阅读说明：本技术 一种真空自耗电弧熔炼熔滴短路控制方法 (Short circuit control method for molten drops in vacuum consumable arc melting ) 是由 李鹏 王文斌 王海龙 王小军 刘凯 张石松 李刚 师晓云 屈晓鹏 于 2021-06-15 设计创作，主要内容包括：本发明公开了一种真空自耗电弧熔炼熔滴短路控制方法,S1混料：按质量配比称取铜粉和铬粉混合；S2压制：将混合粉末压制出合金棒料；S3烧结：将合金棒料放入真空烧结炉中烧结；S4电弧熔炼：将合金棒料放入真空自耗炉中,合金棒料上端接电极杆,下端延伸至水冷铜模底部,施加电压进行熔炼,熔炼电流为2-4KA,熔滴滴数为0.1-0.7d/S,水冷铜模外侧缠绕有线圈,线圈会在熔炼过程中产生一个沿真空自耗炉轴向向上的纵向稳弧磁场,本发明通过短路控制的高温电弧使自耗电极快速均匀的发生层状消熔并滴到水冷结晶器底部,通过控制熔滴数来控制熔炼速度,并配合快速冷却实现铜铬合金铸锭凝固,得到均匀细小的铜铬合金,无气孔、富集等宏观微观缺陷。(The invention discloses a short-circuit control method for a molten drop in vacuum consumable arc melting, which comprises the following steps of S1: weighing copper powder and chromium powder according to the mass ratio and mixing; s2 pressing: pressing the mixed powder into an alloy bar; s3 sintering: placing the alloy bar stock into a vacuum sintering furnace for sintering; s4 arc melting: the alloy bar is put into a vacuum consumable electrode furnace, the upper end of the alloy bar is connected with an electrode rod, the lower end of the alloy bar extends to the bottom of a water-cooling copper mould, voltage is applied to carry out smelting, the smelting current is 2-4KA, the number of molten drops is 0.1-0.7d/S, a coil is wound on the outer side of the water-cooling copper mould, and the coil can generate a longitudinal stable arc magnetic field which is upward along the axial direction of the vacuum consumable electrode furnace in the smelting process.)

1. A short circuit control method for a molten drop in vacuum consumable arc melting is characterized by comprising the following steps:

s1, mixing materials: weighing a certain amount of copper powder and chromium powder, wherein the mass percentages of the copper powder and the chromium powder are Cu: 60-75 wt% of Cr: 25-40 wt% of the raw materials are put into a mixer to be mixed for 4.5-8.5 h;

s2, pressing: putting the mixed powder into a cold isostatic press, pressing the mixed powder at the pressure of 150-300Mpa, and keeping the pressure for 1-10min to prepare an alloy bar (3) with the length of 800mm and the outer diameter of 60-80 mm;

s3, sintering: placing the pressed alloy bar (3) into a vacuum sintering furnace, and sintering at the temperature of 700-1020 ℃ for 10-35 h;

s4, arc melting: placing sintered alloy bars (3) into a vacuum consumable electrode furnace (1), connecting the upper end of the alloy bars (3) with an electrode rod (2), extending the lower end of the alloy bars (3) to the bottom of a water-cooling copper mold (4) arranged in the vacuum consumable electrode furnace (1), closing a furnace door, vacuumizing the vacuum consumable electrode furnace (1) by using a vacuum pump (12) positioned on one side of the vacuum consumable electrode furnace (1), then filling inert protective gas, applying voltage to the bottom of the vacuum consumable electrode furnace (1) for smelting, wherein the arcing current is 2KA, switching to a molten drop control mode for smelting after 3min, wherein the smelting current in the molten drop control mode is 2-4KA and the number of molten drops is 0.1-0.7d/S, a coil (5) is wound on the outer side of the water-cooling copper mold (4), and the coil (5) can generate a longitudinal arc magnetic field which is upward along the axial direction of the vacuum consumable electrode furnace (1) in the smelting process, the arc stabilizing magnetic field intensity is 200-800 Gs.

