 0.001". Cannot recall the straightness but it was very good. The 17/4 shafting is normally heat treated at H1125/H1150.

I still don't like the idea of welding, heat treating, straightening and grinding vs purchasing a shaft off the shelf.

 

[Maui]

Tmoritz, I suggest that you contact Richard Barber at Western Branch Metals. He can advise you on the precautions that should be observed during welding of 17-4PH. He can also advise you on alternative materials for this particular application. The contact information for this company can be found here:

http://www.aqualoy.com/about.asp

Maui