Can welding be performed on high strength anchor bolts and fasteners?

weldingThe short answer is that in most cases, welding high strength bolts is not allowed. In the fastener industry, the term “high strength” typically refers to any medium carbon or alloy steel which undergoes a heat-treating process to develop the strength properties necessary to meet the requirements of a given specification. These ASTM specifications include A449, A325, A193 Grade B7, A320 Grade L7, F1554 Grade 105, A354 Grades BC and BD, and A490 among others. When heat is reapplied to a bolt that has been heat-treated, it is likely that the physical properties (strength) of the bolt may be altered. When heat is applied in an uncontrolled environment, it is impossible to determine what effect this application of heat has had on the fastener. Therefore, welding to high strength bolts is not recommended.

Three references occur to back up this statement.

Section 4.5.1 of the AISC Design Guide 21 addresses most ASTM anchor rod specifications individually and prohibits the welding of all quenched and tempered grades.

On page 2-25 of the Fourteenth Edition of the AISC Manual (American Institute of Steel Construction), the following statement occurs:

“As a heat-treated material, Grade 105 rods cannot be welded.”

The final reference prohibiting the heating of high strength bolts (which would occur during welding) can be found in the ASTM F1554 specification. Section 6.5.3 of the ASTM F1554 specification states:

“The maximum hot bending temperature for heat treated anchor bolts shall be less than…..1000F for grade 105.”

Although this statement refers to hot bending, it implies that any process (including welding) that applies heat approaching or exceeding the tempering temperature to a high strength bolt may potentially alter the mechanical properties of the fastener and should, therefore, be avoided.

The issue of altering the high strength bolt’s mechanical properties when welding can potentially be avoided by performing the welding operation prior to the fastener undergoing the heat-treating process. In other words, a plate, a nut, or another component could potentially be welded to a bolt prior to the fastener being heat treated. The problem is, the base medium carbon or alloy steel used to make high strength bolts is technically not weldable due to high levels of carbon and manganese. This could perhaps be overcome with special welding procedures, but the bottom line is that it would be best to avoid welding high strength bolts altogether.

For anchor bolt applications, instead of welding a nut and/or plate to the bottom of a high-strength anchor rod, consider using an anchor bolt with a forged hex head, peening the thread to prevent the nut from backing off, jamming two nuts together to lock them in place, or sandwiching a square plate between two nuts on the embedded end of the anchor rod.

If welding to material grades mentioned in this FAQ is specified on your project, consult with the Engineer of Record for special welding procedures or guidelines.

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    Wondering if anyone knows if F593 bolts, F594 nuts are weldable? I couldn’t find any information from RSCS and AISC.

    @Danielle- Stainless steel in general is weldable, however the addition of heat during the welding process can affect the grain structure and lessen the corrosion resistance of the bolt and nut. You would need to either solution anneal the parts after welding, or perhaps consult a welding expert who might be more familiar with special procedures.

    I don’t know if this helps
    I used to get Special bolts from Portland … I think the were a “K” type weldable
    The application was to through bolt the pile cap before the cap was welded on to the pile leaving the threaded potion of the bolt “up “ and back welded to the underside of the pile cap .

    They were rated for structural

    My regular supplier was 8 months out
    Portland did a special run and had them to me in 3 weeks

    Great Customer service

    I have an application where I need to weld about a 1.25″ dia fully threaded stud to an embed plate with a stud gun. Prefer at least an Fu of 65 ksi. Trying to avoid a large all-around fillet as fillet will extend out too much and be in the way. Are you familiar with some alternate option? Prep a Gr 55 weldable bolt on end for a CJP?

    @Alan- Apologies, but we are not well versed enough in welding procedures to know what your alternatives are. You’ll probably need to contact a welding shop.

    @Peter- A449, because it is a high strength grade that gets its strength through the heat treating process, should not normally be welded. The addition of heat during welding can adversely affect the steel. That said, we believe there are special welding procedures for heat treated material, but someone with more detailed welding knowledge should be consulted.

    @Ihab- Any bolt made from weldable material an be welded. Typically speaking, SAE grade 2, ASTM A307, and ASTM F1554g36 and G55 can be welded, but the only 100% way to be certain is to look at the MTRs for said bolt and determine if the steel is weldable by plugging it into the carbon equivalency formula.

    @Samuel- I believe class 5.8 steel in simply cold drawn mild steel, so you theoretically should be able to weld to it, but to be certain, you should check the MTRs and make sure the chemistry of your specific material is compatible with that of weldable steel.

    When using anchor bolts ASTM F1554 grade 36. Is it acceptable to weld 1/2″ A36 bar stock to the anchors to create caged sets?

    @Frank – Yes, ASTM F1554 Grade 36 anchor rods (manufactured from A36 steel) and A36 bar stock are both weldable. More information about welding A36 stell can be found in this FAQ.

    Dear sir,

    plz tell me how to select welding rod 2H nut to ms plate welding

    which number rods suitable for this welding

    @Srinivas- Most low carbon, low manganese steels will be weldable, but you will need to look at the MTRs to confirm. However, A194 2H nuts are not weldable. They have a high carbon content, and are heat treated to get their strength, so the addition of welding heat will adversely affect them. You will need to contact someone who is an expert on welding and see what your options are – we are not welding experts.

    I have a requirement to weld the Low Alloy steel sleeve AISI 4140 to cast iron, Can you suggest the filler and weldability of base material.

