Service HotlineThe process factors that affect the quality of high-strength fasteners include steel design, spheroidizing annealing, peeling and dephosphorization, drawing, cold heading, thread processing, heat treatment, etc., and sometimes the superposition of various factors.
High-strength fasteners must be quenched and tempered according to technical requirements. The purpose of heat treatment and tempering is to improve the comprehensive mechanical properties of fasteners to meet the specified tensile strength value and yield ratio of the product. The heat treatment process has a crucial impact on high-strength fasteners, especially its intrinsic quality. Therefore, in order to produce high-quality high-strength fasteners, advanced heat treatment technology and equipment must be available. Due to the large production volume and low price of high-strength bolts, and the threaded part is a relatively fine and relatively precise structure, the heat treatment equipment is required to have large production capacity, high degree of automation, and good heat treatment quality. Since the 1990s, the continuous heat treatment production line with protective atmosphere has dominated, and the shock bottom type and mesh belt furnace are especially suitable for heat treatment and tempering of small and medium-sized fasteners. In addition to the good sealing performance of the furnace, the quenching and tempering line also has advanced computer control of atmosphere, temperature and process parameters, equipment failure alarm and display functions. High-strength fasteners are automatically controlled and operated from feeding-cleaning-heating-quenching-cleaning-tempering-coloring to offline, which effectively ensures the quality of heat treatment. The decarburization of the thread will cause the fastener to trip before the resistance required by the mechanical properties is reached, which will cause the failure of the threaded fastener and shorten the service life. Due to the decarburization of the raw material, if the annealing is improper, the decarburized layer of the raw material will be deepened. In the process of quenching and tempering heat treatment, some oxidizing gas is generally brought in from outside the furnace. The rust of the bar wire or the residue on the surface of the wire rod after cold drawing will also decompose after being heated in the furnace, and some oxidizing gases will be generated by the reaction. For example, the surface rust of steel wire, which is composed of iron carbonate and hydroxide, will be decomposed into CO₂ and H₂O after heating, thus aggravating decarburization. Studies have shown that the degree of decarburization of medium carbon alloy steel is more serious than that of carbon steel, and the fastest decarburization temperature is between 700 and 800 degrees Celsius. Because the attachments on the surface of the steel wire decompose and synthesize carbon dioxide and water very quickly under certain conditions, if the furnace gas of the continuous mesh belt furnace is not properly controlled, it will also cause excessive decarburization of the screw. When the high-strength bolt is formed by cold heading, the raw material and the annealed decarburized layer not only still exist, but also are extruded to the top of the thread. For the surface of the fastener that needs to be quenched, the required hardness cannot be obtained. Its mechanical properties (especially strength and wear resistance) decreased. In addition, the surface of the steel wire is decarburized, and the surface layer and the internal structure have different expansion coefficients, and surface cracks may occur during quenching. For this reason, during quenching and heating, the top of the thread should be protected from decarburization, and the fasteners whose raw materials have been decarburized should be properly carbonized, and the advantages of the protective atmosphere in the mesh belt furnace should be adjusted to the original carbon-coated parts. The carbon content is basically the same, so that the decarburized fasteners are slowly restored to the original carbon content. The carbon potential is preferably set at 0.42% - 0.48%. The carbon coating temperature is the same as the quenching heating, and cannot be carried out at high temperatures , so as to avoid coarse grains and affect mechanical properties. The quality problems that may occur in the process of quenching and tempering of fasteners mainly include: insufficient hardness in the quenched state; uneven hardness in the quenched state; excessive quenching deformation; quenching cracking. Such problems in the field are often related to raw materials, quenching heating and quenching cooling. Correctly formulating the heat treatment process and standardizing the production operation process can often avoid such quality accidents.
The flat key is a key that relies on the two sides as the working surface and transmits the torque by the extrusion of the key and the side of the keyway, and is mostly installed on the shaft. If the flat key is used for a long time or is in a bad working environment for a long time, dust, oil, etc. will inevitably be stuck between the flat key and the keyway. Since the flat key has no ejector threaded hole for disassembly, it is difficult to dismantle, and during the disassembly process A little carelessness will cause damage to the flat key.
In another embodiment of Guangdong Yueluo Hardware Industrial Co., Ltd., the conveying device 3 includes a motor 31 and a circular rotating disk 34, the motor 31 drives the circular rotating disk 34 to rotate, and the circular rotating disk 34 is evenly provided with screws in the circumferential direction. The matching screw accommodating hole 35, the screw enters the screw accommodating hole 35, the motor 31 drives the circular rotating plate 34 to rotate, so that the screw is first slotted by the cutting wheel 42, and then polished by the fixing wheel 48, and the screw is in the screw accommodating hole 35. It is fixed, which is more secure and reliable during the slotting process. Preferably, the circular rotating disk 34 includes a circular rotating disk 32 and a sector-shaped fixed disk 33. The circular rotating disk 32 is evenly provided with screw receiving recesses matching the screws in the circumferential direction, and the recesses and the sector-shaped fixed disk 33 are formed with the screws The matching screw receiving holes face the cutting wheel 42 and the fixing wheel 51 .
In another embodiment of Guangdong Yueluo Hardware Industry Co., Ltd., the discharge port of the vibrating plate 2 is matched with the screw receiving hole 35, and the screws can enter the screw receiving hole 35 through the discharge port after sorting and sorting in the vibrating plate 2. . Preferably, a guide rail 6 is provided between the discharge port of the vibrating plate 2 and the screw accommodating hole 35 , and the screws enter the screw accommodating hole 43 from the discharge port through the guide rail 6 . The slotting is carried out, which improves the efficiency and saves the labor cost.
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