A194 grade 7 nuts are commonly used nuts for both high temperature and low temperature applications, and is commonly paired with bolts made to either A193 or A320. When used in conjunction with A320 bolts in a low temperature application, or if specially requested, they are charpy tested to assure they will perform well in a low temperature environment. When that charpy test passes, the nuts are marked with an “L” to show that they have been tested. The same is true with A194 grade 4 and 4L nuts, although Grade 4 and 4L nuts are being withdrawn from the A194 standard by the ASTM committee due to lack of use and material availability.
Dear Dane,
I would like to know the hardness difference between A194 Gr.7 & A194 Gr.7L nuts.
Does A194 Gr.7(Supplement S3) & A194 Gr.7L means the same product ?
Please clarify.
Thanks.
Regards
Sameer A. Kamble
@Sameer- A194 gr.7 S3 and 7L are the same thing. S3 is the official call-out, 7L is the nut marking. They are the same thing.
What are the differences in a 7 and 7L grade?
@Darab- The 7L nut has been charpy tested and is used in applications where cold temperatures are common.
good afternoon
I have a question
Can a Gr7L Nut be tempered? And if so, how should it be marked according to the standard? such as Gr7LM or Gr7ML
I WOULD LIKE TO KNOW YOUR OPINION THANK YOU VERY MUCH
@David- The A194 7L nut is tempered as part of its initial manufacturing process. If you are wanting to retemper in order to certify it to gr.7M, you will need to make sure all of the additional testing is understood. It would then be marked 7ML.
What about ASTM A194 grade 3 nuts?
Are grade 7 nuts equivalent to grade 3 nuts for use at elevated temperatures (1000 deg. F plus)?
@Dale- A194 grade 3 and grade 7 nuts are both for use at high temperatures, but they are not equivalent. They are made from very different steels, and should not be substituted for each other without approval from the project engineer.
Can Gr 7 bolts be used with Gr 7L nuts, or the other way around, i.e. Gr 7L bolts used with Gr 7 nuts, or must both the bolt and the nut be either 7 or 7L?
Which component is used to give to the material the impact resistance?
@Eli- A320 L7 bolts are required to have a charpy test performed, whereas for A194 gr.7 nuts, the charpy is a supplemental requirement. When the test has been performed, they are then marked and sold as A194 gr.7L nuts. ASTM recommends that charpy’d nuts be used with A320 L7 bolts, so A194 gr.7L nuts should be used. If you are using gr.7 nuts on other grades of bolt (like A193 B7 or B16), then the charpy test is not required and a standard grade 7 is acceptable.
As for what is added to give the bolts and nuts their impact resistance, we are not certain, but the -150F/-100C charpy can be a difficult one to achieve.