Two, background technology:
The efficient numerically controlled plasma cutting machines of China's ship plate relies on import at present, and when this kind equipment of import, must buy simultaneously as annex as the crucial consumable accessory in the equipment " plasma cutting electrode ", and it costs an arm and a leg.And inlet electrode is to adopt copper sheathing seat, silver-colored body and the three coaxial mechanical hot pressings combinations of hafnium filament core, because the condition of work variations in temperature, heat sealing quality directly has influence on the service life of plasma cutting electrode.The article on plasma cutting electrode carries out the research and the test of vacuum brazing technique so we are commissioned.
Vacuum brazing technique is under vacuum heating conditions, utilize the fusing point of solder lower than matrix alloy, solder after dissolving is under the closely spaced capillarity attraction effect of welded piece, fill the parent metal gap and form strong bonded, because the vacuum brazing heating-up temperature is lower, physics, chemical property to parent metal do not have influence less, and some weld seams of complex parts once can be welded into, and obtain the attention and the utilization of industries such as Aeronautics and Astronautics, electronics.But, adopt conventional vacuum brazing method can't make effectively seam between copper sheathing seat in the plasma cutting electrode, silver-colored body and the hafnium filament core three.
Chinese patent 01253592.3 discloses the product constituent and the feature thereof of a kind of " plasma cutting electrode " by name, promptly this plasma cutting electrode internal water coolant jacket has adopted pure white silver to replace copper, and to adopt method for brazing to make its copper, silver, hafnium three seam be one, the compression fit outside the subrogate country.The specific implementation method of the plasma cutting electrode vacuum brazing technique that does not relate in this invention is realized by the present invention.
Three, summary of the invention:
The objective of the invention is to change inlet electrode adopts copper sheathing seat, silver-colored body and hafnium filament core three to cooperate with the axis body mechanical hot pressing, and adopt vacuum brazing to finish, make the effective seam of three assemblies, eliminate inner two bed boundary contact resistance and the gas resistances of plasma cutting electrode, improve the heat radiation and the electric conductivity of electrode.
The present invention is a kind of plasma cutting electrode vacuum brazing method of realizing like this, the structure of the oxygen-free copper block set of plasma cutting electrode, silver-colored body, the combination of hafnium filament core coaxial line is realized that vacuum brazing connects, its process is that sub-assembly assembling, solder are placed, assembly advances vacuum drying oven, vacuumize, heat up (1), insulation (1), heat up (2), insulation (2), inflated with nitrogen, cooling come out of the stove, it is characterized in that:
A) fit clearance between oxygen-free copper block set, silver-colored body, hafnium filament core is chosen at 0.02~0.05mm;
B) the soldering vacuum ranges is controlled at 1 * 10
-1~5 * 10
-2Pa;
C) the vacuum brazing temperature is chosen in 820 ℃~880 ℃.
The technical problem that vacuum brazing technique of the present invention will solve has:
1. the sub-assembly fit-up gap chooses;
2. determining of soldering vacuum ranges;
3. the selection of vacuum brazing temperature.
For solving above technical problem, the present invention takes corresponding technical scheme as follows:
1. plasma cutting electrode pedestal and silver circle, silver circle and hafnium filament combination fit-up gap size are to influence brazing layer compactness and weld strength key factor.The gap is too small, hinders solder and flows into, and is difficult for forming the suitable good joint of rate; Excesssive gap, capillarity weakens, and solder is inserted difficulty, and joint mechanical property is relatively poor relatively.Through repeatedly experiment, the present invention determines that desirable gap is 0.02~0.05mm, and for to guarantee to obtain this desirable gap, and according to the workpiece shape, special positioning fixture specially makes the clearance control of circumferential edge even.
2. plasma cutting electrode vacuum brazing process is finished in vacuum tank.Can learn that by test high vacuum can be aggravated the volatilization of metallic element, brazing member and equipment all are no advantage.Through the repetition test contrast, the present invention obtains desirable soldering vacuum for being controlled at 1 * 10
-1~5 * 10
-2Between the Pa.
3. vacuum brazing temperature is decided according to the fusing point that uses solder, and reasonably the vacuum brazing temperature can make the flowability of solder be in optimum state.By engineer testing, the result shows and selects for use 820 ℃~880 ℃ vacuum brazing temperature can obtain promising result.
Technological process of the present invention is: sub-assembly assembling → solder placement → assembly advances stove → vacuumize → heat up (1) → insulation (1) → heat up (2) → insulation (2) → inflated with nitrogen and cools off → come out of the stove.
Described solder adopts the ag-cu solder sheet at the solder of hafnium filament core and silver-colored body fit clearance and sealing hafnium filament in-core upper surface; Silver body and oxygen-free copper block set fit clearance solder adopt the ag-cu solder silk.
Compared with prior art, the plasma cutting electrode is after vacuum brazing, and surface quality is good, non-oxidation, and coloured light is bright, welding even compact, and steady quality, product percent of pass reaches more than 98%.Adopt 300 of PROCESS FOR TREATMENT plasma cutting electrodes of the present invention, operating mode is used and to be shown, homemade electrode is used to cut the ship plate single-piece life-span and reaches 500 meters, than exceed 200 meters of inlet electrode.At present, just entering the batch process stage.
Five, the specific embodiment:
Embodiment 1:
With reference to the accompanying drawings 1, will press the gap of 0.04mm earlier between oxygen-free copper block set and silver-colored body, silver-colored body and the hafnium filament core and assemble, and at gap location placement ag-cu solder silk and ag-cu solder sheet.Then, assembly is placed on the bin, pushes vacuum drying oven and carry out vacuum brazing.Described vacuum drying oven is commercially available conventional products.Vacuum drying oven is evacuated to 5 * 10
-2Pa, and vacuum drying oven is warming up to 600 ℃ (in block diagrams heat up (1)), be incubated 1 hour (being incubated (1) in the block diagram), and then be warming up to 840 ℃ (heat up in the block diagram (2)), and be incubated 10 minutes (insulation (2) in the block diagram), charge into nitrogen, come out of the stove after the cooling, obtain qualified products.
Embodiment 2:
Choose gap 0.03mm between oxygen-free copper block set and silver-colored body, silver-colored body and the hafnium filament core, vacuum drying oven is evacuated to 3 * 10
-2Pa is warming up to 600 ℃ earlier, is incubated 1 hour, and then is warming up to 830 ℃, is incubated 10 minutes, charges into nitrogen, comes out of the stove after the cooling, obtains qualified products.Other is as embodiment 1.