2. The vacuum consumable arc melting droplet short-circuit control method as claimed in claim 1, wherein during mixing in the step S1, half weight of copper powder and chromium powder are respectively and simultaneously added and mixed for 2-6h, and then the rest of copper powder and chromium powder are simultaneously added and mixed for 2.5h until being uniformly mixed.

3. The vacuum consumable arc melting droplet short-circuit control method of claim 1, wherein in the step S4, the inert shielding gas is argon or nitrogen with a purity of 99.9% and the pressure of the inert shielding gas is 90mbar to 200 mbar.

4. The vacuum consumable arc melting droplet short circuit control method of claim 1, wherein the coil (5) in the step S4 of arc melting has 80-120 turns.

5. The short-circuit control method for the molten drops in the vacuum consumable arc melting according to the claim 1, characterized in that an opening (11) is formed in the top of the vacuum consumable arc melting furnace (1) in the step S4, the electrode rod (2) penetrates through the opening (11) and then is connected with the output end of the servo motor (61), the servo motor (61) is controlled by a PLC (6), and the melting current, the number of the molten drops and the arc stabilizing magnetic field in the arc melting process are controlled by the PLC (6).

6. The vacuum consumable arc melting droplet short-circuit control method according to claim 1, characterized in that a rotatable water tank (7) is arranged at the bottom of the vacuum consumable arc melting furnace (1), a fixed disk (8) capable of rotating relative to the water tank (7) is arranged at the bottom of the water tank (7), a liquid nitrogen cooling pipe (9) is sleeved outside the water-cooled copper mold (4), the liquid nitrogen cooling pipe (9) comprises two groups of arc-shaped pipes (91) which are arranged symmetrically to the water-cooled copper mold (4), a connecting pipe (92) for connecting the arc-shaped pipes (91) and a round pipe (93) for communicating the two groups of arc-shaped pipes (91), the round pipe (93) is positioned at the upper part of the water-cooled copper mold (4), an input pipe (94) and an output pipe (95) of the liquid nitrogen cooling pipe (9) are both connected with the fixed disk (8), the input pipe (94) and the output pipe (95) are respectively connected with the two groups of arc-shaped pipes (91), the sections of the arc-shaped pipe (91), the connecting pipe (92) and the round pipe (93) are all semicircular and are all connected with the water-cooling copper mould (4) in a welding way.

7. The vacuum consumable arc melting droplet short-circuit control method according to claim 1, wherein the arc-shaped pipe (91), the connecting pipe (92) and the circular pipe (93) are made of copper, ceramic and a copper plating layer sequentially from inside to outside, wherein the thickness of the innermost layer of copper accounts for 38-45% of the thickness of the whole pipe wall, the thickness of the middle layer of ceramic accounts for 48-55% of the thickness of the whole pipe wall, and the balance is the copper plating layer.

8. The short-circuit control method for the consumable electrode arc melting droplets in the vacuum manner as claimed in claim 1, wherein the coil (5) is wound between two groups of arc-shaped tubes (91), and the coil (5) is arranged perpendicular to the connecting tube (92).

9. The short-circuit control method for the consumable electrode arc melting droplets in the vacuum manner as claimed in claim 1, wherein the fixed disk (8) is rotatably connected with a limit ring groove (71) at the bottom of the water tank (7) through a limit block (81) convexly arranged on the side wall of the fixed disk, a water inlet (82) is arranged on the fixed disk (8) at two sides of the input pipe (94) and the output pipe (95), and a water outlet (72) is arranged at two sides of the upper part of the water tank (7).

Technical Field

The invention relates to the technical field of manufacturing products by metal powder, in particular to a short-circuit control method for a molten drop in vacuum consumable arc melting.

Background

The microstructure of the copper-chromium alloy material has obvious influence on the electrical property of the contact material, the chromium particles uniformly distributed on the copper matrix are beneficial to improving the service performances of the contact material such as breaking, pressure resistance, fusion welding resistance and the like, the high-temperature electric arc in the consumable process is beneficial to reducing the gas and impurity content in the material, and the comprehensive electrical property of the vacuum arc extinguish chamber is obviously improved.

