i'm not trying to be a nag..... Use low/hy on everything that you have any doubt on. 5p is just not strong enough on most applications I deal with. You're looking at a structural job that requires probably 7018, and in multiple passes. In the pipeline world we use 5p most times because we are making numerous well planned passes. There is an issue of pressure, not weight or movement or weight and pressure. If your weld fails it will likely cost bookoo bucks, or someone's life. If you can sleep with that, go for it. If not, tell them that you will fix it right and they will pay for it........
On many jobs I have had to just agree with the layperson to do it their way. What really happens is that i do it the right way, then tell them after the job is done. I hate to admit that, but if you are having a tumor removed from your brain, are you going to tell the surgeon how to do it? Hell no, you value your life, so you leave it up to God and the pro's! Nuff said.
P.S. If you learn how to run LH well, you will have a ball doing it. You will be doing it on every job! Get a handfull of that stuff and go to town. If you have questions PM me.
Molten Metal,
You should not and I repeat should not weld on a crane boom without a qualified Welding Procedure.
The welding procedure, whether it is your companies or the manufacturer has supplied a WPS,will detail the required electrode, required pre-heat etc.
Crane booms are serious pieces of equipment and contacting the manufacturer for a repair procedure or assistance would be the first thing you should do.
I have written in previous postings about cracking occuring in huge excavator booms due to the wrong tensile strength electrode being used.
There are members on this forum with much better knowledge of metallurgy than myself, so hopefully they will help out but I will try and give you a basic explanation.
When you weld something you are trying to match the filler metal as closely as possible with the parent metal. ie 70,000psi steel = E70XX electrode, 80,000psi = E80XX.
For example if you welded a 70,000psi steel with an E110XX the increased strength may not be beneficial, it may actually be detrimental.
The bottom line is you must know that if you weld a certain steel with a certain electrode that it is not going to fail and cause a major accident. The only way to ensure that is with a qualified WPS.
Hope I have made sense,
Regards,
Shane
Preach It and AMEN Brother/Sister Welders; Weld Procedure Specification (WPS) is the only way to cover the south end and sleep well at night.
Shane.Thanks for that,and I'm sure you are 100% right.I will call and e-mail the co. (CAT),and either get the info,or,refuse the job.I hate to do that,although I surely dont want anything that massive to fail.You just know the guy's just gonna get someone else to "just do it",but at least i can tell him about the inherent risks and hope for the best.They are so concerned about down time there that they are loosing alot of $$ because its the only one they have.They use it to pick up cars to and from the compacter at the recycling yard.I just found out that they'd been using it like that for months and that it's,"getting scary so we probably should get it fixed".There are so many fulcrum and leverage points on this thing that you should probably have an engineer look at it to even see if it CAN be repaired in the manner they wish it to be.I'm not an engineer....I guess I answered my own Q' there eh'?.........................:(
"When you weld something you are trying to match the filler metal as closely as possible with the parent metal. ie 70,000psi steel = E70XX electrode, 80,000psi = E80XX."
Not quite. The base metal strength is given in terms of yield strength, and the filler metal in terms of ultimate tensile strength. So you do want a higher number. The correspondences in D1.5 are like this:
Base metal (ksi) Filler metal (ksi)
36 60 or 70
50 70 or 80
70 90
100 100 or 110
Toward the higher strengths there, yield and ultimate get pretty close together it looks like...
But you're absolutely right in that you don't want to use a higher-strenght electrode than you need to. The stronger the metal, the more brittle it tends to be.
Hg