ATTEN: Manager Liu
ADD: Longhua Development Zone, Jing County, Hengshui City, Hebei Province
1.2 The gap between the standards mentioned above can be seen from the three national standards. The standards of thickness and dimension in "Code for Acceptance and Acceptance of Construction Quality of Steel Structural Engineering" GB50205-2001 and "Code for Design of Steel Structures" GB50017-2003 all point to "Size, Shape, Weight and Allowable Deviation of Hot Rolled Steel Plate and Strip" GB/T709-2006. This standard. However, as a standard for steel products, the allowable deviation of thickness in "Size, shape, weight and allowable deviation of hot rolled steel sheet and strip" GB/T709-2006 does not point to a specific situation alone. When other standards are adopted, because the requirements are not specific and ambiguous, the deviation is very large. 1) First, steel standards are implemented according to species. Classes and accuracy are divided into six different situations, and acceptance and design specifications do not specify which situation to implement. (2) The nominal dimensions in the design specifications are marked in units of room meters, while the nominal dimensions in steel standards include 0.1 and 0.5 millimeter multiples.
The nominal dimensions differ enormously. It is impossible to confirm which size should be adopted because of material use, acceptance and data filling. (3) It can be seen from table 1 of steel standard that the allowable deviation of thickness is different if the width of plate is different, but in the component parts, the deviation of thickness is different because of the different blanking of raw materials with different width. Therefore, for the same nominal thickness plate, the parts produced with different width of plate will produce nearly twice the deviation of thickness. Poor. (4) Because the design specifications do not specify what the allowable thickness deviation is determined by and how much the deviation is reasonable or safe, it is impossible to accurately apply that type or accuracy when quoting steel standards. (5) Since the nominal dimensions of single and continuous rolling, medium and heavy plates are 0.1, 0.5 and 1.0 mm, respectively, there is no misunderstanding and consequence caused by the uncertainty of only 1.3 standard. Because the specific content of the implementation standard is uncertain, the adoption of specific materials is inconsistent, leading to either wave test or potential safety hazard. For example (1) Compared with part A of a certain component, which is designed to be 8-chamber thick, if the same standard of nominal size is 8-chamber-meter thick, two pieces of steel sheet with a width of 4,000 mm (Table 1) and a width of 1,200 mm (Table 5) are purchased to make parts respectively.
It can be seen from the table that the allowable deviation of N-U.S. thickness of single binding plate is (+0.9), while that of continuous binding plate is (+0.32), the difference between them is 058, and the former is more than 2.8 times that of the latter. The gap accounts for 725% of the plate thickness. That is to say, the deviation value is the same, but the material difference is 7.25?, which is equivalent to the production profit of the enterprise. (2) According to the design requirements, the nominal size of part B in a component is 25 cubic meters. If the design is calculated according to the standard of allowable deviation in Table 1 (N), the measured thickness is 25 (+1.2), which means that as long as the thickness is not less than 23.8 room meters, it meets the design requirements. Then let's see what specifications the strip (including the continuous rolling steel plate) can meet this requirement. As the strip and continuous rolling steel plate are manufactured in the nominal unit of 0.1 room meters, it can be seen from Table 5 that the design requirements can be met by purchasing a batch of steel plates with the lowest enjoyment of 234 + 040 and no less than 238 room meters.
It is not difficult to see that the purchase of 234mm steel plate is much better than that of 25-room-meter steel plate economically, but whether the deviation of 1.6mm affects the structural safety is unknown. If it does not affect the safety relative to such a large material savings, whether it can be used or not. (3) Similarly, it is a single steel plate with nominal thickness of 8mm. If the steel plate below 1500mm is used, the maximum thickness deviation is (+0.55mm), and if the steel plate with a width of 4000mm-4800mm is used, the allowable thickness deviation can reach (+0.90mm), the difference is 0.45mm, which is close to absolute. In practical engineering applications, some enterprises and suppliers take advantage of this defect. Zhang Guan Li Dai, with a 25-room meter material sheet, supplies 23.4 mm steel plate 2. For the upper part of the steel plate. The solution of the above problems is that the thickness and size of square cable steel plate is the main factor affecting the bearing capacity, which is related to the waste of materials and the safety of the structure. For the above problems, the specific solutions are as follows: 2.1 Allowable deviation of steel thickness should be included in the main control items and mandatory provisions of the supervision standard.
2.2 The design specifications should be clear and based on GBT709, the specification of dimension deviation of steel products, shape, weight and allowable deviation of hot rolled steel sheet and strip, under the design of nominal size parts.