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1、International Standard f 7788 0 * 4 a! INTERNATIONAL ORGANIZATION FOR STANDARDIZATION*MEXAYHAPOAHAR OPrAHIlJAUblfl n0 CTAHAAPTM3AUblM.ORGANlSATlON INTERNATIONALE DE NORMALISATION Steel - Surface finish of hot-rolled plates and wide flats - Delivery requirements Acier - b) in the case of discontinuit
2、ies appearing in a cluster or line figure 1 b) and 1 cl, the affected area is obtained by drawing a rectangle or a square the sides of which are 50 mm from the rectangle or square circumscribing the cluster or line. 4.1.4 Depending on the steel grade and manufacturing pro- cess, plates and wide flat
3、s may have surface discontinuities, which may be divided into five categories depending on their nature, depth and number as defined in 4.2 and 4.3. II See4.1.1. 21 At present at the stage of draft. 1 IS0 7788-1985 (El 4.2 Imperfections (see annex B, figure 1 and table 1) 4.2.1 Discontinuities not e
4、xceeding the limits of table 1 are regarded as being inherent of the manufacturing process and are permissible irrespective of their number. A surface area with a remaining thickness under the disconti- nuities less than the minimum thickness as specified in IS0 7452 is permissible with a maximum of
5、 15 % of the area of the inspected surface (this does not apply to the applications mentioned in 4.1.1). 4.2.2 Discontinuities with depth exceeding the limits of table 1 but not exceeding the limit of table 2 and of which the sum of the affected areas does not exceed 5 % of the inspected sur- face,
6、may be left unrepaired. A surface area with a remaining thickness under the disconti- nuities less than the minimum thickness as specified in IS0 7452 is permissible with a maximum of 2 % of the area of the inspected surface (this does not apply to the applications mentioned in 4.1.1). 4.3 Defects (
7、see annex B, figure 2 and table I) 4.3.1 Discontinuities with depth not exceeding the limits of table 2, but with an affected surface area of more than 5 % of the inspected surface shall be repaired. 4.3.2 Discontinuities with depth exceeding the limits of table 2 shall be repaired irrespective of t
8、heir number. 4.3.3 Discontinuities like cracks, shell and seams which are in general deep and sharp, and therefore impair the use of the product, shall always be repaired irrespective of their depth and number. Table 1 Values in millimetres Nominal thickness of the product e Maximum permissible dept
9、h of discontinuities 3ec 8 0.2 8e 25 083 25e 40 0,4 4Oe 80 0.5 80e 150 0.6 Table 2 Values in millimetres Nominal thickness of the product e Maximum perhissible depth of discontinuities 3e 8 0.4 8e 25 0,5 25e 40 0,6 4Oec 80 W3 8OelXl 03 2 5 Repair procedures 6.1 Grinding In the case of plates and wid
10、e flats for boilers and pressure vessels, the remaining thickness of the repaired ground area shall not be less than the minimum permissible thickness as specified in the appropriate standard covering tolerances. This disposition may also be applied for other applications as agreed at the time of en
11、quiry and order. Grinding of defects may be carried out subject to the following and the conditions specified in 4.1. 5.1.1 The maximum permissible depth of ground areas is defined as follows: a) for plates and wide flats less than 8 mm thick, repair by grinding is permitted to a remaining thickness
12、 of 0,3 mm below the minimum thickness as specified in IS0 7452 (this does not apply to the applications mentioned in 5.1); b) for plates and wide flats of 8 mm up to and including 15 mm thick, repair by grinding is permitted to a remaining thickness of 0.4 mm below the minimum thickness as specifie
13、d in IS0 7452 (this does not apply to the appli- cations mentioned in 5.1) ; c) for plates and wide flats over 15 mm thick, repair by grinding is permitted to a remaining thickness of 7 % below the nominal thickness. The remaining thickness shall in no case be less than 3 mm below the nominal thickn
14、ess. 5.1.2 For ground areas with a thickness under the minimum permissible thickness, as specified in the tolerance standards, the size of a single ground area shall not exceed 1 I4 m* and the sum of all areas of one side of the product shall not exceed 2 % of the surface under consideration for pla
15、tes having a surface area greater than or equal to 12 m*, and 5 % for plates having a surface area less than 12 m*. The size of the ground area refers only to the size of that area with a remaining metal thickness less than the specified minimum permissible thickness. The distance between two ground
16、 areas shall not be less than their average width. 5.1.3 The requirements of 5.1.1 apply to the remaining thickness between two opposite ground areas on either face of the product. 5.1.4 The defects shall be ground completely. The ground areas shall have a smooth transition to the surrounding surfac
17、e of the product. Complete elimination of the defect may be demonstrated by magnetic particle or dye penetrant test pro- cedures. 5.1.5 The producer is allowed to repair the whole surface by grinding to a thickness not less than the minimum permissible thickness of the product as specified in the ap
18、propriate tolerance standards. All the requirements of 5.1.1, 5.1.2 and 5.1.3 are also applicable. IS0 7788-1985 (E) 5.2 Welding The following notes are for guidance only. For details of permissible welding repair, reference shall be made to the appropriate quality standard. Defects which cannot be
19、repaired by grinding as stated in 5.1 may be repaired by chipping and/or grinding, followed by welding. Unless otherwise agreed at the time of enquiry and order, repair shall be carried out with the agreement of the pur- chaser and/or inspecting authority under the following con- ditions : 5.2.1 The
