National standards for cast iron platforms and cast iron plates
The machinery industry standard of the People’s Republic of China JB/T 7974-1999 replaces JB/T 7974-95 1. Scope This standard specifies the accuracy of grade 000, 00, 0, 1, 2, and 3 cast iron flat plates. Type and size, technical requirements, inspection methods, marking and packaging, etc. This standard applies to cast iron flat plates (hereinafter referred to as flat plates) with a working surface of 160m×100mm～4000mm×2500mm (length×width). 2. Reference standard The provisions contained in the following standards constitute the provisions of this standard through quotation in this standard. When this standard is published, the editions shown are all valid. All standards will be revised, and all parties using this standard should explore the possibility of using the latest version of the following standards. GBT1184--1996 shape and position tolerance, no tolerance requirements. 3. Definition This standard adopts the following definitions: 3.1 Flat plate A plane reference appliance used for workpiece detection or marking, also known as a platform. 3.2 Main fulcrum During processing, verification and use, the plate is used as the main supporting part when it is in contact with the mounting base or special bracket. The support at this time is in a statically determinate state. 3.3 Auxiliary fulcrum When the plate is in use, it is an additional fulcrum to prevent overturning due to the deviation of the load's center of gravity or harmful deformation due to excessive load. The supporting reaction force on the auxiliary fulcrum should be less than the supporting reaction force on the main fulcrum. 4. Type and size 4.1 The type of the plate is shown in Figure 1. The illustration is for illustration only, and does not indicate the detailed structure. 4.2 The distribution of the main fulcrum of the ribbed plate is shown in Figure 2. The auxiliary fulcrum shown in the figure is to prevent the flat plate from overturning due to the shift of the center of gravity. The auxiliary fulcrum for harmful deformation caused by excessive load is designed by the designer, but the data should be controlled to the minimum. The auxiliary bearing surface and the main bearing surface should not be on the same plane, so as to adjust the reaction force of the auxiliary fulcrum. 4.3 The basic dimensions of the plate are shown in Table 1. Specifications Main dimensions abc H1 H2 Allowable deviation of basic dimensions Allowable deviation of basic dimensions (reference) 160×100 160 ±0.02a 100 ±0.02b 10 50 --- 160×160 160 160 10 50 250×160 160 160 12 60 250×250 250 250 14 65 400×250 400 250 16 75 400×400 400 400 18 90 140 630×400 630 400 20 100 630×630 630 630 22 140 220 800×800 800 800 800 24 - 300 1000×630 1000 630 24 160 1000×1000 1000 1000 30 200 400 1250×1250 12500 1250 32 - 450 1600×1000 1600 1000 32 250 - 1600×1600 1600 1600 35 300 530 2500×1600 2500 1600 40 350 - 4000×2500 4000 2500 45 400 - 5. Technical requirements 5.1 The flat working surface shall not have defects such as sand holes, pores, cracks, slag inclusions, shrinkage, scratches, bruises, rust spots, etc., which seriously affect the appearance and performance of the flat panel. 5.2 The casting surface of the slab should be cleaned of sand and smooth, and the paint should be firm. 5.3 Sand holes with a diameter of less than 15mm are allowed to be blocked with the same material on the flat working surface with accuracy grades of 0 to 3, and their hardness should be less than that of the same surrounding material. There should be no more than 4 sand holes blocked on the working face. And the distance between sand holes should not be less than 80mm. 5.4 The flat plate should be made of high-quality and fine-grained gray cast iron or alloy cast iron, and its working surface hardness should be 170-220HB. 5.5 The flat working surface is usually applied with a scraping process. The maximum allowable value of the surface roughness Ra of the 3-level flat working surface during the scraping process is 5чm. 5.6 The flatness tolerance of the flat working surface is specified in Table 2. 5.7 The scraping process of the flat working surface shall be subjected to coloring and researching inspection. The ratio of the area of the contact points displayed after the research is shown in Table 3, or the difference between the number of contact points in 25mm×25mm should be no more than 5 points. If there is a dispute, the assessment shall be based on the ratio of the area of the contact point. 