The sand-iron ratio refers to the ratio of the total mass of the sand used in the same mold to the quality of the casting during the casting production process. At present, the production of large-scale castings mostly relies on the resin sand manufacturing process. The resin and curing agent required by the resin sand process are expensive and are an important part of the cost of casting molding production. Therefore, reducing the amount of resin and curing agent used is an important part of reducing the production cost of castings. First, according to the required sand strength, try to control the low amount of resin curing agent added, and then strictly control the sand-iron ratio in the process to reduce costs. the goal of.
1 The effect of sand to iron ratio
1.1 Impact on cost
The resin curing agent is expensive, reducing the ratio of sand to iron, that is, reducing the amount of molding sand, and reducing the amount of resin curing agent used, thereby reducing production costs. For example, if the ratio of sand to iron is reduced from 6 to 5, 1t of molding sand can be saved for every 1t of casting produced. , The current production cost of resin sand is about 300 yuan / year, if calculated according to the annual output of 10,000t, the annual production cost can be saved by 3 million yuan.
1.2 Influence on the weight loss of recycled sand
In general, the higher the sand-iron ratio, the higher the regenerated sand on ignition, the larger the gas generation of the molding sand when it is reused, and the porosity defects in the castings, which affect the product quality. Therefore, reducing the sand-iron ratio will reduce the ignition loss of the reclaimed sand, and the castings will not be prone to defects such as pores, and the inherent quality of the product will be improved.
1.3 Influence on the temperature of recycled sand
The size of the sand-iron ratio directly affects the average temperature of the old sand and the reclaimed sand. The lower the sand-iron ratio, the higher the average temperature of the old sand. When the temperature is low, it is very beneficial to improve productivity and save energy, but when the temperature is high, in order to ensure the quality of the molding sand, it is necessary to increase the corresponding sand temperature cooling device to reduce the sand temperature to ensure the sand mixing temperature. Best condition at 20-30C.
2 Daily management of sand-iron ratio
In addition to relying on design, daily standardized management is also a very important work link to reduce the sand-iron ratio. Sanzhuji suggests that according to the company''''s sand-iron ratio control ability and design ability, the completion goals of various products and single products should be formulated. For example: large cylinder products ≤ 4, ring products ≤ 8.5, etc. The second is to realize the daily statistics of the amount of molding sand and resin curing agent used in the molding process of a single product, and finally realize the statistics of the completion of the sand-iron ratio of a single product, compare it with the process design value, and carry out corresponding quantitative promotion. , It is also necessary to regularly conduct special statistical analysis on poorly completed single-piece products and classified products, further improve the design and field operations, and achieve the purpose of reducing the sand-iron ratio.
3 Methods of reducing the ratio of sand to iron
3.1 Tooling Design
The design of the sand-iron ratio tooling should be based on ensuring the operability of the product modeling process and the safety of the pouring process. Therefore, the following requirements should be paid attention to when designing the tooling:
3.11 Ensure the sand consumption of the product mold (resin sand thickness)
The appropriate sand intake is determined according to the size of the production castings. Taking large steel castings (generally refers to steel castings with a single weight of more than 10t) as an example, the sand intake of the mold is ≥ 150mm, and the sand intake of the runner is ≥ 200mm.
3.12 The tooling should be assembled as a whole with the sand box as much as possible
Assemble in advance before modeling to reduce the operating intensity of employees during the quicksand process.
3.13 Tooling should be recyclable and reusable
Since the product structure is not the same, it is necessary to design and use detachable and universal tooling as much as possible to save the cost of tooling production.
3.2 Examples of classified product design
Classify according to the type of products actually produced, and give examples of the tooling design of various products as follows. Foundry enterprises can classify according to the types of products they produce, formulate corresponding design standards, guide design and on-site production, and achieve the purpose of reducing the sand-iron ratio. .
