GB/T 41749-2022General requirements for surface condition of hot-rolled sections (English PDF)

3.1 imperfections

Except for cracks, scabs, folds, delamination and cracks, surface discontinuities whose

depth and (or) area are not greater than the specified limit value.

3.2 defects

Cracks, scabs, folds, delamination and splits, as well as surface discontinuities with

depth and/or area greater than specified thresholds.

3.3 area of check

The area where the defect (under) is located.

processing, and the defect is caused by the manufacturer, the manufacturer is allowed

to re-delivery after grinding or welding according to the requirements of this document.

5.1.4 If this document is quoted in the contract or in the product standard, but the surface

condition category and level of the product are not specified, it shall be regarded as

Category A Level 1.

5.2 Determination of depth and affected area of surface discontinuities

5.2.1 Depth determination

Depths of representative surface discontinuities shall be determined, if necessary, in

order to distinguish surface discontinuities from imperfections and defects. The

measurement shall be carried out from the surface of the product. Depth is measured

after grinding to remove representative surface discontinuities.

5.2.2 Determination of affected area

If necessary, the affected area of the surface discontinuity shall be determined according

to the following provisions.

a) For isolated surface discontinuities, draw a continuous line along the perimeter of

the surface discontinuity at a distance of 20mm from it. Then draw a rectangle 20mm

from the edge of the discontinuous defect to determine the affected area, as shown

in Figure 1. If the surface discontinuity is less than 20mm from the rolling edge of

the section, the rolling edge of the section shall prevail.

b) For aggregated surface discontinuities, draw a continuous line along the periphery

of the group of surface discontinuities at a distance of 20mm from it. Then draw a

rectangle 20mm away from the discontinuous line of this group of surfaces. If the

surface discontinuity of this group is less than 20mm from the rolling edge of the

section, the rolling edge of the section shall prevail, as shown in Figure 2.

c) For striped surface discontinuities, draw a rectangle. The distance between the

four sides of the rectangle is 20mm from the edge of the discontinuous defect. If this

group of surface discontinuities is less than 20mm from the edge of the section, the

rolling edge of the section shall prevail, as shown in Figure 3.

d) The surface discontinuity of a strip shall be at least 10 times its greatest width.

Multiple surface discontinuities whose edges are not more than 40mm apart shall be

regarded as one aggregated surface discontinuity (including aggregated surface

discontinuities and striped surface discontinuities).

grinding wheel grinding before welding repair. The bottom of the part where the defect

is removed shall be smooth and free of sharp corners. The parts to be welded shall be

free of grease or other organic substances, water, rust and so on.

7.2.1.5 Appropriate welding rods and welding repair processes shall be used according

to the designation of steel.

7.2.1.6 Use suitable methods such as grinding wheel to grind the welding repair.

Remove the protruding metal. Make weld repairs flush and smooth with the rolled

surface. It shall not be fixed-point continuous grinding. Make the surface bluish.

7.2.1.7 There shall be no undercuts and weld bumps on the welded outer edge of the

section. The weld wave height of the reinforced weld shall be at least 1.5mm higher

than the original rolling surface. Then use mechanical methods such as shoveling or

grinding wheels to clean up the weld wave of the strengthening weld. The thickness of

the ground area after treatment shall ensure the minimum thickness of the section.

7.2.2 Welding repair quality inspection

7.2.2.1 Visually inspect the shape of the weld repair. Weld repairs and heat-affected

areas shall be smooth and beautiful. There shall be no defects such as surface cracks,

undercuts, pores and slag inclusions visible to the naked eye. If there are surface defects,

the defects shall be carefully cleaned up and then welded again. The number of reworks

at the same part of the welding repair shall not exceed 2 times.

7.2.2.2 Weld repairs shall be flush with the rolled surface. After the welding seam and

welding wave are cleaned, the same height as the original rolling surface shall be

guaranteed. However, there may be a protrusion of no more than 0.2mm at the welding

repair.

7.2.2.3 Welding repairs and heat-affected zones shall be inspected by methods such as

ultrasonic, X-ray, magnetic particle inspection or dye penetration. When the user does

not specify the method, it is up to the manufacturer to decide. The inspection shall be

carried out after welding repair for more than 48h. There shall be no remaining fine

cracks. If there is, it shall be carefully cleaned and then welded again.

7.2.2.4 Detailed records shall be made for each weld repair. The content generally

includes: the batch number, steel type, and specification of the section to be repaired by

welding; the type and location of surface defects; whether to take preheating and slow

cooling measures; the brand and specification of the welding rod; inspector's name

(signature); welding repair date.

7.2.3 Contract

Upon mutual agreement, the manufacturer shall provide a welding report, including

size, location and welding conditions.

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