Among several commercial products for preparing the copper-chromium contact material, the copper-chromium contact material prepared by the vacuum consumable arc melting process has the characteristic that chromium is uniformly distributed in copper, and high-temperature electric arc can improve and purify a copper-chromium alloy material, so that the electrical property of an arc extinguish chamber is remarkably improved, and the copper-chromium series contact material prepared by the vacuum consumable arc melting process is the contact material with the best comprehensive electrical property.

However, when the vacuum consumable arc melting process is used for preparing copper-chromium series materials, the melting process is usually controlled by adopting an arc voltage control mode in the consumable electrode bar melting process, that is: the gap between the electrode rod and the molten pool is controlled by controlling the voltage in the smelting process, but when the density difference of the electrode rod is large or the size of the electrode rod is not uniform and the quality of raw materials has large difference, large voltage fluctuation exists in the smelting process, so that the temperature of the molten pool is changed, and the phenomena of air holes, enrichment and the like easily occur in an ingot.

Disclosure of Invention

Aiming at the existing problems, the invention provides a short-circuit control method for a molten drop in vacuum consumable arc melting.

The technical scheme of the invention is as follows:

a short circuit control method for a molten drop in vacuum consumable arc melting comprises the following steps:

s1, mixing materials: weighing a certain amount of copper powder and chromium powder, wherein the mass percentages of the copper powder and the chromium powder are Cu: 60-75 wt% of Cr: 25-40 wt% of the raw materials are put into a mixer to be mixed for 4.5-8.5 h;

s2, pressing: placing the mixed powder into a cold isostatic press to be pressed under the pressure of 150-300Mpa, and keeping the pressure for 1-10min to prepare an alloy bar with the length of 800mm and the outer diameter of 60-80 mm;

s3, sintering: placing the pressed alloy bar into a vacuum sintering furnace, and sintering at the temperature of 700-1020 ℃ for 10-35 h;

s4, arc melting: placing the sintered alloy bar into a vacuum consumable electrode furnace, connecting an electrode rod to the upper end of the alloy bar, extending the lower end of the alloy bar to the bottom of a water-cooled copper mold arranged in the vacuum consumable electrode furnace, closing a furnace door, vacuumizing the vacuum consumable electrode furnace by using a vacuum pump positioned on one side of the vacuum consumable electrode furnace, then filling inert protective gas, applying voltage to the bottom of the vacuum consumable electrode furnace for smelting, wherein the arc starting current is 2KA, and after 3min of smelting, switching to a molten drop control mode for smelting, wherein the smelting current in the molten drop control mode is 2-4KA, the number of molten drops is 0.1-0.7d/S, winding a coil is wound on the outer side of the water-cooled copper mold, and the coil can generate a longitudinal stable arc magnetic field which is upward along the axial direction of the vacuum consumable electrode furnace in the smelting process, and the stable arc magnetic field strength is 800 Gs.

Further, during mixing, in the step S1, half weight of copper powder and chromium powder are respectively and simultaneously added and mixed for 2-6 hours, then the rest copper powder and chromium powder are simultaneously added and mixed for 2.5 hours till being uniformly mixed, so that the powder is more fully and uniformly mixed.

Further, in the step S4, the inert shielding gas in the arc melting is argon or nitrogen with a purity of 99.9%, the pressure of the inert shielding gas is 90mbar to 200mbar, and the inert gas is used for isolating air and is inactive in chemical property, so that no additional reaction is generated.

Further, in the step S4, the number of the coils in the arc melting is 80-120.

Further, an opening is formed in the top of the vacuum consumable electrode furnace in the arc melting in the step S4, the electrode rod penetrates through the opening and then is connected with the output end of the servo motor, the servo motor is controlled by the PLC, and the melting current, the droplet number and the arc stabilizing magnetic field in the arc melting process are controlled by the PLC.

