faq
When and why should Alternatives to Welding be considered?
Answer : Whenever Welding is difficult and expensive and if there is no essential need for the kind of metal continuity provided by welded joints. The main point is that welding processes in general are associated with elevated temperatures.
In many situations the application of heat may have adverse effects like crack formation, hardness and strength changes, production of brittle phases, microstructural modifications affecting corrosion resistance properties, unacceptable deformations, alignment and fit problems, introduction of residual stresses.
If the risks following the above effects entail the adoption of special procedures to counteract them, then welding becomes a much less attractive solution.
Among possible alternatives one could consider the following. Brazing and Soldering that require less heat and may provide adequate properties to the joint. Otherwise Mechanical Fastening, structural Adhesive Bonding, surface modification if effective, elimination of joint by design change.
I am a welder that welds with a lot of different processes. My question is this. We are welding up a fabrication table to build a container box that will weigh 50,000 lbs.I was told that it should be SMAW welded with E-7018 and not to weld it with Mig. The mig wire we use is ER-70. What is the difference in the two processes? Aren't both electrodes classified as being good for 70,000 psi? Should I make this structural weld with the Mig or Stick?
Answer : I feel from it that you are a good, experienced and conscientious welder.
I am sure you will obtain good welds with both processes.
Keep up the good work as you please and it will be OK.
[It is true that inadequately skilled welders may produce low quality welds with any process.]
One of the disadvantages attributed to Mig (GMAW) when performed outdoors is the possible loss of shielding gas due to the wind: this is possibly the concern of those who “told” you to avoid Mig. It depends upon the circumstances, if suitable wind shields can or cannot be set up.
It is accepted that self shielded Flux Cored Arc Welding (FCAW) is less prone to the loss of shielding atmosphere while providing the continuous electrode advantage as Mig does. However breathing FCAW fumes is more dangerous to the welder’s health. And of course slag has to be removed between passes and at the end of the process.
As far as strength and stability are concerned the design has to be adequate but there are no differences between the two processes that should bother you as long as sound welds are produced.
There may be quite a remarkable difference in the cost of welding though, but this is up to the management to decide and be responsible for.
What bothers me is that you are made to work in a vacuum of responsibility.
About a year ago I wrote an article titled “Where is the Welding Management?” that you can find at
http://www.thefabricator.com/article/TECHCELL/where-is-the-welding-managementr
As long as your work is good, you will grudgingly get moderate praise (Not too much, lest you may think you are worth a pay raise).
But should one of your construction collapse or get damaged you will get all of the blame and of the consequences.
If at all possible, you should request from your management precise, written instructions in the form of clear, signed Drawings and Welding Procedure Specifications (WPS).
You are not supposed to be “told” anything, you should get only written instructions. Those who give you welding work must take full responsibility in writing for whatever you are requested to perform at the best of your ability, but not any more than that, including process selection.