How to avoid the phenomenon of stripping the threads of carbon steel full-threaded studs during the tightening process?

Matching Precision: Ensure that the precision levels of the studs and nuts match each other. Generally, products of the same precision level should be chosen, such as both being of the 6g/6H precision grade. A high - precision fit can ensure a uniform gap between the threads, reducing the possibility of local over - stress leading to slipping.
Material and Hardness: The hardness of the nut material should be slightly lower than that of the stud. Usually, the hardness of the nut is 20 - 30 HB (Brinell hardness) lower than that of the stud. In this way, during the tightening process, the threads of the nut are more likely to undergo a certain degree of plastic deformation, thus better fitting with the threads of the stud and dispersing the pressure to avoid slipping. For example, for a 4.8 - grade carbon steel stud, a 3.6 - grade carbon steel nut can be used.

Clean the Threads: Before installation, the threaded surfaces of the studs and nuts must be wiped clean with a clean cloth or a special cleaning agent to remove impurities such as oil, dust, and iron filings. These impurities may affect the fitting accuracy of the threads, resulting in an increase in local friction and, consequently, slipping.
Inspect the Threads: Carefully check whether there are any defects such as damage, deformation, or burrs on the threads of the studs and nuts. For those with problems, they should be replaced in a timely manner to avoid slipping due to stress concentration at the defective parts during the tightening process. Tools such as thread gauges can be used for precise inspection.

Use the Correct Tools: Select appropriate torque wrenches or other tightening tools according to the specifications of the studs and the required tightening torque. The accuracy and range of the tools should meet the actual requirements, and they should be calibrated regularly to ensure the accuracy and reliability of the applied torque.
Reasonable Tightening Speed: During the tightening process, an appropriate speed should be maintained to avoid being too fast or too slow. Excessively fast tightening speed may lead to excessive impact force, causing the local stress on the threads to exceed the allowable range and resulting in slipping. Too slow a speed may cause the threaded surface to anneal due to long - time frictional heat generation, reducing the hardness and making it prone to slipping. Generally, when tightening by hand, the wrench should be rotated at a constant speed. When using an electric tool for tightening, the rotational speed can be controlled at 100 - 300 r/min.
Adopt the Correct Tightening Sequence: For connections with multiple studs, tighten them in a certain sequence. Usually, a symmetrical and cross - wise method is adopted to ensure uniform stress on each stud and avoid slipping of individual studs due to uneven stress. For example, for a quadrilateral connection, first tighten the two studs on the diagonal, and then tighten the other two.

Select Lubricants: Applying an appropriate amount of lubricant on the threaded surface can effectively reduce the friction coefficient, decrease the tightening torque, and prevent the threads from seizing or slipping during the tightening process. Commonly used lubricants include molybdenum disulfide grease, graphite lubricants, etc. The appropriate lubricant can be selected according to the specific operating environment and requirements. For example, in high - temperature environments, molybdenum disulfide grease can be used as it has good high - temperature resistance.
Application Method: Evenly apply the lubricant on the threads of the studs to ensure that the entire threaded surface is lubricated. A brush or a special application tool can be used for application. Be careful not to apply too much to avoid the lubricant overflowing and affecting other components.

Post - Installation Inspection: After installation, check the tightened studs to see if there is any abnormal wear or signs of slipping on the threaded surface. If there are any problems, analyze the causes in a timely manner and take corresponding measures, such as replacing the studs or nuts, adjusting the tightening torque, etc.
Regular Maintenance: During the use of the photovoltaic support, regularly inspect and maintain the stud connections. Check whether the tightening torque of the studs has changed and whether there is any looseness or slipping of the threads. If any problems are found, they should be dealt with in a timely manner to ensure the structural safety of the photovoltaic support.