While imported A307 Grade A hex bolts are readily available and very similar mechanically to F1554 Grade 36, most will not meet the strength requirements of F1554 Grade 36. Very few imported A307 Grade A hex bolts are available with mill test reports or traceability. When paperwork is available for A307 Grade A bolts, the yield strength is often not reported since A307 Grade A does not require a minimum yield strength. Without a reported minimum yield strength, an A307 Grade A bolt cannot be cross certified to F1554 Grade 36.

F1554 Grade 36 is a weldable grade of anchor bolt. If F1554 Grade 55 meets the supplement 1 requirements for ASTM F1554, then it is weldable. Since F1554 Grade 105 is a high strength alloy steel bolt that generates its strength through the heat treating process, welding to this grade of anchor bolt should be avoided. Additionally, welding to Grade 55 anchor bolts that do not meet the weldability requirements of supplement 1 should also be avoided. With regard to F1554 Grade 105 anchor bolts and Grade 55 bolts not meeting supplement 1, Instead of welding a nut to a threaded rod, a headed anchor bolt with a forged head should be considered.

There are two types of nuts to consider that are commonly used in construction applications, structural and non-structural. Structural nuts, such as A563 Grade DH or A194 Grade 2H, gain their strength through the heat treating process and, in general, should not be welded. Non-structural nuts are not heat treated, but are often manufactured from steel that is not weldable due to its high carbon content. This is typical of nuts larger than 1” diameter. For non-structural nuts, such as A563 Grade A, the carbon equivalency should be considered if welding is planned.

AISI Design Guide 21 mentions the following about welding to bolts and nuts:

“Occasionally, it becomes desirable to weld bolts to structural steel, or bolts to nuts. As a general principle, welding should not be done on bolts or nuts. However, if essential, the composition of the bolt (and nuts if involved) must be carefully considered.”

AISI takes the stance that welding to nuts and bolts should be avoided unless absolutely necessary. The simple solution is to use an anchor bolt with a forged head in lieu of a threaded rod with a welded nut.

An anchor Bolt head is not formed by welding a piece of steel to a rod. A headed bolt is made by heating one end of a steel rod and then forging the heated end into a hex, heavy hex, or square head. A common misconception is that a bolt head is made by adding a piece of steel to a rod. The forging process produces a superior fastener by forming the bolt from one piece of material.

It is common for fastener distributors or manufacturers without heading capabilities to attempt to supply a rod with a tack welded nut instead of a headed anchor bolt. These products are not identical and it is not advisable to make any configuration changes, such as the above example, without the approval from the engineer of record. For example, when an engineer specifies a headed anchor bolt they may know that the grade of bolt detailed is not weldable. Keep in mind that any unapproved configuration changes may open your company up to liability issues.

The ASTM F1554 specification does not specify a default head style for headed anchor bolts. Fasteners such as A325 or A490 require a heavy hex head only, while A307 Grade A headed bolts require a standard size hex head. In contrast, F1554 does not specify what type of head is required for the bolt. Certain situations may call for the anchor bolt to provide more pull out resistance, so a heavy hex head may be useful. For circumstances where a head type is not specified by an engineer for F1554 headed anchor bolts, the contractor should seek consultation from the structural engineer or let the manufacturer provide the most economical head style option.

According to ASTM F1554-07a when Grade 36 is specified, a weldable Grade 55 may be furnished at the supplier’s option.

Portland Bolt may use this substitution in situations when it will save the customer time and/or money. This allowance is useful for Portland Bolt when asked to supply Heavy Hex Grade 36 bolts because we stock “blanks” that are already headed with a Heavy Hex head in F1554 Grade 55. Since the “blanks” meets S1 of F1554 (weldable) we are allowed to provide Grade 55 instead of Grade 36 to meet the specified head style.

Please note that this substitution of weldable Grade 55 for Grade 36 is the only substitution of a higher strength bolt for a lower strength bolt that ASTM allows within the context of their fastener specifications. Except for this instance, Portland Bolt estimators will never suggest you substitute one grade of fastener for another grade or suggest you substitute one type of bolt for another type of bolt without first consulting with the Engineer of Record.

Permanently stamping the headed end of F1554 anchor bolts is not required or detailed in the ASTM Specification. Portland Bolt chooses to stamp the headed F1554 anchor bolts that we produce in order to provide an alternative way to identify the bolts before the headed end is embedded in concrete. Anchor Bolts are marked on the threaded end that projects from the concrete with a designating color code, per the F1554 specification. Marking the threaded end that protrudes from the concrete with paint allows engineers and inspectors to identify the grade of anchor bolt that is embedded in the foundation. Permanently stamping the threaded end with the grade identifier and manufacturer’s logo is a supplemental requirement and needs to be specified on the inquiry and purchase order.