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1.2. Surface Condition
ASTM A6/A6M-Section 9 defines the permissible variations in the surface condition for structural shapes and plates in the as-rolled condition. It should be recognized that surface imperfections, such as seams and scabs, within these specified limits may be present on material received at the fabrication shop—particularly on heavyweight sections because of higher finishing temperatures and production characteristics. Certain steel chemistries, such as that for ASTM A588/588M, will also exhibit a higher incidence of surface imperfections.
Special surface condition requirements must be specified in the contract documents. Material purchased to meet the requirements of ASTM A6/A6M is usually subject to acceptance or rejection based upon visual inspection both at the rolling mill and at the time of receipt by the fabricator, although more extensive inspection methods may be used. This inspection is important because mills normally limit their contractual liability to replacement or credit. Because occasional surface imperfections may be discovered after the fabricator’s acceptance of mill material, particularly after blast cleaning, any requirements for remedial work should also be specified in the contract documents.
Similar information is provided in ASTM A500/A500M/A500M Section 16 for HSS and ASTM A53/A53M/53M Section 12 for steel pipe.
1.2.2. What corrective procedures are available to the mill when variations in surface condition do not meet specified tolerances?
ASTM A6/A6M Section 9 specifies limited conditioning that the mill may perform when as-rolled material does not meet specified tolerances. Note that it further states that “conditioning of imperfections beyond the [specified] limits... may be performed by [the fabricator] at the discretion of [the fabricator].”
Unless required in the contract documents, code-compliant surface imperfections generally need not be repaired or removed if they are not detrimental to the strength of the member. When required, they may be repaired by grinding or welding. The responsibility for any required repairs should be assigned in the contract documents so that it is clearly understood by all parties involved, including the owner’s designated representative for construction (usually the general contractor), fabricator, erector and painter
Non-injurious edge discontinuities in statically loaded structures need not be removed or repaired unless otherwise specified in the contract documents. Injurious defects should
be repaired. Repairs may be by grinding and if necessary to restore material, via welding. The provisions of AWS D1.1/D1.1M: Clause 220.127.116.11 for edges that are to be welded are appropriate for non-welded edges, except that:
- Discontinuities need not be explored to a depth greater than 1 in. When the depth of a discontinuity exceeds 1 in., the discontinuity should be gouged out to a depth of 1 in. beyond its intersection with the surface and repaired by the deposition of weld metal as indicated in AWS D1.1/D1.1M: Clause 18.104.22.168.
- For discontinuities over 1 in. long, with depth exceeding 1⁄8 in. but not greater than 1 in., the discontinuity must be removed and repaired, but no single repair should exceed 20% of the length of the edge repaired. Requirements for treatment of such edge discontinuities more stringent than this should be specified in the contract documents, and the repair procedure should be approved by the structural engineer of record.