Further, vacuum consumable stove bottom is equipped with rotatable water tank, the water tank bottom is equipped with can with the relative pivoted fixed disk of water tank, water-cooling copper mould overcoat is equipped with the liquid nitrogen cooling tube, the liquid nitrogen cooling tube include two sets of symmetry in a plurality of arcs that water-cooling copper mould set up, be used for connecting the connecting pipe of arc and the pipe that is used for communicateing two sets of arcs, the pipe is located water-cooling copper mould upper portion, the input tube and the output tube of liquid nitrogen cooling tube all with the fixed disk is connected, input tube and output tube are connected with two sets of arcs respectively, and the cross-section of arc, connecting pipe and pipe is semi-circular and all with water-cooling copper mould welded connection, can improve the cooling effect to the water-cooling copper mould through the liquid nitrogen cooling tube.

Furthermore, the materials of the arc-shaped pipe, the connecting pipe and the circular pipe are copper, ceramic and a copper plating layer from inside to outside in sequence, wherein the thickness of the innermost layer of copper accounts for 38-45% of the thickness of the whole pipe wall, the thickness of the middle layer of ceramic accounts for 48-55% of the thickness of the whole pipe wall, the balance is the copper plating layer, the copper passing through the inner layer can be welded and sealed firmly with the water-cooling copper die, and the ceramic layer arranged at the same time can play a good heat preservation effect, reduce the consumption of liquid nitrogen and also play a certain protection role on the coil.

Furthermore, the coil is wound between the two groups of arc-shaped tubes and is perpendicular to the connecting tube, so that the power of the arc stabilizing magnetic field generated by the coil can be maximized.

Furthermore, the fixed disk is rotatably connected with a limit ring groove at the bottom of the water tank through a limit block which is convexly arranged on the side wall of the fixed disk, so that the fixed disk cannot rotate along with the water tank in the rotating process.

Furthermore, water inlets are formed in the fixed disks on two sides of the input pipe and the output pipe, water outlets are formed in two sides of the upper portion of the water tank, and water cooling circulation is established.

The invention has the beneficial effects that:

(1) the consumable electrode quickly and uniformly generates layered melting elimination under the action of high-temperature electric arc controlled by a short circuit and drops to the bottom of the water-cooled crystallizer, the whole melting process is controlled by the PLC, the melting speed is controlled mainly by controlling the number of molten drops, and the solidification of the copper-chromium alloy cast ingot is realized by matching with the peripheral quick cooling rate, so that a uniform and fine copper-chromium alloy structure is obtained, the copper-chromium alloy structure can be used as an electrical contact material, the material has no macroscopic microscopic defects such as air holes, looseness, impurities, copper, chromium enrichment and the like, and the copper-chromium microstructure structure is less than 30 mu m.

(2) The invention adopts the mode of winding the coil at the outer side to generate a longitudinal arc stabilizing magnetic field which is upward along the axial direction of the vacuum consumable electrode furnace in the smelting process, stirs a molten metal pool in the smelting process, so that molten metal is fully mixed, and meanwhile, the existence of the longitudinal magnetic field can compress electric arcs to a certain degree, thereby preventing safety accidents caused by electric arc discharge between the electric arcs and the crucible.

(3) According to the invention, the cooling mode that the liquid nitrogen cooling pipe is introduced into the liquid nitrogen is adopted, so that the water-cooled copper mold can be efficiently and quickly cooled, the quick solidification of the copper-chromium alloy cast ingot is facilitated, the obtained alloy does not have the phenomena of air holes, enrichment and the like, and meanwhile, the material of the liquid nitrogen cooling pipe can also play a certain role in protecting the coil and the water-cooled copper mold.

Drawings

FIG. 1 is a metallographic graph of a CuCr 40% product under molten droplet short-circuit control in example 1 of the present invention;

FIG. 2 is a gold phase diagram of a CuCr 35% product under molten droplet short circuit control in example 2 of the present invention;

FIG. 3 is a graph showing a phenomenon of tissue enrichment caused by fluctuation of arc melting voltage in a comparative example of the present invention;

FIG. 4 is a schematic view of the internal structure of the vacuum consumable electrode furnace of the present invention;

FIG. 5 is a schematic view of a liquid nitrogen cooling tube configuration of the present invention;

fig. 6 is a schematic view showing the inner material composition of the arc tube, the connecting tube and the circular tube according to the present invention.

