How to deal with the locking problem of non-standard screws and the precautions of special screws Non-standard screws refer to screws that have corrosion resistance and are not easy to rust in the medium of gas, water and so on. The quality of non-standard screws mainly depends on the requirements of specifications, mechanical properties and surface defects. It is widely used in environmental protection machinery, electronic equipment, food machinery and equipment, medical equipment and other fields. When the locking problem occurs when using non-standard screws, the following treatment methods can be taken: Ensure the correct selection of screws: Before using, determine whether the screws meet the requirements of the function of the equipment. Pay attention to the quality of the thread of the screw: if the thread of the screw is rough or there is dirt, such as welding slag or metal chips between the thread, it is easy to lead to locking phenomenon. Control the tightening force and rate: When tightening the screw, too much force or too fast tightening speed will cause the screw temperature to rise rapidly and cause locking.
Pay attention to the direction of the reaction force: when tightening the screw, the screw cap should be rotated vertically and bisect the center line of the screw to avoid skew. Use washers and spring washers: When using screws, installing washers and spring washers can effectively prevent over-tight problems. Some matters also need to be noted in the material selection of special screws: Material selection of flat washers: For flat washers without mechanical properties requirements, they can usually be manufactured using scrap materials, such as Q235A. If there is a hardness requirement but the requirement is not high, thicker Q235A sheet can be used to calendering to achieve the required hardness. Material selection of rivets and pins: generally the same as screws, but the hardness of some rivets can not be too high, and even some require hardness lower than HRB60. The hardness of the general normalized material is between HRB70-80, so some rivets need to be annealed to meet the performance requirements.
Material selection of special screws for welding: For arc welding and gas welding, there are generally no special material requirements. If the customer uses spot welding, low carbon steel materials must be used, and if the strength needs to be increased, some low carbon materials with higher manganese content can be used. When the customer specifies the use of a specific grade of material, and the company temporarily does not have or is difficult to purchase the material on the market, you can understand the customer's use of the special screw, and make a written application to replace the material under the premise of meeting the mechanical properties. Some purchasing customers are not necessarily very professional for special screws, and the choice of materials is not necessarily the best. By correctly dealing with the locking problem and paying attention to the materials used for special screws, the use effect and quality of non-standard screws can be improved.
