Key Manufacturing Technology of casting parts-Shanxi Ductile Iron Cast Pipe

I. definition and classification of Casting

Definition of Casting:It is a method for casting liquid metal into a casting cavity suitable for the shape of the parts. After cooling and solidification, the forming method of the blank metal parts with a certain shape, size and performance is obtained.

Common casting methods include:Sand CastingAndPrecision CastingThe detailed classification method is shown in the following table.

Sand Casting:Sand Casting-casting method for producing castings in sand. Steel, iron, and most non-ferrous alloy castings can be obtained by sand casting. Since the plastic materials used in sand casting are cheap and easy to use, the casting is easy to manufacture and can adapt to the single-piece production, batch production and mass production of castings. It has been a basic process in casting for a long time.

Precision Casting:Precision Casting is a general term for accurately Casting Technology Using Precision Modeling Methods. Its product is precise, complex, and close to the final shape of parts. It can be directly used without processing or rarely processing. It is an advanced process of near-net forming.

Casting Method Classification

 

Ii. Common casting methods and their advantages and disadvantages

1.General Sand Casting

The basic raw materials for sand production are foundry sand and sand binder. The most common casting sand is Silicon Sand. When the High Temperature Performance of Silicon Sand cannot meet the requirements, Special Sand such as Zircon Sand, chromium iron ore sand and corundum sand will be used. The most widely used type sand binder is Clay, and various dry or semi-dry oils, Water-Soluble Silicate or phosphate and various synthetic resins can be used as the type sand binder.

The binder used by the sand type in Sand Casting and the method for establishing strength are dividedClay wet sand type,Clay dry sand typeAndChemically hardened sandThree types.

 

Sand Casting is the most popular and simple type of casting that has been extended for centuries. sand Casting is used to make large-scale components, such as gray cast iron, ductile iron, stainless steel and other types of steel. The main steps include painting, mold, manufacturing core, shape, melting and pouring, and cleaning.

Process Parameter Selection

Machining Allowance:The so-called machining allowance refers to the surface to be machined on the casting, and a certain machining allowance should be set aside in advance, the size of the casting alloy depends on the type, modeling method, casting size, and the position of the processing surface in the mold.

Modulus slope:In order to make it easy to take out the image from the mold, the slope added perpendicular to the vertical wall of the parting surface is called the modulus slope.

Casting rounded corners:In order to prevent the casting from generating stress and cracks at the wall connection and corner, and prevent the sharp corner damage of the casting mold and the formation of sand holes, the connecting and corner parts of the casting wall should be configured as rounded corners during casting design.

Core Head:In order to ensure the positioning, fixing and exhaust of the core in the mold, the core head should be designed for both the appearance and core.

Shrinkage margin:Due to the cool-down shrinkage of the casting after casting, this part of the shrinkage size should be added when making the image.

Advantages:

• Clay resources are rich and inexpensive. The vast majority of Used Clay wet sands can be recycled after proper sand processing;

• Short manufacturing cycle and high efficiency;

• A long time can be used for mixed sand;

• Wide adaptability. Small parts, large parts, simple parts, complex parts, single parts, large batches can be used;

Disadvantages and limitations:

• Because each sand casting mold can only be cast once, the casting mold is damaged after the casting is obtained, and the molding must be re-shaped, so the production efficiency of sand casting is low;

• The rigidity of the casting mold is not high, and the dimensional precision of the casting is poor;

• Casting can easily produce sand, sand inclusion, pores and other defects.

2.Investment Casting

When the wax material is used as the appearance, the melt casting is also called "Wax loss casting ". Melting casting usually refers to the process of forming a shell with several layers of refractory material on the surface of the melting material, and then melting and discharging the shape to obtain a non-parting surface mold, the Casting Scheme that can be filled with sand after high temperature roasting. As the appearance is widely made of wax materials, it is often referred to as "Wax loss casting ".

The alloy types produced by casting can be carbon steel, alloy steel, heat-resisting alloy, stainless steel, Precision Alloy, Permanent Magnet alloy, bearing alloy, copper alloy, aluminum alloy, titanium alloy and ductile iron.

