Quality control details of the hottest cast iron i

Details of quality control in casting of cast iron inspection platform

cast iron riveted flat plate usually gb/t 17898 ⑴ 999 stainless steel in boiling magnesium chloride solution stress corrosion test method is cast with gray cast iron or nodular cast iron. Gray iron is called inoculated cast iron. It is widely used in the foundry industry with low cost, good shock absorption, wear resistance, mechanical properties and casting properties. To use gray cast iron to obtain qualified casting blanks, it must go through many links, such as grinding sand, molding, smelting, pouring, cleaning and inspection. To ensure the quality of castings, it is necessary to control all links in the casting process

1. Control of sand grinding process of inspection platform casting

the performance of molding sand will directly affect the quality of castings. Therefore, molding sand should have good permeability, wet strength, fluidity, plasticity and yield

strong adsorption

green sand should be polygonal or round natural stone sand with particle sizes of 55/1O0, 75/150, 100/200, so as to obtain better surface strength and sand inclusion resistance. When the clay content is the same, the thermal wet tensile strength of bentonite is higher than that of ordinary clay. Adding an appropriate amount of pulverized coal, sawdust, etc. to the wet clay sand can improve the anti sand inclusion ability, and prevent sand inclusion and sand sticking, so as to obtain castings with smooth surface. The moisture content of molding sand is set at about 6% to make it have better comprehensive properties

strictly follow the feeding sequence: old sand - new sand - clay - pulverized coal - water. The mixing and rolling time is set at 6 ~ 7min, and the mixing and rolling is carried out for about 5h. After mixing, sift, loosen and then reuse to make the molding sand loose, so as to improve the permeability and fluidity

2. Control of casting and smelting process of inspection platform

when producing gray iron castings, the quality of man-made furnaces and man-made materials must be strictly controlled, and their composition, block size and physical and chemical properties must be inspected and accepted as required

inoculated cast iron is a kind of gray cast iron with flake graphite, but its manufacturing principle is different from that of ordinary cast iron, and the inoculation process is increased. An appropriate amount of inoculant is added to the molten iron with low carbon and silicon components to inhibit its excessive graphitization. Generally speaking, the carbon content of raw molten iron is between 2.8 ~ 3.0%. Due to the low carbon content of inoculated cast iron, a sufficient amount of scrap steel is added to the furnace charge. The content of silicon is between 0.9 ~ 1.5%, so as to increase the amount of inoculant and improve the mechanical properties of castings. When the sulfur content and manganese content are in the range of 0.08 ~ 0.12% and 0.9 ~ 1.2% respectively, if the manganese content is too high, cementite will appear in cast iron. Phosphorus content is less than 0.12%. If its content is high, it will affect the strength of castings

3. Inspection platform casting molding process control

molding process control is the key process of generating castings, which directly affects the quality of castings. Mainly pay attention to the following aspects:

1) pattern: pattern is the main process equipment of casting production, and it is also the first process of casting production, while ensuring the geometric dimension. Production scale and convenience should also be considered. The first thing to consider in the manufacturing process is its technological structure and performance. On the one hand, improve productivity, on the other hand, ensure quality. In the process of use, the integrity of the pattern should be checked to ensure flawless use. If there is a defect, it can only be used after repair. Pay attention to the knocking force when lifting the mold. The aluminum mold should be knocked with wooden blocks to reduce the damage of the aluminum mold

2) reasonable process: the operator should operate in strict accordance with the process, calculate the casting structure to make the pattern manufacturing simple and convenient, so that the number of parting surfaces is small, with draft angle, the number of sand cores is small, there is a reasonable wall thickness, and there is a transition at the connection. Choose a reasonable gating system to make the castings solidify in order to obtain castings with uniform structure

3) box closing: box closing is an important link that cannot be ignored. The floating sand on the mold surface should be cleaned, aligned according to the mark, and attention should be paid to the amount of wrong boxes, which is an important means to reduce the deviation of castings

4) core lowering: the core lowering shall be stable and the floating sand shall be cleaned. The sand core shall be placed well to prevent the occurrence of eccentric core

5) drying: for the drying process of dry mold molding, it should be operated according to the operating procedures, and the drying time should be more than 8h, so as to prevent sand, pores and other defects caused by impervious drying

4. Inspection platform casting pouring process control

pouring can be carried out through the preparation of the above links. Before pouring, the casting water shall be inoculated and slagged. In the pouring process, the flow should not be cut off and stable, so as to avoid sand washing and the formation of sand holes. In case of fire escape, the parts with missing casting water shall be blocked in time and the casting water shall be supplemented to reduce defects such as cold shut and insufficient pouring

5. Check the control of the cleaning process of cast iron flat casting

the cleaning process is to clean the castings from the mold after the castings are cooled, so as to obtain castings with no defects on the surface

1) sand falling: the casting must be fully cooled before pulling out the mold, which is generally required to be no less than 3H. If the time is too short, surface chilling will occur, resulting in high hardness and difficult cutting. When the casting is large, it may produce hot cracks, and the internal stress of the casting is large, which is easy to cause deformation and affect the overall dimension of the casting

2) sand cleaning: to obtain castings with good surface finish, small live parts can remove the sand on the surface by cleaning the drum. Large live parts shall be shot blasted to remove the sand on the surface. The bonded sand on the non machined surface must be cleaned to prevent it from falling off and entering the bearing chamber when it is loaded into the finished product, which will have a negative impact on the use of the bearing

3) aging treatment: General castings should be aging treated to reduce the internal stress of castings and obtain good performance

4) control of inspection process: through inspection, the defects of castings are fed back, the causes are found and analyzed, and measures are taken in time to reduce the occurrence of casting defects. (end)