Although there are many types of tapping screws, they all have the following similarities: Round head Tapping screw,hex tapping screw,flat head tapping screw,pan head tapping screw,truss head tapping screw Shenzhen Lanejoy Technology Co.,LTD , https://www.compressionspring.net
It is reported that China's calcium carbide production of polyvinyl chloride is developing rapidly, and the use of mercury-containing catalysts in the production process poses a great potential for contamination. During the "11th Five-Year Plan" period, China's ability to safely dispose of hazardous wastes has greatly improved, laying a certain foundation for environmental safety. With the acceleration of industrialization and urbanization, the amount of hazardous waste generated during the 12th Five-Year Plan period will continue to rise, and the pollution prevention and control situation will be severe. According to incomplete statistics, as of the end of 2011, there were about 1,500 units of hazardous waste operation licenses nationwide, and more than 9 million tons of hazardous wastes were used annually.
It is understood that at present, the construction of safe disposal facilities for hazardous wastes in some localities still lags behind. Some enterprises have problems such as inconsistency between hazardous waste treatment processes and environmental assessment documents. They do not exceed the scope of the permit, over-receiving, disposal of hazardous wastes, and even individual The unit resells hazardous waste that has valuable value and transfers the license without authorization. This causes a large amount of hazardous waste to be lost to the environment without being disposed of safely, thus causing serious damage.
At present, China adopts a strict licensing management system for hazardous waste utilization and disposal units, and prohibits the operation activities such as the collection, storage, utilization, and disposal of hazardous wastes without a business license or without complying with the operating license requirements. The license-holding unit must strictly implement various systems such as hazardous waste management plans, transfer of single bills, emergency plans, and routine environmental monitoring and reporting in accordance with relevant laws and regulations.
The Ministry of Environmental Protection requires that the overall level of prevention and control of hazardous waste pollution must be comprehensively improved. The safe disposal of hazardous waste is the last safety line to eliminate environmental risks, and it is imperative to strengthen the disposal capacity.
(1) are generally made of carbonized carbon steel (accounting for 99% of total production). It can also be made of stainless steel or non-ferrous metals.
(2) The product must be heat treated. Carbon steel tapping screws must be carbonized and stainless steel tapping screws must be solution hardened. In order to make tapping screws to meet the requirements of the standard of mechanical properties and performance.
(3) The product surface hardness is high, the core toughness is good. That is, "soft inside strong outside". This is a major feature of tapping Screw performance requirements. If the surface hardness is low, it can not be screwed into the matrix; If the core toughness is poor, a twist will break, can not be used. So "inside soft outside steel" is self-tapping screw to meet the use of performance, very important requirements.
(4) The surface of the product needs surface protection treatment, generally electroplating treatment. Some product surface must be treated by phosphate (photostatting), such as wall panel self - tapping screws for photostatting.
(5) Production by cold heading process. It is recommended to use high-speed cold heading machine and high-speed wire rolling machine or high-speed planetary wire rolling machine. High speed is emphasized here to ensure product quality. Only the head of tapping screw produced by high-speed machine is well formed and the thread quality is high.
The Ministry of Environmental Protection recently issued the Mercury-containing Hazardous Waste Operation Permit to the Guizhou Wanshan Special Zone Silver Star Mercury Recovery Co., Ltd. and Tongren Hongfa Mercury Product Disposal Co., Ltd. of Guizhou Province. The mercury-containing catalysts of the two companies that have been licensed this time will have a disposal capacity of 24,000 tons/year and will play an important role in curbing the use of indigenous mercury in mercury refining and mercury pollution control.