20、 sum of all repaired areas by welding shall not ex- ceed 2 % of the surface under consideration for plates having a surface area greater or equal to 6 m2, 5 % for plates having a surface area less than 6 m2. The distance between two welded areas shall not be less than their average width. 5.2.2 The
21、defects shall be completely eliminated before any filler metal is applied. This procedure shall not reduce the thickness of the product below 66 % of the nominal thickness. For occasional defects having depths exceeding the above- mentioned limits special consideration will be necessary. 5.2.3 The r
22、epair shall be carried out by competent welders using a procedure appropriate to the grade of steel and ac- ceptable to the purchaser. 5.2.4 All welds shall have a reasonable length and shall con- sist of at least three parallel welding beads. The weld shall be free of any lack of fusion, undercutti
23、ng, cracks and other defects, which could impair the workability or use of the pro- duct in question. The deposited weld material shall have an excess of at least 2 mm which subsequently has to be ground smooth and level with the product surface. 5.2.5 After repair, a post-weld treatment may be cons
24、idered, if necessary. 5.2.6 Proper repair may be verified by ultrasonic, radiographic, magnetic particle or dye penetrant inspection. 5.2.7 For every welding repair, the producer shall file on request at the time of enquiry and order reports containing a sketch, showing dimensions and location of th
25、e defect and full details of the repair procedure, including the welding consumables, eventual post-weld heat treatment and non-destructive testing. 3 -,-,- IS0 7788-1985 (El Annex A Definitions (This annex forms an integral part of the Standard.) A.1 plate and wide flat: See IS0 6929. A.2 imperfect
26、ions: Discontinuities that may be left without repair. Discontinuities that shall be repaired are regarded as defects. A.3 Definitions of the most common discontinuities A.3.1 rolled-in scale, pitting: Marks on the rolled surface varying in shape, thickness and frequency. Rolled-in scale results fro
27、m the unsatisfactory subsequent removal of scale from the stock before or during hot-rolling and processing. A.3.2 indentations and roll marks: Indentations (depres- sions) or roll marks (protuberances) can be distributed at definite distances apart or irregularly throughout the length and width of
28、the stock. Roll marks appearing at periodic intervals are caused by dam- aged rolls or pinch rolls. Indentations can be caused, inter alia, by protuberances on rolls or rollers. A.3.3 scratches and grooves: Mechanical damages vary- ing in width, depth and length at the surface. They are mostly paral
29、lel or at right angles to the rolling direction. They may be slightly rolled over and seldom contain scale. These damages are caused by friction between the stock and parts of the equipment due to relative movements. A.3.4 spills and slivers: Minute surface discontinuities of an irregular and flake-
30、like nature. Spills are elongated in the direction of rolling, their extent depending on the degree of reductions. They are still con- nected - as minute particles of shell - to the base metal at certain points. A.3.5 blisters: Blow holes of varying size and shape located closely beneath the surface
31、 and appearing during hot rolling. A.3.6 hot tears: Variably orientated material discontinuities in the surface region. They may vary in length, width and depth and may occur in preferred directions and/or be distributed over a limited area. Hot tears arise in the processing of slab ingots, roughed
32、slabs and continuously cast slabs and are associated with the steel, with stresses in the initial material or with adverse forming con- ditions. A.3.7 sand patches: Non-metallic inclusions in the surface that vary in size and shape. They are elongated in the direction of rolling, randomly localized
33、and they are distinctly coloured, standing out from their background. A.32 cracks: In the region of the surface, localized discon- tinuities of varying length parallel or at right angles to the direc- tion of rolling and which may less frequently occur as crazing. Cracks are due mainly to material s
34、tresses which arise during the cooling of the rolled stock. A.3.9 shell and seams: Overlapping material, the overlap- ping portions of the surface varying in shape and extent, being irregularly distributed over areas of the rolled product and being only partially connected with the base material. Th
35、ere is a preponderance of non-metallic inclusions and/or scale among the shell. Shell can originate during casting or because of the shifting or sliding of layers of the material during hot rolling. Seams are caused mainly when defects in the semi-product parallel to the rolling direction, for insta
36、nce, flame-cutting burrs, are overlapped during rolling. 4 , -,-,- IS0 7788-1985 (El a) Isolated spotlike discontinuity 0 Ln b) Clustered discontinuities Dimensions in millimetres c) Aligned discontinuities Figure 1 - Determination of the areas affected by the surface discontinuities 5 -,-,- Nominal
37、 thickness of the product (mm) , SD , 6,0 , 7,O / t _ , - . . 1 / , / I I -/ / - / . / J Y J I , - a * n -. * * Imperfections inherent in the manufacturing process and always accepted (see 4.2.1) lzzl Accepted imperfections in the limit of 5 % of the inspected surface (see 4.2.2) m Defects to repair (defects with an affected surface area of more than 5 % of the inspected surface) (see 4.3.1) cl Defects to repair or to reject (see 4.3.2) Figure 2 - Limits for discontinuities IS0 7799-1995 (El E G ti - 8 - 2 (LUUI) ssauyoyl eu!wou Molaq fhpuy6 40 qidaa 7 IS0 7788-1985 (El 8 -,-,-