Great problem in welding of 4145 low alloy steel

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i have a project for welding of 4145 rod with SAW process. I using a flux core wire with the same alloy elements and nickle during this project. However i use proper preheat and post weld heat treatment according to ASME Sec IX. According to mechanical test result all of bend test samples failed due to crack in the samples. Whats your recommendations for resolve this problem?Thanks
Reply:I'm confused as to why you'd be using a flux core wire with the submerged arc welding (SAW) process.   Could you elaborate?Also, according to my book there's no nickel in 4145.Last edited by HT2-4956; 10-19-2014 at 12:20 PM.
Reply:My problem is fail of bend test during bending. Due to high strength of base metal i used the FCAW wires and Ni is required for strength and make better ductility of weld metal. But how i can do for fixing the problems?
Reply:Cored wire doesn't hurt sub-arc with neutral flux, I don't think you are helping yourself trying to add nickel though.4145 is gonna be on the ragged edge of "low alloy" for welding, it's more like medium alloy. If you're using composite calculations (pcm) it's not gonna work for pre-heats. With any SAE steel designation that I find with a CE over .65 I work things using the m90 temp (90% martensite formation on cooldown from critical temp (Ac1)) and pin pre-heats and innerpass temps to that or above.PCM calculations are more for low carbon steel content with stuff like boron and vanadium in the mix to jack things up. Running a PCM calc on 4145 gives a safe pre-heat around 320F... Running the CE calc gives .80 to .85 min to max chemistry... Thats pretty high numbers.The only possible filler that could be a close match adding some nickel I can think of would be be SAE-300M with .40/.44C_.65/.90Mn_1.45/1.80Si_.70/.95Cr_1.65/2.00Ni_.35/.45Mo... I've never fiddled with anything like that.Considering the pre-heat is going to be very high I would also think slag removal with sub-arc would be brutal, not to mention keeping the heat input low enough to not cause other problems with the steel impossible.Anyway, follow this link to get an idea of how hot I'm talking about with a lower CE steel (4130) by arc arcspecialties with test results-> http://www.arcspecialties.com/docume...20on%20HAZ.pdfGood luck,Matt(on edit) You can see the hardness results at the bottom of the document, working 600-700F drops things a lot.Last edited by Matt_Maguire; 10-19-2014 at 05:40 PM.Reason: add info