 

Investment Casting Process

Advantages:

• High dimensional precision. Generally up to CT4-6 (Sand Casting for CT10 ~ 13. Die Casting is ct5 ~ 7 );

• It can improve the utilization rate of metal materials. Melting casting can significantly reduce the processing capacity of the Forming Surface and the matching surface of the product, saving the consumption of cutting tools and materials during processing;

• It can maximize the similarity between the blank and parts and bring great convenience to the structural design of parts. The casting with complicated casting shapes can be used to cast casting with complicated shapes, casting with a wall thickness of 0.5mm and a weight smaller than 1g. It can also be combined and integrated casting;

• Not limited by alloy materials. Casting of carbon steel, alloy steel, ductile iron, copper alloy and aluminum alloy can also be casting of High Temperature Alloy, magnesium alloy, titanium alloy and precious metal. It is particularly suitable for casting of alloy materials that are hard to forge, weld, or cut;

• High production flexibility and adaptability: melting casting is applicable to mass production, small batch production, and even single-piece production.

Disadvantages and limitations:

The casting size cannot be too large. The cool-down speed of complicated castings is slow during the process. Among all the blank forming methods, the casting process is the most complex and the cost is also high. However, if the product is selected properly, the part design is reasonable, high casting costs are compensated for reducing cutting, assembly, and saving metal materials, so investment casting is highly economical.

3.Die Casting

The principle of Die Casting Process is to use high pressure to quickly press the metal liquid into a precise metal mold cavity, the metal liquid under the pressure of cooling solidification and the formation of casting.

 

Pressure Casting A) clamping casting B) injection c) Opening top parts

Cold and Hot Chamber Die Casting are two basic die casting methods.Cold Chamber Die CastingThe medium metal liquid is poured into the pressure chamber by hand or automatic pouring device, then the injection head is pushed forward, the metal hydraulic pressure into the cavity. InHot Chamber Die CastingIn the process, the pressure chamber is perpendicular to the Crucible, and the metal liquid automatically enters the pressure chamber through the feed port on the pressure chamber. The injection head moves downward to push the metal liquid through the goose neck pipe into the cavity. After the metal liquid is solidified, the die casting mold is opened and the casting is taken out to complete a Die Casting cycle.

 

 

Die Casting Process Flowchart

Advantages:

• Product quality is good. The casting has a high dimensional precision, which is generally equivalent to 6 ~ Grade 7, or even Grade 4; good surface finish, generally equivalent to 5 ~ Grade 8; high strength and hardness, generally increased by 25 ~ 30%, but the elongation is reduced by about 70%; the size is stable and the swapping is good; the casting can be die-casting thin-walled and complicated;

• High production efficiency. High machine productivity, such as domestic J ⅲ 3 Horizontal cold air Die Casting Machine average eight hours can die casting 600 ~ 700 times, small hot Chamber Die Casting Machine can be die-cast 3000 ~ on average every eight hours ~ 7000 times; long life of die-casting model, one-fu Die-Casting Model, die-casting clock alloy, with a life cycle of up to 100,000 times or even times; easy to achieve mechanization and automation;

• Excellent economic performance. The die casting has the advantages of precise size and wide smooth table. Generally, it is not directly used for mechanical processing, or the processing volume is very small, which not only improves the utilization rate of metal, but also reduces a lot of processing equipment and working hours; the casting price is easy; it can be combined with other metal or non-metallic materials. It saves both assembly time and metal.

Disadvantages and limitations:

• During die casting, due to the high speed of filling the cavity of liquid metal and unstable flow pattern, the general die casting method is adopted, and the casting is prone to pore holes and heat treatment is not allowed;

• It is difficult to die-casting the Inner Concave and complex castings;

• High melting alloy (such as copper and black metal), low Die Casting life;

• It is not suitable for small batch production. The main reason is the high cost of die casting, the high production efficiency of die casting machine, and the low cost of small batch production.

4.Metal casting

It is also called hard Mold Casting. It is a casting method for Casting by pouring liquid metal into the metal mold. The cast is made of metal and can be used multiple times (hundreds to thousands of times), also called permanent casting.

Metallic structure

Generally, the metal type is made of cast iron and cast steel. The casting can contain both metal cores and sand cores. There are many types of metal structures, such as horizontal classification, direct duplication classification, and composite classification. Vertical Parting makes it easy to open inner gate and take out castings. Horizontal Parting is used to produce thin-walled rotavirus castings. The upper half of composite parting is made of hinge links of the two half vertical parting models, the lower half is a fixed horizontal bottom plate, which is mainly used in casting of complicated castings.