The device comprises a vacuum consumable furnace 1, an opening 11, a vacuum pump 12, an electrode rod 2, an alloy bar 3, a water-cooled copper mold 4, a coil 5, a PLC controller 6, a servo motor 61, a water tank 7, a limiting ring groove 71, a water outlet 72, a fixing disc 8, a limiting block 81, a water inlet 82, a liquid nitrogen cooling pipe 9, an arc pipe 91, a connecting pipe 92, a circular pipe 93, an input pipe 94 and an output pipe 95.

Detailed Description

Example 1

A short circuit control method for a molten drop in vacuum consumable arc melting comprises the following steps:

s1, mixing materials: weighing a certain amount of copper powder and chromium powder, wherein the mass percentages of the copper powder and the chromium powder are Cu: 60 wt% of Cr: 40 wt% of the copper powder and the chromium powder are put into a mixer to be mixed for 4.5h, half of the weight of the copper powder and the chromium powder are respectively and simultaneously added to be mixed for 2h, then the rest copper powder and the rest chromium powder are simultaneously added to be mixed for 2.5h until the mixture is uniformly mixed;

s2, pressing: putting the mixed powder into a cold isostatic press, pressing the mixed powder at the pressure of 300Mpa for 10min, and preparing an alloy bar 3 with the length of 800mm and the outer diameter of 80 mm; the chromium content is higher, so that the pressure during pressing is higher and the pressure maintaining time is longer;

s3, sintering: placing the pressed alloy bar 3 into a vacuum sintering furnace, and sintering for 35 hours at 1020 ℃; higher sintering temperatures are required due to the higher chromium content;

s4, arc melting: placing sintered alloy bar 3 into a vacuum consumable electrode furnace 1, connecting the upper end of the alloy bar 3 with an electrode rod 2, extending the lower end of the alloy bar 3 to the bottom of a water-cooled copper mold 4 arranged in the vacuum consumable electrode furnace 1, closing a furnace door, vacuumizing the vacuum consumable electrode furnace 1 by using a vacuum pump 12 positioned at one side of the vacuum consumable electrode furnace 1, then filling inert protective gas, wherein the inert protective gas is argon with the purity of 99.9%, the pressure of the inert protective gas is 200mbar, applying voltage to the bottom of the vacuum consumable electrode furnace 1 for smelting, the arcing current is 2KA, switching to a molten drop control mode by a PLC (programmable logic controller) 6 for smelting after 3min, the smelting current in the molten drop control mode is 2KA, the number of molten drops is 0.1d/S, winding a coil 5 on the outer side of the water-cooled copper mold 4, the coil 5 being 80 turns, and generating a longitudinal arc magnetic field which is upward along the axial direction of the vacuum consumable electrode furnace 1 in the smelting process, the arc stabilizing magnetic field intensity is 200Gs, an opening 11 is formed in the top of the vacuum consumable electrode furnace 1, the electrode rod 2 penetrates through the opening 11 and then is connected with the output end of the servo motor 61, the servo motor 61 is a commercially available AKM2G servo motor, the servo motor 61 is controlled by the PLC 6, and the smelting current, the number of molten drop drops and the arc stabilizing magnetic field in the arc smelting process are controlled by the PLC 6. The PLC controller is a BT-GLKZ-2X PLC intelligent boiler controller system for metallurgy sold in the market. When the PLC 6 controls the servo motor 61 to send the electrode rod 2 and the alloy bar 3 to the designated position, the opening 11 is sealed to prevent the inert gas from leaking.

Example 2

This example is substantially the same as example 1, except that the raw material ratio is different, and thus the pressing parameters and sintering parameters are different.

S1, mixing materials: weighing a certain amount of copper powder and chromium powder, wherein the mass percentages of the copper powder and the chromium powder are Cu: cr 65 wt%: 35 wt% of the copper powder and the chromium powder are put into a mixer to be mixed for 6.5 hours, half of the weight of the copper powder and the chromium powder are respectively and simultaneously added to be mixed for 4 hours, then the rest copper powder and the rest chromium powder are simultaneously added to be mixed for 2.5 hours until the mixture is uniformly mixed;

s2, pressing: putting the mixed powder into a cold isostatic press, pressing the mixed powder at the pressure of 200Mpa for 5min, and preparing an alloy bar 3 with the length of 800mm and the outer diameter of 70 mm; the pressing pressure and the dwell time were appropriately reduced due to the reduced chromium content compared to example 1;

s3, sintering: placing the pressed alloy bar 3 into a vacuum sintering furnace, and sintering at 900 ℃ for 20 h; the sintering temperature was appropriately lowered because the chromium content was reduced as compared with that of example 1.

