CN111230239A

CN111230239A - Efficient spark electrolysis jet processing method for impact breaking of oxidation film

Info

Publication number: CN111230239A
Application number: CN202010095798.8A
Authority: CN
Inventors: 刘洋; 曲宁松; 沈志豪; 孔黄海
Original assignee: Nanjing University of Aeronautics and Astronautics
Current assignee: Nanjing University of Aeronautics and Astronautics
Priority date: 2020-02-17
Filing date: 2020-02-17
Publication date: 2020-06-05
Anticipated expiration: 2040-02-17
Also published as: CN111230239B

Abstract

The invention relates to a high-efficiency spark electrolysis jet flow processing method for breaking an oxidation film by impact, belonging to the field of electrochemical processing. The process method comprises two steps, wherein in the first step, a tube electrode vibrates up and down at a high speed in the Z direction, an oxide film on the surface of a workpiece is quickly punctured point by point at a high speed and removed through electric spark and efficient electrolytic combined machining in a small gap, and then the tube electrode moves to the next position in the horizontal direction at a high speed to repeat the process; and the second step is to reversely carry out high-speed horizontal jet flow machining according to the original machining track or the original machining track, and to flatten the machined rugged surface by jet flow machining. The high-speed vibration of the tube electrode can rapidly break the arc while breaking the oxidation film, so that continuous arc discharge is avoided. The high speed up and down vibration of the electrode facilitates the discharge of the processed product. The invention quickly removes the oxide film on the surface of the workpiece by the combined action of high-speed vibration spark discharge of the tube electrode and high-efficiency electrolysis, and greatly improves the efficiency of jet flow processing.

Description

Efficient spark electrolysis jet processing method for impact breaking of oxidation film

Technical Field

The invention relates to a high-efficiency spark electrolysis jet flow processing method for breaking an oxidation film by impact, belonging to the field of electrochemical processing.

Background

With the development of science and technology, a large amount of metal materials such as high-temperature alloys, titanium alloys and the like are used in the industrial fields such as modern aviation, aerospace, ships and the like. For example, titanium alloy accounts for 41% of the total amount of material used in the fourth generation fighter F-22. The commercial production of titanium began in 1948. The need for the development of the aerospace industry has led the titanium industry to grow at an average annual growth rate of about 8%. The annual output of the world titanium alloy processing materials reaches more than 4 ten thousand tons, and the titanium alloy grades are nearly 30. The most widely used titanium alloys are Ti-6Al-4V (TC4), Ti-5Al-2.5Sn (TA7) and commercially pure titanium (TA 1, TA2 and TA 3). The titanium alloy is mainly used for manufacturing parts of an air compressor of an aircraft engine, and is a structural part of rockets, missiles and high-speed airplanes. In the middle of the 60 s, titanium and its alloys have been used in general industries for making electrodes for the electrolysis industry, condensers for power stations, heaters for petroleum refining and seawater desalination, and environmental pollution control devices. Titanium and its alloys have become a corrosion resistant structural material. However, the titanium alloy has the characteristics of high strength, small density, good mechanical property, good toughness and corrosion resistance, so that the titanium alloy has poor technological property and difficult cutting processing; in the thermal processing, impurities such as hydrogen, oxygen, nitrogen, carbon and the like are very easily absorbed; also has poor abrasion resistance and complex production process. These present a number of challenges to conventional fabrication techniques.

