water on a hot weld

Date 06-19-2011 13:11

blacky1

Welcome to the American Welding Society Online Forum

Not enough information

Farm Code probably allows it. :wink:

But I don't know anywhere any cooling is to be performed using water.

Even heat straightening restricts cooling to dry air I believe

Good Luck

Marshall

By blacky1 Date 06-19-2011 13:57

2" pipe .218 thickness 3" .300 thickness 2" P/L is a gas lift line 3" is a flow line for oil. Like I said they are putting water right after they make the butt weld on the pipe

By NWPAwelder (**)

Date 06-19-2011 14:05

I'm not a metallurgist, but I was always taught that water quenching a weld was a bad thing as it cools the weld/HAZ so quickly that the tempering effect created can actually cause it to crystallize and be brittle. Like I said I'm no metallurgist but I am sure this topic will be a good one to keep an eye on and learn a few things.

By 803056

Date 06-19-2011 15:58

Quenching is most effective when the rapid cooling is performed from the austenitizing temperatures to drive the decomposition of Austenite to form other microstructures, i.e., Martensite, Pearlite, or Ferrite. When the steel is austenitized and it is force cooled to transform from a face centered cubic crystalline structure into a body centered cubic or elongated body center cubic unit cell. In the face centered cubic phase, the austenite is able to allow carbon to go into solution interstitially. Think of the FCC structure as an empty box that can accommodate the carbon atom. Cooling the Austenite below the transformation temperature causes the atoms to be rearranged so that the empty box is no longer empty. The FCC Austenite decomposes into a body centered or elongated body centered crystalline structure that can no longer accommodate the carbon or very little carbon in the case of the latter, i.e., elongated BCC.

Think of Austenite as a box that is empty. As the steel cools from the austenitizing temperature the atoms rearrange themselves to form a body centered structure which has an atom of iron inside the box. Since the atom takes up residence in the box there is no room for the carbon. In order for the iron atom to take up residency, it has to evict the carbon atom. It is the rate at which the cooling takes place that determines whether the iron is successful in tossing the carbon atom out of the box or if the carbon gets trapped in the box with the iron atom. The only way the box can accommodate both the iron atom and the carbon atom is if the box stretches to become elongated and highly stressed. When that occurs, the microstructure formed is called Martensite. Martensite is characterized as being hard and brittle, but quite strong. The amount of Martensite is dependent on the amount of carbon in the mix of iron atoms and how rapidly the steel is cooled from the austenitizing temperatures (think of cooling the steel from red to orange hot temperatures). The more carbon in the steel and the faster it is cooled, the harder, stronger, and the more brittle the steel becomes.

Slow cooling allows most of the carbon to diffuse from the austenite. Slow cooling results in softer, more ductile, but "weaker" steel. This is of benefit when it is desirable to have steels that exhibits good ductile behavior and where high strength isn't necessary.

Note that the properties are dependent on how the steel is allowed to cool (slowly or quickly) from the austenitizing temperature range and how much carbon or carbon like elements are present. Once the steel cools to a temperature below the lower temperature of transformation, the damage is done. That is, once the steel is cooled below the temperature at which it has formed either Ferrite (soft iron), Pearlite (steel composed of a matrix of Ferrite and Cementite), or Martensite, rapid cooling to ambient temperature is going to have little further effect.

There are some alloy systems that continue to form Martensite all the way down to room temperature. In other alloy systems it is necessary to chill the steel to very low temperatures to ensure all the retained Austenite is decomposed into Martensite, but that isn’t the case with most low carbon, low alloy steels used for line pipe and structural steel. For the most part, once the steel is cooled to a temperature below "black heat", rapid cooling has little effect.

I am not advocating rapid cooling without knowing more about the particulars of the steel alloy being used or uncontrolled cooling. However, it isn't necessarily the end of the world if this is in fact low carbon steel. Further investigation is warranted before a final decision is made. Whether the procedure being followed by the contractor is acceptable is beyond the purvey of a CWI that doesn't have a solid back ground in metallurgy. That fact that the contractor says, "This is the way we always do it." is hardly comforting until all the facts are known.