5.8 For flat working faces that are inconvenient to use coloring to research and inspect, the plane fluctuations of the working faces should be checked. See Table 4 for the plane fluctuations of the working faces. Specification diagonal d mm Accuracy class 000 0 0 0 1 2 3 Flatness tolerance value чm 160×100 189 1.5 2.5 5.0 10 - - 160×160 226 250×160 297 3.0 5.5 11 250×250 353 22 400× 250 472 6.0 12 24 400×400 566 2.0 3.5 6.5 13 25 62 630×400 746 7.0 14 28 70 630×630 891 4.0 8.0 16 30 75 800×800 1131 9.0 17 34 85 1000×630 1182 2.5 4.5 18 35 87 1000 ×1000 1414 5.0 10.0 20 39 96 1250×1250 1768 3.0 6.0 11.0 22 44 111 1600×1000 1887 12.0 23 46 115 1600×1600 2262 3.5 6.5 13.0 26 52 130 2500×1600 2968 - 8.0 16.0 32 64 158 4000×2500 4717 - - - 46 92 228 Note: 1. The values in the table are given at a standard temperature of 20°C. 2. Calculation formula: In the formula: d----the length of the diagonal of the flat working surface, mm. 3. The flatness tolerance within the range of 0.02a (maximum 20mm) from the edge of the working surface is not counted, and any point shall not be higher than the working surface. Table 3 Accuracy level of test items 000 00 0 1 2 The ratio of contact point area per unit area ≥20% ≥16% ≥10% The number of contact points in a 25mm×25mm square area ≥25% ≥20% ≥12 Note: Distance from working surface The ratio of the contact area or the number of contact points within the range of 0.02a (maximum 20mm) of the edge is not counted, and any point shall not be higher than the working surface. Table 4 Accuracy level 000 0 0 0 1 2 3 Fluctuations of the working plane of the plate 2 4 8 16 32 80 5.9 The perpendicularity tolerance of the side of the plate to the working surface and the perpendicularity tolerance of the two adjacent sides of the plate are all specified in GB/T1184. class. 5.10 The concentrated load area in the center of the flat working surface, the applied rated load and the allowable deflection value are specified in Table 5. Table 5 The rated load N of the circle with the фD diagonal concentrated load zone of the specification. Allowable deflection чm mm 160×100 189 ------ ------- ----- 160×160 226 250×160 297 250×250 353 ф120 375 1.5 400×250 472 400×400 566 500 2 630×400 746 630×630 891 ф190 800×800 1131 1000×630 1182 1000×1000 1414 625 2.5 1250×1250 1768 ф300 750 3 1600× 1000 1887 1600×1600 2262 2500×1600 2968 1000 4 4000×2500 4717 1500 6 5.11 The plate should be demagnetized and treated for stability 5.12 On the opposite sides of the plate, there should be threaded holes (or cylindrical holes) for installing handles or lifting ring devices , And the design of the device location should minimize the deformation caused by handling. 5.13 If a threaded hole (or groove) is provided on the working surface of the plate, its position should not be higher than the working surface. 6. Inspection method 6.1 The ratio of the area of the contact point: Coat the display agent on the inclined surface of the tested flat panel, grind it on a flat panel of no less than its accuracy level, and show an obvious contact point on the tested flat panel, and then use a A transparent sheet (such as a plexiglass plate) with 400 small squares of 2.5mm×2.5mm engraved in the range of 50mm×50mm. Place it on any position of the working surface of the tested plate, and observe in turn that each square contains contact The ratio of the area occupied by the point (in 1/10 as the unit). Calculate the sum of the above ratios and divide by 4 to get the ratio of the area of the contact point of the detected part. To obtain a typical value, it should be measured at another location Find the ratio of the area of the contact point. Find the average of the two results. 6.2 Plane fluctuations Place the plane wave meter on the working surface of the flat plate and move the plane wave meter along any straight line. The moving distance is the diagonal length of the flat panel Half and should not be less than 200mm. Take the difference between the highest value and the minimum value on the indicator table of the plane wave instrument (graduation value is 0.001mm). That is the plane wave amount of the tested flat working surface. The plane wave instrument is shown in Figure 3. 6.3 Deflection Put the detection device on the working surface of the tested plate; when no load is applied, the probe of the torsion spring comparator is in contact with the working surface (in order to make the measurement accurate, a piece can be placed between the probe and the working surface. Thin gauge block) and record the reading. Then apply force according to the rated load specified in Table 5 and record the reading; the difference between the two readings is the deflection value of the working surface of the tested plate under the rated load. The testing device is shown in Figure 4. 7. Marking and packaging 7.1 The plate shall be marked with a) manufacturer’s name or registered trademark; b) product name; c) specification and accuracy grade; d) product serial number and manufacturing date; e) standard number of this standard ; 7.2 The flat box should be marked with: a) manufacturer’s name or registered trademark; b) product name; c) specification and accuracy grade; d) product serial number and date of manufacture; e) vibration-proof, waterproof, moisture-proof and other marks . 7.3 The flat plate should be rust-proofed and properly packaged before packaging, and the product should not be damaged during transportation due to improper packaging. 7.4 After the flat panel is verified to meet the requirements of this standard, it should be accompanied by a product certificate; the product certificate should have the standard number and product serial number of this standard.
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