Electrolytic machining is a special machining method for machining and shaping workpieces by utilizing the principle that metal generates electrochemical anodic dissolution in electrolyte. During machining, the workpiece is connected with the positive pole of a direct current power supply, the tool electrode is connected with the negative pole, and a small gap is kept between the two poles. The electrolyte flows through the interelectrode gap to form a conductive path between the two electrodes, and generates a current under a power supply voltage, thereby forming electrochemical anodic dissolution. With the continuous feeding of the tool relative to the workpiece, the metal of the workpiece is continuously electrolyzed, the electrolysis product is continuously washed away by the electrolyte, finally, the gaps at all positions between the two electrodes tend to be consistent, and the surface of the workpiece is formed into a shape basically similar to the working surface of the tool. In principle, the electrochemical machining can process almost all conductive materials, is not limited by mechanical and physical properties such as strength, hardness, toughness and the like of the materials, and basically does not change the metallographic structure of the processed materials. In addition, the tool and the workpiece are not contacted in the electrolytic machining process, no mechanical cutting force exists, no residual stress and deformation are generated, no flash and burr exist, and the cathode of the tool is free of loss. The great advantages of the electrolytic machining greatly solve the problems existing in the mechanical machining of the titanium alloy, so that the electrolytic machining of the titanium alloy is one of the main methods for machining the titanium alloy at present.

In the electrolytic jet, a hollow metal tube is generally used as an electrolyte nozzle to form a machined surface by controlling the numerical control trajectory of the tool cathode in a milling-like manner. During the machining process, the current mainly reaches the surface of the workpiece from the inner side wall of the nozzle through the electrolytic jet. The electrolyte is impacted on the surface of the workpiece and then is scattered to form an electrolyte flowing film, compared with the size of a jet liquid column, the thickness of the electrolyte flowing film is extremely thin, most of current is bound under the electrolyte column, and the current density at the electrolyte flowing film is rapidly reduced. Therefore, for the titanium alloy surface dense oxide film, the electrolytic machining is difficult to remove rapidly in a large area, which seriously reduces the efficiency of the jet machining of the titanium alloy.

Disclosure of Invention

A high-efficiency spark electrolysis jet processing method for impact-breaking an oxidation film is characterized by comprising the following steps:

step 1, carrying out electrolytic jet machining and electrolytic electric spark composite machining at intervals

Step 1-1, under the condition of ensuring that the machining gap between the tube electrode and the surface of the workpiece is not changed, the tube electrode is at a horizontal speed V₁Rapidly translating from the current electric spark machining point to the next electric spark machining point, wherein the translation distance is delta X, and carrying out electrolytic jet machining on the surface of the workpiece by using the pipe electrode in the translation process;

step 1-2, at an electric spark machining point, vibrating the tube electrode vertically at a high speed at a speed V2 along the Z vertical direction, wherein in the vibration process, a machining gap is h₁And h₂Is constantly changing, wherein h₂Less than h₁(ii) a In the high-speed vibration process and the rapid compression process of the machining gap, the energy density is greatly improved, so that a discharge channel is formed, high-energy-density spark discharge is carried out on the tube electrode during the electrolytic machining, and an oxide film on the surface of the titanium alloy workpiece and part of metal machine body materials are rapidly broken; meanwhile, the periodic rapid change of the gap in the vibration impact process is utilized to quickly discharge products, break the electric arc and place the arcGenerating continuous arc;

since the removal of the oxide layer by the spark discharge is completed in a moment, it takes several seconds or even ten seconds to remove the oxide layer compared with the electrolytic machining, which greatly improves the machining efficiency. The high-speed vibration of the tube electrode along the Z direction enables the flow field of the processing area to fluctuate greatly, and is beneficial to the quick discharge of products. In addition, the high-speed vibration of the tube electrode along the Z direction can cause the machining gap to be changed continuously, and when the machining gap is large enough, the discharge channel is automatically disconnected, so that the workpiece and the cutter can be prevented from being burnt due to continuous arc pulling.

At each electric spark machining point, continuing to rapidly translate after the tube electrode vibrates for 1-2 periods, repeating the steps 1-1 to 1-2 until all points on the machining path are removed of the oxide film, and finishing the removal work of the oxide film on the surface of the titanium alloy workpiece on the machining path;

the low-temperature electrolytic jet flow flowing at high speed in the machining process cools the tube electrode and the titanium alloy workpiece, so that the heat affected zone is reduced;

step 2, electrolytic jet flow finish machining

After the first step is finished, the tube electrode horizontally moves reversely at a high speed according to the original processing track or the original processing track, and the electrolytic jet flow finish machining is carried out on the surface of the rugged titanium alloy workpiece after the oxide film is removed.

