Kelpie
Well-Known Member
G40 has higher strength/hardness.
Buying chain
- Thread starter bigwow
- Start date
G40 has higher strength/hardness.
alahol2
Well-Known Member
rickym
Well-Known Member
Just sourced some chain from my local chandlers. His chain is from a reputed UK supplier/manufacturer but it appears the chain comes from either South Africa or the far east!
However it conforms to; Grade 30 Calibrated Short Link Chain, manufactured to DIN766 and ISO4565. Galvanized finish to ISO1461. Batch tested and supplied with Certificate of Conformity
So yer pays your money??
However it conforms to; Grade 30 Calibrated Short Link Chain, manufactured to DIN766 and ISO4565. Galvanized finish to ISO1461. Batch tested and supplied with Certificate of Conformity
So yer pays your money??
vyv_cox
Well-Known Member
Grade 40 is around 25% stronger than Grade 30. I have not been able to ascertain exactly what the difference is metallurgically. Grade 70 is considerably stronger again, this has a higher carbon content, some alloying elements and is heat treated. I'm not sure whether Grade 40 is heat treated, so I assume it has a higher carbon content than G 30. I would welcome any information that can be provided.
RobBrown
Well-Known Member
Is the G grading re the galvanising rather than the steel?
Vyv
When I did a seach on this some time ago, I came across references to the G30, G40 etc grades as relating to the thickness of the zinc coat on galvanised steel, rather than the nature of the steel itself. I was a bit surprised at that so was inclined to dismiss it as inaccurate but as a result of this thread, I did another search and came up with a no of similar infos eg:
http://www.steelmillsoftheworld.com/activities/datacenter/G_Note1.pdf
Rob
Vyv
When I did a seach on this some time ago, I came across references to the G30, G40 etc grades as relating to the thickness of the zinc coat on galvanised steel, rather than the nature of the steel itself. I was a bit surprised at that so was inclined to dismiss it as inaccurate but as a result of this thread, I did another search and came up with a no of similar infos eg:
http://www.steelmillsoftheworld.com/activities/datacenter/G_Note1.pdf
Rob
alahol2
Well-Known Member
According to this the actual spec of the steel is left to the discretion of the manufacturer so far as I can see. Other sources seem to say G30 is low carbon steel and G40 is high carbon steel with no heat treatment to either. The G30 and G40 etc specs seem to relate more to the physical properties of the finished article than to the metalurgical properties.
vyv_cox
Well-Known Member
I think that is a completely different coding, nothing to do with chain. Samples of Grade 40 in my possession have particularly poor galvanising and I know of at least one buyer who returned 60 metres of Grade 40 chain to a well-known supplier on the grounds that the galvanising was so poor.
vyv_cox
Well-Known Member
That's my thinking, as I said above. When I worked in the steel industry many grades were sold by mechanical properties, rather than composition.
[2574]
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Is grade 30 strong enough?
I'm buying new chain this season so have been looking at what's available and it has caused me to wonder whether grade 30 is strong enough. According to this website: http://www.williamhackett.co.uk/products/chain-products/bulk-chain/grade-30-short-link grade 30 (10mm) has a 1250kg working load and a 5000kg breaking load. The question is what load does the boat impose upon the chain? She's a 12m, 9,500kg Nauticat Pilot House so has a bit of windage. Anyone got any ideas?
rob
I'm buying new chain this season so have been looking at what's available and it has caused me to wonder whether grade 30 is strong enough. According to this website: http://www.williamhackett.co.uk/products/chain-products/bulk-chain/grade-30-short-link grade 30 (10mm) has a 1250kg working load and a 5000kg breaking load. The question is what load does the boat impose upon the chain? She's a 12m, 9,500kg Nauticat Pilot House so has a bit of windage. Anyone got any ideas?
rob
vyv_cox
Well-Known Member
I answered a question similar to this for YM some time ago. You can find the full response on my website here. Its the fifth one down. I cannot post the ABYC table here but it is in my response. Their figure for a boat of 40 ft is from 300 pounds in 15 knots of wind to 4800 pounds in 60 knots. Many people who have made their own calculations find the ABYC ones to be on the high side, but as they are 'official' many anchor manufacturers use them. The John Knox equation has been verified by strain gauge (Anchorwatch) and seems to be pretty accurate.
ithet
Well-Known Member
Securefix can supply a Certificate of Conformity for their Grade 30 chain. What information should one expect to be on this, and does having it mean anything worthwile?
vyv_cox
Well-Known Member
A standard to which it is formed, e.g. DIN766 and maybe a proof stress, which proves that a sample length was pulled to a certain figure well below the UTS without deforming or breaking.
[2574]
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Thanks Vyv, that's very helpful. The John Knox equation suggests that grade 30 is adequate for my needs though the ABYC table suggests its marginal. I think I'll sleep easy with John Knox!
Rob
Rob
ithet
Well-Known Member
Securefix SOC
Just got a reply from securefix, "The Breaking Load for the 8MM chain is 3300kgs, this would be on the statement of conformity."
Just got a reply from securefix, "The Breaking Load for the 8MM chain is 3300kgs, this would be on the statement of conformity."
Slowly Duzzit
New Member
calculation of chain grade strength & size
The grades G30&G40 refer to the ultimate breaking strain in newtons per sq.mm. So a 8mm grade 30 chain is calculated by multiplying the material grade (use the three digit representation, i.e. Grade 300, not Grade 30 or Grade 3) times the metric area of the two cross-sections of a link.
Area of chain is pi x radius sq. x 2 for the two sides = 3.14 x (4mmx4mm) x2 =100.48 x Grade 300=30,144newtons or divide 9.81 =3072kg or about 3tonnes ultimate breaking strain.
If this was used for lashing say on a truck it would have a safety factor of 2:1 or 1500kgWLL.
If used for lifting a 4:1 safety factor is used (although G30 is not used for lifting. G80 would be)
Area (mm2) x Grade (Newtons/ mm2) = Newtons (metric Ultimate Breaking Strength)
I hope this helps.
The grades G30&G40 refer to the ultimate breaking strain in newtons per sq.mm. So a 8mm grade 30 chain is calculated by multiplying the material grade (use the three digit representation, i.e. Grade 300, not Grade 30 or Grade 3) times the metric area of the two cross-sections of a link.
Area of chain is pi x radius sq. x 2 for the two sides = 3.14 x (4mmx4mm) x2 =100.48 x Grade 300=30,144newtons or divide 9.81 =3072kg or about 3tonnes ultimate breaking strain.
If this was used for lashing say on a truck it would have a safety factor of 2:1 or 1500kgWLL.
If used for lifting a 4:1 safety factor is used (although G30 is not used for lifting. G80 would be)
Area (mm2) x Grade (Newtons/ mm2) = Newtons (metric Ultimate Breaking Strength)
I hope this helps.
vyv_cox
Well-Known Member
IIRC that is the minimum value for the DIN standard.
