Drawing lubricant is a process lubricating material during the wire drawing process. Its function is to form a lubricating film between the drawn metal and the wire drawing die wall to reduce the friction between the interfaces and prevent The metal is bonded to the mold wall due to heat generation to reduce energy consumption and temperature rise during drawing, extend the service life of the mold, ensure the surface quality of the product, and make deformation uniform. Improving the lubrication performance of lubricants plays an important role in achieving high-speed drawing and strengthening the drawing deformation process. Generally, there are special drawing lubricants suitable for this process for drawing mild steel, copper, aluminum and their alloys. Here is a brief introduction to the common drawing lubricants:
1. Bars, Lubricant for wire drawing
(1) Steel drawing lubrication Due to the tendency of the film to stick during steel wire drawing, dry film lubrication is often used as the initial protective layer. Low and medium carbon steel wire drawing lubricants can use lime or borax, or general drawing oil. Borax will revert to its crystalline state at high humidity, but has good corrosion protection properties at moderate humidity. If no cleaning is required after drawing, it is best to use special drawing oil as lubricant. If annealing treatment is required, the residue must be removed before annealing, otherwise the residue will be converted into carbonized deposits during heat treatment, and part of it will be deposited on the metal surface, affecting the quality of the drawn products.
(2) Drawing lubrication of aluminum and aluminum alloys Aluminum is similar to stainless steel, with a fragile oxide film on the surface, but it is much easier to pull than stainless steel. For drawing aluminum and aluminum alloy strips and bars, special drawing oil with sulfurized lard as the main additive is commonly used. The amount added depends on the type of alloy, drawing size and speed. It can be used in drawing soft metal strips. and rods to prevent adverse situations such as sticking film and sintering. The viscosity of the lubricating oil used for aluminum wire drawing depends on the size of the aluminum wire drawn, the drawing speed, the drawing diameter reduction ratio and the required roughness.
(3) Drawing lubrication of copper and copper alloys The selection of lubricant for drawing of copper and copper alloys is affected by many factors such as drawing speed, rod diameter and mold. Generally speaking, it is sufficient to use grease or high-viscosity mechanical lubricant when drawing bars at low speeds. However, sometimes in order to further improve the processing quality, an appropriate amount of vulcanized extreme pressure additives can be added. The high-speed wire drawing production lines developed in recent years have put forward higher requirements for drawing oil, such as appropriate lubricity to reduce wear and improve the life of the mold; good cleanability to prevent copper powder from sticking around the mold. And cause wear; it must have good cooling effect and long service life to ensure drawing quality and high production efficiency. At present, the development of high-speed wire drawing lubricating coolants with the above-mentioned good comprehensive properties is an urgent requirement to further improve wire drawing technology.
2. Lubricant for pipe drawing
(1) For steel pipe drawing, the blank pipe is generally pickled to remove oxide scale, and then the surface is preliminarily prepared by phosphating and saponification. Treatment, so that the formed lubricating film can meet the requirements of the drawing process. Good lubrication status has a great impact on pipe quality, mold life and production efficiency. Seamless steel pipes are produced using a perforated hot rolling process. The perforated center rod needs to be lubricated with lubricant. The main components of the lubricant used include graphite, metal powder, vulcanized lard, etc.
(2) High-viscosity lubricating oil is generally used for cold drawing of aluminum tubes, and sometimes an appropriate amount of oily anti-wear agent, extreme pressure anti-wear agent and antioxidant is added. When drawing small-diameter aluminum tubes at high speed, using special drawing oil with low viscosity and extreme pressure and anti-wear additives can greatly reduce oil stains and eliminate the trouble of solvent cleaning, because it has been widely used. Generally, the roughness of drawn aluminum tubes is affected by factors such as the viscosity of the lubricating oil, drawing speed and mold geometry. In order to keep the aluminum tube bright, paraffin lubricant can also be used for aluminum tube drawing, that is, the tube blank is immersed in a solvent-diluted paraffin solution or emulsion, and then drawn after soaking. In this way, three consecutive drawings can be made without applying lubricant, and the drawn aluminum tube can be lubricated and cleaned with paraffin wax.
(3) There are two processes for copper tube drawing: linear drawing and disc drawing. Disc stretching has the advantages of long material pulling and high speed, but also has high requirements for lubricants. For example, the refrigeration copper tubes used in refrigerators require good internal and external surface cleanliness. If the lubricating oil contains a lot of residual carbon, the copper surface will turn black during the annealing treatment. In the early stage of copper pipe drawing, oil-based lubricants based on mineral oil or vegetable oil were often used, but they had the disadvantage of polluting the environment and easily producing oil spots. At present, special drawing oils are mostly used. Drawing lubricating oils with sulfurized fatty acid ester as the main additive have better comprehensive properties and are widely used.