Residual phytotoxicity: This phytotoxicity is characterized by the fact that after the application, the seasonal crops do not cause phytotoxicity, and the pesticides remaining in the soil produce phytotoxicity to crops that are more sensitive to squatting. As the use of corn field herbicide simazine, they tend to produce on the Following injury canola, beans and other crops. This injury in multi-stage Xiacha crop seed germination occurs, the light tips, shoot buds and other parts or brown rot, affecting the normal growth; severe bad species bud rot, seedling emergence or completely reduced emergence. This injury is difficult to diagnose, easy and fertilizer damage and so confused. Diagnostic measures can be used to understand the management of previous crop cultivation, pesticide use, soil testing, to prevent misdiagnosis and losses.
In chronic injury: This injury after spraying the symptoms do not show up immediately, with a certain latent, blocked the growth of vegetables, fruit and other flavors worse. This phytotoxicity is often difficult to diagnose and is easily confused with other physiological diseases. At the time of diagnosis, diagnosis can be made by understanding the occurrence of pests and diseases, the type, quantity, area and plant control of the application.
Acute phytotoxicity: This phytotoxicity has the characteristics of rapid occurrence and obvious symptoms. Generally, symptoms may appear within a few hours to a few days after application. Generally, the leaves of the vegetables are spotted, perforated, anxious, curled, deformed, Withered, yellowed, chlorotic or whitened. The root damage is characterized by short and thick roots, rare root hairs, yellow or thick roots, brittleness, and rot. Seed damage is manifested as failure to germinate or slow germination. Plant damage is characterized by falling flowers, falling buds, fruit deformity, small, spotted, brown fruit, rust fruit, fruit drop and so on. This phytotoxicity is mostly caused by improper use of pesticides or pesticides for improper seed treatment.
Although there are many types of tapping screws, they all have the following similarities:
(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.
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