Protection and repair technology of machine tool g

According to different conditions, the protection and repair process of machine tool guide rail

with the development of large machine tools towards high-speed and heavy load, the former requires the use of coarse abrasive, high precision and automation to improve the working conditions of machine tool guide rail. How to improve and maintain the accuracy of machine tool guide rail is attracting more and more attention. Cast iron guide rail has been the first choice of most machine tool designers because of its good vibration and wear resistance, stability and low cost. However, cast iron has weaknesses such as low hardness, loose structure and many blank defects. Large machine tools with heavy load are easy to cause wear and tear of guide rails, which reduces the accuracy of machine tools and affects the quality of products. Therefore, it is necessary to improve the wear resistance of the guide rail surface and the rapid repair of surface defects. Practice has proved that surface quenching, brush plating to protect the guide rail and brush plating brazing to repair the damage of the guide rail are ideal means at present

I. electric contact surface quenching of guide rail

the main principle of electric contact surface quenching is: use an electrode (graphite or red copper roller) to make close contact with the workpiece (Fig. 1), through the low-voltage strong current of the roller, form resistance heat on the contact surface between the electrode and the workpiece to quickly heat the contact surface, and quickly cool the workpiece surface through compressed air to ensure the formation of very fine martensite and sheet graphite on the guide rail surface, To achieve the purpose of surface quenching, at the same time, the roller moves forward at a certain speed, so that the requirements of surface quenching for the whole guide rail can be achieved. After actual testing, the quenching layer with this method can be widely used in medical devices, packaging and other standardized markets. The utilization of cellene TPE particles can reach 0.3 ~ 0.4mm, and the hardness is 59 ~ 61hrc. After quenching, the surface is ground with a grinder, It completely guarantees the design requirements of machine tool guide rail. At the same time, due to the adoption of this method, the guide rail deformation is small, the investment is small, the operation is simple, the speed is fast, and the economic benefit is very obvious. At present, the flat guide rail and V-shaped guide rail of large machine tools of the group company adopt this quenching and grinding method, which is simple and effective. One quenching machine can complete the surface quenching of 3 ~ 5 machine tool guide rails with a length of 12 ~ 15m in one day

second, protect the machine tool guide rail with brush plating

brushing metal or alloy on the guide rail surface as the working layer can also strengthen its surface hardness, improve wear resistance, and meet the requirements of further reducing roughness. Generally, quick nickel, nickel drill tungsten alloy, nickel tungsten D alloy are selected as the working layer. Among them, the rapid nickel alloy electrodeposition speed is fast, the hardness is equivalent to that of 45 steel, and the wear resistance is better than that of quenched 45 steel; Nickel tungsten alloy and nickel tungsten D alloy have similar properties, both of which have high hardness (58 ~ 60 HRC) and wear resistance twice that of 45 steel, but the electrodeposition speed is faster and nickel is slower. Therefore, for general medium and small machine tools, rapid nickel brush plating can achieve the purpose of protecting the guide rail. For large machine tools or machine tools with high precision requirements, nickel tungsten D alloy or nickel tungsten alloy working layer is ideal

1. brush plating formula

(1) fast nickel formula. Nickel sulfate 254g/l; Salicylate 56g/l; Acetic acid money 23g/l; Oxalic acid is 0.1g/l; 105ml of ammonia (25% - 28%); Specific gravity 1.15; Power consumption coefficient 0.104a h/dm2 μ m 。

(2) nickel tungsten D alloy formula. Nickel sulfate 393g/l; Sodium tungstate 23g/l; Boric acid 31g/l; Citric acid 42g/l; Sodium sulphate 6.5g/l; Cobalt sulfate 2g/l; Additive 2.8g/l; Glacial acetic acid 20ml/l; Sodium fluoride 5g/l; Sodium dodecyl sulfate 0.01 ~ 0.001 g/l; PH value 1.4 ~ 2.4; Power consumption coefficient 0.214 a h/dm2 μ m 。

(3) brush plating pretreatment process. Industrial gasoline cleaning guide rail surface → water sandpaper grinding → acetone fine cleaning → electrolytic degreasing (voltage 12V, machine tool connected to negative) → water washing → No. II electric net (workpiece connected to positive, voltage 7V) → water washing → No. III electric net (workpiece connected to positive, voltage 10 ~ 14V, and then workpiece connected to negative, voltage 6 ~ 8V) → water washing. Special nickel is used as brush plating transition layer, water washing, brush plating fast nickel or nickel tungsten D alloy or nickel diamond tungsten alloy

