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One. The basic concept of screw production:
 
 
1. Screw manufacturing methods can be divided into: cold heading, hot hitting, machining (turning, milling, etc.). (We mainly introduce cold heading, hot hitting and turning as an understanding of knowledge)
2. The definition of cold heading is to use the plasticity of metal to apply pressure or cold drawing with cold mechanics to achieve the purpose of solid metal deformation. A forging method that thickens the top of a bar or wire at room temperature.
3. Application range of cold heading: Mainly used in the manufacture of bolts, nuts, nails, rivets, steel balls and other parts. The forging material can be copper, aluminum, carbon steel, alloy steel, stainless steel, titanium alloy, etc.
4. The superiority of cold heading: the material utilization rate can reach 80-90%, and the production efficiency is high, reaching more than 300 pieces/min.
5. The definition of hot upsetting: hot upsetting is to heat the material and perform pressure processing to make the shape of the material meet the design requirements. It is a method of forging and forming in a mold of a certain shape after heating the material. It is also called hot processing or red hitting. These are all big bolts made with red.
6. Machining: The hexagon heads of small batches of special or special bolts are milled after turning.
7. Thread rolling: The thread of the bolt has mechanical threading, which is similar to manual die. The bolts with large diameters can only be machined by machine tools. There is also "thread rolling", which uses a "thread rolling machine" to extrude the threads with a "thread rolling board". The diameter of the unthreaded part of this bolt is slightly smaller.
8. Tail milling: Generally done by tail cutting machine.
9. The difference between cold heading and hot heading: ①The surface of the bolts of cold heading is more beautiful, and the surface of the bolts of red heading is unsightly; ②The production efficiency of cold heading is high. ③The bolts of M24 and above generally need red heading.
 
two. Process and process of screw production:
 
 
(1) A process of screw manufacturing: plate element-annealing-pickling-wire drawing-heading-thread rolling-heat treatment-electroplating-packaging
(2) Processes of screw manufacturing:
⒈Pan Yuan:
①Definition: refers to the original wire rod purchased from the manufacturer. A disk element mainly includes the following parameters: brand, product name, specification, material, furnace number or batch number, quantity/weight; ②Main chemical composition in steel There are: C, Mn, P, S, Si, Cu, Al, the lower the content of Al and Cu, the better.
⒉ Annealing:
①Definition: Heat the wire to an appropriate temperature, keep it for a certain period of time, and then slowly cool it to adjust the crystal structure, reduce the hardness, and improve the wire processing at room temperature.
②Operation process: feeding-heating up-keeping warm-cooling down. ③Quality control: Hardness: the material is 1018, 1022 wire rod after annealing, the hardness is HV120-170, the material is medium carbon wire rod after annealing, the hardness is HV120-180; Appearance: there should be no oxide film and decarburization on the surface.
⒊Pickling:
① Purpose: Remove the oxide film on the wire surface and form a layer of phosphate film on the metal surface to reduce the scratches on the tool and die during the wire drawing and cold forging or forming processes.
②Operation process:
Ⅰ. Pickling: Immerse the entire disk element into three hydrochloric acid tanks with a concentration of 20-25% at room temperature for a few minutes. The purpose is to remove the oxide film on the surface of the wire.
Ⅱ. Clean water: remove hydrochloric acid corrosion products on the wire surface.
Ⅲ. Oxalic acid: increase the activity of metals to make the film formed in the next process more dense.
Ⅳ. Coating treatment: The disc element is immersed in phosphate, the surface of the steel is in contact with the chemical conversion treatment solution, and the steel is dissolved to form insoluble compounds (such as Zn2Fe (Po4) 2.4H2o), which adhere to the surface of the steel to form a coating.
Ⅴ. Clean water: remove the residue on the surface of the film.
Ⅵ. Lubricant: Since the friction coefficient of the phosphate film is not very low, it cannot give sufficient lubricity during processing, but it reacts with metal soap (such as sodium soap) to form a hard metal soap layer, which can increase its lubricating performance.
 
