The chemical milling process uses chemical solutions to react with metals, and with the help of effective protection measures,
A special processing method for corroding and dissolving the unwanted part of the metal of titanium parts to obtain the required size and shape of the parts. This paper introduces the design of special tooling for chemical milling titanium alloy parts, and points out its shortcomings.
1. Special tooling design
1.1, material selection
The materials used in the tooling of chemical milling titanium alloy parts must first be able to withstand concentrated hydrofluoric acid and concentrated nitric acid.
Corrosion, on-site to non-metallic materials: glass fiber reinforced plastic, plexiglass, dragon, ABS, polyurethane board, soft
Polyvinyl chloride, polytetrafluoroethylene, PVC, neoprene, nitrile rubber, natural rubber, black oil-resistant rubber, and polypropylene were subjected to a 280-hour immersion test in chemical milling fluid. The test found that the states of polypropylene, polytetrafluoroethylene and nitrile rubber have not changed, and the color of the PVC material has changed slightly, and the other materials have changed in performance, including color, hardness, brittleness, strength, etc.; Stainless steel material OCr17Ni2Mo2 (SUS316) and OCr18Ni9 (SUS304) are tested and compared, SUS316 is better than SUS304 in corrosion resistance, but when using the two, protective glue must be applied.
PP material: scientific name is polypropylene, good acid resistance, good welding performance; good mechanical processing
It has a wide range of performance and can be used for welding of the same material, so it can be used as a structural part, but the strength is not high. As a load-bearing part, it needs to be lined with steel or increase the thickness of the material; if industrial PP materials cannot be purchased,
Civilian PP-R materials can also be used, such as hot water pipe fittings, etc., but the corrosion resistance is not as good as the former, and only hot melt can be used.
Welding; industrial PP material, the purity can be guaranteed, for chemical milling tooling, it is best to use industrial grade
PP material, it is not recommended to use civil PP pipe fittings, if it must be used, PP-R hot water pipe is preferred
pieces.
1.2, bonding technology
In the process of I-pack design, it is inevitable to use adhesives. By testing various adhesives
It shows that: epoxy resin, 502 glue, PVC, upper and lower water glue have good performance.
Epoxy Adhesive: Excellent adhesion, heat resistance, insulation, rigidity to metals and non-metals
It has good hardness and softness, and can be used for the bonding of metals, non-metals and other materials; on site, epoxy resin solution can be used for bonding between tooling parts and filling large gaps, and it can also be used for filling and wear during repairing. Surface, hole repair, etc.; when it is in contact with the milling fluid for a long time, it will corrode and thin, so it should be recoated in time.
502 glue: It has very good bonding properties to metals, non-metals, etc.
The parts can be immersed in the milling solution for a long time without cracking, such as the bonding of nitrile rubber and PP materials, and the bonding of PP materials and stainless steel, but the surface of the bonding must be rough.
PVC upper and lower water glue: yes- a special adhesive for bonding PVC materials, including upper and lower water glue, water release glue
Adhesive is often used in home decoration, but the bonding strength is not large and cannot withstand large impacts when necessary
It should be fixed by screws, etc.; it also has a fixed bonding effect on PP materials.
1.3 Special welding technology
Plastic welding: PP material has excellent welding ability and is widely used in chemical milling tooling; welding
The connection adopts PP welding rod (usually made by the manufacturer and also sold in the market) through a hot air blower (plastic welding
machine, air above 500 degrees) for welding to ensure the welding quality.
Hot-melt welding: If the civil PP-R material is used, if the plastic welding is used, the welding performance is not good, and the construction
It is recommended to use hot-melt welding machine butt welding; this method can use standard PP-R material upper and lower water pipe fittings, such as elbows, etc., which can be used for the design and manufacture of milling equipment and related equipment.
1.4. Coating technology
Since stainless steel is often used as a load-bearing member in tooling, its protection is the top priority.
To the following coating methods:
(1) Hot dip PVC method: that is, put the tooling into the PVC solution, and apply the solution layer by layer to the tool.
On the parts, the adhesion is good, and the coating can resist slight impact.
(2) Coating method: Using the properties of PP material that can be welded, the workpiece is assembled by using pipes, plates, etc.
The body is packaged, and the connection C is sealed by welding; the thickness can be freely selected, but there is no combination
Force, for packaging only, may be considered in conjunction with bonding methods.
(3) Spraying PVC method: use plastic spraying equipment to spray the tooling, and the effective thickness is one
Generally, the use of 1.5mmI will be limited.
(4) FRP lining method: using epoxy resin and fiber cloth (or polyester cloth), on the surface of the part
For wrapping, about 10 layers of 3-4mm are wrapped, and the fixing time is 24 hours. Any type of surface can be lined, with good adhesion and high strength, but the adhesive must be epoxy resin.
1.5. Selection of tooling structure
Since continuous stirring is required in chemical milling to ensure the same corrosion rate of each machining surface, the fixture is preferred.
The wheel spoke composite structure can be horizontal or vertical, and can rotate slowly under the drive of the motor.
Lightweight, high strength and good corrosion resistance. The milling fixture is mainly composed of a fixed frame, a movable central axis, a gasket, a locking nut and a fastener.
1.6. Problems that should be paid attention to in tooling design
(1) The nitrile rubber gasket cannot be fixed: the bonding surface is not roughened, the 502 glue is not applied enough, and there is no gasket limit groove.
(2) The surface of the nitrile rubber gasket loses its elasticity: the material is aged, or 502 glue is applied to the surface.
(3) The surface of the coated glass fiber reinforced plastic is bulging: the air permeability of the fiber cloth is not good, and there is air in it that is not discharged
net.
(4) There are pits on the surface of the coated glass fiber reinforced plastic: if the coating is not in place, add epoxy resin.
(5) After chemical milling_1 is used, there is chemical milling fluid in it, and there is no designed discharge hole or the hole is blocked.
(6) The surface of the screw position collapses after use: PP material is relatively soft, and when tightening with force, the material will
Raw plastic deformation; can be repaired with epoxy resin liquid, or add large gaskets to disperse compressive stress.
2. Insufficiency and prospect of chemical milling tooling technology
The chemical milling process has its own unique advantages. With the advancement of processing technology, the demand for tooling will increase.
However, the tooling methods for design and manufacture have great limitations. This article only expounds the chemical milling tooling from the perspective of testing, and does not involve more materials. There are still great limitations, especially for the use state data of materials , including the service life, etc., there is no exact data support; in addition, no research has been carried out on the structural strength of the tooling.
Company: Baoji Dynamic Trading Co., Ltd
Country:China
Add:Baoti road,Jintai,Baoji city,Shaanxi,China
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