Crack appears in weld as it cools

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Folks,I'm a novice, but am having fun learning. Sometimes - too often - when I weld (with oxy-acetylene) a butt joint the weld looks OK, but as it cools a crack will suddenly appear along the length of the weld. Today this happened as I welded two 3/16" thick 2"x2" angle irons 18 inches long together (welding them together to form a U-channel). I don't bevel the edges - just butt them together. Any ideas what I'm doing wrong?Thanks,Jack
Reply:Probably not enough weld since you have no bevel. The strength of the steel moving as it cools is stronger then the weld.
Reply:Try preheating your workpiece a little with the torch before u start welding.  Take it slow. A pic would help in diagnosis
Reply:Hot cracking takes place at temperatures over 1000 deg F and occurs almost immediately when the weld solidifies. There are three common types of hot cracking: segregation, bead shape and crater cracking. Segregation cracking is a type of centerline cracking, which (as its name implies) occurs through the center of the weld. It results when low melting point elements are concentrated in the center of the weld after it hardens.  It is common when welding metals that have higher sulfur and phosphorous content, ones with zinc plating or galvanized coatings, and on materials that have been painted or primed.There are several options to help prevent this type of cracking:(1)  Order steels with low residual phosphorous and sulfur (less than 0.05 percent), if possible.(2)  Reduce heat input during welding, which lessens the time for segregation to occur.(3)  Modify the joint design so that depth-to-width ratio is not too great or too small.(4)  Make welds with more throat thickness or that are less concave.I would clean back the weld area to bright metal and include a slight bevel, turn the heat down (amps) basically any of the above 4Hope that helpsLast edited by Gerry1964; 12-29-2012 at 02:42 PM.
Reply:Originally Posted by Gerry1964I would clean back the weld area to bright metal and include a slight bevel, turn the heat down (amps) basically any of the above 4Hope that helps
Reply:Originally Posted by FODFAHow do you turn down the amps on OA Cheers Andrew
Reply:Hmmmmmmm OA......I would guess your not adding enough filler or like mentionedthere is some plating present? Pics would help  Miller Dynasty 350Twenty Six HammersThree Crow BarsBig Rock
Reply:Angle iron?  Grind the mill scale off first.  The carbon in the mill scale can make things brittle.My name's not Jim....
Reply:This angle you have isn't from a bed frame is it?__________________
Reply:Thanks, folks. This is great information. I've attached a pic. The angle iron is just stock from Tractor Supply.Alas, by uploading this picture you'll see just how poor my welding skills are!Jack Attached Images
Reply:Originally Posted by zekeThis angle you have isn't from a bed frame is it?
Reply:Originally Posted by zekeThis angle you have isn't from a bed frame is it?
Reply:More filler please Thermal Arc 210 FabricatorHypertherm PM 45and lots of other tools the wife doesn't know about
Reply:Originally Posted by FODFAHow do you turn down the amps on OA Cheers Andrew
Reply:That's nice that you've tried a butt joint, but you haven't mastered puddling with o.a.. Cut some coupons and practice puddling. Do not play with filler rod until you've achieved something close to perfection pushing the puddle on coupons. Or waste your time.http://www.facebook.com/LockhartMetalArthttp://www.facebook.com/pages/Grumpy...44306259043484
Reply:Originally Posted by zekeThis angle you have isn't from a bed frame is it?
Reply:Originally Posted by DSWDon't shuffle your socks on the carpet as much.
Reply:jackganssleEvery piece of steel I have O/A welded isn't silver when finished.It always has pronounced thermal-gradient bands  -  HAZ.In the picture, there appears to be: faint spectral temp. colors - parallel with the joint, but not consistent with steel.Your coupon look like T6 Aluminum fried with O/A.  6000 series aluminum contains iron as a trace alloy; possibly responsible for the faint colors.Weldable steels don't behave this way. In keeping with: your self acknowledged novice-spirit, can you please have the material positively identified by an authority, because;I would like to know how you got these results as much as you.Opus
Reply:I am with BC, Rkott and the cricket. Number one, need a bit more of a real puddle. Number 2, gotta add filler. Steels tend to lose important properties when joined without filler. The welds look nice, but will crack, and crack and crack.And then, after so much work...... you have it in your hand, and you look over to your side...... and the runner has run off. Leaving you holding the prize, wondering when the runner will return.
Reply:your picture wasn't very clear but from what i could see (as other's have too) you don't have enough filler metal in the joint. try making straight soapstone lines on a piece of flat stock and make practice beads after you get pretty good with that then try joining two pieces together. get a book on oa welding or look online to see what your beads should look like. keep practicing and don't give up.i.u.o.e. # 15queens, ny and sunny fla
Reply:The strength of the steel moving as it cools is stronger then the weld.
Reply:Originally Posted by jackganssleThanks, folks. This is great information. I've attached a pic. The angle iron is just stock from Tractor Supply.Alas, by uploading this picture you'll see just how poor my welding skills are!Jack
Reply:Don't get discouraged some guys take more time than others just make sure you have GOOD practice because bad habits are hard to get rid of.......  Miller Dynasty 350Twenty Six HammersThree Crow BarsBig Rock
Reply:Originally Posted by SnuffyI thought bed frames were friction welded
Reply:Assuming the material you have is indeed steel, you may want to double check your flame adjustment.  How does the puddle behave when you are welding?  Is the puddle glossy and well behaved or does it bubble and fizz?Others have given good advice above - practice forming and moving a puddle on a flat piece of stock.  Taking the time to master this before moving on to actually joining metals is key.  Yes, it will take some time but it is the best way to learn about the puddle.  While you're learning about the puddle on a plate, be sure to play with different levels of heat and both oxidizing and carbuerizing flames so you get a feel for how each will affect the metal.  You will only want to weld with a neutral flame, but its good to see how the different flames influence the molten metal.OA welding is a fun process and its what I learned with, still learning actually.  There are some good videos on youtube that will show you what the puddle is supposed to look like.  Keep after it, it will all click soon and then its smooth sailing!Victor OAHobart Stickmate LX 235AC/160DC