Features of metal casting:The fast thermal conductivity and non-concession properties of the metal model make the casting easy to produce defects such as insufficient pouring, cold isolation, crack and white mouth. In addition, the metal type is repeatedly washed by hot metal liquid, which will reduce the service life. Therefore, the following auxiliary process measures should be adopted.

Preheating metal:Preheated metal type before casting can reduce the cooling capacity of the cast, which is conducive to the filling process of the metal liquid and the process of cast iron. Production of cast iron, metal push to 250 ~ 350 ℃; production of non-ferrous metal parts preheating to 100 ~ 250 deg C.

Paint Brush:To protect the metal type and facilitate the exhaust, the Refractory Coating Layer is usually sprayed on the metal surface to prevent the metal type from being directly affected by the erosion and heat of the metal liquid. The reason is that the cool-down rate of each part of the casting can be changed by adjusting the thickness of the coating layer, which is conducive to the gas discharge in the metal shape. Different alloys should be cast and different coatings should be sprayed. For aluminum alloy casting, the coating made of zinc oxide, talcum powder and water glass should be sprayed; for gray cast iron, the coating should be composed of graphite powder, talcum powder, refractory clay powder, peach gum and water.

Casting:The metal type has a strong thermal conductivity. Therefore, when the metal cast is used, the casting temperature of the alloy should be 20 ~ higher than that of the sand type ~ 30 deg C. Generally, the aluminum alloy is 680 ℃ ~ 740 ℃; cast iron is 1300 ℃ ~ 1370 ℃; Tin Bronze is 1100 ~ 1150 deg C. The upper limit of thin-walled parts and the lower limit of thick-walled parts. The thickness of cast iron cannot be less than 15mm to prevent white-mouth structure.

On:The later the opening period, the larger the shrinkage of the casting in the metallic model, the more difficult it is to take out, and the casting is prone to high internal stress and cracks. Generally, the output temperature of cast iron is 700 ~ 950 ℃, opening time is 10 ~ after pouring ~ 60 seconds.

Advantages:

Compared with sand casting, metal casting has the following advantages:

• It is highly reusable and can be "one-type multi-casting", saving modeling materials and styling work hours.

• Due to the strong cooling ability of the casting, the casting structure is tight and its mechanical performance is high.

• The casting has high dimensional precision and the tolerance level is it12 ~ It14; low surface roughness, Ra is 6.3 m.

• Metal casting does not require sand or less sand, improving working conditions.

 

Disadvantages and limitations:

High manufacturing cost, long cycle, and strict process requirements of the metal model are not applicable to the production of single-piece small batch castings, but mainly applicable to the mass production of non-ferrous alloy castings, such as aluminum pistons, cylinders, cylinders, oil pump casings, and bearing bush and Bushing of copper alloys for aircraft, automobiles, internal combustion engines, motorcycles, etc. For black alloy castings, it is also limited to medium and small castings with simple shapes.

5.Low Pressure Casting

Low-pressure casting is used to instruct the liquid metal at a low pressure (0.02 ~ 06MPa) filling the mold and crystallization under pressure to form the casting method.

Principle diagram of Low-Pressure Casting Process: 1-heat preservation chamber 2-crucible 3-liquid upgrade tube 4-storage tank 5-Mold

The working principle of low-pressure casting is shown. Pour the melted metal liquid into the heat preservation crucible, install a seal, and upgrade the liquid catheter to connect the metal liquid with the mold, lock the mold, and slowly enter the dry compressed air into the furnace, the metal liquid is under the action of gas pressure. It fills the cavity along the liquid-increasing tube and the pouring system from the bottom to the top, and is crystalline under the pressure. After the casting is formed, the pressure in the Crucible is removed, the liquid metal in the liquid tube drops back to the metal liquid in the crucible. Turn on the mold and take out the casting.

 

Low Pressure Casting

Advantages:

• The rising speed and crystallization pressure of the metal liquid can be adjusted during casting, so it can be applied to various casting types (such as metal and sand), casting various alloys and castings of various sizes;

• The bottom Injection Filling Type is used, and the metal liquid filling type is stable and free of splash. It can avoid gas and erosion to the wall and core, and the casting has fewer defects, such as porosity and slag inclusion, the pass rate of casting is improved;

• Casting crystals under pressure, the casting structure is tight, the contour is clear, the surface is smooth, and the mechanical properties are high, especially for the casting of Large Thin-walled parts;

• The metal utilization rate is increased to 90% ~ 98%;

• Low labor intensity, good labor conditions, simple equipment, easy to achieve mechanization and automation.

