The following will introduce the processing technology of precision castings and their respective characteristics.

1. Investment casting

Investment casting is a high-precision and high-quality casting process, which is suitable for the production of precision castings with complex shapes and high precision requirements. It is characterized by the use of refractory materials to make molds, heating the molds to a high temperature state, and then injecting high-temperature molten metal materials for casting. Due to the small thermal expansion coefficient of the mold and the good surface quality of the casting, it is suitable for producing parts with high precision requirements.

2. Low pressure casting

Low pressure casting is a casting process based on gravity and pressure, which is suitable for the production of castings with high precision requirements. Its characteristic is to put the pretreated metal rod or block into the mold, and then use the force of low-pressure gas or vacuum to push the metal liquid into the mold. Low-pressure casting is suitable for producing high-quality precision castings due to its ability to reduce gas defects and impurities.

3. Precision die casting

Precision die casting is a high-precision and high-yield casting process, which is suitable for producing a large number of precision casting stainless steel castings. It is characterized by the use of high pressure to inject metal materials into the mold, and the use of high-speed cooling and rapid discharge to achieve rapid production. Because of its high production efficiency and low cost, it is widely used in automobile, electronics, aviation and other fields.

4. Precision casting

Precision casting is a high-precision and high-quality casting process, which is suitable for the production of precision castings with complex shapes and high dimensional accuracy requirements. It is characterized by the use of special molds and heating equipment to make the metal material flow at high temperatures, so as to achieve precise pouring. Precision castings have the ability to control material flow and solidification processes, and are suitable for producing high-quality precision castings.

In industrial production, purification methods such as clarification, flux and steam are mainly used, and some also use fixed solidification and filtration methods for purification.

1. Flux purification: Flux purification refers to the application of viscous discharge composed of many fluxes contained in aluminum liquid, so that metal oxides in aluminum liquid are absorbed and dissolved by this discharge, forming new discharge rising to the surface, and forming sludge to be removed after cooling. The flux used for purification is composed of salts with low melting point, low relative density, low surface support, high vitality and strong adsorption to air oxidation slag. When applying, first put a small piece of flux into the cage, and then insert it into the bottom of the mixing furnace to stir back and forth. Alloy steel precision castings can be removed from the cage after the flux is melted and stopped for 5-10 minutes to remove surface sludge. Depending on requirements, the flux may also be removed from the surface to provide a capping effect.

2. Steam purification Gas purification is one of the main raw material aluminum purification methods, commonly used in chlorine, nitrogen or chlorine and nitrogen mixture.

(1) chlorine purification. Previously, active steam chlorine was used as a scavenger (chloride method). During the chloride process, when chlorine gas enters the aluminum liquid, many unusually thin AlCl3 and bubbles are formed, which are fully mixed in the aluminum liquid. The hydrogen dissolved in the aluminum liquid, together with some impurities of the alloy aluminum precision casting equipment, is adsorbed on the AlCl3 bubbles, and then the AlCl3 bubbles rise to the surface of the aluminum liquid and are discharged. When entering chlorine, it can also chlorinate some elements that are more negatively charged than aluminum, such as calcium, sodium, magnesium, etc. These elements produce corresponding chlorides due to entering chlorine and are separated. Therefore, the chloride method is a very effective method for purifying primary aluminum. The use of chlorine is 500-700 grams per ton of aluminum, but because O2 is harmful and precious, in order to avoid gas damage and reduce the cost of waste aluminum production, it has been gradually replaced by Noble gas nitrogen purification method in the contemporary aluminum industry.

(2) nitrogen purification method. It is also known as a smoke-free continuous purification method, using alumina balls (418mm) as a filter material. N2 immediately enters the aluminum liquid. The aluminum liquid was continuously fed into a purging furnace, passed through a filter layer of alumina balls, and subjected to a nitrogen purge. Therefore, the non-metallic material impurities in the aluminum liquid and its dissolved hydrogen are removed, and then continuously discharged, so that the slender nitrogen bubbles in the dissolved aluminum liquid are evenly distributed, which has a purification effect. Nitrogen has zero pollution to the air, and the purification output is large, which can solve 200-600kg of aluminum liquid per minute. The amount of aluminum loss generated during the entire purification process is relatively reduced, so it is now widely used. But unlike chlorine, it removes calcium, sodium and magnesium from molten aluminum.

