How to refill a hole bored on a large casting HELP 1

[sacem1]

This question has also been posted on other groups as I'm really pressed on this one:

We were drilling a 3/8" diameter hole for a lubrication supply line in a cast steel adjustment ring for a conical crusher (around 3 ton weight) the hole is 8 1/2" deep at 8" of depth the drill shattered and stuck inside the body.

We tryed several ways to pull the drill bit out but only the first inch got out so we finally after many trials made a drill bit 1" diameter with a 10 mm cutout in the center and bored around the remains of the drill, half inch at a time then extracted the piece of broken drill also 1/2 inch at a time, the job has been excruciting to everyone involved but finally the full 8" were removed (last piece was only 1/2" long) but it left me with a 1" hole in the casting.

I have to fill the hole and redrill the 3/8" oil passage but the original idea of inserting a bar in the hole in a tight fit and welding the last inch flat with the rest of the casting has been vetoed by the customer as the part has to go thru an ultrasound test and the bar fill up will appear as a casting defect (our customer is the foundry, but they are not the end user wich contracts a third party company to do the ultrasound testing).

Up to now the only solution we have comed up with is filling in the hole by welding with 7024 electrodes but the fear is that some slag can get caught up inside the hole as it is extremly deep with respect to the diameter, MIG/MAG welding would be ideal as it does not leave any slag inside but the hole is to deep and narrow as to allow the welder to move the nozzle inside the hole (we have been trying the welds in scrap pieces with same dimensions)

If we go the electrode way the gases do not allow the welder to see inside the tube and we have fitted a small copper tube to a CO2 supply in order to blow out the gases and allow improved viewing, but still CO2 is not completly clear so we might switch to Argon gas blowing, anyway the Argon or CO2 will provide an inert gas or active gas atmosphere wich should not be harmfull to the weld as it will also protect it.

Question: Is there a better way of doing this?

I have not try it yet but maybe I will have to drill a LARGER hole in order to allow enough space for the welder to see and to direct the electrode but I rather not in order to avoid affecting the strength of the casting even thou it is very solid.

Please HELP

I really have a very short deadline to complete this job.

SACEM1

 

[rnd2]

What you are attempting is an extreme form of narrow gap welding. Have you detected cracks as a result of weld shrinkage? I would hold very little hope for a 100% crack free repair. How about a fully threaded plug? That way you could pre-drill the plug before insertion.

 

[metengr]

One option other than welding is to enlarge the hole from 1" diameter to 1.5" in diameter and prepare to install a solid steel insert whose length matches the thickness of the casting. The solid insert could be machined from mild steel bar stock and installed using an interference fit of 0.003"/diameter. In addition, I would stake it at three spots (anti -rotation) using small set screws.

Once the solid insert has been installed with a shrink fit of 0.003" in the casting and staked, you can drill the 3/8" diameter hole thru the center of the insert.

A second option along the same lines is to use a partial penetration weld to install the insert versus the interference fit and staking. You could bevel only the OD side of the casting to accommodate a 2" groove weld depth. The partial penetration groove weld would secure the solid insert. The partial penetration groove weld will require preheat and control of interpass temperatures. Keeping the weld deposit at a 2" depth would avoid post weld heat treatment.

 

[Carburize]

In spite of the ultrasonic indication issue - one of the sleeve approaches that have been suggested would be far superior to trying to weld through the thickness.

 

[arunmrao]

As the casting is a carbon steel casting,welding it is easier. However, the accesibity to weld is an issue. You can consider opening it wider and then weld using TIG process. This will ensure quality of weld deposit and fuse with the parent metal.

You can always ask the foundry if they do not salvage defective castings on a regular basis? My answer is everyone does it. The weld procedure is qualified by an inspection agency.

The alternate route suggested of having a metal insert is attractive,but you need to prepare the cavity in the casting too,so that you get a good fit. Ofcourse UT will also show discontinuity.

Reindex the holes so that you need not drill a hole on the insert and the holes are now located on a fresh surface.

Please keep us informed about the progress.

Good Luck!!

 

[bmoorthy]

What you may do as an alternative is that leave the hole size as is and have the external connection to adapt to the size.

You may also weld a set on type adapter on the hole.

I have also heard a term called Key hole welding. You may try in welding form regarding key hole welding.

 

[MetalsInc]

Keyhole welding is a PTAW method that, without knowing too much about this project, seems to be an unlikely candidate. KHW creates a very deep, narrow weld pool with a plasma jet. Great for some forms of heavy wall butt welds. I don't see it being applicable in this case.

I think the solid bar as suggested by metengr is the way to go. I'd think the end user would accept if if they knew ahead of time what was happening.

 

[EdStainless]

I know that the horses are gone, but I have used EDM to remove broken drills. It is slow and messy, but you can usually salvage the hole.

Is there a 'no weld repair allowed' clause on these castings? How would the foundry do it? That is a very good question.

