Sand casting, also known as a sand molded casting, is a metal casting process characterized by using sand as the mold material. The term “sand casting” can also refer to an object produced via the sand casting process. Sand castings are produced in specialized factories called foundries. Over 70% of all metal castings are produced via a sand casting process.
We made a short description below to show you how a crusher wear part been made and packed in GUBT.
Technological process of sand casting
1. Drawing check
When we get the original drawings from the customer, the engineer examines the drawings and converts them into the production drawings with software. Finally, the production drawings will be handed over to the model department.
2. Wood mold
There are three steps of the mold production: At the first step, the model department will make the wood pattern blank according to the drawings from the customer. Then, the CNC is supposed to use to refine the wood pattern. The finished wood pattern must be in accordance with the drawings completely to retain the machining allowance and draft angle, which is the second step in the wood mold production process. Finally, the model department will take fine-tuning and verification of the finished wood pattern before it enters the sand mold department.
According to the drawings and wood mold, the sand mold department designs the number and configuration of the sandbox. The small castings just need the single or double sandboxes, the medium using 3 sandboxes, larger castings using four sandboxes or even more. The material of the castings is a combination of olivine sand and sodium silicate, which is used to make sure the finished products have the best quality，figure，and intensity. Besides, the Engineer will design the pouring gate and the riser based on the product size, shape, and materials from the customer requirements. [Remark 1]
Our factory is always smelting and pouring at night because the tremendous heat and energy will be released during the casting process. To make sure no impurities exist in the molten steel, the skilled workers are supposed to filter the impurities out of the smelting furnace when impurities float to the surface at the time of smelting. Simultaneously, the QC department will take out the molten steel samples with a spectrometer for chemical composition analysis, then check the chemical composition of molten steel and adjust the ratio of the material to reach the standard before start casting. The samples will be kept at least three years for traceability in the end. There are four melting furnaces in the factory, and two melting furnaces can produce 6 tons of the largest single crusher wear part.
According to the different sizes and shapes of the products, the casted sandboxes will natural cooling for 12 to 48 hours to ensure product quality and integral appearance. The skilled worker will take the castings out of the sandbox and get rid of the riser after natural cooling, and the blank with lividity color has been formed basically at that time.
The blank will be heat-treated in a heat treatment furnace that controlled and record the heat treatment report by computer completely. The blank is heated to the target temperature in the heat treatment furnace gradually and will stay for a period in a specified temperature range. After heat-treating, the blank need to hung up into the pool for quenching to make sure the integrity of the metal structure and the properties of the metal.[Remark 2]
Normally, there are two ways to make the cooling system for the heat treatment pool. The 1st way is injecting the cool air into the bottom of the pool to cooling the pool water, the 2nd ways is water circulation system, The second is through the establishment of water circulation system, by the water tank A cold water into the heat treatment pool, hot water discharged to the reservoir B for natural cooling. The second water cycle system, while increasing the cost of infrastructure, but can greatly improve the efficiency of the pool temperature control. To ensure quality and improve efficiency, we chose the second one.
After heat-treating, the blank will be sent to the skilled worker of the hand-polished group for grinding and trimming the burr of the product. At the same time, the QC department will issue a report with the metallographic examination for verifying and guaranteeing the metal structure and properties under the heat-treatment process.
Attachment：Mn steel metallographic test report.
To ensure the products meet the requirements of the drawings completely. The workers from the machining group who received the blank from the hand-polished group are supposed to cut off the excess parts from the roughcast with the CNC. The surface needs to be machined is always reserved in the wood pattern process, which guarantees enough working allowance during the blank production process. The QC department will check the appearance and size of the blank by the original drawing. Then the blank will be turned over to the next part after passing the check.
The finished castings needed to be painted with the color according to the RAL color chip system from the customer requirements in the paint workshop. On the one hand, the painting process is used to deal with non-processing sides, which makes the surface much more beautiful. On the other hand, anti-rust oil painted for the machining face, incase oxidative damage from long-term transport and storage.
11.Packaging and delivery
The composite material box is used for the smaller castings, such as cutting ring, distributor cone, lining plate, etc. There are a metal pallet, non-fumigation pallet or Solid wood pallet with an IPPC fumigation mark shall be used for packaging the jaw plate, cone, and other bigger castings. All castings are subject to secondary reinforcement during transport.
Remark 1. There are some noteworthy items during the sand mold process. The most important thing is to make sure the draft angle exists of the wood pattern no matter the original drawings require or not. The second is to make sure no damage for the internal structure of the sand mold production after the wood pattern out of the sandbox. The last is to cut off the draft angle during the polishing and machining process.
Remark 2. There is no need to quenching for high chromium products because of the special material and composition. High chromium products only need to heat and cooled in the heat treatment furnace to reach the quality standards.