Tek-Tips is the largest IT community on the Internet today!
Members share and learn making Tek-Tips Forums the best source of peer-reviewed technical information on the Internet!
-
Congratulations MintJulep on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!
Galvanized A193 B7
- Thread starter cal123
- Start date
Bolting materials supplied under this specification are for high temperature service (400 deg F to 800 deg F), and would not be galvanized nor need they be galvanized - why are you asking this question?
Under normal use, these bolting materials would not be galvanized. I would not recommend it.
Under normal use, these bolting materials would not be galvanized. I would not recommend it.
- Thread starter
- #3
We try to use it for outdoor application as anchor rod/bolts and was wondering whether it would have any issues.
A reputable bolt supplier I talked to indicated it would have no problem with hydrogen embrittlement and they do sell them galvanized.
A reputable bolt supplier I talked to indicated it would have no problem with hydrogen embrittlement and they do sell them galvanized.
metengr - Though the ASTM specification classifies this material as typical for high temperature applications, A193 B7 is acceptable as is often used for a substitute for the more typical F1554 GR105 anchor bolt material per AISC (see Table 2-3 p2-26 LRFD Vol 3).
cal123 - found this about the galvanization:
"If the customer requests plating, we will certify the material as A193 B7 "prior to plating." Because the plating process involves high temperatures, reheating the steel can create "Hydrogen Embrittlement" weak spots in the steel. As a rule, we do not want to quote B7 hot dip galvanized."
cal123 - found this about the galvanization:
"If the customer requests plating, we will certify the material as A193 B7 "prior to plating." Because the plating process involves high temperatures, reheating the steel can create "Hydrogen Embrittlement" weak spots in the steel. As a rule, we do not want to quote B7 hot dip galvanized."
B7 fasteners are used extensively in offshore applications. For many years they were cadmium plated but as this process has become rarer galvanizing has replaced it. Provided good practices for hydrogen control are used there are no problems with glavanized B7 parts.
Once bolting materials are supplied under a particular specification, their use depends on good engineering practices.
With that said, what you do with these bolting materials is your choice. Considering the risks associated with galvanizing on high strength materials, and the necessity for hydrogen controls, more attention to detail is required.
With that said, what you do with these bolting materials is your choice. Considering the risks associated with galvanizing on high strength materials, and the necessity for hydrogen controls, more attention to detail is required.
According to ABS & the Naval ships tech manual, ASTM B-633 does not provide sufficient bake-out to prevent hydrogen embrittlement.
ABS Guide for Building & Classifying Naval Vessels: 3.8 Recognized problems:
… “SAE J429 Grade 8, AISI grade 4340, ASTM A574 alloy steel fasteners, and other high strength fasteners over HRC 34 shall not be zinc coated or they could be susceptible to hydrogen embrittlement. Hydrogen can be introduced during the plating operations or in service via the galvanic interaction with the coating. Traditional four hour baking operations are not sufficient to remove hydrogen absorbed during the plating operation. A minimum of 23 hours is needed to remove the hydrogen from the fastener; four hour bakes have been reported to cause the hydrogen to migrate to the fastener/coating interface and make the fastener more susceptible to brittle fracture. When zinc coated steel fasteners are exposed to temperatures over 149°C (300°F) for long periods of time intermetallic compounds form that can embrittle the fastener.” …
Even if you had them baked out for a longer time, it would be difficult to segregate them out from ones with the standard bake - Dacromet might be the way to go
ABS Guide for Building & Classifying Naval Vessels: 3.8 Recognized problems:
… “SAE J429 Grade 8, AISI grade 4340, ASTM A574 alloy steel fasteners, and other high strength fasteners over HRC 34 shall not be zinc coated or they could be susceptible to hydrogen embrittlement. Hydrogen can be introduced during the plating operations or in service via the galvanic interaction with the coating. Traditional four hour baking operations are not sufficient to remove hydrogen absorbed during the plating operation. A minimum of 23 hours is needed to remove the hydrogen from the fastener; four hour bakes have been reported to cause the hydrogen to migrate to the fastener/coating interface and make the fastener more susceptible to brittle fracture. When zinc coated steel fasteners are exposed to temperatures over 149°C (300°F) for long periods of time intermetallic compounds form that can embrittle the fastener.” …
Even if you had them baked out for a longer time, it would be difficult to segregate them out from ones with the standard bake - Dacromet might be the way to go
- Status
Similar threads
- Locked
- Question