1. The role of lubricants
(1) Lubrication. Between the deformed metal and the mold cavity, a lubricating film is maintained to avoid direct contact and bonding between the mold and the wire, reducing the friction coefficient, thereby reducing energy consumption and processing passes, and extending the service life of the mold.
(2) Cooling effect. The use of a cooling lubricant can reduce the temperature of the wire rod and die hole, prevent the wire rod from being oxidized and discolored due to excessive temperature, and improve the wire speed.
(3) Cleaning effect. During the drawing process, fine metal dust is continuously generated, and the lubricating fluid continuously flushes the die hole to eliminate the effect of metal dust in the die hole.
2. Influence factors of lubricant on wire drawing
(1) Concentration. The concentration of lubricant is large, which improves its lubricating effect. The friction coefficient between the metal wire and the wall of the die hole is small, the corresponding friction force is also reduced, and the tensile force is also reduced. However, if the concentration is too large, the viscosity of the lubricant will also increase, its flushing effect will also decrease, and the metal chips in the die hole will not be easily taken away, resulting in poor wire surface quality. If the concentration is too large, the metal chips will not precipitate and be suspended in the lubricant, which will affect the lubrication effect.
(2) Temperature. The temperature of the lubricating fluid is too high, and it loses its cooling effect, which increases the temperature of the metal wire and the mold, the wire is oxidized and discolored, the life of the mold is reduced, and the strength of the grease lubricating film is also affected, and the lubricating effect is reduced. If the temperature is too high, the viscosity of the lubricant will increase, which is not conducive to stretching.
(3) Cleanliness. The mixing of acid substances into the lubricant will cause the lubricant to stratify and lose its lubricating effect. The increase of alkali content in the lubricant will cause corrosion damage to the stretched metal wire. There are solid impurities in the lubricant, which affect the lubrication system of the equipment, resulting in an insufficient supply of lubricating fluid and reducing the role of the lubricant.
3. Basic requirements for lubricants
(1) Good adhesion, the lubricant can effectively adhere to the surface of the drawn wire.
(2) It can withstand the high pressure between the wire and the mold, and has good thermal stability.
(3) No corrosive effect.
(4) The cooling effect is good.
(5) There is no irritating smell.
(6) Easy to remove after drawing.
4. Drawing lubrication method
(1) Dispersion lubrication of single die groove is mainly used for one-time wire drawing machines or accumulating multi-die wire drawing machines without sliding, which has no restrictions on the form of lubricant. Cooling is achieved by circulating water in the die cavity. Since the die groove is open, the lubricant can be directly observed, which is convenient for adjustment. But it is easy to soil equipment and venues.
(2) The immersion type lubrication adopts emulsion strong and liquid oily lubricant, which is suitable for sliding type continuous wire drawing machine. The lubricant is contained in the special groove of the wire drawing machine. The drum, wire segment, and die are all immersed in the lubricant. The structure is simple and can ensure the continuous lubrication and cooling of the die, drum, and wire.
Its disadvantage is that the metal chips generated during the wire drawing process have no possibility of precipitation, and are continuously brought into the die hole and the drum, which affects the life of the die and the drum, and also affects the quality of the wire surface. The lubricating tucks need to have cooling devices to prevent the lubricating fluid from getting too hot.
(3) Circulating lubrication system On the sliding type continuous wire drawing machine, to ensure that the lubricating fluid has a fixed composition and a certain temperature, it can be used by a single machine, or it can be used by several wire drawing machines collectively. Its advantage is that the metal chips in the lubricating fluid can be fully precipitated, and regular cleaning can ensure the cleanliness of the lubricating fluid. Its disadvantage is that it needs to analyze the lubricating fluid from time to time and replenish the lubricant in time.
