Mig welding heavywall hydraulics

Date 01-09-2008 12:52

Below is a thread from another forum regarding mig welding on hydraulics/heavywall pipe. I was beat out by a competitor who is doing mig on the hydraulics for a steel mill. My spec/code was to tig all hydraulic piping. Thanks PipeIt

Does anybody have any incite regarding achieving a coded procedure for MIG welding Hydraulic pipe that would be acceptable, generally, in industry?

I am currently utilising sched 80 2.5" & 3.0" N.B. Pipe (for high pressure oil hydraulics). I am utilising a company procedure that requires one root run of TIG followed by one capping run of MIG. It is relatively time consuming although I've never had a failure when pressure tested.

It would only be for time saving that I would like to employ MIG only but when I tried to obtain coding for this type of procedure many years ago, I was informed that, although MIG is Low Hydrogen, there was no known way to get a coding.

Has anything changed towards acceptance to MIG only procedure? Any incite would be greatly appreciated! Thanks in advance!

By js55

Date 01-09-2008 14:38

What code?

By PipeIt

Date 01-09-2008 14:44

Sorry I should have left the /code out, tig is what I meant to do, sometimes I will stick out also.

By 803056

Date 01-09-2008 20:56

AS JS asked, what welding code or standard is referenced by the customer?

Al

By 803056

Date 01-10-2008 03:36

Welding standards allow GMAW using short circuiting transfer (I believe that is what you are asking about) with certain restrictions. The restrictions limit the thickness range of the production WPS based on the thickness of the test coupon used to qualify the precedure, i.e., PQR.

I am not familiar with any welding standard that permits the use of GMAW-S without qualification by testing, i.e., there is no "prequalification" as there is by AWS D1.1 for several listed welding processes.

Another consideration when qualifying the welding procedure is the type of base metal used for the hydraulic cylinder. High strength low alloy steels are commonly used and require preheat and in some cases post weld heat treatment. These variables must be taken into account when qualifying the procedure.

Once again, you did not state what welding code or standard you are working to. Without that information we can not provide you with better direction. However, most welding standards or codes allow you to do what you want if you "prove" the process will produce the required results and you control the process in production.

Best regards - Al

By d-on Date 01-10-2008 17:42

Pipeit,
It really is necesary for a sound answer to know the code, but Al is right in saying that most codes allow you to test and qualify. I use to be in the hydraulic cylinder manufacturing business and used both D1.1 and D14.3 to meet different customer specs.

This will sound like a broad sweep at an answer but is not intended to.

Through testing for both codes mentioned we found that metalcore wire was exceptional on hydraulic tubes and tubing, due to its penetration pattern with 90/10 argon/CO2. It also had the benefit over flux cored in interior contamination of the cylinder and it was able to be pulse welded where flux cored can not due to flux entrapment. Travel speeds also increased by 20% average over solid wire and our distortion decreased.

I have not tried metalcore with the Miller RMD process but there have been excellent advances with it in reducing the need to TIG weld roots.

Now if your customer requires TIG by contract then your stuck, but if you can show by qualification and they will accept it then your in business.

Please keep in mind that my testing was very specific to develop a process focussed on a providing a solution targeted at reducing cycle times and not a budgetary constraint. However in the end spending a little more paid dividends.