Screw auger shaft and flights
Screw auger shaft and flights
(OP)
I want to fabricate an auger screw out of two dissimilar materials. Normally we use an SAE 8620 hot rolled material for the shaft and an 8620 casting for the flight. In this process we preheat the shaft to 400-500 deg F prior to welding the flights to the shaft.
We now have a very severe application in which we would like to use an ASTM A128-B3 'Hadfield' material for the cast flight, as it has work hardening properties. With this material it is recommend that there is no preheat prior to welding. The question I have is: Is there a good shafting material with properties better or equal to 8620 that the A128-B3 flights could be welded to, that would require little or no preheat?
We now have a very severe application in which we would like to use an ASTM A128-B3 'Hadfield' material for the cast flight, as it has work hardening properties. With this material it is recommend that there is no preheat prior to welding. The question I have is: Is there a good shafting material with properties better or equal to 8620 that the A128-B3 flights could be welded to, that would require little or no preheat?





RE: Screw auger shaft and flights
2. The Mn steel really works best when it is pre-work-hardened.
This is often done by either heavy peening or explosive surface hardening.
What weld filler are you using?
Have you thought of trying Mn steel weld overlay?
These high Mn alloys are common in railroad work and there is a lot of information available on how to form and weld them.
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Plymouth Tube
RE: Screw auger shaft and flights
Second, if you are going to use the Hadfield steel in combination with the 8620 shaft material, local preheat will be needed for the 8620 steel, regardless. What is good is that the carbon content is on the low (0.20 mass percent) end, which will improve weld ability.
As for filler metal, I would suggest using 309 stainless steel filler metal to join the Hadfield (high Mn-austenitic steel) to the low alloy steel. You could also look into a filler metal SFA 5.13 molybdenum-manganese steel EFeMn-B. However, this is more applicable for hardfacing/repair application on Hadfield substrate material or for welding over carbon or low alloy steel substrate materials.
Either way, I would strongly suggest you qualify a welding procedure using ASME Section IX as a guide to ensure adequate strength and ductility of the weld region.
RE: Screw auger shaft and flights
I'd go for a ductile butter layer (307-16 or similar) on the manganese steel, before welding it onto the shaft.
beware, if you preheat the shaft, it will shrink afterwards when it cools down. as the flight shouldn't be preheated (!!!), it will remain the same dimension. Regard both actions together, and you'll see a rather large shrinking stress which will aid cracking in the welded zone.
I wouldn't trust this without further investigation.
RE: Screw auger shaft and flights
RE: Screw auger shaft and flights
It will be fine for re-heat to 275C (500F) for even very long hold times.
If you choose to weld with a low alloy (softer) filler you may need to watch for wear of the welds.
The welds may need to be overlayed to prevent them from being the weak link.
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Plymouth Tube
RE: Screw auger shaft and flights
I disagree, that temperature of 275°C won't hurt the casting. Carbide precipitation happens rather fast in base material when welding. interpass temp should be kept as low as possible ( < 200°C).
Preheating only promotes higher material temp, so precipitation will happen faster and more easily.
Please do elaborate your point of view, maybe I can learn something as I'm currently having problems with repair welding of large Hadfield castings.
Problems we're encountering are of a somewhat different nature (casting porosities which crack through our butter layer) but carbide precipitation also causes loss of material (chips, crumblings upto several cm's large, depending on crack length). Gouging and/or grinding away defects can be enough to initiate crack growth, let alone welding.
RE: Screw auger shaft and flights
If there are areas where the Mn is a bit low and C a bit high then carbide precip will happen 10x as fast.
Most of my experience is with wrought material, we used some preheat, only about 200F, and our sections were not very thick.
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Plymouth Tube