Neeves
Well-Known Member
G120 chain is simply G100 chain with a different wire shape, square instead of round. The square shape has extra volume over round and this imparts the extra strength. I have not checked but I very much doubt there are windlass gypsies taking links made from square wire. G120 chain is inordinately expensive (and would never merit use in an anchor rode - but never say never!)
There is some G120 coming out of China now. I have not tested it and reserve comment, but their G30 is G40 quality and their G80 is a match for chain from Europe.
G70, G80, G100 (and G120) are all Q and T chain ( same Q and T as better anchor shanks). The higher the G number the lower the Tempering temperature. The coating process used for my chain is an update on the British Sherardizing process and its a thermal diffusion process - but still needs heat. Any heat imposed on a Q&T product, by HDG (hot dipped galvanising) or TDG (thermal diffusion galvanising) can impact the final Tempering in a Q&T process. As the G Number increases the tempering temperature reduces. TDG overcomes the thorny issue of Hydrogen Embrittlement by not using any acid in the process.
HDG is usually conducted at 450 deg C, most TDG is conducted at 400 deg C but after numerous trials we worked at 375 deg C (as here there are many Q&T items that need to be gal coated). I have a trial, short length of G100 to be tested next week - it is claimed its possible, I'll wait and see. The TDG process (HDG is worse) effectively retempers the chain, there is some strength loss but extension to break for TDGincreases to a level similar to G30 and G40. I don't know what might happen with G100.
There are now some 'special' G80 chain made, obviously, with a different alloy over conventional G80 that must be processed at a higher tempering temperature - as they can be used in high temperature environments (think foundries, steel works). Max application temperatures are quoted at 400deg C. They offer another option, that I have not looked at - and they might be expensive. The high temperature G80 chains are not commonplace, I've not looked that hard but Kito (who own Peerless) in Italy and there is a S African source.
But even with my 370 deg C there was some strength loss - but not enough to worry about. TDG can be conducted at lower, much, temperatures but throughput reduces and costs rise. Anything is possible - you need to make some choices - its for an anchor, compromises are necessary!
The G80 chain made here (Australia) is made to a link size that does not match any known windlass gypsy, hence use of European or chain made to European standards.
The TDG coating is harder than the HDG coating. It is possible to define within about 10 microns TDG coating thicknesses. The US Navy have fixed on 80 micron (different application), I fixed on 100 micron. I did 2 x 70 days intense abrasion tests on a cross section of TDG and HDG chain coating thicknesses.
It might all sound very complicated, it took 2 years to sort out. But now the TDG operator here and I know what we are doing its relatively easy.
My new chain has a harder and thicker coating than most HDG chain, it should last at least as long as the best HDG coatings. The 6mm chain is cheaper, lighter and stronger than 8mm Grade L (G30) here and at least as strong as the best 8mm HDG G30. The extension to break is similar to some G30 chain and better than most. I have been using it now for 11 months without issue - it will be years before there is a real comparison with normal HDG.
As I mentioned in an earlier post one advantage of what I have done is I have matching components to join chain to anchor and snubber to chain. They match for size and strength.
I omit a lot of detail, anyone who seriously wants to consider this could contact me - after they have defined where they will have the coating completed.
I had wanted to write this up, in detail, for YM - they were not interested.
Jonathan
Edit There is a school of thought that suggests you cannot re-galvanise G70 or G80 chain - making it a once used only product. The background thought is that as you reheat, with subsequent re-galvanising, you slowly reduce the strength back to the base, non Q&T steel. Someone, who should know as they are in the industry and business and are therefore not an armchair internet guru, has suggested this is a load of rubbish. I am testing this out, I have actually had both used G70 and used TDG G80 recoated (the G70 with HDG and the G80 with new TDG) and will test for strength loss (or difference) next week.
close edit
There is some G120 coming out of China now. I have not tested it and reserve comment, but their G30 is G40 quality and their G80 is a match for chain from Europe.
G70, G80, G100 (and G120) are all Q and T chain ( same Q and T as better anchor shanks). The higher the G number the lower the Tempering temperature. The coating process used for my chain is an update on the British Sherardizing process and its a thermal diffusion process - but still needs heat. Any heat imposed on a Q&T product, by HDG (hot dipped galvanising) or TDG (thermal diffusion galvanising) can impact the final Tempering in a Q&T process. As the G Number increases the tempering temperature reduces. TDG overcomes the thorny issue of Hydrogen Embrittlement by not using any acid in the process.
HDG is usually conducted at 450 deg C, most TDG is conducted at 400 deg C but after numerous trials we worked at 375 deg C (as here there are many Q&T items that need to be gal coated). I have a trial, short length of G100 to be tested next week - it is claimed its possible, I'll wait and see. The TDG process (HDG is worse) effectively retempers the chain, there is some strength loss but extension to break for TDGincreases to a level similar to G30 and G40. I don't know what might happen with G100.
There are now some 'special' G80 chain made, obviously, with a different alloy over conventional G80 that must be processed at a higher tempering temperature - as they can be used in high temperature environments (think foundries, steel works). Max application temperatures are quoted at 400deg C. They offer another option, that I have not looked at - and they might be expensive. The high temperature G80 chains are not commonplace, I've not looked that hard but Kito (who own Peerless) in Italy and there is a S African source.
But even with my 370 deg C there was some strength loss - but not enough to worry about. TDG can be conducted at lower, much, temperatures but throughput reduces and costs rise. Anything is possible - you need to make some choices - its for an anchor, compromises are necessary!
The G80 chain made here (Australia) is made to a link size that does not match any known windlass gypsy, hence use of European or chain made to European standards.
The TDG coating is harder than the HDG coating. It is possible to define within about 10 microns TDG coating thicknesses. The US Navy have fixed on 80 micron (different application), I fixed on 100 micron. I did 2 x 70 days intense abrasion tests on a cross section of TDG and HDG chain coating thicknesses.
It might all sound very complicated, it took 2 years to sort out. But now the TDG operator here and I know what we are doing its relatively easy.
My new chain has a harder and thicker coating than most HDG chain, it should last at least as long as the best HDG coatings. The 6mm chain is cheaper, lighter and stronger than 8mm Grade L (G30) here and at least as strong as the best 8mm HDG G30. The extension to break is similar to some G30 chain and better than most. I have been using it now for 11 months without issue - it will be years before there is a real comparison with normal HDG.
As I mentioned in an earlier post one advantage of what I have done is I have matching components to join chain to anchor and snubber to chain. They match for size and strength.
I omit a lot of detail, anyone who seriously wants to consider this could contact me - after they have defined where they will have the coating completed.
I had wanted to write this up, in detail, for YM - they were not interested.
Jonathan
Edit There is a school of thought that suggests you cannot re-galvanise G70 or G80 chain - making it a once used only product. The background thought is that as you reheat, with subsequent re-galvanising, you slowly reduce the strength back to the base, non Q&T steel. Someone, who should know as they are in the industry and business and are therefore not an armchair internet guru, has suggested this is a load of rubbish. I am testing this out, I have actually had both used G70 and used TDG G80 recoated (the G70 with HDG and the G80 with new TDG) and will test for strength loss (or difference) next week.
close edit
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