CN115476008A - Titanium or titanium alloy inert atomization medium electric discharge machining method - Google Patents

Abstract

The invention relates to a method for electric discharge machining of titanium or titanium alloy inert atomized medium, comprising the following steps: (1) feeding an inert gas medium and a liquid medium into an atomizing device at the same time to form an inert atomized medium; The liquid medium is a substance that does not chemically react with titanium or titanium alloy at high temperature, preferably argon or helium; (2) continuously pass the inert atomizing medium into the gap area of electric discharge machining; (3 ) connecting the tool electrode to the negative pole of the pulse power supply, and connecting the titanium or titanium alloy workpiece to the positive pole of the pulse power supply to form a discharge circuit, and performing electric discharge machining on the excess material of the titanium or titanium alloy workpiece. The method of the invention has the advantages of high discharge machining energy utilization rate, good machining stability, high machining efficiency, good workpiece machining shape accuracy and surface quality, etc. for machining titanium or titanium alloy.

Description

Titanium or titanium alloy inert atomization medium electric discharge machining method

technical field

The invention relates to the technical field of titanium or titanium alloy material processing, in particular to a method for electric discharge machining of titanium or titanium alloy inert atomization medium.

Background technique

Titanium or titanium alloy materials have the characteristics of high specific strength, corrosion resistance, excellent high-temperature mechanical properties and good biocompatibility, and are widely used in aerospace, weapon industry, medical equipment, ships and many other fields. With the expansion of the application range of titanium alloys in various fields, people's requirements for the size, shape and surface quality of titanium alloy parts continue to increase, and research on titanium alloy processing technologies and methods has attracted much attention. However, due to the high specific strength and low elastic coefficient of titanium or titanium alloy, high and concentrated cutting force will be generated in the machining process, which will easily generate vibration and cause tremor during cutting, which will affect the machining accuracy; the thermal conductivity of titanium or titanium alloy is poor. , the heat generated during cutting is not easy to dissipate, and it is easy to accumulate on the tool to accelerate tool wear. Therefore, titanium or titanium alloy materials are considered as difficult-to-cut materials in the field of cutting.

In order to overcome the above-mentioned problems that are difficult to solve by traditional mechanical processing methods, EDM uses the electric erosion phenomenon during the pulsed spark discharge between the workpiece and the tool to remove excess metal materials, which is suitable for the processing of mostly difficult-to-cut conductive materials. Machining without macroscopic cutting force, its processing performance has nothing to do with the mechanical properties such as hardness and brittleness of the material, but only with the electrical conductivity and thermal properties of the processed material.

EDM is usually performed in liquid or gaseous dielectrics. The research on the processing mechanism in liquid is relatively mature, and there are many research results, but the use of liquid medium after processing will seriously pollute the environment, so it requires additional costs for harmless treatment. For example, when using kerosene working fluid, under the action of high temperature Will decompose producing off gas and presents a fire hazard. EDM in air has low processing efficiency. When using air medium, the processing efficiency is only 1/6 of the working fluid, and the short circuit rate is relatively high. The molten metal generated during the processing is not easy to cool and solidify in time during the splashing process, and some of it will stick. Knots on the surface of the workpiece affect the machining accuracy. Due to its own physical and chemical characteristics, especially the chemical activity of titanium, titanium or titanium alloy is very active under high temperature conditions, and it is very easy to chemically react with oxidizing substances. Under the instantaneous discharge high temperature condition of 3000-6000°C, elements such as C, O, and N in the liquid medium and gas medium can easily react with titanium or titanium alloys to form nitrogen oxides of titanium with high melting point and high resistance value, etc. Impurity substances are deposited on the surface of the workpiece, forming processing defects such as pits, spots, and holes on the surface, and changing the mechanical properties of the workpiece such as strength, hardness, wear resistance, etc., seriously reducing the precision of the processed surface, and greatly restricting titanium and its Production and application of titanium alloy.

In the prior art, for example, the application number CN201010544351.0 discloses an electric spark induced controllable explosion and erosion removal processing method for titanium or titanium alloy. This method is to intermittently inject a gas that can produce violent oxidation heat with titanium metal and form a detonation effect into the processing area during the conventional electric discharge machining of titanium or titanium alloys, so as to achieve a large amount of rapid erosion of titanium or titanium. The purpose of the alloy matrix material. However, this processing method uses a gas medium that is prone to oxidation reactions with titanium or titanium alloys, and titanium or titanium alloys are prone to explosion during processing, which poses a serious threat to the integrity of the shape and size of the workpiece. The publication number is CN 110605442 A, which proposes a controllable discharge ablation processing method for flammable and difficult-to-process materials with adjustable concentration of combustion-supporting gas. When processing titanium alloy materials, the phenomenon of explosion or excessive ablation can be avoided by adjusting the concentration of oxygen medium. happened. However, after the discharge machining is completed in this machining method, a very thick oxidized recast layer will remain on the surface of the workpiece, resulting in the formation of a machined surface with large surface roughness and microcracks on the processed part, requiring further post-processing procedures.

