Definition WithCastingObtained by means of metal objects, that isMeltingA good liquid metal, withPouring, Injection,InhalationOr other means into a pre-preparedCasting, The cooling off by the sand,CleaningAndReprocessing, Received a certain shape, size and performanceObject.
Casting History Casting ApplicationHistoryLong. Ancient people used to make castingsMoney,Sacrificial,Weapon,Tools, And some other appliances. In modern times, mainly for casting machine partsBlankSome precision castings, may also be used as a machine parts. Casting in mechanical products account for a large proportion, such as theTractor, The casting weight machine weight of approximately 50 ~ 70%,Farm machineryAccounts for 40 ~ 70%,Machine,EngineAnd so on in the 70 ~ 90%. Various types of castings in order toMechanicalCastings used in most varieties, the shape of the most complex, dosage is also the largest, accounting for 60% of the total cast. FollowedMetallurgyUsed in ingot mold and theEngineeringUsedPipeline.
Casting is also closely related to everyday life. For example, frequently used door handles,Lock,RadiatorUp and down the water pipes,Wok, Gas stove frame,IronAnd so on, are casting.
Casting Category Casting a variety of classifications: According to its useMetalThe different materials, divided into steel castings,Cast Iron, Bronze pieces, cast aluminum parts, cast magnesium parts, cast zinc parts, cast titanium parts and so on. Each type casting can also according to their chemical composition orMetallographicOrganizations to further divided into different categories. Such as the cast iron pieces can be divided into gray iron castings, ductile iron parts, compacted graphite iron castings, malleable iron, alloy cast iron, etc.; according to different methods of casting molding, casting can be divided into ordinary sand castings, metal type casting,Casting, Centrifugal casting, continuous casting parts, Investment Casting, ceramic-type casting, electroslag remelting, casting, metal castings, etc. pairs. Among them, the most widely used ordinary sand castings, accounting for 80% of the total casting production. TheAluminum,Magnesium,ZincEtc.Non-ferrous metalsCasting, mostlyCastingPieces.
Casting Properties and Uses Castings have excellent mechanical, physical properties, it can have a variety of differentStrength,Hardness, Toughness with the overall performance, but also combine one or more special properties, such as theWear, High temperature and low temperature, corrosion-resistant.
Casting weight and size range is very wide, only a few grams of the lightest weight, most weight up to 400 tons, the thinnest wall thickness of only 0.5 mm thick can exceed 1 m in length by a few millimeters to 10 meters can meet the differentIndustryApplication requirements.
Casting quality Include appearance quality, internal quality, andUse quality. Appearance refers to the quality of casting surfaceRoughnessSurfaceDefectSizeDeviation, Shape bias, weight deviation; inherent quality mainly refers to the chemical composition of castings,Physical properties,Mechanical Properties,MicrostructureAnd the existence of the internal castingHoles,Crack,Inclusion,Segregation, Etc.; the use of the quality of castings in different conditions refer to the work of endurance, including wear, corrosion resistance, thermal shock cold shock,Fatigue, Shock absorbers and other performance, and have been cutting nature ofWeldabilityEtc.Technology performance.
Casting quality of the performance of mechanical products have a great impact. For example, the machine tool castings wear resistance and dimensional stability, a direct impact on the accuracy of machine tools to maintain life; all kinds ofPumpsTheImpeller,ShellAs well as the cavity size of hydraulic parts, profile accuracy and surface roughness, a direct impact on pump andHydraulic SystemWorking efficiency, energy consumption andCavitationThe development, etc.; internal combustion engine cylinder block,Cylinder, Cylinder liner,Piston, Exhaust pipes and other castings of the strength and resistance to cold shock heat shock, a direct impact onEngineOf his working life.
There are many factors affecting the quality of casting, the first is the casting of the design process. Design, in addition to working conditions and under the metallic casting material properties to determine the geometry of size, but also must beCasting AlloysAnd the casting process characteristics of the design point of view to consider the reasonableness of the significant size effect andSolidification,Contraction,StressAnd so on, in order to avoid or reduce the casting composition segregation,Deformation, Cracking and other defects. The second should be a reasonable casting process. Namely, according to casting structure, weight and size, castingAlloyCharacteristics and production conditions, select the appropriatePartingAndModeling, Building core method, a reasonable set casting bars, cold iron,RiserAnd pouring systems. In order to ensure access to quality castings. The third is the quality of casting materials. MetalBURDEN,Refractory,Fuel,Flux, Metamorphic agent andFoundry Sand,Molding sand binder,PaintSuch as sub-standard quality of materials, will produce casting porosity,Pinhole,Slag, Sticky sand and other defects affecting the appearance quality and internal quality casting, casting serious cause scrapped. Fourth, technical operation, it is necessary to develop a reasonable process rules to enhance the skill level of workers, so that technical rules are correctly implemented.
Casting, it is necessary to control the quality of the casting and testing. First, to formulate fromMaterials, Auxiliary materials to each product-specific process control and inspection codes and technological conditions. Every rightProcessStrict codes of practice and technical conditions according to process control and testing. Finally, the finished casting for quality inspection. Detection methods should be equipped with a reasonable and appropriate testing personnel. The general appearance of the quality of the casting can be used to judge the comparative sample block casting surface roughness; surface cracks can be subtle shading method, magnetic particle inspection method. Internal quality of the casting can be usedAudio,Ultrasound,Eddy,X-rayAndγ-rayAnd other methods to check and judge.
How to picec up casting bug：
Casting a variety of factors, often occur pores, pinholes, slag, crack, pit defects. Repair equipment commonly used in welding machines, resistance welding machine, cold welding and so on. For the quality and appearance of the casting defects can be less demanding welding machines and other heat large, fast welder to repair. However, in the field of precision casting defect repair, due to argon welding heat-affected large casting repair will result in deformation, the hardness reduced trachoma, partial annealing, cracks, pinholes, abrasion, scratching, biting edge, or a combination of not enough and inner strength stress injury and other secondary defects.Cold weldingJust to overcome the above shortcomings, the advantage is mainly manifested in the heat-affected area is small, casting without preheating, at room temperature cold welding repair, and thus no deformation, biting edge and residual stress, will not produce partial annealing, the metal structure does not change the state of casting. So cold welding for precision casting surface defect repair. The range of cold welding welding welding Φ1.5-Φ1.2mm repeated melting point of the process of accumulation, in the large area defect repair process, the repair efficiency is widely used in constraining the only factor. For large defects, recommends the traditional welding processes and casting defect repairing machine composite applications.
Casting hardness to detect
Casting itself a direct impact on the properties of the quality of processing, which is to determine the hardness of the casting process is an important indicator.
1. Brinell hardness: mainly used to determine castings, forgings, nonferrous metal workpiece, hot-rolled billets and annealed pieces of the hardness measurement range ≯ HB450.
2. Rockwell Hardness: HRA is mainly used for high hardness specimens were measured hardness of HRC67 or more above the material and surface hardness, such as carbide, nitride steel and so on, determined the scope of HRA> 70. HRC is mainly used for steel parts (such as carbon steel, tool steel, alloy steel, etc.), after quenching, or tempering the hardness measurement, measurement range HRC20 ~ 67.
3. Vickers hardness: thin pieces and steel plate used to determine the hardness of workpiece can also be used to determine carburizing, cyanide, nitrogen and other surface hardness of hardened workpieces.
本文转自：China Industry News