3.2.1 Large cylinders and
Valve shell products The shape of large cylinder products is relatively uniform, generally semi-circular arc shape, with the characteristics of large wall thickness and heavy weight; valve shell products are irregular in shape, and the number and direction of nozzles are different. These two types of products, The measures to reduce the ratio of sand to iron are generally composed of unilateral tooling: the unilateral tooling is mainly assembled with an N-shaped L-shaped screw, and then connected to the inner side of the sand box with a screw. The N-shaped L-shaped is welded with ordinary carbon steel plates. The size of the sand box and the amount of sand eaten are different, so it is necessary to design different sizes of tooling to meet the needs of use.
3.2.2 Rotary body and ring products
Rotary body products have a lot of process information in the inner cavity, and the inner cavity part is not easy to assemble the tooling. Only the outer part can be assembled on the premise of satisfying the sand consumption. Ring products are currently found in castings One of the products with the highest iron ratio. This type of product has the characteristics of large outline size, small wall thickness, and low product weight. If all resin sand is used for modeling, the sand-iron ratio will reach at least 15. There is a large drop space. At present, the design of the sand-iron ratio of ring products is divided into two parts: the inner cavity part is placed with circular and polygonal tooling, and the outer part is assembled with corner box belts.
4 Modeling operation methods
4.1 Filling dry sand blocks: Filling dry sand blocks is the most common measure in the process of reducing the ratio of sand to iron. By recycling some undisintegrated sand blocks in the process of falling sand, the parts with a large amount of sand eat randomly during the molding process. It is filled and placed to replace the volume of resin sand, so as to achieve the purpose of reducing the sand-iron ratio.
4.2 Standard tool loading sand block:
According to the tonnage of the castings and the size of the sand box, standard tooling sand blocks of different specifications can be made. The size should not be too large. It should be mainly carried by people. It can be used in both casting molds and sand cores. Attention should be paid to: When using multiple sand-packing blocks at the same time in an area, ensure that the amount of sand between the sand-packing blocks is greater than 50mm. The sand-packing blocks should be connected with the main board, box belts, connectors and other parts of the sand box with reinforcing ribs as much as possible. The core bone (suspended tire skeleton) is connected to ensure the strength and prevent the problem of mold cracking.
4.3 Run dry sand:
When modeling, according to the size and shape of the internal sand consumption of the product, various shapes of tooling can be assembled to fill the dry sand, thereby saving the amount of resin and reducing the sand-iron ratio.
5 Conclusion
The reduction of the sand-iron ratio can greatly reduce the production cost and reduce the porosity defects of the castings, but at the same time it will bring about the problem of the increase of the sand temperature. It is necessary to take the control measures of the sand temperature to ensure the quality of the molding sand; the reduction of the sand-iron ratio, in addition to In addition to the standardization of the design, the daily management of the sand-iron ratio is also very important. How to motivate the operators to strictly implement the design through quantification and system improvement is an important part of reducing the sand-iron ratio. Quantitative promotion of the target value of similar products, and regularly analyze the reasons for the design and operation of poorly completed products, so as to continuously improve, improve and innovate; a large part of the reduction of the sand-iron ratio depends on the standardization of tooling design. Through the accumulation of daily experience and design innovation, find various methods suitable for you, summarize and formulate design standards and specifications, and reduce the sand-iron ratio from the design; the reduction of the sand-iron ratio depends not only on design, but also ultimately depends on On-site implementation, on the basis of strictly implementing the tooling process, corresponding measures such as filling dry sand blocks, standard tooling sand blocks, and drying sand are taken to further reduce the sand-iron ratio.
Qingdao Sanzhuji Equipment Manufacturing Co., Ltd. specializes in the production of Green Sand Molding Line,Self-hardening sand molding line,foundry machines,Sand molding machine,Sand casting equipment,sand mixer,GS high efficiency rotary mixer,Resin sand mixer,no-bake resin sand mixer,Jolt squeeze molding machine/Jolt-squeezing moulding machines,Multi- Piston Moulding Machine/Hydraulic multi-piston moulding machine,sand casting molding machine,sand reclamation equipment，foundry molding machine,flaskless moulding machine,shot blasting machine,dust collector,according to the amount of old sand recovered Carry out plan customization, and provide sand reclamation equipment installation, commissioning, and training. Welcome guests to visit the factory.