It sounds like they want to hide this issue.
Is the 1" hole unacceptable for some technical reason? Using the larger hole is the cleanest way to do this.

= = = = = = = = = = = = = = = = = = = =
Corrosion, every where, all the time.
Manage it or it will manage you.

http://www.trent-tube.com/contact/Tech_Assist.cfm

 

[arunmrao]

At times I have encountered broken taps especially in heat resistant steel castings. I have used EDM which is very slow and expensive to remove the broken tap from the casting..

In my 25 years of casting experience I have never seen a NO Weld clause. All standards permit it. Also the casting is not being used as a rotating component it is only a structural reinforcement member in a cone crusher which may not be a critical application.

 

[sacem1]

Thaks to all for your answers, for each one:

To Rnd2: Cracks and voids in the welding are one of my main concerns and thats the reason of this thread, the plug is perfect but not accepted by my customer (the foundry)

To Metengr: I have considered opening up the hole for welding in order to give more space for the welder to work. The insert is not acceptable as a solution by my customer, I really thought more in this way for the plug, a shrink fit instead of threading it and then weld the last inch of the hole with MAG and that would leave a clean surface but as I said not allowed by my customer.

To Carburize: I agree completly with you same situation as before, not allowed

To Arunmrao: As I said to Metengr opening up for welding was and is still considered as the only option in order to allow the welder enough room to manipulate the welding rod and getting out the slag. I have not considered the TIG process because I think it will be too slow in progress, If I open up to 1.5" diam the volume to fill up is 14+ cu.in. (230 cc) even thou I agree that it will give the best possible quality of weldment, maybe I will go that route as by now I have already lost my shipping deadline, better late and well done than late and pourly done.
Reindexing was out of the question as very strict tolerances are enforced for the piece, even thou the only thing that goes to that hole is a copper tube carrying oil for lubrication, that would have been done without pulling the drill out, just welding the outside original hole and redrilling a new one just 1/2" to one side or below and that would have been finished, but I have no liberty to make such a change.

To Bmoorthy: Right now if the casting was mine or if I was installing it directly for the customer I would just do that a 1" oil passage with the output the same size would do no harm or change in the oil flow. (this hole connects to another hole drilled at 90º from the first and 6" long.

To MetalsInc: About keyhole welding I do not have access to that process so its out of the scene. and besides if you say its not applicable more reason to it.
I am waiting for an inspector to come over from the foundry and talk a way to solve this problem, I have printed this thread and am planning on letting him also read it so that your opinions count a lot for us.

Thanks again to all.

I will keep you posted on the results.

SACEM1

 

[sacem1]

I missed the last two entries in my answers before so here they go:

To Edstainless: The piece is big (3 ton weight), about 8 ft across, like a gigantic nut, the hole is perpendicular to the main axis that is it goes horizontally into the side of the "nut" when it is laying down flat, I don't think it would fit in an EDM, and I don't have that machine here at my shop. However the advice is good and may be of help in another similar situation, I'll look into the EDM equiped shops to see if its possible for them to handle those jobs.
There is no clause stating "no weldment".
The hole is unacceptable only because it goes out from the stated dimensions in the drawings and it has no negative effect into the casting operation except that it is supposed to be an OEM part and they are not willing to send out a non standard part.

To Arunmrao: That experience with the taps reinforces the idea to search for a standby provider of the service as I stated before.
The casting is really a static clearence regulator in a conical crusher and it is really very sturdy and it really fails by breakage of the screw threads (it has a 2" pitch monoconical inside thread).

One final question to consider, will a 1.5" diameter hole filled with TIG welding warp a 3 Ton casting with 8" of height and 12" of thickness, maybe we will just have to do it and pray, any ideas.

SACEM1

 

[DAVIDSTECKER]

Quite a few years ago I used a welding rod from "Certanium", it was amasing the arc control that I had and I am a self taught shade tree welder.
The rod I used was used in many cases to go down a hole a build up a broken stud with out fusing to the side wall.
I would suggest you locate a dealer of this product and see if they can use this product to fill the hole or if they have another rod to do the job.
I found some hits on Google.

 

[unclesyd]

You are probably a long way from one of these "BoreTech" bore welding machines but you might want to get into the business. We have one of the larger machines and it does and excellent job.

http://www.bortech.com/default.asp

If you were around a Railway of Ship Yard there might be a possibility of Thermite welding.

If everything else fails get some of arunmrao’s foundry man’s putty and use it without telling anyone.

 

[unclesyd]

sacem1,

Is the hole all way through the part?

If so do you have access to both sides?

If the above was in the positive I was thinking about sticking in plug with a pilot hole and welding from one side then drilling out the plug and welding from the other side. This would cut the depth of the weld by one half. Still tough but better than the worst case.

 

[sacem1]

Well, just to keep you up to date on how things are going:

The casting has been bored to 40 mm at a third of the depth, to 32 mm for another third and the rest is left at 1"
in order to give more room for the welder to work with.

