CN115922006A - Vacuum brazing method for throttle hydraulic valve assembly with filter screen of aircraft engine - Google Patents

Abstract

The invention relates to a vacuum brazing method for a throttling hydraulic valve component with a filter screen of an aero-engine, which designs a special welding device for a throttling hydraulic valve structure with filter screens on two sides, solves the problem of bidirectional welding by means of accurately controlling the using amount of brazing filler metal, heating temperature, vacuum pressure and the like, realizes the detection of a welding component through industrial electronic computed tomography (industrial CT for short), well controls the welding quality of the component, and enables the throttling hydraulic valve component with the filter screen of the aero-engine to meet the design requirements.

Description

Vacuum brazing method for throttle hydraulic valve assembly with filter screen of aircraft engine

Technical Field

The invention discloses a vacuum brazing method for a throttle hydraulic valve component with a filter screen of an aircraft engine, and belongs to the technical field of heat treatment of vacuum brazed components.

Background

According to the construction planning arrangement, measures for adding the filter screen to the throttling hydraulic valve are made. On the premise that the size and the functional performance of the throttling hydraulic valve used in the current state of batch production are not changed, the structure of the part of the product is optimized and improved, and the throttling hydraulic valve with the filter screen is designed, as shown in figure 1. Under the unchangeable condition of valve body hole diameter, increase the filter screen around the valve body, further filter the pollutant to solve the diameter and pass through the choke valve and get into pump regulator pressure boost valve position, cause the not enough problem of fuel feeding more than 0.3 mm's particulate matter. At the initial stage of process planning, an electron beam welding assembly is adopted, but the situation that a small filter screen is melted occurs in the test process, because the small filter screen and the throttling hydraulic valve are made of the same material (1 Cr18Ni 9), but the wall thickness difference of the welding position is too large, when an electron beam emitted with minimum power irradiates the contact surface of the filter screen and the throttling hydraulic valve, the filter screen with the wall thickness of only 0.2mm reaches the melting temperature firstly, the edge of the filter screen is melted into liquid beads, the throttling hydraulic valve is not melted at the moment, an effective molten pool cannot be formed between the filter screen and the throttling hydraulic valve, and therefore electron beam welding cannot be adopted.

Disclosure of Invention

The invention provides a vacuum brazing method for a throttle hydraulic valve component with a filter screen of an aero-engine, which is designed and provided aiming at the prior art, so that the throttle hydraulic valve component with the filter screen of the aero-engine meets the design requirement.

In order to achieve the purpose, the technical scheme of the invention is changed into vacuum brazing welding, and the design idea is to form a compact welding seam and a firm joint by means of melting, flowing and solidifying of brazing filler metal. Therefore, the throttling hydraulic valve component with the filter screen does not adopt the traditional pre-embedded closed welding, but adopts the completely open welding, namely the welding flux is exposed outside, but the difficulty of controlling the volatilization of elements in the welding flux is increased because the welding flux is sensitive to the environmental factors in the furnace; meanwhile, because the two filter screens are respectively placed at the two ends of the valve body and belong to bidirectional welding, the structure causes that the welding of the filter screen at one end belongs to antigravity brazing, is not beneficial to brazing filler metal wetting, and easily causes incomplete filling of the brazing filler metal in a welding seam. In order to overcome the technical difficulties, the technical scheme of the invention adopts the following technical scheme:

in the vacuum brazing method for the throttling hydraulic valve component with the filter screen of the aero-engine, the throttling hydraulic valve component with the filter screen of the aero-engine comprises a valve body 7 and the filter screens 8 at the front end and the rear end of the valve body 7, wherein the wall thickness of each filter screen 8 is 0.2mm, the filter screens are all made of 1Cr18Ni9, and the vacuum brazing method is characterized in that: the valve body 7 and the filter screens 8 at the front end and the rear end are connected by vacuum brazing, the valve body 7 and the filter screens 8 at the front end and the rear end are vertically placed before brazing, the selected welding brazing filler metal is Bag54CuPd900/950 in national standard GB/T18762-2017 noble metal and alloy brazing filler metal specification, the shape of the welding brazing filler metal is an annular shape with the inner diameter phi of 2.5mm, the thickness of a brazing filler metal ring 9 at the joint of the upper end of the valve body 7 and the filter screen 8 is 0.33-0.35 mm, and the thickness of the brazing filler metal ring 9 at the joint of the lower end of the valve body 7 and the filter screen 8 is 0.30-0.32 mm;

during brazing, the joint of the valve body 7 and the filter screens 8 at the front end and the rear end is synchronously and bidirectionally welded, the welding temperature is increased from 920 ℃ to 990 ℃, the time of the heating process is 6-8 min, the pressure in the welding process is more than or equal to 300Pa, after the welding is finished, the workpiece in the furnace is cooled to 780 ℃ along with the furnace, the workpiece in the furnace is air-cooled in an argon filling mode, and the workpiece is discharged after the temperature is reduced to below 80 ℃.