Example 3

This example is substantially the same as example 1, except that the raw material ratio is different, and thus the pressing parameters and sintering parameters are different.

S1, mixing materials: weighing a certain amount of copper powder and chromium powder, wherein the mass percentages of the copper powder and the chromium powder are Cu: 75 wt% of Cr: 25 wt% of copper powder and chromium powder are put into a mixer to be mixed for 8.5h, half of the weight of the copper powder and the chromium powder are respectively and simultaneously added to be mixed for 6h, then the rest copper powder and the rest chromium powder are simultaneously added to be mixed for 2.5h until the mixture is uniformly mixed;

s2, pressing: putting the mixed powder into a cold isostatic press, pressing the mixed powder at the pressure of 150Mpa for 1min, and preparing an alloy bar 3 with the length of 800mm and the outer diameter of 60 mm; the copper content is higher, so that the pressure during pressing is lower and the pressure maintaining time is shorter;

s3, sintering: putting the pressed alloy bar 3 into a vacuum sintering furnace, and sintering at 700 ℃ for 10 h; the sintering temperature does not require a higher temperature due to the lower chromium content.

Example 4

This example is substantially the same as example 1 except that the melting parameters in the arc melting in step S4 are different.

S4, arc melting: placing sintered alloy bar 3 into a vacuum consumable electrode furnace 1, connecting the upper end of the alloy bar 3 with an electrode rod 2, extending the lower end of the alloy bar 3 to the bottom of a water-cooled copper mold 4 arranged in the vacuum consumable electrode furnace 1, closing a furnace door, vacuumizing the vacuum consumable electrode furnace 1 by using a vacuum pump 12 positioned at one side of the vacuum consumable electrode furnace 1, then filling inert protective gas, wherein the inert protective gas is argon with the purity of 99.9%, the pressure of the inert protective gas is 120mbar, applying voltage to the bottom of the vacuum consumable electrode furnace 1 for smelting, the arcing current is 2KA, switching to a molten drop control mode by a PLC (programmable logic controller) 6 for smelting after 3min, the smelting current in the molten drop control mode is 3KA, the number of molten drops is 0.4d/S, winding a coil 5 on the outer side of the water-cooled copper mold 4, the coil 5 being 100 turns, and generating a longitudinal arc magnetic field which is upward along the axial direction of the vacuum consumable electrode furnace 1 in the smelting process, the arc-stabilizing magnetic field intensity is 500 Gs.

Example 5

This example is substantially the same as example 1 except that the melting parameters in the arc melting in step S4 are different.

S4, arc melting: placing sintered alloy bar 3 into a vacuum consumable electrode furnace 1, connecting the upper end of the alloy bar 3 with an electrode rod 2, extending the lower end of the alloy bar 3 to the bottom of a water-cooled copper mold 4 arranged in the vacuum consumable electrode furnace 1, closing a furnace door, vacuumizing the vacuum consumable electrode furnace 1 by using a vacuum pump 12 positioned on one side of the vacuum consumable electrode furnace 1, then filling inert protective gas, wherein the inert protective gas is nitrogen with the purity of 99.9%, the pressure of the inert protective gas is 90mbar, applying voltage to the bottom of the vacuum consumable electrode furnace 1 for smelting, the arcing current is 2KA, switching to a molten drop control mode by a PLC (programmable logic controller) 6 for smelting after 3min, the smelting current in the molten drop control mode is 4KA, the number of molten drops is 0.7d/S, winding a coil 5 on the outer side of the water-cooled copper mold 4, the coil 5 is 120 turns, and the coil 5 can generate a longitudinal arc magnetic field which is upward along the axial direction of the vacuum consumable electrode furnace 1 in the smelting process, the arc-stabilizing magnetic field intensity is 800 Gs.

