ASTM A194 GR 4 NUTS VERSES GR7 1

[sjjptp]

I HAVE A CUSTOMER THAT IS REQUIRING A194 GR 4 METRIC NUTS TO BE USED WITH A ASTM A320 L7 STUD. THE QUANTITY IS TO LOW HAVE BAR MADE (I HAVE LOOKED EVERYWHERE FOR IT), AND I AM SUGGESTING GR 7. THEY INSIST IT MUST BE GR4. WHY WOULD THEY DO THIS AND HOW CAN I CONVICE THEM THE GR 7 WILL WORK?

 

[VeryPicky]

It would help if you specified the application.

Putting Human Factor Back in Engineering

 

[TVP]

They are likely requiring Grade 4 because that is what they have always used or what is indicated on their engineering drawing. If you understand the differences between Grade 4 and Grade 7, then you should be able to convey to your customer that they have the same strength, hardness, high temperature performance, etc. Grade 4 may be a cheaper option from the perspective of alloy content, but in today's steel market, the alloy cost is not nearly as important as availability.

 

[sjjptp]

The exact application I am not sure about, all I do know is they are for a Russian plant being bult by Exxon. I am dealing with the middle man who is doing the fab work.
IVP hit it on the head! Because they are metric they had to be cut from bar stock. Gr 4 stock is not avaliable unless you want a mill to run some (more then they are willing to pay for). Their main concern is thier po from Exxon says Gr 4 and they don't want to change it to Gr 7. I have expressed that we supplied a better material a number of times and was interested to see if I am missing something more important then the material differences.

 

[metengr]

In addition to TVP's comments, I would have expected a Grade 4 nut for use on an ASTM A320 L7 stud, as well. The L7 stud is an AISI Type 4140 alloy steel as is an ASTM A 194 Grade 7 nut. Thus, it would not be out of the ordinary to use a different alloy combination like Grade 4 (carbon moly) against an AISI Type 4140 steel to avoid galling.

 

[sjjptp]

If the parts were HDG would galling still be a factor?

 

[TVP]

Galling should not really be a concern when thick coatings like hot-dipped galvanized zinc are used.

 

[sjjptp]

Thank you everyone.
Stanley