When implementing, valve body 7 and the filter screen 8 of front and back end are vertical places on anchor clamps in order to keep its vertical state, and this anchor clamps include upper, middle, lower three layer construction, and the upper strata is the mounted position of upper screen guard plate 1 in order to keep and fixed valve body 7 upper end and filter screen 8, and the middle level is the vertical state of fixed plate 2 in order to keep and fixed valve body 7 of valve body 7, and the lower floor is the lower filter screen fixed plate 3 that has the circular arc recess, and the filter screen 8 of valve body 7 lower extreme is located in this circular arc recess in order to keep and fix the mounted position of valve body 7 lower extreme and filter screen 8.

Furthermore, the material of the clamp, the valve body 7 and the filter screens 8 at the front end and the rear end is 1Cr18Ni9.

Furthermore, the upper layer structure, the middle layer structure and the lower layer structure of the clamp are arranged on the corresponding upper layer square plate, the middle layer square plate and the lower layer square plate, so that the welding method can be used for welding the connection of a plurality of valve bodies 7 and the front end filter screen 8 and the rear end filter screen 8 at the same time, and guide columns 4, cylindrical pins 5 and diamond pins 6 are arranged on the upper layer square plate, the middle layer square plate and the lower layer square plate to ensure that dislocation does not occur among the three layer structures.

Furthermore, load temperature control thermocouples are arranged at the center positions of the upper, middle and lower layers of square plates to control the real-time temperature in the brazing process.

Further, before welding, the upper, middle and lower layers of square plates are subjected to integral dry sand blasting and then subjected to vacuum purification treatment.

In the implementation, before brazing, the valve body 7 and the front and rear end screens 8 are subjected to uniform temperature treatment of 870 to 880 ℃ in a furnace.

In the implementation, before brazing, the workpiece and the solder are cleaned by absolute ethyl alcohol through ultrasonic waves, the solder ring 9 is placed in a welding process groove of the valve body 7, the filter screen 8 is installed, the filter screen 8 is visually checked to be installed without deflection, and then a layer of solder resist is coated among filter holes of the filter screen 8 to prevent the solder from blocking the filter holes.

The technical scheme of the invention has the characteristics and beneficial effects that:

1. reliable brazing results are ensured by the welding jig. The fixture ensures that the assembled throttling hydraulic valve assembly can be vertically placed in the heat treatment process, effectively avoids the dislocation of the light and thin filter screen in the vacuum brazing process, and obtains a reliable brazing result. Because the strength of the part material is not high and the wall thickness of the filter screen is thin, collision damage and crush damage are easy to generate, when the welding device is designed, the lower filter screen fixing plate 3 for supporting the whole component is in surface contact with the filter screen by adopting the arc groove, so that point contact is avoided, and the stress of the filter screen is reduced; meanwhile, according to the test result, the upper filter screen protection plate 1 does not form an initial design for applying pressure to the filter screen, and the filter screen crush injury caused by improper force application is avoided. In order to ensure the dimensional stability during the brazing process, the fixture should be subjected to a simulated brazing cycle to relieve stress before being put into use, and the welding device is subjected to dimensional stability and surface purification under the conditions of high temperature and high vacuum degree.

In addition, the load temperature control thermocouple is used for accurately monitoring the welding temperature, so that the high level of the heat treatment industry is achieved. In order to improve the machining efficiency, the fixture can be loaded with a plurality of workpieces, and in order to ensure that each workpiece can achieve the same welding result at the process temperature, the actual heat treatment temperature needs to be grasped. A plurality of thermocouples are arranged in a hearth temperature field, the measurement result is combined with the quality of a real object, the central position of the clamp is determined, no part is placed, but a load temperature control thermocouple is arranged, and the actual temperature in the brazing process can be accurately controlled.