There are many types of steel available to the design engineer. Higher strength steels are of interest because the completed structure is lighter and less expensive, but high strength steels are not as forgiving as the lower strength steels. What was done on the last project may have little to no bearing on the success of the current project. A little caution is a good thing. Assume the worst until the contractor can prove otherwise. The contractor should be able to demonstrate the procedure used on the current project will produce acceptable results.

One way the contractor can demonstrate the procedures in use are acceptable is to qualify the welding procedure following exactly the same procedures proposed for use in production. If the contractor wants to water cool the welded pipe from a high temperature, e.g., 1100 degrees, he should do so as part of the welding procedure qualification to demonstrate the properties of the completed weld meet the requirements of the applicable welding standard. Once the WPS is properly qualified, the inspector only has to monitor the welding to verify the qualified procedure is followed to ensure the results are predictable.

As a point of information, all metals are crystalline structures. There are 14 different crystalline structures possible when all the different alloy systems are considered. In the pure state, metals crystallize either as a body centered cubic crystal (unit cell), face centered cubic, or hexagonal close packed unit cell. A face centered cubic structure is more ductile than a body centered cubic structure and in general, metals that are hexagonal close packed tend to be corrosion resistant.

A number of metals can transform from one crystalline form to another. Those metals that can transform are said to be allotropic. Examples include iron, chrome, titanium and a number of others. The allotropic transformation is driven by temperature and is a reversible process. Both the mechanical and physical properties change when the metal undergoes allotropic transformation.

The size of the crystalline clusters, i.e., grain size, influences certain properties. Large grains tend to resist high temperature creep and fine grains tend to be tougher. When held at high temperature, large grains tend to absorb smaller grains, thus the larger grains get larger. Grain coarsening can be experienced in the HAZ when very slow cooling is permitted. However, rapid cooling from the austenitizing temperatures may result in the formation of brittle Martensite in the HAZ and a host of other problems may result.

I hope this helps clarify some of the possible metallurgical problems that the inspector can encounter. It can be beneficial to know what questions to ask when you have a "gut feeling" something isn't right.

Best regards - Al

By Blaster (***)

Date 06-19-2011 18:05

Thanks for posting all the info Al. Very interesting.

I have virtually no metalurgical knowledge... read a few books over the years but without practical application and observation of outcomes I find it quite dificult to retain much of the info and theory.

Anyhow I was curious one day about the this topic as I have seen locals welding out in the rain here in the coastal PacNW. Where I come from in the SW welding frequenty shuts down until it stops raining. For fun I heated up a bunch of A36 3/8 x 1 flat bar red hot with a rose bud and quenched it in different ways before attempting to bend it in a press brake.

After doing this on numerous occassions with A36 over the years, I have found the outcome can vary a fair bit. With a full immersion and swishing around from red heat I have had bars snap like a candy can with virtually no deformation at all. Once a piece snapped and shot out of the brake with considerable force, almost hitting a bystander in the head. On other occaissions the bars have not broken in half but only cracked open on the outside of the bend. (Different lots of steel, same grade, same bend radius, all bars bent cold)

I have also heated the bars red hot and sprayed with a squirt bottle to simulate rain. These have always bent the same as bars that weren't heated at all. Even when slowly pouring the contents of the squirt bottle so that it would run down the bar, like may be the case if rain were running down a column I have not seen any real difference in how the bars bent v. unheated bars.

At the recommendation of a colleague (Allan maybe?) I have done something similar with the bars, arc striking them rather than heating and quenching. Then bending after having ground the arc strikes smooth. These samples have always opened cracks on the outside of the bend. Same with a small tack weld that is ground smooth and bent.

That info may not be usuable in its self, but I think doing activities like this do help one to understand and retain some very basic principles.

By DaveBoyer (*****)

Date 06-20-2011 01:18

Quenching A36 gives variable results because A36 is not an alloy formula, but a mechanical property based description. Some A36 has has enough carbon & other alloys to respond somewhat to heat treatment, particularly when quenched very rapidly.

There is a home brew quenchant called "superquench" used in the blacksmithing community to heat treat A36, but once again, due to the variability of the carbon & other alloys in A36 sometimes it gets pretty hard while other heats may not.

