Factors affecting no-bake furan resin sand casting

There are many factors that affect the quality of furan resin no-bake sand, such as the properties of raw sand and reclaimed sand, the type of resin and curing agent, and the amount added. The factors of sand quality also include sand mixing ratio, raw material viscosity, sand temperature, compactness, humidity, and the type of Resin sand mixer.

1. Influencing factors
1.1 Sand mixing ratio
During the use of resin sand, there must be a process of alternating old and new sand, regenerated sand is eliminated, and new sand is replenished, so that the entire sand system can continue to operate. However, the proportion of sand mixing must be properly controlled, adding too much, although the quality of the molding sand is improved, but the regeneration frequency of the old sand is reduced, and the sand resources are wasted. Sanzhuji carried out experiments on mixed sands of 1:9, 2:8, 3:7, 4:6, 5:5, new sand and other proportions of all old sand respectively. From this, it can be concluded that it is very meaningful to adjust the sand mixing ratio from the whole old sand to 1:9, 2:8, or even 3:7. Not only the strength of the resin sand is doubled, but the resin content can also be reduced, which is beneficial to the quality of the site. and cost control.

1.2 Raw material viscosity
Under the same conditions, the viscosity of resin and curing agent varies greatly, and the flow rate will also change. The viscosity of raw materials varies greatly between different foundries and even different batches. Therefore, the change of the viscosity of the raw material affects the accuracy of the added amount. When replacing, when the viscosity changes, the frequency of the pump should be checked to ensure sufficient flow.

1.3 Humidity
When the resin and the curing agent undergo polycondensation reaction, water is precipitated, and in the case of high ambient humidity, the water is not easily volatilized, resulting in poor hard permeability of the molding sand and reduced strength. For the variable of humidity, the study found that under the condition of humidity of 93%, the difference in tensile strength between 24h and 48h is about 0.3MPa. It can be seen that humidity mainly affects the hardness and permeability of resin sand. This guides the foundry to properly extend the use time of resin sand in the actual production process in the case of high humidity, so that it is completely hard and penetrated.

1.4 Strength of no-bake sand.
Many foundries use tensile strength as a testing method. As the final strength, the result can only be obtained after 24 hours. It is difficult to guide the actual production of the day, which makes the production task lag. This requires us to find a quick way to judge the strength. Sanzhuji combined with the foundry through a large number of tests to detect the strength values at different times. The study found that after 2MPa, the molding sand has been completely hardened, and this strength can be used to estimate the 24H tensile strength. The research results show that the final strength is about 2.5~3 times of the initial strength, and the strength basically does not change after 8 hours of sand mixing, which is almost equal to the final strength.

1.5 hardness
The surface hardness of the mold is very high after the hardening of the resin self-hardening sand. Many foundries touch the mold and core surface after curing, feel and estimate its strength value. In fact, what we feel is only hardness, not strength. Surface hardness and mold strength are not the same concept. Sanzhuji studied the strength and hardness of the samples by tamping, layer-by-layer compaction, and vibrating table vibrating, and found that no matter what kind of molding method has no effect on the hardness, this shows that as long as the mold can be hardened, the hardness is high, but It does not represent the strength of the shape and core.

1.6 firmness
Furan resin self-hardening sand has good fluidity, even if it is not compacted, it will be self-hardening. Although the degree of compaction has no effect on the hardness, it has a significant impact on the strength. The strength of the vibrating table is almost no compaction. The strength of layer-by-layer compaction is also better. In actual production, compactness and air permeability are contradictory. We need to classify it. Many foundries use the step-by-step method for compaction. Some corner bosses, cold iron and other positions are compacted manually. For some important cores or those severely washed by molten iron, a 3D Vibration Table must be used to ensure the casting mold. strength and improved surface stability.

1.7 Sand temperature
The lower the sand temperature, the longer the usable time, the slower the reaction, but the lower the final strength. It is appropriate to control the sand temperature at 20~30℃, not only the final strength is high, but also the usable time is moderate, which is easy to control the hardening speed in each season. A lot of experience has shown that it is very beneficial to heat metal molds or resins in winter, which ensures the hardening speed of the mold and the mold-releasing time. In the summer when the ambient temperature is high, the production task is urgent, and the sand temperature is difficult to reduce, in order to control the available time, increase the proportion of mixed sand, and mix a certain proportion of curing agent.

2. Sanzhuji suggested
2.1 The sand mixing ratio should be 1:9, 2:8 and 3:7.
2.2 When the raw materials of different foundries and batches are replaced, the resin and curing agent pump flow must be calibrated.
2.3 In the case of high humidity, the use time of resin sand should be appropriately extended to make it completely hard.
2.4 The hardness of the surface and the strength of the mold are not the same concept, and the strength of the mold and core sand cannot be judged by the hardness.
2.5 The degree of compaction obviously improves the strength of resin sand, but it will affect the air permeability. Different compaction methods can be selected according to the needs.
2.6 The sand temperature should be controlled at 20~30℃. In winter, pay attention to heating the metal mold and resin. In summer, you can adjust the curing agent or use two liquid pumps to adjust the hardening speed of the resin sand.
2.7 It is recommended to use self-hardening sand recycling equipment to recycle old sand, which can efficiently remove impurities on the surface of old sand.

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.