1. Porosity is this failed to escape of gas in the metal solidification process in metal forming inside the small hole, its inner surface is smooth, containing gas, ultrasound has high reflectivity, but also because its basically spherical or elliptic ball, i. e. to point defects, affect the reflection amplitude. Porosity after forging or rolling of steel ingot is squashed into area type defects and benefit was found by ultrasonic testing. 2. Shrinkage cavity and loose casting or ingot solidification cooling, volume shrinkage, in the final solidification liquid metal part not able to add and will form the hole shape defect. Large, concentrated hole known as shrinkage cavity, small and scattered space is known as osteoporosis, they are generally located in the heart of the ingot or casting solidification last section, its inner surface is rough, surrounding with many impurities and tiny pores. Due to the laws of heat bilges cold shrink, shrinkage is inevitable, just with different processing methods have different shape, size and location, or when it is extended to casting ingot is defect in ontology. Ingot at sufficiently forging without removing shrinkage cavity clean and into forging becomes residual shrinkage cavity ( Shrinkage cavity residual residual shrinkage tube), 。 3. Slag in the process of smelting slag or crucible furnace refractory material peeling off into the liquid metal, when casting were involved in casting or ingot, slag inclusion defect was created. Slag does not usually single, often in dense state or dispersed in different depth, it was similar to the type of defect volume yet often have certain which affects. 4. Mixed reaction products in the process of smelting, Such as the oxide and sulfide, etc. ) - Non-metallic inclusions, or metal components to add some ingredients in the material not completely left by the melting metal inclusions formed, such as high density, high melting point elements - Tungsten, molybdenum, etc. 5. Segregation segregation mainly refers to the smelting process of casting or ingot or metal melting because of the composition distribution in the process of composition segregation, there is a segregation area of its mechanical properties is different from the mechanical properties of matrix, and the difference is beyond the scope allowed standard is defect. 6. Casting casting crack when the crack is mainly due to the metal cooling solidification contraction stress exceeds the limit of material strength and cause, it is related to the shape of the casting design and casting process, also with some high content of impurities in the metal materials caused by cracking sensitivity ( Sulfur content such as high brittleness, high phosphorus content with cold brittleness, etc. ) 。 Also can produce in the ingot axis of intergranular crack, if not in the subsequent breakdown of forging forging close, will be forging internal cracks in forgings. 7. Cold shut it is a kind of stratification peculiar to the casting defects, mainly related to the casting casting process design, when it is pouring liquid metal, due to interruption of splash, double wave, pouring, or from two different directions ( Or more shares Metal flow meet, because the liquid metal semi-solid film on the casting cooling formation on the surface of the body and form a membrane of the area of defects. 8. Skull patch from ladle to this is when the steel ingot mold casting, because the pouring interrupt, pause, the first poured into the surface of the liquid metal rapidly cooled in air oxidation film formation, pouring on stylish poured into the liquid metal to break through its turn into steel ingot and formed a kind of stratification ( Area type) Defect, it cannot be forged in subsequent breakdown of ingot forging or eliminated. 9. Anisotropy of the casting or ingot solidification cooling, cooling rate from the surface to the center is different, so can form different crystal structure, characterized by the anisotropy of mechanical properties, also caused the acoustic performance of anisotropy, i. e. from the center to the surface have different sound velocity and acoustic attenuation. Of this anisotropy, ultrasound detection of casting size and location of the defect in the assessment of adverse effects.