    @Prasobh- Normally welding 4140 is not recommended because the heat can adversely affect it. You will need to contact someone with more welding knowledge to answer this question.

    Do you know where in the AISC 14th Edition the following statement is located:

    “On page 4-4 of the Ninth Edition of the AISC Manual (American Institute of Steel Construction), the following statement occurs:

    “Anchor bolt material that is quenched and tempered (heat treated) should not be welded or heated.”

    @Kristine- The reference I found to welding anchor bolts in the 14th Edition AISC Manual is on page 2-25, under “Other Products”. It states, in reference to anchor bolts per ASTM F1554, “As a heat treated material, Grade 105 rods cannot be welded.”

    Can F1554 – GR50 anchor bolts be welded to 1/2″ bar stock to create bolt pattern cages. Is this welding to anchor acceptable?

    @Frank- Typically, F1554 G55 bolts are weldable, however to be certain, you would need to specify supplement S1 for weldability. If you already have the bolts, you can also tell by looking at the mill cert and plugging the chemistry into the weldability formula. We can help with that if you like to contact us directly.

    @Ken- Many times they are made from a low carbon steel like AISI 1008, but I believe they can vary. You may need to contact a weld stud manufacturer for more information.

    @Robert- No, tack welding to A325 bolts is not normally permitted. That said, there are some applications where it may be allowable, but that determination is made by the project engineer.

    Recently we manufactured a lot of A490 bolts for a company who used it to build a steel structure. After they were done with the work, they decided to weld the structures together as an extra precaution. Can this have a negative effect for the bolt? They said that welding the structures pretty much makes the A490 bolts useless. Im worried they might break?

    @Carlos- Yes, if they applied heat to the A490s, they could adversely effect the bolt. However, it would be up to the engineer as to if this was detrimental to the overall structure.

    I am a Welder, I was just asked to extend anchor bolts in order to raise the elevation of Posts and Beams in a prefabricated warehouse that has settled over 7″. The bolts would then have concrete poured around them and the plates would be 1″ non-shrink grouted. What type of weld should be used and what kind of prep should be done to the all-thread and existing anchor?

    @Travis- I am sorry, but we are not well versed in welding procedure. If you have any questions regarding the anchor bolt material we can likely help, but we cannot recommend a weld procedure. Apologies.

    Ok I just inspected the welding of anchor bolts that were too short. Engineer sent a fix where the welder spliced it, extending the length, using a cjp. Is this a big no no?

    @Eric – The AISC allows welding in some applications, so it may be permissible to extend anchor bolts through welding, it will just depend on the specifics of the anchor bolt and the job. The ultimate call is really up to the engineer.

    Dane McKinnon says
    Hello Dane,
    My Designers quoted AISC 9th Edition page 588 where it is noted Heat treated and Quenched bolts should not be heated or welded.

    We are Designers in between Client and Engineers. Client sides, “..ah…” but cannot proceed..

    Engineer who stamps cannot approve. Please note that these are bolts used for LIFT LUGS of a skid which weighs more than 200 tons. 10 lifting lugs and 40 bolts.


    It is is said that it is common practice (In western Canada) to weld high strength lifting lug bolts (probably A325)

    1. two tack welds on the bottom
    2. seal weld where it comes out of the beam or plate. – and flush grind

    this is because the skid under side is sprayed insulation foam.

    they want the bolts located and retained before the spray.

    two – they want the seal weld to prevent leakage from skid floor.

    Is it common?
    Is it prohibited?

    @Procyon Systems – Common? Perhaps. Prohibited? Likely. Every application will have its own reasons for or against this procedure. If the fastener is being used in such a way that its being compromised does not adversely affect its function, then the engineer may decide that it is acceptable in that specific case. Generally speaking however, the AISC does not condone welding to high strength, heat treated materials. As always, the project engineer should be consulted.

    Can you tell me if an A615 Grade 75 threaded anchor bolt can be heated and straightened without reducing the strength. We have several bars that are roughly 8′ long which are bent about 1/2″ out of straight over the last 1′-6″ foot of length.

    @Ted Welti: High strength nuts used with A325 bolts are heat treated and should not be taken past their tempering temperature (i.e. welding), since this can change the mechanical properties. Although, we often see engineer’s designs that include high strength nuts welded to plates. The main concern is that it is impossible to know, without testing, what effect the welding will have on the nut’s strength. Many believe that a few tack welds will not significantly alter the strength of the nut. We have no engineers on staff and don’t make any recommendations about this method.

    Is it allowed to weld a nut to the back side of a steel plate for a slip-critical ASTM A325 bolt connection? There would be no welding done to the bolt itself, just the nut. The nut would be centered over a hole in the steel plate and welded to the plate in the shop. This is so in the field the bolt could be installed without access to the backside to hold the nut from spinning when the bolt was tightened. This is for attaching a brick shelf angle to the outside of a cold-formed steel wall that will be sheathed in the shop before being tilted into place in the field.

    @Ben Valdez: Any quenched and tempered bolt that has a minimum tensile strength lower than 150ksi can be galvanized. There is no problem galvanizing A193 B7. However, any quenched and tempered fastener (A193 grade B7 included) that develops its strength properties through a heat treating process should not be welded. If you need to weld to the fastener, the highest strength bolt available would be F1554 grade 55.

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