4. Draw line:
①Purpose: cold-draw the plate element to the required wire diameter. In practice, some products can be divided into two stages: rough extraction (peeling) and fine extraction.
②Operation process
ⅠSmall wire drawing: Since the minimum specification of the general disk element is 5.5mm (depending on the specific circumstances of each company), most small screws (under 14# (inclusive) in the British system, under M5 in the metric system) require relatively small wire diameters , And the small screw deforms greatly when forming. In order to reduce the processing stress caused by cold drawing and ensure the workability of the wire, the cold drawing of the wire is divided into two stages. First, the coil element is roughly drawn to a certain wire diameter by a continuous wire drawing machine (to ensure the fine drawing The reduction rate is less than 15% as the principle), and then annealed to eliminate the processing stress caused by rough drawing.
Ⅱ Large wire drawing: After pickling, the plate element is cold drawn to the required wire diameter by a wire drawing machine. Suitable for wires used in large screws, nuts, and threaded rods
 
 
3. Analysis of the undesirable phenomena that are easy to occur during the molding process and their causes
 
 
1. Eccentricity: Poor installation of the second punch and improper adjustment of the machine.
2. Tilted head: Poor installation and improper adjustment of the first punch.
3. The head is not round: the selection of a die is improper or the molding is not full enough.
4. Die cracks: The die is broken or the R angle of the die is improper, causing the die to be scratched by the second impact.
5. Double-layer head: Poorly formed in one punch.
6. Burr: Poor forming in one punch, mainly caused by too large gap between punching rod and die hole or too short punching rod.
7. Crack angle: the punching needle is broken or the second punch is not heavy with the punching die.
8. Cracking of the head: material problems, or the wrong use of a die (such as a die with a hexagonal washer head for the pan head), and the cause of lubricating oil.
 
Fourth, tooth rolling is easy to produce bad phenomena and cause analysis
 
 
1. Processing cracks: the tooth plate is worn out and the machine is improperly adjusted.
2. Blunt tail: improper adjustment of the machine, too old tooth plate.
3. Fire: The distance between the two tooth plates is too large, or the feeding time is wrong.
4. Crooked tail: The control screw on the tooth plate seat is too tight.
5. Tail docking: tooth plate wear and improper adjustment of the machine.
6. Asan is not full: improper adjustment of the machine
7. The tail teeth are not rubbed to the tip of the tail.
8. Crooked bar: The correction block is not well corrected.
9. Rough tooth base: The tooth distance has not been adjusted properly.
 
5. The process and flow of nut production
 
(1) Nut forming:
①、Operation process:
Ⅰ. Cutting: The inner die and the shearing knife are matched to cut the wire into the required blank.
Ⅱ. One punch: the front punch die, the stroke die, and the back punch bar cooperate to shape the deformed cut blank, and the back punch pushes the blank.
Ⅲ. Second punch: The rotating clamp clamps the blank from one punch to the second punch. The front punch die, the stroke die, and the back punch are matched to further shape the blank, and strengthen the flattening and fullness of the first punch. Afterwards, the blank is pushed out by the back punch.
Ⅳ. Three-stroke: the rotating clamp clamps the blank from two-stroke to three-stroke. The front punch die, stroke die, and back punch are matched to squeeze the blank again so that the lower punch can be completely formed. The blank is launched.
Ⅴ. Four-stroke: The rotating clamp clamps the blank from three-stroke to four-stroke. The front punch die, stroke die, and back punch are matched to form the nut completely, and the thickness of the nut is adjusted by controlling the thickness of the iron filings. The blank is pushed out by the back punch.
Ⅵ. Five punches: The rotating clamp clamps the blank from four punches to five punches. The front punch and the stripper are matched to punch the completely formed blank, and the punched iron filings enter the lower core of the punching die. And finally the forming of the nut is completed. The head mark of the nut is formed during this process.
②The production process of nuts:
Nuts below grade Ⅰ and 8
⑴. Pan element---pickling---drawing line---cheng---tapping---surface treatment---packing
⑵. Hot-dip galvanizing: plate element---pickling---drawing line---forming---hot-dip galvanizing---tapping---packing
Ⅱ, 8 level nut
Pan element---annealing---pickling---drawing line---forming---tapping---surface treatment---packing
Ⅲ. Metric level 10, 12, and British level 5 and above nuts
Pan element---annealing---pickling---drawing line---forming---tapping---heat treatment---surface treatment packaging
(2) Tapping is to use a wire tap to tap the formed nut to form the required thread.
①Quality control: The quality problem that often occurs during the tapping process is tightness. The tightness is usually caused by the bending of the straight line of the tapping handle, the dullness of the tapping, the over-tolerance of the effective diameter, and the irregularities of the upper and lower tracks. In view of the reasons for the tightening of the teeth, measures such as orthodontic taps, replacement taps or runway adjustments can be taken.
 
 

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