2. Brush plating anode material and bath circulation

(1) anode material. At present, graphite is widely used as anode in brush plating. Graphite has good conductivity and no other metal ions pollute the plating solution. However, due to the brittleness of graphite, it is easy to collapse under high-density current. At the same time, the strength of graphite is low, it is not easy to make large electrodes, and the metal is easy to form and has high strength. Therefore, high-purity metal can be used as anode, but metal as anode is easy to cause a large number of metal ions to be included in the plating solution, Therefore, it is required that the electroplating solution must contain a complexing agent with strong complexing force, complexing excess metal ions, so as to ensure the stability of the electroplating solution and prevent the passivation of the metal anode under high-density current. Electrolytic metal nickel is used as anode for brush plating of fast nickel, nickel tungsten D alloy or nickel diamond tungsten alloy

the anode made should be flat. The conductive plate and nickel plate should be spot welded evenly with stainless steel electrodes, and 3mm plum shaped holes should be drilled on the nickel plate at the bottom of the anode. See Figure 2 for brush plated anode

(2) bath circulation. Closed method and intermittent pouring method can be adopted. Sealing method: the plating solution is sealed in the bath, and the anode is immersed in the plating solution for brush plating. At this time, all the brush coatings are immersed in the plating solution. The plating solution is not easy to be oxidized by air and affect the quality of brush plating. It is generally suitable for alloy plating solutions with expensive plating solutions and slow electrodeposition speed. Intermittent pouring method: it is to pour the electroplating solution on the anode intermittently, so that it can be consumed naturally. In order to reduce the loss of the electroplating solution once a serious fire hazard is exposed, a groove can be machined on the back of the anode, and a small hole can be drilled at the bottom of the anode. The plating solution penetrates into the absorbent cotton from the small hole for coating. This method has a lot of loss of plating solution, which is generally used for brush plating with fast speed and relatively cheap plating solution

(3) coating thickness control. Coating thickness calculation formula: δ= I t/C S。 among δ Is plating thickness（ μ m) I is the current (a), t is the time (H), s is the area (DM), and C is the power consumption coefficient of the plating solution (a h/dm2 μ m）。 The more uniform the coating thickness is, the higher the precision of the guide rail is. The uniformity of the coating is affected by the anode shape, the uniformity of the anode sheath thickness, the anode conductivity, etc. generally, the thickness of the plating layer is 0.05 ~ 0.08mm, and the non-uniformity can be controlled within 0.003mm

III. repair guide rail damage with brush plating brazing method

cast iron has high carbon content, loose structure, and poor brazing bonding force directly on it. Therefore, nickel can be used as the transition layer, and alkali copper can be used as the intermediate layer, in which nickel is used as the transition layer or the bottom layer has good bonding force with the matrix. Alkali copper can be used as the intermediate layer, which can be firmly bonded with nickel and tin alloy of the brazing layer, and tin alloy has low melting point, liquidity, toughness The wear resistance is relatively good, and its hardness and melting point can be adjusted within a certain range according to the alloy composition. Combined with the actual situation, the specific process is formulated as follows:

1 Surface treatment

guide rail surface treatment (oil and dust removal). Electrolytic oil removal → water washing → II electric cleaning → III electric cleaning → brushing transition layer nickel 2 ~ 3 μ M → water washing → brush plating alkaline copper → water washing → pickling → brazing tin secret alloy → grinding the brazing layer → pretreatment before brush plating → brush plating

it is particularly emphasized that before brush plating, the oil, ash and sand at the damaged part of the guide rail must be cleaned with gasoline and the serious fatigue layer must be removed, otherwise the bonding strength of the welding layer will be seriously affected. When brushing the alkaline copper layer, it is easy to oxidize, and the oxide layer will affect the bonding strength of the solder layer. Therefore, before welding, wash the oxide film with hydrochloric acid, and at the same time, do not apply too much hydrochloric acid, otherwise it will corrode the substrate and cause many pinholes in the solder layer of the solder layer of the solder layer of the solder layer of the solder layer of the solder alloy

2. Nickel formula and process

nickel sulfate 330g/l; Glacial acetic acid 30ml/l; Aminoacetic acid 20 ml/l, power consumption coefficient 0.42 a h/dm2 μ m； PH 0; The relative movement speed of anode and cathode is 10 ~ 25m/min; The voltage is 8 ~ 10V

3. Alkali copper formula and process

copper sulfate 250g/l; Ethylenediamine 250g/l; Triethylamine increases the amount of CPE acid by 150 g/L; Sodium sulfate 20 g/l; Nitric acid hinge 50g/l; PH value 7 ~ 8; The relative movement speed of anode and cathode is 10 ~ 20m/min; Voltage 6 ~ 15V; Power consumption coefficient 0.18 a h/dm2 μ m。

the above methods can be applied according to different conditions of machine tool manufacturing or maintenance. The newly processed machine tool guide rail can be treated by surface quenching or brush plating; The damaged guide rail can be repaired by brush plating and brazing, and then the whole guide rail surface can be quenched or brushed with a layer of metal or alloy. This can not only solve the repair problem, but also protect the whole machine tool guide rail and prolong the service life of the machine tool guide rail. Atlas air compressor accessories valve