Example 6

In this embodiment, a vacuum consumable electrode furnace 1 is improved based on embodiment 1, and a liquid nitrogen cooling pipe 9 is additionally arranged outside a water-cooled copper mold.

As shown in fig. 4-6, a rotatable water tank 7 is arranged at the bottom of a vacuum consumable electrode furnace 1, a fixed disk 8 capable of rotating relative to the water tank 7 is arranged at the bottom of the water tank 7, the fixed disk 8 is rotatably connected with a limit ring groove 71 at the bottom of the water tank 7 through a limit block 81 convexly arranged on the side wall of the fixed disk 8, a liquid nitrogen cooling pipe 9 is sleeved outside a water-cooled copper mold 4, the liquid nitrogen cooling pipe 9 comprises two groups of arc-shaped pipes 91 symmetrically arranged on the water-cooled copper mold 4, a connecting pipe 92 for connecting the arc-shaped pipes 91 and a round pipe 93 for communicating the two groups of arc-shaped pipes 91, the round pipe 93 is arranged at the upper part of the water-cooled copper mold 4, an input pipe 94 and an output pipe 95 of the liquid nitrogen cooling pipe 9 are both connected with the fixed disk 8, the input pipe 94 and the output pipe 95 are respectively connected with the two groups of arc-shaped pipes 91, the cross sections of the connecting pipe 92 and the round pipe 93 are all semicircular and are welded with the water-cooled copper mold 4, a coil 5 is wound between the two groups of arc-shaped pipes 91, the coil 5 is perpendicular to the connecting pipe 92, the materials of the arc-shaped pipe 91, the connecting pipe 92 and the circular pipe 93 are copper, ceramic and copper-plated layers from inside to outside in sequence, wherein the thickness of the innermost layer of copper accounts for 38% of the thickness of the whole pipe wall, the thickness of the middle layer of ceramic accounts for 55% of the thickness of the whole pipe wall, the balance is the copper-plated layer, the fixed disks 8 on two sides of the input pipe 94 and the output pipe 95 are provided with water inlets 82, and two sides of the upper portion of the water tank 7 are provided with water outlets 72.

The working principle of finishing the step S4 vacuum melting by applying the vacuum consumable electrode furnace is as follows:

s4, arc melting: placing sintered alloy bars 3 into a vacuum consumable electrode furnace 1, wherein the upper end of each alloy bar 3 is connected with an electrode rod 2, the lower end of each alloy bar 3 extends to the bottom of a water-cooled copper mold 4 arranged in the vacuum consumable electrode furnace 1, a PLC (programmable logic controller) 6 controls a servo motor 61 to convey the electrode rods 2 and the alloy bars 3 to a specified position, then opening 11 positions are formed, namely, the vacuum consumable electrode furnace 1 is sealed, after a furnace door is closed, a vacuum pump 12 located on one side of the vacuum consumable electrode furnace 1 is used for vacuumizing the vacuum consumable electrode furnace 1, then inert protective gas is filled, the inert protective gas is argon with the purity of 99.9%, the pressure of the inert protective gas is 200mbar, coils 5 are wound on the outer side of the water-cooled copper mold 4, the number of the coils 5 is 80, and the coils 5 are uniformly wound on the outer side of each group of connecting pipes 92;

applying voltage to the bottom of the vacuum consumable electrode furnace 1 for smelting, wherein the smelting current is 2KA, the droplet number is 0.1d/S, the coil 5 can generate a longitudinal arc stabilizing magnetic field which is upward along the axial direction of the vacuum consumable electrode furnace 1 in the smelting process, the arc stabilizing magnetic field intensity is 200Gs, water cooling and liquid nitrogen cooling are used for rapid condensation, the liquid nitrogen enters the liquid nitrogen cooling pipe 9 from the input pipe 94, the liquid nitrogen rises through the arc-shaped pipe 91 and the connecting pipe 92 to finish cooling the water-cooled copper mold 4 on one side, then the liquid nitrogen enters the liquid nitrogen cooling pipe 9 on the other side from the circular pipe 93 to finish cooling the water-cooled copper mold 4 on the other side, and finally the liquid nitrogen is discharged through the output pipe 95;