Disadvantages and limitations:

The lifting pipe has a short life, and the metal liquid is prone to oxidation and slag inclusion during the thermal insulation process. It is mainly used to cast aluminum alloy and magnesium alloy castings with high quality requirements, such as the cylinder, cylinder head, crankcase, and aluminum piston of High-speed internal combustion engines.

6.Centrifugal Casting

Centrifugal Casting is a method of Casting by pouring the metal liquid into the rotating mold and filling the mold with centrifugal force and solidification.

Classification of Centrifugal Casting

According to the space position of the rotation axis of the mold, the common centrifugal casting can be divided into two types:

Horizontal Centrifugal Casting:Centrifugal Casting when the rotation axis of the cast is in the horizontal state or the angle between it and the horizontal line is small (<4 °.

Vertical Centrifugal Casting:Vertical Centrifugal Casting is called vertical centrifugal casting.

The rotation axis of the cast has a large angle with both the horizontal and vertical lines. Centrifugal Casting is called inclined shaft centrifugal casting, but it is rarely used.

 

A) Vertical Centrifugal Casting B) Vertical Centrifugal Casting c) Horizontal Centrifugal Casting

-Pouring package-casting mold-Liquid Metal 4-with wheel and with 5-rotating shaft 6-casting 7-motor 8-casting system 9-cavity 10-core 11-above 12- lower 15-casting slot 17-End Cover

Advantages:

• The core, casting system and riser can be omitted when hollow revolving body casting is produced by centrifugal casting;

• Due to the centrifugal force produced by the liquid metal during rotation, the metal with high density is pushed to the outer wall, while the gas with low density and slag move to the free surface to form the Al solidification from the outside, therefore, the casting has good filling conditions, the casting structure is tight, and the mechanical properties are good;

• Easy pouring of "bimetal" bushing and bearing bush, such as casting a thin layer of copper Bushing in the steel sleeve, can save more expensive copper;

• High scalability;

• Eliminate and reduce the consumption of the casting system and riser.

Disadvantages and limitations:

• The free surface of the casting is rough, the size error is large, and the quality is poor;

• It is not applicable to alloys with high density segregation (such as lead bronze) and alloys such as aluminum and magnesium.

 

Iii. casting defects and Control Methods

There are many kinds of casting defects, and the causes of the defects are also very complicated. It is not only related to the casting process, but also related to a series of factors such as casting alloy properties, alloy melting, and shape material properties. Therefore, when analyzing the causes of casting defects, we should make a comprehensive analysis based on the characteristics, position, process, sand and other factors of the defects, then take appropriate technical measures to prevent and eliminate defects.

1.Failed to pour

The casting part is incomplete and often appears in the thin-walled part, the farthest part from the pouring path, or the top part of the casting. The broken corners are smooth and bright without sticking to the sand.

Cause:

• Low pouring temperature, slow pouring speed or intermittent pouring;

• Small cross-sectional area of horizontal and inner sprue;

• The content of medium and silicon in molten iron is too low;

• The sand contains too much moisture and pulverized coal, a large amount of air, or a large amount of mud, poor air permeability;

• The sand loading height is not enough, and the molten metal pressure is insufficient.

Prevention Method:

• Increase the pouring temperature, speed up the pouring, and prevent intermittent pouring;

• Increase the cross-sectional area of the horizontal and inner tunnels;

• Adjust the ingredients after the furnace to properly increase the carbon and silicon content;

• Strengthen the exhaust in the cast to reduce the amount of pulverized coal and organic matter in the sand;

• Increase the height of the sandbox.

2.Not full

The upper part of the casting is incomplete. the horizontal plane of the iron water in the direct casting channel is equal to the horizontal surface of the molten metal in the casting, and the edges are slightly circular.

Cause:

• The water in the watering case is insufficient;

• The pouring path is narrow and the pouring speed is too fast. When the molten metal overflows from the pouring cup, the operator mistakenly believes that the casting mold is full and it is too early to stop pouring.

Prevention Method:

• Correctly estimate the amount of iron in the watering case;

• The casting speed should be appropriately slowed down to ensure the casting speed is full.

3.Damage

Casting defects.

Cause:

• The casting sand is too violent, or the casting is damaged by collision during the handling process;

• When the drum is cleaned, the casting parts are improperly loaded, and the weak parts of the casting parts are broken when rolling;

• The size of the cross section is too large; the cross section (groove) is not made ). Or the drop-out method is incorrect, so that the casting body is damaged by meat shortage.