2. Aiming at the characteristic of bidirectional welding, the using amount of brazing filler metal is accurately controlled, the welding strength is ensured, and the blockage of filter screen holes is avoided. In the common vacuum brazing part, the gravity and the capillary action direction of the brazing filler metal are consistent, so that the filling of the brazing filler metal is facilitated. The lower end filter screen welding of the throttling hydraulic valve conforms to the rule, but the upper end filter screen welding is that the gravity of the brazing filler metal is opposite to the capillary direction, so that the brazing filler metal is blocked from being filled. This structure has decided under the same clearance, and the required solder quantity of both ends filter screen exists the difference, and the solder quantity of lower extreme filter screen must be less than last filter screen, just can guarantee that the solder spreading degree of both sides is close. Too much brazing filler metal can block the filter screen holes and influence the filtering effect; the brazing filler metal is too little, can reduce welding strength, has the filter screen risk of droing. Through a plurality of tests, the proper brazing filler metal material is determined.

3. And determining brazing heat treatment process parameters according to the structural characteristics of the throttling hydraulic valve. The method comprises the following steps:

3.1 because the effective heating thicknesses of a valve body 7 and a filter screen 8 of the throttling hydraulic valve are greatly different, in order to reduce stress concentration caused by thermal deformation, performing uniform temperature treatment at 870-880 ℃ before welding;

3.2 because the solder used for welding contains volatile alloy elements such as silver, copper and the like, in order to prevent the solder from volatilizing in a large amount in a high-temperature state, the solder needs to be inhibited by a method of increasing the pressure in the furnace through a backfilling gas. According to the covering condition of the brazing filler metal of the test piece, the situation that the brazing filler metal is prevented from spreading due to overlarge pressure intensity and filter meshes are blocked due to overlarge spreading intensity due to undersize pressure intensity is found, and finally, it is determined that the high-purity argon is refilled with the pressure of more than or equal to 300Pa after preheating and temperature equalization treatment is finished;

3.3 the solidus temperature of the solder determined experimentally is 900 deg.C and the liquidus temperature is 950 deg.C. Between the two temperatures, the brazing filler metal exists in solid and liquid together, the welding temperature is higher than the liquidus temperature of the brazing filler metal, and the liquid brazing filler metal wets, flows in a capillary way, fills, spreads and is cooled to form a firm joint in the gap and on the surface of a base metal. The load couple detects the temperature of the test piece in the processing process, and the melting of the brazing filler metal at 920 ℃ and the complete melting at 990 ℃ can be calculated by combining the real object welding condition. Aiming at the structural characteristics of the throttling hydraulic valve component, the brazing heat treatment process is designed to keep the temperature at 920 ℃ for a certain time to complete melting and spreading of the brazing filler metal, so that full weld joint filling can be realized, and the brazing filler metal cannot be spread excessively to block filter screen holes;

3.4 in order to avoid the cracking of the welding joint and the oxidation color generated by early discharging after the cooling speed is too high, the welding joint is cooled to 780 ℃ along with the furnace after the welding is finished, high-purity argon gas is backfilled to 80 ℃ after the welding is cooled, and then the welding joint is discharged.

4. The quality inspection of the interior of the brazing seam is creatively carried out by using industrial CT. The general vacuum brazing part uses X-ray to check the internal quality, and the throttling hydraulic valve assembly is small in size and very narrow in welding line, so that the X-ray inspection is not suitable for being used. The industrial CT is short for industrial computer tomography technology, a welding seam section is scanned at a certain distance from a welding seam of a throttling hydraulic valve assembly, the total welding rate is calculated according to the filling proportion of brazing filler metal, and the total welding rate is required to be more than or equal to 75%.

Drawings

FIG. 1 is a schematic structural diagram of an aircraft engine throttling hydraulic valve assembly with a filter screen according to the present invention

FIG. 2 is a cross-sectional view of FIG. 1

FIG. 3 is a schematic view of a welding fixture for an aircraft engine with a screen throttling hydraulic valve assembly according to the present invention

FIG. 4 is a top view of FIG. 3

FIG. 5 is a perspective view of FIG. 3

Detailed Description

The technical scheme of the invention is further detailed in the following by combining the drawings and the embodiment:

referring to the attached drawings 1-2, the aero-engine throttling hydraulic valve assembly with the filter screen in the embodiment comprises a valve body 7 and the filter screens 8 at the front end and the rear end of the valve body 7, the wall thickness of each filter screen 8 is 0.2mm, the filter screens are made of 1Cr18Ni9, referring to the attached drawings 3-5, a welding clamp and a welding workpiece are made of the same material, and the thermal expansion coefficient, the thermal conductivity and the high-temperature strength of the welding clamp and the welding workpiece are kept the same as those of parts. In terms of structure, in consideration of reducing thermal stress as much as possible, the clamp is structurally composed of an upper layer, a middle layer and a lower layer, wherein the upper layer is an upper filter screen protection plate 1, so that a workpiece can be kept vertical, and meanwhile, the impact of air flow on an upper filter screen 8 when air is inflated is relieved; the middle layer is a throttle hydraulic valve fixing plate 2 for fixing a throttle hydraulic valve; the lower filter screen fixed plate 3 that the lower floor has the circular arc recess, the filter screen of being convenient for is fixed, and this anchor clamps for welding guarantee that three layer construction does not take place the dislocation through the guide pillar 4, two cylindric locks 5 and a diamond-shaped round pin 6 in four corners. The welding device can fix the assembled welding assembly at a corresponding position to prevent the welding workpiece from moving in a brazing process, and a load temperature control thermocouple is arranged at the central position to control the real-time temperature in the brazing process so as to obtain a reliable brazing result.

The vacuum brazing process for the throttle hydraulic valve component with the filter screen of the aircraft engine comprises the following steps:

the method comprises the following steps: cleaning of parts, solder, and soldering apparatus

Cleaning parts, welding flux and tools by using a hydrocarbon vacuum cleaner, wherein the parts are prevented from being collided and damaged in the cleaning process, and the surfaces of the parts are visually inspected to have no obvious dirt after cleaning;

step two, pretreatment of the welding fixture

The whole welding fixture is subjected to dry sand blasting, and vacuum purification treatment is carried out before use;

step three, solder preparation

The selected welding solder is Bag54CuPd900/950 in the national standard GB/T18762-2017 noble metal and alloy solder Specification, the shape of the welding solder is annular with the inner diameter phi of 2.5mm, the thickness of a solder ring 9 at the joint of the upper end of the valve body 7 and the filter screen 8 is 0.33-0.35 mm, and the thickness of the solder ring 9 at the joint of the lower end of the valve body 7 and the filter screen 8 is 0.30-0.32 mm;

the brazing filler metal ring 9 is firstly polished to remove an oxide layer, is further wound and processed into a string of annular brazing filler metal by a lathe, and is manually sharpened to smooth and tight notches after being cut into single material rings, so that the consistency of the diameters of the brazing filler metal is ensured. One side of the brazing filler metal ring is further ground into a plane, so that a filter screen can be conveniently placed;

step four, assembling and assembling

Cleaning parts and welding flux with absolute ethyl alcohol by ultrasonic wave, and further checking the inner cavity of the throttle nozzle, phi 0.3 holes and small holes of a filter screen by a digital electron microscope to ensure that no burrs and other redundancies exist; further placing the solder ring into a throttling hydraulic valve welding process groove, respectively placing and mounting filter screens at two sides, and visually checking whether the filter screens are mounted obliquely; further manually smearing a layer of solder resist among the filter holes of the filter screen, and placing the solder to stop the filter holes from being blocked;

step five, fixing assembly of welding device

A welding fixture is placed downwards at one end of a hexagonal valve body jar of the throttling hydraulic valve, a lower end filter screen 8 is placed on arc grooves which are distributed at intervals on a lower filter screen fixing plate 3, and then the welding fixture is placed in an effective heating zone of a vacuum furnace;

step six, vacuum brazing

After the furnace door is closed, further starting pre-vacuumizing, raising the temperature until the temperature of a load couple reaches 870-880 ℃, preserving the heat for 6min, and then refilling high-purity argon gas at a pressure of more than or equal to 300Pa; further heating until the temperature of the load couple reaches 920 ℃, starting timing, continuing to heat to 990 ℃, and stopping heating; the time of the welding process is 6-8 min, the pressure in the welding process is more than or equal to 300Pa, after the welding is finished, the workpiece in the furnace is cooled to 780 ℃ along with the furnace, the argon is filled for carrying out air cooling on the workpiece in the furnace, and the workpiece is discharged after the temperature of the workpiece is reduced to below 80 ℃;

step seven, industrial CT detection

Horizontally scanning welding parts at two ends of a throttling hydraulic valve component with a filter screen, scanning the cross section of each welding line at intervals of 0.1mm, and calculating the total welding rate according to the filling proportion of brazing filler metal, wherein the total welding rate is required to be more than or equal to 75%; and checking that the inner cavity of the throttling hydraulic valve assembly with the filter screen does not allow excess substances to exist, and the hole wall of the internal oil path does not allow solder to accumulate.