Contents of the invention

In order to solve the technical problem of low machining quality of the surface of the workpiece existing in the processing of titanium or titanium alloy materials using air, oxygen, nitrogen, etc. method. The method of the present invention has the advantages of high utilization rate of electric discharge machining energy, good machining stability, high machining efficiency, good machining shape accuracy and surface quality of workpieces for machining titanium or titanium alloys, and also inherits the advantages of conventional atomization EDM In the processing technology, the electrode loss is small, the recasting layer is thin, and it is friendly to the environment.

In order to solve the above technical problems, the present invention is realized through the following technical solutions:

A method for electric discharge machining of titanium or titanium alloy inert atomized medium, comprising the steps of:

(1) The inert gas medium and the liquid medium are passed into the atomizing device at the same time to form an inert atomizing medium, which is used as a discharge medium for EDM; the inert gas medium is not mixed with titanium or titanium alloy at high temperature Gases undergoing chemical reactions;

(2) Continuously passing the inert atomized medium into the EDM gap area to adjust the machining gap between the tool electrode and the titanium or titanium alloy workpiece;

(3) Connect the tool electrode to the negative pole of the pulse power supply, connect the titanium or titanium alloy workpiece to the positive pole of the pulse power supply to form a discharge circuit, and perform electric discharge machining on the excess material of the titanium or titanium alloy workpiece.

Further, the inert gas medium is one of argon and helium; the liquid medium is one of water, ethylene glycol, electric spark oil, and vegetable oil. It is not suitable to adopt the scheme of inert gas + kerosene, because sputtering will occur during the actual operation, and the protection requirements for operators are relatively high.

Further, the machining gap between the control tool electrode and the titanium or titanium alloy workpiece is greater than 0.01mm.

Further, the pressure of the inert gas medium is 0.08-5MPa; the flow rate of the liquid medium is 2-500mL/min.

Further, the material of the titanium or titanium alloy workpiece is one of pure titanium, α-type titanium alloy, α+β-type titanium alloy, and β-type titanium alloy.

Further, the inert atomizing medium mentioned in step 2 is continuously injected through the hollow tool electrode or by side spraying of the atomizing device, so as to provide a discharge medium for continuous electric discharge machining. Among them, the shape of the hollow tool electrode can be cylindrical, trimmed, spiral, polygonal rotating hollow electrode or other non-rotating hollow forming electrodes. The outer diameter of the cylindrical hollow electrode ranges from 1mm to 100mm and the inner diameter ranges from 0.3mm to 80mm.

Further, the EDM described in step 3 is copy machining, or milling on the surface of the workpiece layer by layer to obtain the required size and shape of the workpiece, and select immersion EDM or non-immersion EDM according to needs. For processing, the working fluid of submerged electric discharge machining can be water-based or oil-based according to the needs, and the immersion depth is ≥15mm. During EDM, the tool electrode can rotate to improve the degree of deionization and EDM efficiency; during EDM, the tool electrode can be lifted or shaken to improve the discharge state between EDM electrodes , thereby improving the efficiency of electrical discharge machining.

Furthermore, the process parameters of the electric discharge machining are: the rotation speed of the tool electrode is 50-5000rpm, the current is 400mA-120A, the pulse width is 10μs-5ms, the pulse gap is 10μs-2ms, and the open circuit voltage is 15- 450V.

Beneficial technical effects:

1. The inert atomization medium EDM method can further improve the EDM state and improve the EDM stability on the basis of inheriting the characteristics of the conventional atomization EDM method, such as increasing the EDM gap and stabilizing the EDM process;

2. The EDM method of inert atomizing medium can avoid impurities such as nitrogen oxides of titanium with high melting point and high resistance value generated on the processed surface of titanium and titanium alloys, and at the same time improve the utilization rate of electric energy in the process of EDM;

3. The inert atomization medium EDM method uses an inert gas that does not chemically react with titanium and titanium alloys, and can obtain better surface quality and a thinner recast layer than the conventional atomization EDM method ;

4. The use of an inert atomization medium composed of an inert gas medium and a liquid medium can reduce the breakdown voltage between the two poles, and the same discharge Under the conditions, the number of discharge breakdowns between the two poles can be increased, that is, the effective pulse discharge probability between the two poles can be increased, thereby improving the EDM efficiency of titanium and titanium alloys;

5. Only gaseous and liquid media that do not react with titanium and titanium alloys are used during processing, which will not produce harmful gases that are harmful to the human body and the environment, and do not require harmless treatment of the working fluid, which is in line with the trend of green manufacturing.