The high-efficiency spark electrolysis jet processing method for breaking the oxidation film by impact is characterized by comprising the following steps of: h above₁Determined according to the electrolytic process, h₂And determining the delta X as 1-2 times of the diameter of the tube electrode according to an electric spark process.

Because the invention mainly depends on the electrolytic jet flow to remove the surface material of the titanium alloy workpiece, h₁Determined according to the electrolytic process. Meanwhile, in order to rapidly remove the oxide layer on the surface of the titanium alloy workpiece by utilizing spark discharge and prevent the oxide layer from generating adverse effects on the subsequent jet flow electrolytic machining, the machining gap must be shortened to a gap h capable of generating spark discharge₂. The delta X is 1-2 times the diameter of the tube electrode, so as to ensure that most of the oxides on the processing path can be effectively and quickly removed by the spark discharge at the end part of the tube electrode. According to addingAs can be seen from the experience, during the spark discharge machining of the tube electrode, the tube electrode has a removing effect on the surface of the workpiece within the range of 1-2 times the diameter of the tube electrode, so that the translation distance DeltaX of the tube electrode is set to be 1-2 times the diameter of the tube electrode.

Drawings

FIG. 1 is a schematic view of a rapid jet machining titanium alloy without breaking an oxide film;

FIG. 2 is a schematic view of efficient milling of titanium alloy after rapid rupture of an oxide film by high-speed vibration impact;

FIG. 3 is a schematic diagram showing the relationship between the processing gap IEG between the electrode and the workpiece and the horizontal displacement X of the electrode during rapid rupture of the oxide film by high-speed vibration impact;

wherein the label names are: 1. a tube electrode; 2. an oxide film; 3. a titanium alloy workpiece; 4. spark discharge; 5. and (4) electrolyzing jet flow.

Detailed Description

FIG. 1 is a schematic view showing rapid jet machining of a titanium alloy without breaking an oxide film, wherein only electrolytic jet machining is performed on a tubular tube electrode 1) in FIG. 1 (a), and a machining gap h between the tube electrode 1 and the surface of a workpiece₁. When the electrolytic jet 5) is sprayed from the inner side wall of the tube electrode 1 and impacts the surface of the workpiece, the electrolyte is scattered to form an extremely thin electrolyte film. The current in the electrolyte is mostly confined under the electrolyte column and the current density at the electrolyte membrane drops rapidly. Therefore, only a small area of the titanium alloy dense oxide film 2 under the liquid column of the electrolytic jet 5 can be dissolved. At the guarantee of the machining clearance h₁Under the same condition, when the tube electrode 1 is at the horizontal speed V₁When the translation is performed rapidly and the stay time of the tube electrode 1 in a unit area is insufficient, the titanium alloy oxide film 2 cannot be completely dissolved. Some oxide film 2 that is not dissolved and removed appears in fig. 1 (b), so that the surface is dimpled. If the corresponding dense oxide film (2) of titanium alloy is to be completely dissolved, the horizontal movement speed of the tube electrode 1 must be slowed down, but this greatly reduces the efficiency of the jet machining.