Claims (8)

1. The utility model provides an aeroengine takes filter screen throttle hydraulic valve subassembly vacuum brazing method, this kind of aeroengine takes filter screen throttle hydraulic valve subassembly includes filter screen (8) of valve body (7) and valve body (7) front and back end, and the wall thickness of this filter screen (8) is 0.2mm, and its material is 1Cr18Ni9, its characterized in that: the valve body (7) and the filter screens (8) at the front end and the rear end are connected by vacuum brazing, the valve body (7) and the filter screens (8) at the front end and the rear end are vertically placed before brazing, the selected welding brazing filler metal is Bag54CuPd900/950 in national standard GB/T18762-2017 noble metal and alloy brazing filler metal specification, the welding brazing filler metal is in the shape of a ring with the inner diameter phi of 2.5mm, the thickness of a brazing filler metal ring (9) at the joint of the upper end of the valve body (7) and the filter screen (8) is 0.33-0.35 mm, and the thickness of the brazing filler metal ring (9) at the joint of the lower end of the valve body (7) and the filter screen (8) is 0.30-0.32 mm;

during brazing, the joint of the valve body (7) and the filter screens (8) at the front end and the rear end is synchronously and bidirectionally welded, the welding temperature is increased from 920 ℃ to 990 ℃, the time of the temperature increasing process is 6-8 min, the pressure in the welding process is more than or equal to 300Pa, after welding is finished, the workpiece in the furnace is cooled to 780 ℃ along with the furnace, the workpiece in the furnace is air-cooled in an argon filling mode, and the workpiece is discharged after the temperature of the workpiece is reduced to below 80 ℃.

2. The vacuum brazing method for the hydraulic valve assembly with the screen throttle of the aircraft engine according to claim 1, characterized in that: valve body (7) and filter screen (8) of front and back end are vertical to be placed on anchor clamps in order to keep its vertical state, this anchor clamps include, in, three layer construction down, the upper strata is last filter screen guard plate (1) in order to keep and the mounted position of fixed valve body (7) upper end and filter screen (8), the middle level is the vertical state of fixed plate (2) in order to keep and fixed valve body (7) of valve body (7), the lower floor is lower filter screen fixed plate (3) that has the circular arc recess, filter screen (8) of valve body (7) lower extreme are located in this circular arc recess in order to keep and the mounted position of fixed valve body (7) lower extreme and filter screen (8).

3. The vacuum brazing method for the hydraulic valve assembly with the screen throttle of the aircraft engine as set forth in claim 2, wherein: the clamp, the valve body (7) and the filter screens (8) at the front end and the rear end are made of 1Cr18Ni9.

4. The vacuum brazing method for the hydraulic valve assembly with the screen throttle of the aircraft engine as set forth in claim 2, wherein: the upper layer structure, the middle layer structure and the lower layer structure of the clamp are arranged on the corresponding upper layer square plate, the middle layer square plate and the lower layer square plate, so that the welding method can be used for welding the connection of a plurality of valve bodies (7) and front and rear end filter screens (8) at the same time, and guide columns (4), cylindrical pins (5) and diamond-shaped pins (6) are arranged on the upper layer square plate, the middle layer square plate and the lower layer square plate to ensure that dislocation does not occur among the three layer structures.

5. The vacuum brazing method for the hydraulic valve assembly with the screen throttle of the aircraft engine as set forth in claim 4, wherein: and load temperature control thermocouples are arranged at the center positions of the upper, middle and lower layers of square plates to control the real-time temperature in the brazing process.

6. The vacuum brazing method for the hydraulic valve assembly with the screen throttle of the aircraft engine as set forth in claim 4, wherein: before welding, the upper, middle and lower layers of square plates are subjected to integral dry sand blasting and then subjected to vacuum purification treatment.

7. The vacuum brazing method for the hydraulic valve assembly with the screen throttle of the aircraft engine according to claim 1, characterized in that: before brazing, the valve body (7) and the front and rear end screens (8) are subjected to 870-880 ℃ temperature equalization treatment in a furnace.

8. The vacuum brazing method for the hydraulic valve assembly with the screen throttle of the aircraft engine according to claim 1, characterized in that: before brazing, cleaning a workpiece and a solder by absolute ethyl alcohol ultrasonic waves, putting a solder ring (9) into a welding process groove of a valve body (7), then installing a filter screen (8), visually checking that the filter screen (8) is installed without deflection, and then coating a layer of solder resist among filter holes of the filter screen (8) to prevent the solder from blocking the filter holes.

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