Description of drawings

Fig. 1 is a comparison chart of the material removal rate data of the electric discharge machining of the embodiment 1 and the comparative example 1.

Fig. 2 is the workpiece surface element composition figure after the electric discharge machining of embodiment 1 and comparative example 1, wherein (a) figure is the air+water atomization medium of comparative example 1, (b) figure is the argon gas+water of implementation 1 Atomization medium.

Fig. 3 is the comparison diagram of the workpiece surface topography after the electric discharge machining of embodiment 1 and comparative example 1, wherein (a) figure is the air+water atomization medium of comparative example 1, (b) figure is the argon of embodiment 1 Air + water atomization medium.

Fig. 4 is the comparison diagram of the workpiece section recasting layer after the electric discharge machining of embodiment 1 and comparative example 1, wherein (a) figure is the air+water atomization medium of comparative example 1, (b) figure is the embodiment 1 Argon + water atomization medium.

detailed description

The following will clearly and completely describe the technical solutions in the embodiments of the present invention in combination with the embodiments of the present invention and the accompanying drawings. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of them. The following description of at least one exemplary embodiment is merely illustrative in nature and in no way taken as limiting the invention, its application or uses. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

The numerical values set forth in these examples do not limit the scope of the invention unless specifically stated otherwise. Techniques and methods known to those of ordinary skill in the related art may not be discussed in detail, but under appropriate circumstances, the techniques and methods should be regarded as a part of the specification. In all examples shown and discussed herein, any specific values should be construed as exemplary only, and not as limitations. Therefore, other examples of the exemplary embodiment may have different values.

The experimental methods without specific conditions indicated in the following examples are usually measured according to national standards; if there is no corresponding national standard, then the general international standards or the standard requirements proposed by relevant enterprises are followed. All parts are by weight and all percentages are by weight unless otherwise indicated.

Example 1

This embodiment is TC4 titanium alloy inert atomization medium EDM processing, including the following steps:

(1) Pass argon and tap water into the atomization device at the same time to atomize to form an inert atomization medium, which is used as the discharge medium for EDM; the pressure of argon is 0.3MPa, and the flow rate of water is 20mL/min; That is, the discharge medium in this embodiment is abbreviated as argon+tap water;

(2) The inert atomizing medium is continuously passed into the EDM gap area through the hollow tool electrode, and the tool electrode is controlled to be 2mm away from the machining gap of the TC4 titanium alloy workpiece (the size is 30mm×20mm×10mm) (the tool electrode lifts the knife height 2mm); the material of the hollow tool electrode is copper, the length is 5mm, the outer diameter is 5mm, and the inner diameter is 1.5mm;

(3) Connect the negative pole of the tool electrode to the pulse power supply, and connect the positive pole of the pulse power supply to the TC4 titanium alloy workpiece to form a discharge circuit, set parameters: average current 15A, voltage 250V, pulse width 500 μs, pulse gap 100 μs, for TC4 titanium alloy The workpiece undergoes electrical discharge machining to remove excess material and form it.

Comparative example 1

The EDM process of this comparative example is the same as that of Example 1, except that the discharge medium is a conventional atomizing medium: air+tap water.

The EDM material removal rate data of the above Example 1 and Comparative Example 1 are shown in Figure 1, as can be seen from Figure 1, the material removal efficiency of EDM using the argon+water inert atomization medium of the present invention is about 5.2 mm ³ /min; while the material removal efficiency of Comparative Example 1 is about 3.4mm ³ /min by using the conventional atomization medium of air+water for EDM. Compared with the electric discharge machining using the conventional atomizing medium, the material removal efficiency of the electric discharge machining using the inert atomizing medium in the present invention is increased by about 33.3%. This is because under the condition of high discharge temperature, the chemical activity of titanium and titanium alloy is very active, and it is very easy to chemically react with nitrogen and oxygen in the air, while the argon gas in the inert atomization medium is extremely inactive, and it is extremely It greatly reduces the chemical reaction of the workpiece material and improves the processing efficiency of titanium alloy.

