Regarding fasteners for pressure vessel flanges according to NB/T47027-2012
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Regarding 4.6: Alloy steel fasteners shall be blued. The ones we commonly use are 40Cr and 35CrMoA. Is galvanizing considered to be non-compliant with the standards? Also, does 35# count as alloy steel? I checked and found that 35# steel also contains elements other than carbon and iron, which seems to fit the definition of alloy steel as well. . . Solve it, thank you!
1. Personally, I think that unless there are special requirements from the owner (or designer), it should be manufactured according to standards. 2.35# is high-carbon steel, not alloy steel.
35# is generally not considered an alloy steel; ordinary carbon steels contain some alloying elements, but only in very small amounts
If galvanizing is required, will it still meet the 47027 standard? The standard specifies the blue that should be used. Does it have to be blue? Newcomers have many questions; after all, I’m just a purchaser, not a technician~
Requiring galvanizing is an additional requirement only on the condition that the bolts meet the requirements of standard 47027.
I still don’t understand. . . Such as 40Cr. The user requires the 47027 standard, with galvanizing. Is it possible to meet both of these conditions at the same time? According to my understanding of the standards, galvanizing does not fall under 47027
First, it is necessary to meet requirement 47027; thereafter, galvanizing is required. It’s similar to buying bolts that meet the standards first (so that you have the necessary certificates and documents), and then carrying out the galvanizing process yourself (to fulfill the customer’s requirements). Both galvanizing and blueing are anti-corrosion measures that do not affect the performance and usability of the bolts.
It was purchased as standard and comes in blue; if galvanizing is required, additional treatment will be needed, right? The processing process will still affect the strength, right?
I don’t know much about this; you can refer to the answers above – some of them are quite detailed and professional
The blueing treatment mentioned in energy standards is commonly referred to as blackening treatment; it is likely used to prevent chemical corrosion. Galvanizing cannot prevent chemical corrosion