This standard specifies the depth of surface defects of hot-rolled steel plates, the affected area, limits, requirements for repair and the limits of steel plate thickness. This standard applies to hot-rolled steel plates with a thickness of >4mm to 200mm. GB/T 14977-1994 General requirements for surface quality of hot-rolled steel plates GB/T14977-1994 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
General requirement of surface finish for hot rolled steel plates
1 Subject content and scope of application
GB/T 14977—94
This standard specifies the depth, influence area, limit, requirements for finishing and limit of thickness change of surface defects (hereinafter referred to as defects) of hot rolled steel plates.
This standard is applicable to hot rolled steel plates with a thickness of >4mm~200mm. 2 Definition
The definition of defects in this standard is as described in Appendix A. 3 Limits of defectsbZxz.net
3.1 Limits of defect depth and influence area
3.1.1 Depth
The depth of defects shall be measured from the product surface after removing the oxide scale near the defects. 3.1.2 Influence area
3.1.2.1 For isolated point defects, the influence area is determined by drawing a circle around the defect with a radius 50mm larger than the circumscribed circle of the defect, as shown in Figure 1.
Figure 1, isolated point discontinuity influence area If this defect is close to the edge of the plate, the influence area is determined by the actual area of ​​the circle drawn in the plate. 3.1.2.2 In the case of defects appearing in agglomeration or linear shape, the influence area is determined by drawing a rectangle or square 50mm away from the circumscribed rectangle or square of the aggregated or linear defects, as shown in Figures 2 and 3. Approved by the State Administration of Technical Supervision on June 13, 1994 and implemented on January 1, 1995
GB/T 14977-94
Figure 2 Influence area of ​​clustered discontinuities
Figure 3 Influence area of ​​point-shaped discontinuities
If this defect is close to the edge of the plate, the actual area of ​​the rectangle or square drawn in the plate is used to determine the influence area. 3.1.3 Limits of defect depth and influence area Defects are divided into five levels: A, BCD, and E according to depth and expansion area. 3.1.3.1 Grade A defects Deep and sharp defects such as bubbles, scars, cracks, rips, folds, inclusions, and scales are not allowed on the surface of steel plates. These defects are harmful to the use of the product, regardless of their depth and number. All grade A defects need to be repaired. 3.1.3.2 Grade B defects: Defects that are unavoidable in the production process with a depth not exceeding that specified in Table 1 are allowed, regardless of their number.
Except as specified in 3.2.2, Class B defects do not require trimming. 3.1.3.3 Class C defects: Depth exceeds that specified in Table 1 but does not exceed that specified in Table 2, and the total affected area is not more than 5% of the inspection area.
Except as specified in 3.2.2, Class C defects do not require trimming. Table 1 Depth limits of Class B defects
Nominal thickness of steel plate
Maximum allowable depth of defects
3.1.3.4 Class D defects: Depth exceeds that specified in Table 1 but does not exceed that specified in Table 2, and the total affected area is more than 5% of the inspection area. Class D defects all require trimming.
Nominal thickness of steel plate
GB/T14977-94
Table 2 Depth limits of C-level and D-level defects
Allowable depth for large defects
3.1.3.5E-level defects: Defects with depth exceeding that specified in Table 2. All E-level defects require repair
3.2 Limits on the thickness of the plate below the defect
The thickness limit is applicable to the remaining thickness between two opposite defects (or repaired surfaces) on both sides of the steel plate. mm
3.2.1For steel plates for boilers, pressure vessels, hull structures and steel plates for special purposes specified in the contract, the thickness of the steel plate below the defect shall not be less than the minimum allowable thickness specified in the corresponding steel plate product standard. 3.2.2 For steel plates other than those specified in 3.2.1, if the thickness of the steel plate below the defect is less than the minimum allowable thickness specified in the corresponding steel plate product standard:
Class B defects with a total affected area exceeding 15% of the inspection area need to be repaired. Class C defects with a total affected area exceeding 2% of the inspection area need to be repaired. 3.3 When the steel plate is delivered without removing the scale, if there are visible defects on the surface, the depth of the defect and the limit of the affected area shall not exceed the provisions of 3.1 and 3.2. After processing, if the defects caused by the production process exceed the provisions of 3.1 and 3.2, the steel plate is allowed to be repaired in accordance with the provisions of 4.
3.4 ​​When the steel plate is delivered without removing the scale, if there are defects, they shall not exceed the limits specified in 3.1 and 3.2. 4 Repair of defects
Repair of steel plates can be carried out by the manufacturer or the user. 4.1 Grinding: All A, D, E grade defects, and R and C grade defects exceeding the limits specified in Article 3.2 shall be ground locally or completely.
The defects shall be completely ground.