the cooling water is injected into the water tank 7 from the water inlet 82 on the fixed disk 8, the further cooling of the water-cooling copper mold 4 is completed, the cooled cooling water is discharged from the water outlet 72 of the water tank 7, the water tank 7 is rotated in the water-cooling process, the cooling effect is more sufficient, the water tank 7 is cylindrical, the top of the water tank 7 is connected with the vacuum consumable furnace 1 in a rotating and sealing manner, the limiting block 81 arranged on the fixed disk 8 rotates relative to the limiting ring groove 71 at the bottom of the water tank 7 in the rotating process, the fixed disk 8 cannot rotate along with the water tank 7 in the rotating process, the fixed disk 8 is always fixed, and the input pipe 94 and the water inlet 82 are continuously injected.

Example 7

This embodiment is substantially the same as embodiment 6 except that the material composition of the arc tube 91, the connection tube 92 and the circular tube 93 is different.

The thickness of the innermost layer copper accounts for 45% of the whole tube wall thickness, the thickness of the middle layer ceramic accounts for 48% of the whole tube wall thickness, and the balance is a copper plating layer.

Example 8

This embodiment is substantially the same as embodiment 6 except that the material composition of the arc tube 91, the connection tube 92 and the circular tube 93 is different.

The thickness of the innermost layer copper accounts for 40% of the whole tube wall thickness, the thickness of the middle layer ceramic accounts for 50% of the whole tube wall thickness, and the balance is a copper plating layer.

Comparative example

In comparison, the same materials as in example 1 were used in the comparative example, and the melting process was controlled by means of conventional arc pressure control, namely: the gap between the electrode rod and the molten pool is controlled by controlling the voltage of the smelting process.

Examples of the experiments

The strength tests were performed on the copper-chromium alloys prepared by the methods of examples 1 to 6 and comparative example, and the test results are as follows:

properties of the copper-chromium alloys prepared in examples 1 to 6

It can be seen that the hardness and the conductivity of the copper-chromium alloy prepared by the methods in examples 1 to 6 are far better than those of the copper-chromium alloy prepared in the comparative example, because the smelting process is controlled by the arc pressure control mode in the smelting method used in the comparative example, as shown in fig. 3, when the density difference of the electrode rod is large or the size of the electrode rod is not uniform, and the quality of the raw material has large difference, large voltage fluctuation exists in the smelting process, the temperature of a molten pool is changed, and the phenomena of air holes, enrichment and the like appear in the ingot.

The results of comparative examples 1 to 3 show that the prepared copper-chromium alloy has different properties due to different raw material ratios and different copper-chromium mass percentage contents, but examples 1 to 3 all maintain a higher quality level, and different copper-chromium mass ratios can be selected according to requirements in actual production;

as shown in FIG. 1, the CuCr 40% alloy prepared by the method of example 1 has a complete metallographic structure, no macroscopic microscopic defects such as pores, porosity, inclusions, Cu and Cr enrichment and the like, and the microstructure of Cu and Cr is less than 30 um.

As shown in FIG. 2, the CuCr 35% alloy prepared by the method of example 2 has the same complete metallographic structure, no macroscopic microscopic defects such as pores, porosity, inclusion, Cu and Cr enrichment and the like, and the microstructure of Cu and Cr is less than 30 um.

Comparing the results of examples 1, 4 and 5, it can be seen that changing the melting parameters in the arc melting in step S4 has a certain influence on the performance of the copper-chromium alloy, wherein the performance of the copper-chromium alloy obtained by changing the melting parameters in example 4 is optimal, the melting current is 3KA, the droplet number is 0.4d/S, and the number of turns of the coil 5 is 100 turns.

Comparing the results of examples 1 and 6, it can be seen that the hardness and conductivity of the copper-chromium alloy prepared by using the improved vacuum consumable electrode furnace 1 and the intensified cooling are improved, which indicates that the use of liquid nitrogen cooling in combination with water cooling is more beneficial to the condensation of cast ingots and the effect of gas removal is better.