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I am student working on a project to design a cooling fixture to cool a PTA welded steel without forming any cracks in the metal and also achieve a hardness value of around 53-58 HRC. The welding is done on a workpiece about 45x48 mm with a thickness of 8.5mm. The current setup involving water as a coolant results in frequent cracking of the steel. Should we pre-heat the steel before welding? and try other coolants available? Our main objective is to achieve the required hardness.
Reply:Give these folks a call and see what they say. They may recomend a diffenent material but 4140. Thats about the limit for heat treating that material.Dan D. NATIONAL HEAT TREAT6923 Brittmoore RoadHouston, Texas 77041Email: [email protected] (855.648.4328)Manipulator Of Metal
Reply:I'm really confused by the question. 4140 isn't going to survive the phase transformations with a violent quench from a heat treat operation. "Transformation stress failure" cracks start at the surface when it gets to the martensite start range below 800F (usually lots of them), while the area just below is still increasing in volume.Welding by any means adds an area of coarse grain, and with this material welded without safe preheat, some retained ferrite, carbides & possibly some pearlite in the mix with untempered martensite in the HAZ.Also the reason you need something that is in the 270 - 290ksi strength range that has to be welded doesn't add up???More info needed, please.Matt
Reply:That's going to require nearly 100% transformation to martensite. What equipment do you have? You could try different (less severe) quenchants, but martempering may be the only way you can avoid cracking.Dynasty 300DXSmith He/Ar gas mixerMM350PHobart Handler 120Smith LW7, MW5, AW1A |
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发表于 2021-8-31 23:00:00