Effects of hot dip galvanizing on G7 steel chain

[Asteryx]

I have a general query relating to the HDG of G7 (700 MPa) high tensile steel chain. Unfortunately I do not know the composition or treatment of the steel, only that it's sold by apparently reputable manufacturers in a HDG finish.

I have been trying to work out if the heat the chain is exposed to during the dip is likely to adversely affect the mechanical properties of the steel.

Given the manufacturer supplies it in confidence, may it be assumed that there is no effect (if that is indeed possible?), or that there must be some negative effect - in which case re-galvanizing in the future would be inadvisable?

~

I have a second question relating to this, which is the case for hydrogen embrittlement courtesy of the hydrochloric acid in the HDG pickling process. I can find sources which state that this is a real problem, and others (including the AGA) which maintain it's only an issue with steels of strengths 1,000 MPa and above. A realistic problem in G7 steel or no?

 

[TVP]

All consensus standards related to hydrogen embrittlement use a threshold of 32 HRC (320 HV), which is equivalent to an ultimate tensile strength of approximately 1000 MPa.

 

[Asteryx]

Good.

What can we say about the effect of the heat of the dip on G7 heat treated carbon steel?

 

[Wrenchbender]

The question is 'will the heat from the HDG bath (800+ deg F) have an effect on the mechanical properties?' Depends on what the chain is made of and the heat treatment the supplier used to attain the G7 rating. Not enough information, so ask the chain manufacterer.

(Just some speculation: Not familiar with G7 chain, but if the links are welded its probably hypoeutectoid carbon or low-med carbon alloy. Most likely the links are normalized when made(ambient air cooled after welding), so the microstructure would be fine pearlite. So what does heat do to fine pearlite? It makes it coarser = lower UTS, YS, CVN.)

This site may help.

http://www.cruisersforum.com/forums/f55/g70-or-g7-galvanized-chain-supplier-3512.html

You can also do an experiment, esp if safety is involved. Get a hundred links, dip half, send them to a lab...

 

[Asteryx]

ACCO describe their G70 material as "high strength heat treated steel". They used to offer it galvanized but current catalog omits the option.

Maggi in Italy still do HDG G70:

http://www.maggigroup.com/cgi-bin/W...rate+per+verricello.Catena+Aqua+7.prestazioni

They're all very cagey about the actual steels though...

I wouldn't trust anything on the forum you linked to, nobody authoritative there.

I hear you re the welding related speculation.

I guess I'm trying to figure if it's likely, or even possible, that Maggi (for example) is using a G7 steel that would not be affected by the bath, or if there must inevitably be some damage for every dip.

 

[arunmrao]

Instead of hot dip,is it possible to spray ,so that some of the risks you high lighted are minimised. Alternately can you consider using rust preventive paint.

 

[Asteryx]

I'm talking about chain that's already been HDG by the manufacturer. I'm interested in two aspects - the likely true characteristics of their product as new (essentially damaged by the dip?), and the prospects of future maintenance.