By Lawrence (*****)

Date 06-19-2011 14:50

Tell us the actual temperature of the pipe when it is being treated with water.

By blacky1 Date 06-19-2011 15:00

with in 5 sec. they are putting water on it

By blacky1 Date 06-19-2011 15:08

after they are finishedmaking the weld they are putting water with in 5 sec. before I got on the job and told them no way as long as Iam Inspecting the job

By ssbn727 (*****)

Date 06-19-2011 17:44

Hi Blacky1!

"WELDCOME TO THE WORLD'S GREATEST WELDING FORUM!!!"

Now that the pleasantries are done, I have some questions for you... Are you the Engineer of Record (EOR) who approved the WPS's for this project, or site engineer who should be familiar - if not also involved with developing the WPS's for this project as well, or Company/Contractor's representative who are also familiar with the WPS's used for this project, or are you just the CWI on the job? Another question would be to ask whether or not you were involved in developing the same WPS's used for this project and know what was approved by the EOR?

I ask you this because if you're not any one of the of the persons I just mentioned and are just the CWI on the job, then if I were you, I would first seek clarification from the EOR or whomever the powers that be in order to be sure that they're running this job under the "Farm" code or are not in compliance to the specific code under which this project falls under.

If you attempt to shut down a project just because of your gut feelings telling you so, and being absent of the facts, then you're looking for some trouble from the powers that be - comprende?

Remember the chain of command first, then understand that even if you follow it, you still do not have the authority to stop the welding unless you have been given this authority in writing by the EOR or any other powers that be unless you just happen to be an owner of the project - Capeche?

So CYA (Cover Your Arse) first and seek clarification and then write out the NCR (Non Conformance Report) because you do not have the authority as just a CWI to stop a project unless you have expressed written consent from the applicable higher up person in charge of the project - entiende? (all of those foreign words mean "understand?")

Respectfully,
Henry

By blacky1 Date 06-19-2011 18:18

Already talk to the major company that the contractor are laying the P/L for and they said that the contractor are not surpose to hose down the welds right after they finished making the butt weld on the pipe. But I still can't figure why the welders and the forman for the contractor said they been doing that for a long time. I been a pipe welder and fabricator 38 yrs. and a CWI for almost 8 yrs. and I never ran across a situation like this before. I never heard of doing that or seen doing it

By 99205

Date 06-19-2011 20:10

Ya really have to wonder about the training/background of the foreman and welders on that barge.

By 803056

Date 06-19-2011 20:56 Edited 06-19-2011 21:05

Hello Blaster;

I've tried experiments as you have. The difference being that I tested my samples in a guided bend tester using a plunger and die with a 1 1/2 inch diameter plunger.

In my case, I attempted to bend welded samples prepared in accordance with D1.1 and bent them while they were still hot from grinding the backing bars off. I found that the samples that were bent while still too hot to hold in my hand (without gloves) usually failed. The samples that were allowed to cool to the point where I could handle them comfortably bent without cracking. The results appeared to contradict some literature that states the ductility increases with increasing temperature and strength and hardness decrease with temperature. However, the general statement doesn't consider the blue brittle range where some steels experience increased embrittlement at elevated temperatures that are still below the lower temperature of transformation.

I have even welded test coupons in the vertical position using rather large single pass groove welds with E7018. I tossed the red hot coupons into the snow and into water. In both cases the guided bend tests for both face and root passed the bend tests. The steel coupons were 3/8 inch thick ASTM A36.

Like you, I was curious to see what would happen. Once I was satisfied with the results I used to drive the pipefitter crazy when I would weld my coupons and toss them into the cold water to cool them just before cutting them for bend testing. “It’s going to crack when you bend them!”

To their surprise they never did crack. They would just shake their heads and say, “You’re just lucky this time.” I won my fair share of free coffee from the fitters. That being said, playing games in the welding booth is not the same as welding on the job. There is too much at stake to play games on the job site. The approved WPS is the working document that I used to work with. Right or wrong, I did what it said. If I disagreed with it, I made my concerns known, but until the WPS was changed, I followed it to the letter.

It is all in knowing what you are working with. Low carbon steel will not harden too much when heated and quenched. Mild steel will harden to a limited extent and high carbon steel will harden easily when quenched from the austenitic temperatures.