Carry out element energy spectrum analysis to the workpiece surface after the electric discharge machining of embodiment 1 and comparative example 1, the result is as shown in Figure 2, it can be seen that the surface after comparative example 1 adopts the conventional atomization medium of air+water to contain 15.55% relatively A large amount of oxygen element and 4.83% a small amount of nitrogen element, this is due to the high temperature generated in the EDM process, which makes the oxygen, nitrogen and Ti in the atomization medium air react chemically, and Ti oxides and nitrides are formed on the surface , nitrogen oxides and other impurities, so oxygen and nitrogen elements were detected; while the surface oxygen content of Example 1 after processing with the inert atomization medium of argon + water was 3.22%, and the oxygen element was relatively small and undetected Nitrogen, less oxygen may come from dissolved oxygen in water, and this very small amount of oxygen will not have a substantial impact on the surface quality after processing.

The surface and cross-sectional recast layer morphology of the workpiece after EDM in Example 1 and Comparative Example 1 are shown in Figure 3 and Figure 4 respectively. It can be seen from Fig. 3 and Fig. 4 that a relatively smooth and uniform surface can be obtained by using the EDM of the inert atomized medium of the present invention, and the recast layer of the workpiece is extremely thin and evenly distributed and continuous without microcracks. In comparison example 1, the surface of the workpiece processed by conventional atomization EDM can be observed to have a large amount of residual impurity substances after EDM, the recast layer of the workpiece is relatively thick and unevenly distributed, and the surface quality of the workpiece after processing is poor. Larger, low machining accuracy, and contains microcracks.

The invention uses an inert atomization medium for electric discharge machining of titanium or titanium alloys, which has the advantages of high utilization rate of electric discharge machining energy, good machining stability, high machining efficiency, good workpiece machining shape accuracy and high surface quality, and tool electrodes. The relative electrode loss rate is extremely low, and the recast layer obtained is thin and uniform. The atomized medium electric discharge machining of the present invention is environmentally friendly and is a typical green manufacturing and processing method.

The above examples only show the case of argon and water as the inert atomization medium, but in reality helium and argon have the same properties, and because the price of helium is higher than that of argon, argon is preferred in consideration of cost . The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto, any person familiar with the technical field within the technical scope disclosed in the present invention, according to the technical solution of the present invention Any equivalent replacement or change of the inventive concepts thereof shall fall within the protection scope of the present invention.

Claims (8)

1. The electric spark machining method for the titanium or titanium alloy inert atomizing medium is characterized by comprising the following steps of:

(1) Simultaneously introducing an inert gas medium and a liquid medium into an atomizing device to form an inert atomizing medium; the inert gas medium is a gas that does not chemically react with titanium or titanium alloy;

(2) Continuously introducing the inert atomizing medium into an electric spark discharge machining gap area, and adjusting a machining gap between a tool electrode and a titanium or titanium alloy workpiece;

(3) And communicating the tool electrode with the cathode of a pulse power supply, communicating the titanium or titanium alloy workpiece with the anode of the pulse power supply to form a discharge loop, and performing electric spark machining on redundant materials of the titanium or titanium alloy workpiece.

2. The inert titanium or titanium alloy atomizing medium spark machining method as claimed in claim 1, wherein said inert gas medium is one of argon gas and helium gas; the liquid medium is one of water, glycol, electric spark oil and vegetable oil.

3. The inert atomizing medium electric discharge machining method for titanium or titanium alloy according to claim 1 or 2, characterized in that the machining gap between the tool electrode and the titanium or titanium alloy workpiece is controlled to be more than 0.01mm.

4. The process for the electro-discharge machining of an inert atomising medium for titanium or titanium alloys according to claim 1 or 2, characterised in that the pressure of said inert gaseous medium is comprised between 0.08 and 5MPa; the flow rate of the liquid medium is 2-500mL/min.

5. The inert atomizing medium electric spark machining method for titanium or titanium alloy as set forth in claim 1 or 2, wherein the workpiece of titanium or titanium alloy is made of one of pure titanium, α -type titanium alloy, α + β -type titanium alloy and β -type titanium alloy.

6. The process for the spark erosion of an inert atomizing medium of titanium or titanium alloy as set forth in claim 1 or 2, wherein the inert atomizing medium is continuously introduced in step 2 by means of a hollow tool electrode or by side-spraying with an atomizing device.

7. The inert atomizing medium electric spark machining method for titanium or titanium alloy according to claim 1 or 2, characterized in that the electric spark machining in step 3 is copy type machining or milling machining layer by layer on the surface of the workpiece, and immersion type electric discharge machining or non-immersion type electric discharge machining is selected according to requirements to obtain the required size and shape of the workpiece.

8. The method for the electric spark machining of the titanium or titanium alloy inert atomizing medium as claimed in claim 1 or 2, wherein the technological parameters of the electric spark machining are as follows: the rotation speed of the tool electrode is 50-5000rpm, the current is 400mA-120A, the pulse width is 10 mus-5 ms, the pulse gap is 10 mus-2 ms, and the open-circuit voltage is 15-450V.

Images