1. Cold core box core shooting method
1. Introduction of cold box
At room temperature, the method of making the sand core in the core box by hardening quickly is called the cold core box method. The cold core box is an efficient core making process. Compared with the hot core box and shell core, it has the advantages of high efficiency, energy saving, and good working conditions. It is now widely used in casting production.
The quality and speed of core making in the cold box method are closely related to the ambient temperature, humidity, blowing temperature, blowing pressure, and blowing time. The measures that should be taken to ensure the quality of the sand core are: Shorten the storage time of the sand mixture; when the temperature of the original sand is low, the sand temperature regulator should be opened to appropriately increase the sand temperature to ensure the hardening speed of the sand core; Blowing time; different blowing gas requires different blowing temperature, SO2 at room temperature means that the gas does not need to be heated, and triethylamine and methyl formate are liquid at room temperature, and it is easy to condense in the pipeline in winter. Temperature and heat preservation measures to ensure that the content of triethylamine (methyl formate) in the hard-blow gas is relatively stable; the triethylamine method, modified silicate sand carbon dioxide / compressed gas composite blowing method is very sensitive to air humidity, compression Air needs to be dehumidified.
2. The cold box method includes:
Amine blowing core box method, SO2 cooling core box method, basic phenolic resin blowing methyl formate cooling core box method, water glass blowing methyl formate cooling core box method, basic phenolic resin blowing carbon dioxide gas cooling core box method, water Glass sand blowing carbon dioxide cold core box method, water glass sand blowing methyl formate cold core box method, modified silicate sand blowing carbon dioxide / compressed gas composite blowing method, basic phenolic resin sand blowing carbon dioxide cold core box method, double Component basic phenolic resin sand blowing carbon dioxide cold core box method
3. Composition of cold box
A casting binder aimed at the problem of low fluidity leading to low strength and providing extended storage life leading to higher tensile strength, which is made of (a) epoxy resin, (b) acrylic acid Esterified polyisocyanate, (c) reactive unsaturated acrylic monomer and / or acrylic polymer, and (d) oxidizing agent. The binder is a casting mold that is mixed with cast aggregate and cured with a gaseous amine by a cold box core making method to obtain a mold that can be used as a cast metal part.
2. Hot core box shot core method
1. Brief introduction of hot box
The hot core box method is a method for manufacturing cores in casting production. The sand mixed with foundry sand, thermosetting resin and curing agent is injected into the core box with a heating device and heated to 180-250 ° C to heat the sand material close to the surface of the core box. The agent can be polycondensed and hardened in a short time to form a core, which does not need to be baked in the oven, which has the advantages of shortening the production cycle. Moreover, as long as the surface of the sand core has a hard shell of 5-10 mm, it can be taken out from the core box. The core sand in the center part can make the residual sand harden by itself under the effect of the residual heat and the heat released by the hardening reaction. The production of medium and small sand cores with high dimensional accuracy (the maximum wall thickness of sand cores is generally 50-75mm) provides a very effective method, especially suitable for the production of large batches of castings in automobiles, tractors or similar industries.
2. What are the characteristics of the hot core box making process
The core is made by the hot core box method. The core sand is prepared by using liquid thermosetting resin and catalyst, and filled into the core box heated to a certain temperature. The sand core close to the surface of the core box is heated, and the binder is in
It can be polycondensed and hardened in a short time (it only takes a few minutes to cure). It provides a very effective method for the rapid production of medium and small sand cores with high dimensional accuracy (the core thickness of the sand core is 50 to 75mm), especially suitable for the production of small and medium sand in the automobile, tractor or similar industries. core.
However, the core made by this method has the following disadvantages: high energy consumption; more gas generation, which makes the operator feel uncomfortable; because the core box needs to be heated to a higher temperature, it must be made of metal, and the manufacturing process is relatively complicated: the thickness of the sand core is limited In particular, when there is a sudden change in the size of the cut, some cuts are prone to excessive hardening, while others have insufficient hardening, and the core sand core breakage rate is human. If the sand core is too thick, it is designed as a block, and then bonded into a medium and narrow sand core, which is not only conducive to the solidification of the sand core, but also saves the original sand and resin.
The core-making process of the hot box adopts furosen resin as the binder, and also uses thermosetting phenolic resin and urea-formaldehyde resin. However, the shelf life of thermosetting phenolic resin is short, generally only can be stored for three months, and it is shorter in summer. Phenolic resin sand is not as good as urea-formaldehyde resin in normal temperature strength and hardening speed, but it has very little nitrogen content, and its thermal strength, gas generation and moisture resistance are better than urea-formaldehyde resin sand. Urea-formaldehyde resin has lower cost, high strength at normal temperature, fast curing speed, good sand core performance, but resin viscosity is large, small and easy to mix, sand core has low thermal strength, large gas output, high hygroscopicity, high nitrogen content . During casting, the urea-formaldehyde resin is decomposed by heat, and ammonia (NH3) will be generated. The ammonia is further decomposed into nitrogen and hydrogen, and at the same time will diffuse into the metal. Therefore, the higher the nitrogen content in the resin, the hotter the porosity of castings. Therefore, some foundries that do not use a good amount of resin are often accustomed to using furan resin.
3. Operation process of hot box method
1. Observe the general operating rules of casting equipment.
2. Before work, you must also observe:
a. Check whether the position of the travel switch and the bumper on the equipment are correct. If they are not correct, they must be adjusted.
b. Turn on the power supply, open the compressed air valve, first manually jog the various agencies, then use the automatic method to perform a cycle test, and confirm that everything is normal before production.
3. You must also observe:
a. After the equipment is started, when one cycle is not completed, it is not allowed to adjust the electrical midway, so as to avoid malfunctions and cause personal accidents;
b. After each cycle of the equipment, the residual sand on the core box must be removed with a nozzle and sprayed with a parting agent;
c. It is forbidden to put your hand into the gap between the core box and the clamp, or put your hand on the guide rail before cutting off the power supply and the air source, to avoid personal accidents.
d. Air injection is generally not allowed. If air injection is necessary, the compressed air valve must be closed.
e. If operated by hand, it is not allowed to operate two electrical switches at the same time.
4. After work, you must also observe:
a. Operate all electrical switches to restore each mechanism of the equipment to its original position, and then cut off the power supply and air supply;
b. Fold down the sand-blasting head to clean up the accumulated sand and sticky sand;
c. Remove the sticky sand in the exhaust plug;
d. Remove the sand shooting cylinder, remove the sticky sand in the gap, and finally use paraffin to wipe the inner wall, but do not block the gap;
e. Remove the accumulated sand on the gate and apply graphite powder on the gate to reduce friction;
f. Remove the dust and sand on the guide rails and guide rods, and apply a layer of lubricant.