Prevention Method:

• During sand drop cleaning and handling of castings, pay attention to avoid excessive collision and vibration in various forms, and avoid unreasonable losses;

• The drum is cleaned up in strict accordance with the technical procedures and requirements;

• Modify the size of the inner and inner neck, make the inner neck knock section, and correctly grasp the direction of the sprite.

4.Sand Sticking and rough surface

Sand Sticking is a kind of casting surface defect, which shows that the casting surface is attached with sand particles that are difficult to clear. For example, the casting surface is not smooth after sand particles are removed, and the casting surface is rough.

Cause:

• The size of the sand is too coarse and the size of the sand is insufficient;

• The Type Sand contains too much water, making it difficult to tighten;

• The pouring speed is too fast, the pressure is too high, and the temperature is too high;

• There are too few Pulverized Coal in the sand;

• The template drying temperature is too high, resulting in dry surface sand; or the template drying temperature is too low, type sand adhesion on the template.

Prevention Method:

• When the air permeability is sufficient, use the fine-grained sand and appropriately increase the tightness of the sand;

• Ensures stable and effective pulverized coal content in the sand;

• Strictly control sand moisture;

• Improve the pouring system, improve the pouring operation, and reduce the pouring temperature;

• Control the template baking temperature, which is generally equal to or slightly higher than the molding sand temperature.

5.Sand eye

Fill holes with sand in the casting or on the surface.

Cause:

• The surface strength of the sand is insufficient;

• There is no rounded corner on the image or the draft angle is small, which leads to hook sand and mold damage. The box is merged without repair or repair;

• The sand type is placed for a long time before casting, and the surface strength decreases after drying;

• The mold is damaged during packing or handling;

• When the box is combined, the floating sand inside the model is not cleared, the pouring cup after the box is not covered, and the crushed sand falls into the mold.

Prevention Method:

• Increase the viscosity content in the sand, add new sand in time, and increase the surface strength of the sand;

• The appearance finish should be high, and the draft angle and casting rounded corner should be reasonably made. The damaged mold should be repaired and then combined;

• Shorten the time of sand type placement before pouring;

• Be careful when packing or carrying the mold to avoid damage or falling into the sand cavity;

• Clear the Internal Floating sand in front of the box and cover the gate.

6.Padding and Expansion

The ripple usually appears on the parting surface of the casting. It is a thin metal protruding part perpendicular to the casting surface and uneven thickness. The expanded sand is the local expansion of the inside and outside of the casting, forming irregular tumor-shaped metal protruding.

Cause:

• Insufficient or uneven closeness;

• Insufficient surface sand strength, or high type sand moisture;

• The liquid metal indenter is too large and the casting speed is too fast.

Prevention Method:

• Improve the mold tightness and avoid local looseness;

• Adjust the sand mixing process and control moisture to improve the sand strength;

• Reduce the indenter of liquid metal and the pouring speed.

7.Box lifting

The casting has a large area of seams at the parting surface, which changes the shape and size of the mold. The lifting case is too large, leading to the overflow of hot metal self-parting surface, resulting in insufficient pouring.

Cause:

• The sandbox is not fastened, the iron press quality is insufficient, or it is too early to remove iron;

• Pouring is too fast, and the impact is too large;

• Template wing.

Prevention Method:

• Increase the iron press weight, and then remove iron after Solidification;

• Reduces the position of the package and the pouring speed;

• Modify the template.

8.Sand drop

The appearance of block metal protruding on the casting surface is similar to that of the falling sand block. In other parts of the casting, there are often sand eyes or defects.

Cause:

• There is a deep and small groove on the appearance, which is equivalent to the structural characteristics or a small draft angle. When the mold is started, the sand belt is broken or split;

• Uneven tightness, insufficient local strength of the cast;

• When packing and carrying the mold, the partial sand blocks of the mold are accidentally dropped.

Prevention Method:

• Proper draft angle and smooth surface;

• The casting mold is highly solid and uniform;

• Be careful when packing and handling.

9.Error (error box)

The part of the casting and the other part are staggered at the joint of the parting plane, causing relative displacement, so that the casting shape does not match the drawing.