We have a similar hole bored on a scrap foundry piece and tried the TIG solution, well not good a lot of spatter as the welder is not able to see or calculate the position of the welding point so it gets stuck and overheated, this welder is very experienced in TIG but mostly in Inox work but he gave up after several trys and TIG rods so we just decided to use welding rods.

We will use AWS 7024 welding rods, but to work with those the casting has to be standing on its side, slightly slanted to help view into the hole.

Right now we are positioning the casting with the crane on a pit we have at one side of the radial arm drill to be able to drill really tall pieces (that's a good thing to have at one side of every radial drill) and it will help us in this situation.

TO Davisstecker: Thanks for the tip but I'm in Lima, Peru and there is no dealer for those products around here.

TO Unclesyd: I'm going to look at it and comment latter on it, and that putty I'm sure would have solved the problem if we could have relocated the hole and gotten the UT guy drunk.
No the hole is blind and it has the 2" pitch threads allready finished on the other side, it has to connect with a vertical hole at 90º with the first drilled vertically. But the idea of the welding from both sides with a temporary plug inserted first and then drilled out, thats a good idea to keep in mind for other works.

Thanks. I'll keep you posted

SACEM1

 

[macmil]

I've been watching and I go with unclesyd; I would have filled the hole with a good epoxy ( no trade names ! ) plastic steel. I have used this in similar situations in the past where the stress levels are acceptable, as would appear from the description so far. No thermal distortion, and with good surface preparation, an excellent repair strategy.

 

[MikeHalloran]

I'd use bar solder instead of epoxy.



Mike Halloran
Pembroke Pines, FL, USA

 

[arunmrao]

sacem1
I hope the foundry inspector has visited and cooperated in salvaging the casting.

Quite often it happens that a wrong part is ordered or there is an inventory available or the machine is in disuse. In such circumstances to coverup,the customer tries to pass the buck on someone else and cancels the order. I have frequently come across such instances. Hope you are not a victim and the concern is genuine.

 

[rnd2]

Well it looks like you have committed to repair by welding. It is a pity the foundry would not agree to discussing the entire issue with the end client. IMO, 7024 welding electrodes have quite a heavy flux coating and a heavy slag results. There is no doubt in my mind that filling the hole with 7024 will be slow, with real risk of slag inclusions because of frequent stopping and re-establishing the arc.
Can you get access to 6011 or if you have dc welding power, 6010 or even 7010? These are cellulose coated electrodes and develop very little slag. The slag does not interfere with the fierce deeply penetrating arc. Buy the biggest diameter you can, preferably 6mm. Pre-heat the job to about 150 ~ 200 deg. C, increase the welding current to maximum recommended for electrode, strike the arc and swirl the electrode by feel. Keeping the arc going until the stick needs changing.
Try some practice runs first to establish a procedure and test for cracks.
And good luck. I think you will need it.

 

[sacem1]

Well folks here is the last update:

We finished welding the hole with 7024, process was done in the following sequence:

Weld a small layer 2-3 mm thick stop the welding
Clean the slag by hammering and air blowing several times to eliminate residues
Verify the hole was clean by a supervisor

Repeat the sequence for about 100 times (no kiding)

Finish the last 25 mm of the hole depth with ER70S (MAG) as this welding has the same superficial color of the machined casting.

Let it cool overnight

The casting never got heated at 10" from the hole, the steel casting has such a huge mass in comparison with the welding and the really long time this process took (more than 4 hrs) that no risk of warpage happened.

The weld today morning did not showed any contraction at the weld and we proceed to load it again on the Horizontal Boring Machine to redrill it.

And .........

THE DRILL BROKE AGAIN at 4" of depth, now we are in the process of extracting it and starting the work again.

New plan calls for new drilling process:

We are drilling the first 3" with a standard HSS-Co Drill 3/8" diameter

Then we will switch to a 5/16" longer drill and go deeper for about 1/2" then switch to a long 3/8" drill and rebore that last 1/2" repeat this process for 11 times and we should have reached the necesary depth, i am not risking a third drill bit breakage.

The tools are all US made top quality and the HBM is a really solid machine with no wobble in its spindle, the piece is very heavy and compleatly clamped down on the large table, feed is by hand, speed is low and I am switching from soluble oil coolant to plain oil for the next redrill work.

If I am missing something please let me know

By the way the casting carries 4 holes and the other three have been done with no problem at all, and this is the third casting we are machining, previous two with no incidents at all, maybe its just plain bad luck but just imagine how I was feeling when the second one broke.

thanks for your support.

To arunmrao: The folks at the foundry really are long time bussiness partners turned into friends and I do know that the final customer (from the States) is really picky, specially if the pieces are manufactured in Peru of all places.

The same explanation goes to Macmil and MikeHalloran

I´ll keep you posted

SACEM1