That is why it is so important to understand the fundamentals of metallurgy for the material you are welding. In this case, the line pipe can range from low carbon steel to high strength low alloy steel. The differences can be significant and their response to heat treatment can vary coinsiderably. Regardless of the steel alloy, the greatest response is when the steel is quenched from austenitic temperatures, i.e., above red heat. In this case, I doubt the welds and the adjacent heat affected zones are still austenitized when the contractor pours water on them. Still, until proven otherwise, a little caution is always prudent.

I agree with Henry's council. It is the inspector's responsibility to notify the client of his concerns and it is the Owner's responsibility to initiate appropriate action if he has any concerns. The written report can be an appropriate vehicle for the inspector to use to inform the different parties of those concerns. It is rare that the inspector has the authority to pull the plug on a project. That being said, it sounds as if the inspector has been retained by the contractor. Who does the inspector complain to if that is the case?

Since it appears that the field foreman and the welder have taken it upon themselves to hasten the cooling rate, the inspection report may still be the best vehicle to make known the inspector’s concerns. Upper management may be totally in the dark with regards to the field crew’s practices.

The bottom line is that the inspector could lose his job if he does not tread lightly. A few well phrased questions to the appropriate people might be in order. Perhaps the inspector could ask the contractor’s upper management for clarification on how the welds should be "artificially cooled" before being radiographed. A simple question might tweak their interest as to why an inspector would ask such a question. I can imagine the expression on a manager's face when he reads the report and ask, "What the heck does artificially cooled mean?"

If the contractor hired the inspector to radiograph the completed welds, it isn't the inspector's responsibility to question the contractor's procedures. It is the inspector's responsibility to determine if the welds are sound at the time they were radiographed. It can be a sticky situation for the inspector to say the very least.

With regards to who trained the welder or the foreman; who says they received any training other than on-the-job experience? It is common practice to make the individual with the least knowledge and skill the foreman. After all, there's little else he can do that is usefull, so make him the foreman! :yell:

Best regards – Al

By the way, Happy Father's Day!

By blacky1 Date 06-19-2011 21:57

I am not hire by the contractor. But by the Client. Every thing is documented each day. It is a sticky situation for the inspector. The Client want a 100% radiographed on the first 5 welds then mixed it up to radiographed every 4, 5, or 6 weld after the first 5 welds on the pipe line. So dam if you do or dam if you don't. So who do I answer to?

By 99205

Date 06-19-2011 22:08

You answer to the person signing your check.

By blacky1 Date 06-19-2011 23:25

Thanks to all for the information

By dbigkahunna (****)

Date 06-20-2011 10:33

THAT is my response.
If the client does not want the welds quenched, then the contractor should stop.
Be sure you have this cleared with the pipeline owner as you are going to start a po po storm when you start rejecting the welds.
That said, if the contractor has worked for the owner before, this was accepted by someone above you in the food chain in the past. If this person is still working for the owner and has achieved a higher position, you are going to open a can of worms. If this is a new contractor, then they are just seeing what they can get away with.

By blacky1 Date 06-20-2011 10:39

Thats right a new contractor trying to see how for they can milk the cow

By blacky1 Date 06-20-2011 02:23

If you read what I worte I didn't say I was going to shut the job down I said as long as I was there there be no water put on the weld right after it is welded The Client dose not want to put water on the welds to start with. I am just following my instruction from the client. The weld really have a chance to knot the slag off before they are putting water on it with a hose

By ssbn727 (*****)

Date 06-21-2011 00:10

Well,

If you then have some sort of documentation which explicitly prohibits the use of rapid quenching or something similar in description, then it should be what you need to convince the contractor to cease the rapid quenching and follow the inspection procedures to the letter as my good friend Al would state. :wink:

Now if you want to go back and pull out the preceding pipe that's already been laid in order to re-evaluate the welds, you might be walking on egg shells in doing so, but if you can convince the company that it is in their best interest, and have physical proof showing that some of the welds are indeed later found to be defective, then that is a way of circling the proverbial wagons around the project in order to maintain integrity of the pipe laying project.

Respectfully,
Henry