Cause:

• Poor Profile preparation, no align or deformation of the upper and lower models;

• Inaccurate positioning of sandbox or template, or loose positioning pin;

• Wear and tear of parts on extrusion machine, such as lining plate under positive pressure plate and bearing of reverse pressure plate;

• The box used for casting is deformed, but you do not pay attention to it during handling and packing, so that the upper and lower cast is displaced.

Prevention Method:

• Strengthen template inspection and repair;

• Check the positioning pin and pin holes of sandbox and template, and install them properly;

• Check the relevant parts of the extrusion machine and adjust them in time. Replace the parts with high wear;

• Perform fixed box shaping on a regular basis. Be careful when handling the mold after removing the box. For the sand type cast on the surface, a row of sand layout should be made.

10.Ash mouth and pitting

The fracture surface of the casting is gray-black or black, with many central parts and few edges. flake graphite can be seen in Metallographic observation.

Cause:

• The chemical composition of molten iron is not required, and the content of carbon and silicon is too high;

• It is too early or too late to add the bismuth from the front of the furnace, or the amount of Bismuth is insufficient.

Prevention Method:

• Correct Selection of chemical components, reasonable ingredients, so that the amount of carbon and silicon in hot metal is within the specified range;

• Increase the amount of bismuth and strictly develop the process before furnace.

11.Crack (hot split, cold split)

The casting has external or internal penetration or non-penetration cracks. The appearance of the oxidation surface with a dark or black color is tortuous during hot split. Cold split is a clean brittle crack with a flat fracture surface and a metallic luster or slight oxidation color.

Cause:

• The content of medium carbon and silicon in molten iron is too low, and the content of sulfur is too high;

• The pouring temperature is too high;

• Too large and too short the inner neck may cause serious local overheating, or too small a heavy mouth, which may lead to poor contraction;

• The impact on castings during cleaning and transportation is too large.

Prevention Method:

• Control the chemical composition of molten iron within the prescribed scope;

• Reduces the pouring temperature;

• Reasonable Design of the counterfeit system;

• Avoid excessive impact on castings during cleaning and transportation.

12.Pore Size

The hole wall of the pore is smooth and bright, and has a circular shape, a pear shape and a needle shape. The hole size is large and small, and is generated on the casting surface or inside. The pores inside the casting can only be found after being cracked or machined.

Cause:

• Small charge wet, serious corrosion or oil pollution, so that the amount of molten iron containing too much, serious oxidation;

• The strip hole, strip slot, lining, and lining are not dry;

• The low pouring temperature makes the gas too late to rise and escape;

• The charge contains a large amount of aluminum, which may easily lead to hydrogen holes;

• Poor permeability of sand type, high moisture of sand type, containing pulverized coal or organic matter, so that a large amount of gas is generated during casting and not easy to discharge.

Prevention Method:

• The charge should be properly managed and the surface should be cleaned;

• The cylinder, front furnace, exit Iron Port, exit Iron tank, and pouring package must be dried;

• Increase the pouring temperature;

• Do not use scrap steel with an excessively high amount of aluminum;

• Appropriately reduce the moisture of sand, control the amount of pulverized coal, and tie ventilation holes.

13.Loose and loose

Scattered and small shrinkage holes, with branches and close crystals, are more small and loose than loose. It often appears in the hot world.

Cause:

• The content of medium carbon and silicon in molten iron is too low, resulting in great shrinkage;

• The pouring speed is too fast and the pouring temperature is too high, which causes the liquid to shrink;

• The casting system and sp are improperly designed, and sequence solidification cannot be achieved;

• The counterfeit port is too small to be supplemented.

Prevention Method:

• The chemical composition of molten iron should be controlled within the prescribed scope;

• Reduces the pouring speed and temperature;

• Improve the gate system and use sequential solidification;

• Increase the volume of the counterfeit port to ensure full contraction.

14.Anti-white port

The white mouth occurs inside the fracture surface of the casting, and the ash mouth appears on the edges.

Cause:

• Hot Metal with high carbon and silicon content has a high hydrogen content;

• Too many white ports, such as chromium, are introduced into the charge;

• Serious element analysis;

Prevention Method:

• The contents of chemical components, carbon and silicon should not be too high;

• Lining and lining should be dried; Type Sand Moisture should not be too high;

• Strengthen charge management to reduce the amount of white elements.