FIG. 2 is a schematic view of efficient milling of titanium alloy after rapid rupture of an oxide film by high-speed vibration impact. As shown in the figure, the tube electrode 1 is translated at a horizontal speed V1 for electrolytic machining, and moved to a certain extentAfter the distance, the tube electrode 1 vibrates up and down in the Z-vertical direction at a high speed V2. In the vibration process, the machining gap is h₁And h₂As shown in fig. 2 (a) and 2 (b). As can be seen from fig. 2 (b), the rapid compression of the machining gap greatly increases the energy density, so that a discharge channel is formed, the tube electrode 1 is subjected to high-energy-density spark discharge 4 while being subjected to electrochemical machining, and the oxide film 2 and part of the metal body material on the surface of the titanium alloy workpiece 3 are rapidly broken. The surface quality after rough machining is as shown in fig. 2 (c), and the machined surface is free of the oxide film 2. However, the machined surface is rough because it is subjected to spark discharge explosion impact during machining. After the rough machining is completed, the rapidly horizontally moving tube electrode 1 is returned to the original machining trajectory, and the electrolytic jet finishing is performed on the rough machined surface having irregularities, as shown in fig. 2 (d). Finally, the surface of the titanium alloy workpiece 3 is finished smoothly and flatly, as shown in fig. 2 (e).

FIG. 3 is a schematic diagram showing the relationship between the processing gap IEG between the electrode and the workpiece and the horizontal displacement X of the electrode during rapid rupture of the oxide film by high-speed vibration impact. As can be seen from fig. 3, the motion trajectory of the tube electrode has periodicity, and the machining gap also changes periodically.

The high-efficiency spark electrolysis jet processing method for impact-breaking the oxidation film can rapidly break the oxidation film 2 on the surface of the titanium alloy workpiece 3 through the high-energy-density spark discharge 4, solve the problem of low titanium alloy electrolysis processing efficiency caused by the oxidation film 2, and greatly improve the efficiency of jet electrolysis processing of the titanium alloy. The above description should not be construed as limiting the present patent. It should be noted that several improvements can be made without departing from the inventive concept, which shall all fall within the protection of the present patent.

Claims

1. A high-efficiency spark electrolysis jet processing method for impact-breaking an oxidation film is characterized by comprising the following steps:

Step 1-1,Ensuring that the machining gap between the tube electrode (1) and the surface of the workpiece is h₁Under the condition of constant, the tube electrode (1) is at horizontal speed V₁Rapidly translating from the current electric spark machining point to the next electric spark machining point, wherein the translation distance is delta X, and carrying out electrolytic jet machining on the surface of the workpiece by using the pipe electrode in the translation process;

step 1-2, at an electric spark machining point, vibrating the tube electrode (1) at a high speed up and down along the Z vertical direction at a speed V2, wherein in the vibration process, a machining gap is h₁And h₂Is constantly changing, wherein h₂Less than h₁(ii) a In the high-speed vibration process and the rapid compression process of the machining gap, the energy density is greatly improved, so that a discharge channel is formed, high-energy-density spark discharge (4) is carried out on the tube electrode (1) during electrolytic machining, and an oxide film (2) on the surface of the titanium alloy workpiece (3) and part of metal machine body materials are rapidly broken; meanwhile, products are quickly discharged by utilizing the periodic rapid change of the gap in the vibration impact process, the electric arc is broken, and the continuous arc discharge is prevented;

at each electric spark machining point, the tube electrode (1) continues to rapidly translate after vibrating for 1-2 periods, and the steps 1-1 to 1-2 are repeated until all points on the machining path are removed of the oxide film, so that the removal work of the oxide film (2) on the surface of the titanium alloy workpiece (3) on the machining path is completed;

the low-temperature electrolytic jet flow (5) flowing at high speed in the machining process cools the tube electrode (1) and the titanium alloy workpiece (3) and reduces a heat affected zone;

step 2, electrolytic jet flow finish machining

After the first step is finished, the tube electrode (1) moves horizontally at a high speed in a reverse direction according to the original processing track or the original processing track, and electrolytic jet flow finish machining is carried out on the surface of the rugged titanium alloy workpiece (3) from which the oxide film (2) is removed.

2. The high-efficiency spark electrolysis jet processing method for impact-breaking an oxide film according to claim 1, wherein:

h above₁According toDetermination of the electrolytic Process h₂The delta X is determined by an electric spark process to be 1-2 times of the diameter of the tube electrode (1).