Quality is critical to achieving automated control of the precision casting process. I will introduce how to realize the automatic control of the precision casting process from the aspects of mold design, process planning, equipment selection and production control.

First, in the mold design. Mold is an important tool to realize casting process, and its reasonable design directly affects the quality and production efficiency of castings. In automatic control, mold design needs to consider the following points: First, use CAD/CAM technology for mold design, through simulation analysis and optimization design, make the mold structure more reasonable and reliable, and can meet the requirements of various complex shapes of castings; Second, combined with mold sensor technology, collect mold deformation, temperature, pressure and other information, used to monitor and control the mold condition, timely repair the mold, to ensure the continuous stability of production; the third is the application of rapid prototyping technology, the use of rapid manufacturing and maintenance of mold methods, reduce manual intervention, improve production efficiency and mold service life.

Second, in terms of process planning. The process requirements of precision casting factories are very strict, and it is necessary to select the appropriate process path according to the specific product characteristics and production requirements. In automation control, process planning needs to consider the following aspects: First, use numerical simulation technology to optimize process parameters to ensure the requirements for flow performance, solidification thermal conductivity and interface compatibility; second, according to the requirements of product shape and size Determine the casting process, including gating system design, temperature control, cooling parameters, etc.; the third is to combine intelligent sensor technology, real-time monitoring of liquid metal temperature, flow, casting morphology and other data. The stability and repeatability of the casting process can be improved by adjusting the process parameters through the feedback control system.

At present, the global investment casting forming process is developing rapidly and widely used. Judging from the current situation, the future development trend of the process is that casting products are getting closer and closer to parts products, and traditional precision castings are only used as blanks and are no longer suitable for the rapid changes in the market.

The complexity and quality level of component products are constantly improving, and the research and development methods are becoming stronger and stronger. Professional collaboration began to appear, and the application of CAD, CAM and CAE has become the main technology of component product development. From the analysis of the current development situation, the application of casting technology is very extensive, and its future development prospects are quite broad.

Generally speaking, the dimensional accuracy of precision castings is affected by many factors, such as casting structure, casting material, mold making, shell making, baking, pouring and so on. The reasonable setting and operation of any link will lead to the change of the shrinkage rate of the casting, resulting in the deviation between the dimensional accuracy of the casting and the requirements. The following are factors that can cause defects in the dimensional accuracy of precision castings.

1. Hinge

It is made of iron, copper and stainless steel. It is one of the necessary hardware for doors and windows.

2. Hinge

Hinges are divided into bright hinges and dark hinges, and bright hinges are often used on doors and windows.

3, the track

Sliding doors and windows need to be installed door and window slide rails, often equipped with ball bearings, so that doors and windows push and pull.

4. Door suction

The door suction is a hardware accessory installed behind the door to prevent the door from automatically closing when the wind blows.

5. Door Closer

The door closer can ensure that the door is opened and closed to the initial position accurately and in time. It is a hydraulic device that can automatically close or fix the opened door leaf in a certain position. The types include floor spring, door top spring, door slingshot, magnetic door suction head, etc.

Except that the outermost electron number of a few metals such as tin, antimony and bismuth is greater than or equal to 4, the outermost electron number of most metal atoms is less than 4. The peripheral electron arrangement of main group metal atoms is ns1 or ns2 or ns2 np(1-4), and the peripheral electron arrangement of transition metal can be expressed as (n-1)d(1-10) ns(1-2). The atomic radius of the main group metal elements is larger than the atomic radius of the non-metallic elements (except rare gases) of the same period.

1. Ferrous metals: iron, chromium and manganese.

2. Non-ferrous metals: aluminum, magnesium, potassium, sodium, calcium, strontium, barium, copper, lead, zinc, tin, cobalt, nickel, antimony, mercury, cadmium, bismuth, gold, silver, platinum, ruthenium, rhodium, palladium, osmium, iridium, Beryllium, lithium, rubidium, cesium, titanium, zirconium, hafnium, vanadium, niobium, tantalum, tungsten, molybdenum, gallium, indium, thallium, germanium, rhenium, lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium, yttrium, silicon, boron, selenium, tellurium, arsenic, thorium.