 

Iv. New technologies and directions of automobile casting

1.Development Trend of sand Forming Technology

The shape of the tide model has undergone several stages of development, including manual compaction, earthquake strike, compaction, high pressure, micro-seismic compression, gas compression, and static pressure compression.Static Pressure Modeling TechnologyThe essence is "pre-tightening and compaction ". It has the following advantages: Clear Mold profile, high surface hardness and uniformity, low mold starting angle, high utilization rate of the type plate, low wear rate of the process equipment, high surface finish of the mold, and low waste rate of the mold type. Therefore, it is the latest and most advanced modeling technology and has become the mainstream solid-state technology.

 

At present, the famous manufacturers of static pressure molding equipment in foreign countries include kW companies in Germany, HWS companies and saravideo Italian companies. Most domestic car foundry manufacturers use HWS or kW equipment, such as Faw Foundry Company, Dongfeng Automobile foundry, Shanghai shengdeman Foundry Company, East China Taike west, Shanxi Sanlian, Guangxi Yuchai, Wuxi Diesel Engine Factory, etc.

2.Development Trend of near-Net Technology

Casting Process

Lost Foam CastingIt is also known as gasification casting, solid casting, and non-cavity casting. It has been hailed as "New Casting Technology in the 21st Century" and "green casting engineering ". This process adopts the non-binder dry sand and vacuuming technology. More than one hundred enterprises in China use this process to produce Box Castings, pipe fittings, heat-resistant and wear-resistant alloy steel castings with a total output of over 0.1 million TB. In the future, this process will adopt a large number of rapid manufacturing and simulation technologies to shorten the production preparation period and achieve fast production of castings.

Melting mold Precision Casting Molding Process

The Precision Casting Process of melting mould includes water glass shell process, composite shell process, and silica sol shell process. Automotive products include carbon steel, alloy steel, non-ferrous alloy and ductile iron. High alloy steel and super alloy materials outside China. The smelting equipment adopts common and fast Medium Frequency Furnace in China, and vacuum furnace, turning furnace, and high frequency furnace technology in foreign countries. Future Development Trend of the molding technology of the melt casting technology is that the product is getting closer and closer to the product. The traditional precision casting is only used as the blank and cannot adapt to the rapid response of the market; the complexity and quality of products are getting higher and higher. R & D methods are getting stronger and stronger, and professional collaboration begins to emerge. The application of CAD, cam, and CAE has become the main technology of product development.

3.Development Trend of core Manufacturing Technology

At present, there are three core manufacturing processes for automobile casting at home and abroad. In modern automobile casting, the main technologies used in parallel include hot-Core Box Manufacturing, shell-core manufacturing, and cold-core manufacturing, traditional grease or oil sands cores have been eliminated.

The core manufacturing technology has a development trend focusing on the Cold Core Box technology. FAW Foundry Company, Dongfeng Automobile foundry, Shanghai Shengman Foundry Company, East China Taike west, and Shanxi International Foundry Company all adopt cold-Core Box-making technology.

4.Development Trend of cast iron smelting technology

At present, there are two main methods of cast iron smelting technology at home and abroad: one is to use large hot air dust chongtian furnace and power frequency Insulation Furnace dual melting process; the other is to use medium frequency induction furnace melting technology.

The zhongfrequency furnace technology produced by INDA and pile is becoming more and more important. The technology is becoming increasingly mature, and its advantages in cleaning, environmental protection, energy saving, efficiency, and security are outstanding, which is the future development direction. FAW Foundry Company and Dongfeng Motor Company adopt the zhongfrequency furnace and Insulation Furnace technologies produced by INDA company and pile company. The Development and Application of the globalizer, pregnancy agent, peristaltic agent and other additives products form commercialization, standardization, normalization, serialization.

5.Die Casting Technology for Alloy Cylinder Blocks and cylinder heads

Aluminum alloy is the fastest and most widely used light metal in automobiles, because its performance has reached the requirements of light quality, high strength and corrosion resistance. Initially, aluminum alloy is used only for parts that are not affected. Later, the strength of aluminum alloy was greatly improved by strengthening alloy elements. Due to its light weight and good thermal dissipation, it can meet the requirements of Engine Pistons, cylinders, and cylinders in harsh environments. The core technology of Die Casting for Aluminum Alloy Cylinder Blocks and cylinder heads can improve material quality control, such as purification, refining, refining, and deterioration, so that the quality of aluminum castings can reach consistency and stability.

