Weld over weld 1

[bljnv]

In our design, a circular disc is welded on its circumference by fillet weld to the inside of a pipe. To improve yield the pipe is made of two piece and joined circumferentially by submerged arc welding. The fillet weld of the disc-pipe and pipe circumferential joint submerged arc weld fall at same location and this happens to be a fillet weld over submerged arc weld all over. I request the experts on the board to clarify me the following:
(a) Is it acceptable to have weld over weld all through?
(b) What are the safety and quality requirements specifically to be met in such designs?
(c) Request quote any standard / literature to support so as to convince the customer?
Both pipe and disc are of carbon steel St-42 grade. (UTS 420 Mpa/ Yield 230 Mpa)
Regards

 

[desertfox]

Hi bljnv

What is this device? is it a pressure vessel? if so it would be governed by an appropriate code like ASME or BSEN, normally a wld over a weld is not a good idea particularly with the heat effecrted zones over lapping.
Without proper information regaarding its use etc its difficult to help further.

 

[metengr]

(a) Is it acceptable to have weld over weld all through?

Yes, provided a qualified welding procedure specification and welders are used.

(b) What are the safety and quality requirements specifically to be met in such designs?

Safety requirements depend on the code of construction. Quality requirements would be as a minimum volumetric nondestructive testing.

(c) Request quote any standard / literature to support so as to convince the customer?

What is the code of construction for design?

 

[bljnv]

desertfox and metengr, thanks for the reply.

Please find additional information below.

The product is steel wheel used for on road and off road vehicles.The steel wheel is a welded fab consisting of a rim and a disc. The rim is made up of two or three cylindrical band. Individual bands are joined by submerged arc weld (circumferential joint) to form a rim (length of one rim will be the total of lengths of individual bands used in construction). Steel plate of required thickness is coiled and butt welded (longitudinal joint of the cylindrical band) to form each cylindrical band. A circular disc for mounting the wheel onto an axle face using fasteners is welded to the inside of the rim by either submerged arc or MIG welding. The wheel is subjected to vertical(radial) , axial and torsional loads during operation of the vehicle. The wheel rim is subjected to tire inflation pressure on the rim outer surface.

All welds are done according to internal quality procedures developed based on AWS,and are acceptable to the customers.

Thanks

 

[desertfox]

This might help a little:-

http://www.twi-global.com/technical...-implications-of-welding-over-existing-welds/

The article mentions the problems with different heat inputs, heat affected zones etc

 

[tbuelna]

Is the fillet weld around the circumference of the disc actually located coplanar with one of the circumferential welds joining two of the rim sections? Or does the circumferential fillet weld around the disc simply pass over one of the linear welds used to make a rim section? Since this is a wheel structure where the rim is composed of three sections, I would think it would be best to weld the center disc to the middle rim section, so that all of the forces being transmitted from the tire to the axle are better distributed between both outer sections of the rim, and the circumferential weld joints between the rim sections are more equally stressed.

 

[bljnv]

tbuelna
The location of the disc is decided by the wheel offset (distance between rim centreline and the axle/hub mounting face) requirements. Some applications require wheel offset such that the disc is positioned outboard the rim center line. Most of our designs have the disc welded to the rim at locations away from the rim circumferential joints. In certain cases, driven by wheel offset requirement, disc weld happens to fall right on the circumferential joint. Changing the circumferential joint to a different location causes change in band width and the associated problems of raw material yield.

 

[BillPSU]

I'm surprised you are using multiple bands to create your rim blank. My experience was to make the rim blank out of a single sheet of material. Roll form the blank and then submerged arc weld the rim blank. The rim blank was then rough roll formed stretching the rim into a rough shape. The rim was then final rolled formed putting in the necessary drops and knurling the tire grip knurl. The final operation was to size the rim ID using an expanding mandrel. The valve stem hole was punched internal to one of these processes.

The wheel centers were then welded into the rims. The rims were also used in double and triple wide configurations and would have wheel spacing assemblies welding on the inside of the rims. These rims were large tractor rims up to 32" wide. The company no longer makes rims but purchases them.

Your company must have experience with the performance of the current rims in the field. If they are seeing issues with weld failures then obviously you will have to correct the manufacturing process to eliminate and avoid these problems.

Bill

 

[Tmoose]

What kind of NDT is done to the welds, if any?

Can you provide pictures of the failures?

I'm guessing there are potential design or manufacturing issues closer to the front of the line of suspects than welds-on-welds.

 

[bljnv]

BillPSU
Tractor rims are manufactured from single plate with drop centre as you explain. For off highway application, rims are made by joining two or three circular bands.
Timoose
There are no failures in the weld over weld design. There is an apprehension from one of our customer that it can fail or can have lower fatigue life. The circumferential welds joining two circular bands are done by SAW and quality checked using UT technic. They are full penetration joints. One sample , cut from the rim fabrication, for a batch is inspected for fusion, penetration and subjected to micro examination. We have around 600 wheels of this design working in the field till date without any problem.
My question to the members is how to convince the doubting customer with proper technical back-up, literature, though there is a proof of the design from the field.
Regards

 

[tbuelna]

So you are first rolling sheet into a hoop and butt welding the free ends to form a band. Then you perform additional forming operations on these bands to produce rim sections of various sizes that are then circumferentially welded to create rims of various widths. Then a center hub disc is welded into the rim ID at various offsets to produce the finished wheel. If this is correct, one question I have is are there any operations done on the rim or hoop after each welding operation? Is the welded rim rolled to true or straighten it? Is the rim circumferential weld cold-worked or planished to smooth it out and/or improve its mechanical properties? Are either the band or rim weldments stress relieved after welding?

It can be difficult to establish precise fatigue properties for fusion welded materials, since even an automated fusion welding process can have wide variations in the quality of the finished weld joint. There are published specs that provide guidance on qualifying a weld process, including the number of weld examples required, and the number of samples and testing that are needed to validate the weld quality. The qual process is a bit of work since it requires producing some documentation and metallurgical testing of some weld specimens, but it is not outrageously expensive and should not take more than a few weeks to complete. Definitely worth the effort if this is for a valued customer. The results from a weld qual process should easily satisfy your customer.

 

[bljnv]

Thanks for the inputs. If need be I will come back with the feedback from the Customer later.