Casting quality inspection results

Casting quality inspection results are usually divided into three categories: qualified products, repaired products, and scrap products.
1) Qualified products refer to castings whose appearance quality and internal quality meet relevant standards or delivery acceptance technical conditions;
2) Reworked products refer to castings whose appearance quality and internal quality do not fully meet the standards and acceptance conditions, but are allowed to be repaired and can meet the standards and technical requirements for casting delivery acceptance after repair;
3) Scrap products refer to castings that are unqualified in both appearance and intrinsic quality and are not allowed to be repaired or that still fail to meet the standards and casting delivery acceptance technical requirements after repairs. Waste products are divided into two types: internal waste and external waste. Internal waste refers to the waste castings found in the foundry or casting workshop; external waste refers to the waste found after the delivery of the castings, which causes far greater economic losses than internal waste.
Factors affecting the solidification mode of castings
There are many ways to solidify castings. During the solidification process of a casting, its cross section is generally divided into three zones: 1-solid phase zone 2-solidification zone 3-liquid phase zone. The greater influence on the solidification zone is the width of the solidification zone, and the solidification mode is divided accordingly. First, intermediate solidification: The solidification of most alloys is between layer-by-layer solidification and pasty solidification. Second, solidification layer by layer: Pure metals and eutectic alloys have no solidification zone during the solidification process. The liquid and solid phases are clearly separated by a boundary. As the temperature decreases, the solid phase layer continues to increase and the liquid phase layer continues to decrease. Straight to the center. Third, pasty solidification: The alloy crystallization temperature range is very wide. During a certain period of solidification, there is no solid layer on the surface of the casting. The solidification zone runs through the entire section, first mushy and then solidified. Relevant experts said that the factors affecting the solidification mode of castings are summarized: first, the temperature gradient of castings. When the alloy crystallization temperature range is constant, the width of the solidification zone depends on the temperature gradient between the inner and outer layers of the casting. The smaller the temperature gradient, the wider the solidification zone. (The temperature difference between inside and outside is large, cooling is fast, and the solidification zone is narrow). Second, the crystallization temperature range of the alloy. Small range: The solidification zone is narrow, the more likely it is to solidify layer by layer. For example: sand casting, low carbon steel solidifies layer by layer, and high carbon steel solidifies in the form of paste.
The casting defect repair agent is a two-component, clay-like, room-temperature curing polymer resin glue, a polymer-metal composite cold welding repair material with metal and alloy as reinforcing filler. It has high bonding strength with metal, can basically keep the same color, and has the characteristics of wear resistance, corrosion resistance and aging resistance. The cured material has high strength, no shrinkage, and can be processed by various types of machinery. It has excellent properties such as anti-wear, oil resistance, waterproof, and various chemical corrosion resistance, and can withstand high temperatures of 120°C.
use
Casting defect repair agent is a high-performance polymeric metal material compounded by a variety of alloy materials and modified toughened heat-resistant resin. It is suitable for repairing various metal castings and various casting pores, blisters, and pits with defects greater than 2mm. , repair and bonding of cracks, wear and corrosion. It is generally used to repair various casting defects that do not have strict color requirements. It has high strength and can be processed together with the base material for various types of machining. [2]
How to detect
The properties of the casting itself directly affect the quality of processing, among which the hardness value is an important indicator that determines the processing of castings.
1) Brinell hardness: It is mainly used to measure the hardness of castings, forgings, non-ferrous metal parts, hot-rolled billets and annealed parts. The measurement range is ≯ HB450.
2) Rockwell hardness: HRA is mainly used for high-hardness specimens to measure materials and surface hardness with hardness higher than HRC67, such as cemented carbide, nitrided steel, etc., and the measurement range is HRA>70. HRC is mainly used to measure the hardness of steel parts (such as carbon steel, tool steel, alloy steel, etc.) after quenching or tempering. The measurement range is HRC20~67.
3) Vickers hardness: used to measure the hardness of thin parts and steel plate parts, and can also be used to measure the hardness of surface hardened parts such as carburizing, cyaniding, and nitriding.