With the development of China's automobile industry, especially the rapid increase of household cars and the export of automobile parts, the aluminum casting of automobiles will grow greatly. There are two main types of Forming Process for aluminum cylinder heads. One is the gravity casting process represented by Europe and America. Shanghai pilborg, Nanjing taikxi and other companies use the Italian fatatag gravity casting machine to produce aluminum cylinder heads. Second, it is a low-pressure casting technology represented by Japan and South Korea. It is an Aluminum Die Casting workshop of Dongfeng Nissan engine branch, Guangdong Zhaoqing casting Company, and Tianjin Toyota casting Company. It uses a low-pressure casting machine from Japan to produce aluminum cylinder heads.

6.Semi-solid Die Casting Technology

Semi-solid state technology originated in the United States, so this technology has basically matured in the United States, in the world's leading position, known as the most promising material forming processing technology in the 21st century. Alumax took the lead in converting the technology into productivity. The size of the Blank Body of the brake general pump for aluminum alloy cars is close to the size of parts, and the processing volume accounts for 13% of the casting quality, the machining margin of the same metallic castings accounts for 40% of the casting quality. Since 1980s, Europe and other countries have done a lot of research and application work in semi-solid state applications.

7.Development Trend of Cast Iron

Technology of thin-walled High Strength Gray Cast Iron

Gray Cast Iron is widely used in automobiles because of its low cost and excellent casting performance. With the lightweight requirements of automotive technology, the growth and development of Gray Cast Iron will be affected to some extent. Therefore, the development and application of thin-walled High Strength Cylinder Blocks and cylinder heads casting technology will be the development trend.

Mo Cast Iron Technology

Compared with gray cast iron, Mo Cast Iron has similar anti-vibration, thermal conductivity and casting properties, and has good plasticity and heat resistance fatigue properties, which can solve the Thermal Fatigue Crack Problem of rolling force cylinder head. The huge potential market for the wide application of Mo Cast Iron is in the automotive industry. Its main products are Engine Cylinder Blocks and high-power diesel engine cylinder heads. With the increase of light weight and specific power (kW/displacement), the operating temperature of Cylinder Blocks and cylinder heads is getting higher and higher, and the operating temperature of many parts exceeds 200 ℃, the strength of the aluminum alloy is greatly reduced, while the titanium has a great advantage.

Ductile Iron Technology

Due to its high strength, high toughness and low price, there is still great development in the automotive market. In the automobile casting industry, there are four main types of product technology development trends. 1. Cast-state pearlile, high-strength truck and car crankshaft, as-cast ferrite, high-elongation automobile exhaust pipe and axle housing chassis casting, and 2. Security casting, as-cast production cars steering section; three is heat-resistant iron parts, high silicon molybdenum, medium silicon molybdenum, High Nickel Cast iron, the production of the exhaust pipe fittings of this material; the fourth is the Oracle bulb iron, mainly used to produce crankshaft and other products. In addition to the above, the automobile foundry has produced a cold-excited camshaft of the Cast-type ductile iron.

8.Development Trend of Computer Application Technology in Casting Process

With the rapid development of automobile casting technology, in order to shorten the casting production preparation period and reduce the risk of new product developmentRapid Prototyping, computer simulation, 3D modeling, and numerical controlMore and more applications. Rapid prototyping technology is used to develop the appearance of new products for trial production and the wax mold used for melting casting. It can also be used to make phenolic resin shell and shell cores and directly assemble them into sand. The modeling process is becoming one of the leading fields of international automotive foundry. Use magma and casting software to simulate and analyze the filling and solidification temperature fields and flow field of new casting products, and predict and analyze casting defects.

9.Casting Detection Technology

Non-destructive testing technology is widely used, and fluorescent magnetic powder is often used to detect surface cracks for important parts. Ultrasonic or audio is used to detect the bulk rate of cast iron; matrix Structure of eddy current casting (pearlile content ). To meet the requirements of important parts detection, some of the above three detection instruments are combined into an automatic detection line.

10.Development Trend of green Casting Technology

"Green casting" minimizes the negative impact on the environment and has the highest resource efficiency in the entire product lifecycle from design, manufacturing, packaging, transportation, use to decommission. The casting industry has always been regarded as an industry with high energy consumption and high pollution. It is necessary to continuously develop new energy-saving, clean, low emission and low pollution casting materials for production and use.

Shanxi Centrifugal Ductile Iron Cast Pipe-Jincheng jianniu yezhu Co., Ltd.

Key Manufacturing Technology of casting parts-Shanxi Ductile Iron Cast Pipe