The ground surface shall smoothly transition to the steel plate surface, and the width-to-depth ratio shall not be less than 6:1. 4.2 Limits of grinding degree
4.2.1 For steel plates for boilers, pressure vessels, hull structures and special purposes specified in the contract, the thickness after grinding shall not be less than the minimum allowable thickness specified in the steel plate product standard. 4.2.2 For steel plates other than those specified in Article 4.2.1, the thickness after grinding shall comply with the following provisions: 4.2-2.1 For steel plates with a thickness of less than 7.5 mm, it shall not be less than 0.31 mm less than the minimum allowable thickness specified in the product standard. 4.2.2.2 For steel plates with a thickness of 7.5~15mm, it shall not be less than 0.4mm less than the minimum allowable thickness specified in the product standard. 4.2-2.3 For steel plates with a thickness greater than or equal to 15mm, it shall not be less than 7% of the nominal thickness. In any case, the thickness of the steel plate after grinding shall not be less than 3mm less than the nominal thickness. 4.2.3 For the grinding area of ​​the thickness below the minimum allowable thickness specified in the relevant product standards: 4.2.3.1 The single grinding area shall not be greater than 0.25m2. 4.2.3.2 The total grinding area of ​​the steel plate shall not be greater than 5% of the area for steel plates with a surface area of ​​less than 12m2. For steel plates with a surface area of ​​not less than 12m2, it shall not be greater than 2% of the area. GB/T14977-94 The distance between two grinding surfaces shall not be greater than their average width. Note: The grinding area refers to the area where the thickness of the remaining copper plate is less than the specified minimum allowable thickness. 4.2.4, the technical requirements in Article 4.2.2 also apply to the remaining thickness between the two relatively ground surfaces on the two sides of the steel plate. 4.3 Welding repair
4. 3. 1 If there are defects on the surface of the steel plate, if the defects cannot be cleaned by grinding according to Article 4.2, with the consent of the user or the inspection department, it can be welded after grinding with a shovel.
The regulations for welding repair must refer to the corresponding quality standards and be determined by negotiation between the supply and demand parties. 4.3.2 For the welding repair used, the manufacturer should provide a report with a sketch,Describe the size and location of the defect and all details of the welding repair process, including welding repair consumables, so that non-destructive testing and post-weld heat treatment can be used. A1 Rolling scale and pits
GB/T 14977-94
Appendix A
Definition of typical pits
(Supplement)
The scars on the rolled surface vary in shape, depth and occurrence rate. Rolling scale is caused by insufficient removal of scale before or during hot rolling and processing. A2 Pressing and rolling
Indentations (pits) and rolling marks (0 start) can be distributed at intervals of a certain distance or randomly distributed over the entire length and width of the rolled piece. Periodic rolling marks are caused by damage to the rollers or clamping rolls. Scratches are caused by foreign matter attached to the rolling yoke or other rolls.
43 Scratches and grooves
Mechanical damage of different width, depth and length on the surface. They are basically parallel or perpendicular to the rolling direction. There may be slight folding and rarely contain scale.
This kind of damage is caused by the friction between the rolling piece and the equipment. 4. Scale
Irregular and scaly small surface defects. The scale extends along the rolling direction, and its extent depends on the size of the deformation disk. In some parts, they are still connected to the base metal and appear as fine scab particles.
Scale is caused by the cold, scale and scab on the surface of the ingot are not cleaned up or the cleaning depth-to-width ratio is not enough, the surface of the bad material is not half, and the rolling shape A5 bubble
The bubble is located below the tight skin, its shape and size are different, and it appears during hot rolling. The bubble is caused by poor degassing during the smelting process and the pouring process. A6 Hot tear
Defects with variable orientation within the surface range. Its length, width and depth may be different, and it may occur in a preferred direction or be distributed within a limited range.
Hot-tight cracks occur during the processing of fan ingots, primary rolling and continuous casting, and are related to the steel grade, internal stress of the material or unfavorable forming conditions.
Non-metallic inclusions on the surface, with different sizes and shapes. The inclusions extend along the rolling direction, are randomly distributed, and their color is significantly different from the matrix.
Inclusions are mainly caused by non-metallic inclusions adhering to the surface of the ingot, which did not fall off during rolling. It may also be inclusions brought in during smelting and casting, and exposed after rolling.
A8 cracks
Defects distributed on the surface range, with different lengths, parallel or perpendicular to the rolling direction, and rarely appear in the form of network microcracks. GB/T14977--94
Cracks are mainly caused by stress generated during the cooling process of the rolled piece. A9 scars and scars
Overlapping materials, overlapping parts of the surface with different shapes and degrees. Irregularly distributed in the entire surface of the rolled piece and partially connected to the missing metal, there are more non-metallic clamps or iron oxide scales in the scars. Scars can be generated during ingot casting or caused by surface displacement or sliding of the material during rolling. Scars are mainly caused by defects in the rolling direction of semi-finished products, such as flame cutting burrs, which are caused by heavy deafness during rolling. Additional notes:
This standard was proposed by the Ministry of Metallurgical Industry of the People's Republic of China. This standard is under the jurisdiction of the Information Standards Research Institute of the Ministry of Metallurgical Industry. This standard was drafted by the Information Standards Research Institute of the Ministry of Metallurgical Industry, Anshan Iron and Steel Company, and Fushun Steel Plant. The main authors of this standard are Huang Dong and Deng Xian.
The level of this standard is marked as GB/T14977-941
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