What grade of nuts and washers are compatible with ASTM A320 Grade L7 bolts and rods?

ASTM A320-L7 is a specification covering bolts, studs, and screws intended for low temperature service. Portland Bolt regularly supplies both plain finish and hot-dip galvanized A320-L7 fasteners to numerous customers in Canada and Alaska. Recently in our Portland Bolt Live Chat, an engineer asked this question as he needed to know what grade of nuts and washers to specify on his project plans.

  • Nuts: The compatible nuts for use with A320-L7 are either ASTM A194 Grade 4 or A194 Grade 7 heavy hex nuts.  Grade 7 nuts are more readily available and are most frequently used with A320-L7 bolts, but Grade 4 nuts may be used in cases where Grade 7 is not readily available. Since the assumption is that in most cases the A320-L7 bolts will be used in a cold temperature environment, Supplement 3 of the ASTM A194 specification should be specified which requires the nuts to undergo Charpy impact testing which confirms their ability to perform in low temperatures. An “L” is added to the grade marking of these nuts.
  • Washers: The compatible washer for use with A320-L7 bolts is ASTM F436. Made from heat treated, hardened steel, F436 washers are capable of withstanding a broad range of environments including low temperature service.

Note: A194 Grade 4 and Grade 7 nuts are typically only available in plain finish. Galvanized Grade 4 or Grade 7 nuts will normally have to be specially made on a per order basis, as plain nuts cannot be used with galvanized bolts.   

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20 comments

    Could you quote us 120 BOLTS WITH TWO NUTS AS FOLLOWS:
    BLT+2N 3″x665 A320/A194-L7/Gr4
    We are in Queretaro México. Phone Tel. 442 1955019 Móvil: 5540102069.
    Regards.
    F. Martínez

    Can 7M nuts be used with 2HM bolts.

    Which combination would be better suited with each other and why..
    -B7M Bolts with 7M Nuts
    or
    -B7M Bolts with 2HM nuts.

    Service is not for low temperature.

    @Hani- ASTM leaves the decision of which nut-bolt combination is best up to the end user, so either combination is acceptable per ASTM. The down side of using the Gr.7M nut is cost – the 2HM nut will be less expensive, so if you do not need the alloy steel of the grade 7M, then you can save money by using the 2HM.

    @Hisham- Unfortunately there is nothing within ASME that we are aware of that defines torque values. Torque is unpredictable and can vary significantly. Additionally, the torque needed for one application may not be the same as that needed for a different one. The best way to determine what is needed for your application is to do some testing in a skidmore tension measuring device. That said, we do have a torque chart on our website that can be used for reference, but it again may not be exactly what is correct for your application, so due diligence is required. https://www.portlandbolt.com/technical/bolt-torque-chart/

    @Deon- Yes, electroplating would not adversely affect the mechanical properties, so they would not need any additional thermal treatment.

    Hello,

    I am loking for a small quantity of anchor bolts produced per ASTM A320 Grade L7. I will send through email about details for the dimensions. I need the following informations:
    1. Availability in your stock;
    2. The price information;

    Regards,
    Puntsag

    we’re thinking of machining A-320 L7 bolts to be used as tapered plugs for heat exchangers. The tapered plugs needs to be seal welded to the tube/ tubesheet. My question is, in view that bolts have been hot-wrought-is it recommended to (fillet) weld A-320 L7 bolts to A-334 tube?

    @Jeanette- We don’t ever recommend welding to A320L7 materials. A320 L7 gets its strength from a heat treat process, so adding heat during welding is sure to adversely effect that strength.

    We are looking for ASTM A320 Gr.L7 bolts and nuts, are you supplying hot-dip galvanized locknuts, and what kinds of locknuts?
    Do you have local vendor in Singapore?
    Thank you.

    @Liu- We can supply hot dip galvanized A320L7 materials upon request. There are several types of lock nuts available, so you would need to specify what kind you prefer. We only have one location here in Portland OR. We do not have a distributor in Singapore, but can ship there easily.

    How much the cost difference between A320 L7 and A193 B8 bolts?
    Since B8 material can be used under much lower temperature conditions, if the cost difference is not too much, it will make more sense to specify only one type fasteners for a project.

    Thanks,

    @Jonathan- A193 B8 is stainless steel, and so therefore will be inherently more expensive than A320 L7, which is alloy steel. However, without specifics we can’t ballpark a price difference since there are so many variables.

    @Tommy- ASTM does not address application temperatures, and instead leaves that up to the application governing body, i.e. ASME, SAE, etc. The only information we have, ASME B31.1 does not specifically list temperatures for A194 gr.7, so we are unable to answer. Apologies.

    Some 7/8 threaded steel rods 15″ long are needed with low temperature performance. They’re welded on one end to an L3x3x1/4. Can we specify A320? Can we get off-the-shelf A1554 GR36 and have them Charpy V Notch tested? Your website says there are A320 studs — what lengths and diameters are available? Could we just get long bolts and cut off the heads?

    @Bruce- F1554g36 rods will not usually perform well on charpy tests, but that will depend on the temperature you want to test at. A320 rods can easily be made in any diameter and length, and will do well on the charpy, but are not considered a weldable steel. Another option is F1554g55, it is weldable and will pass a charpy down to about 20F. So it will depend on your temperature as to which grade might work best.

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