3. Common metals: such as iron, aluminum, copper, zinc, etc.

4. Rare metals: such as zirconium, hafnium, niobium, tantalum, etc.

5. Light metal: metal elemental density less than 4500 kg/m³, such as titanium, aluminum, magnesium, potassium, sodium, calcium, strontium, barium, etc.

6, heavy metals: metal elemental density is greater than 4500 kg/m³, such as copper, nickel, cobalt, lead, zinc, tin, antimony, bismuth, cadmium, mercury, etc.

7. Precious metals: the price is more expensive than commonly used metals, the crustal abundance is low (also known as the Clark value (CLARKE value), a value that represents the average content of chemical elements in the crust), and it is difficult to purify, such as gold, silver and platinum group metals.

8, metalloid elements: properties between metal and non-metal, such as germanium, antimony, polonium and so on.

9. Rare metals: including rare light metals, such as lithium, rubidium, cesium, etc.; rare refractory metals: such as zirconium, molybdenum, tungsten, etc.; rare dispersed metals: such as gallium, indium, germanium, thallium, etc.; rare earth metals: such as scandium, Yttrium, lanthanide metals; radioactive metals: such as uranium and thorium in radium, francium, polonium and actinides.

It includes: investment casting, ceramic casting, metal casting, pressure casting, lost foam casting.

One of the more commonly used is investment casting, also known as lost wax casting: the selection of appropriate investment materials (such as paraffin wax) to make investment; repeat the process of dipping refractory paint and sprinkling refractory sand on the investment, hardening the shell and drying;

Then melt the internal melting mold to obtain the cavity; Bake the shell to obtain sufficient strength and burn off the residual melting mold material,;

The metal material required for pouring; solidification and cooling, sand removal after shelling, so as to obtain high-precision finished products. According to the product needs or heat treatment and cold working and surface treatment.

Wax pressing (wax injection wax model)-wax repair-wax inspection-group tree (wax model tree)-shell making (first dipping, sand leaching, then dipping, finally air drying of the mold shell)-dewaxing (steam dewaxing)-mold shell roasting-chemical analysis-pouring (pouring molten steel in the mold shell)-vibration shelling---

Casting and casting rod cutting separation-grinding gate-initial inspection (blank inspection)-shot blasting cleaning-machining-polishing-finished product inspection-warehousing casting production process is generally divided into wax pressing, shell making, pouring, post-treatment and inspection.

Pressure wax includes (pressure wax, repair wax, group tree)

Wax pressing-wax pressing machine is used to make wax molds.

Wax repair-correction of wax model

Group tree-group the wax model into a group tree

Shell making including (sand hanging, slurry hanging, air drying)

Pouring includes (roasting and chemical analysis are also called spectroscopy, pouring, shelling, gate cutting and gate grinding)

Post-treatment including (sand blasting, shot blasting, correction, pickling)

Inspection includes (wax inspection, initial inspection, intermediate inspection and finished product inspection)

A device that automatically closes or fixes an open door leaf in a certain position. Some have both the role of the leaf, and some have fire performance. The main varieties are ground spring, door top spring, door slingshot, door system, door chuck, magnetic door suction head, etc.

1. Floor spring: also known as earth dragon. It is installed in the lower part of the door and window. The use of gray cast iron, carbon steel, spring steel, cast steel and other processing into parts, after assembly.

2, the top of the door spring: the use of spring spring spring or spiral spring to make the door leaf closed the automatic door closing device. There is a buffer cylinder inside, which can reduce the closing speed.

4. Door slingshot: It is punched by low-carbon strip steel, and is equipped with low-carbon cold-drawn steel top rod, which uses elastic force to close the door.

5. Door-making device: a simple locator for braking the door leaf and avoiding the collision between the door leaf and the wall. Installed in the outer corner of the door leaf, the door leaf can be positioned at any angle.

6. Door chuck: a device for fixing and opening the door leaf. It consists of a knife-edge base and a triangular steel collet. There are two kinds of horizontal and vertical. The base is made of gray cast iron; the chuck is made of spring steel skin, and the surface is treated with blue.

7. Magnetic door suction head: The function is the same as the door clip door and window hardware head, and the door leaf is fixed by the suction force of the permanent magnet, and there is no noise when in use.