Knowledge

Section 1: Bead Sand and Alkaline Phenolic Resin Self-Hardening Sand ​​​​​​​

The production of cast steel parts used to commonly employ water glass self-hardening sand, furan resin self-hardening sand and alkaline phenolic resin self-hardening sand for molding and core making.

I. Characteristics of Alkaline Phenolic Resin Self-Hardening Sand

Alkaline phenolic resin self-hardening sand is a high-performance casting material with the following features:

1. Good collapsibility: After the casting solidifies, the molding sand is easy to collapse, facilitating cleaning.

2. Fast hardening speed: It can complete hardening in a relatively short time, improving production efficiency.

3. Wide usable time range: The usable time of the molding sand is long, which is convenient for production planning.

4. Stable quality: As it does not contain furfural alcohol, no nitrogen, phosphorus, sulfur and other elements are produced during the curing process, avoiding defects such as sulfur penetration and needle-like pores on the surface of cast steel parts.

5. Good environmental friendliness: Few toxic and irritating gases are released during the curing process, having a small impact on the working environment.

 

II. Characteristics of Baozhu Sand

Baozhu sand is a non-quartz artificial sand with the following excellent physical and chemical properties:

1. Spherical particle shape: Baozhu sand particles are spherical, with a smooth surface and good fluidity, making it easy to fill complex sand cores.

2. High refractoriness: Baozhu sand has a high refractoriness and is neutral, suitable for various casting alloys, including stainless steel, manganese steel, and chromium steel.

3. Low gas evolution: Under the same strength requirements, using Baozhu sand can reduce the amount of resin used, thereby reducing the gas evolution of the mold (core) sand.

4. High strength and low breakage rate: Baozhu sand has high strength and a low breakage rate, with high durability and a high recycling rate, which can reach up to 98%.

5. Environmental advantages: Baozhu sand generates less casting waste (spent sand) and exhaust gas, and is hailed as a green casting material for the 21st century.

 

III. Application Advantages of Baotizhu Sand in Alkaline Phenolic Resin Self-Hardening Sand

1. Reducing resin usage: Due to the spherical shape and smooth surface of zircon sand, the resin usage can be reduced by 30% to 40% under the same strength requirements, thereby lowering production costs.

2. Improving casting quality: Zircon sand has a high refractoriness and is less prone to defects such as sand sticking. Moreover, the molding (core) sand has good fluidity, making it easy to fill complex cores and helping to enhance the surface quality of castings.

3. Enhancing working environment: Zircon sand releases less toxic and irritating gases during the processes of mixing, molding, core making, pouring, and shakeout, having a smaller impact on the working environment.

4. Increasing recycling rate: Zircon sand has high strength and a low breakage rate, with a recycling rate as high as 98%. This helps reduce the addition of new sand, lower production costs, and decrease the discharge of old sand, protecting the environment.

The application of zircon sand in alkaline phenolic resin self-hardening sand fully leverages the excellent properties of zircon sand, improving casting quality, reducing production costs, and enhancing the working environment. With the deepening of the green casting concept and the continuous advancement of casting technology, the zircon sand alkaline phenolic resin self-hardening sand process will play an increasingly important role in future casting production.

 

Section Two: Properties of Cinnabar and Comparative Experiments

I.Performance of Ceramic Foundry Sand

Al₂O₃ ≥72%

SiO₂ 12 - 25%

TiO₂ ≤4%

Fe₂O₃ ≤3%

K₂O + Na₂O ≤1%

Spherical shape

Bulk density: 2.0

Refractoriness: >1800℃

Thermal expansion coefficient: 7.2

PH: 7.0 - 8.0

Compared with silica sand and others, it has significant casting performance advantages:

The grains are spherical with a smooth surface. Under the same strength, the resin usage can be reduced by 30 - 40%, and the gas evolution of the molding sand is low. It has a high refractoriness and is neutral, suitable for various casting alloys. It has good fluidity, is easy to fill, can be reused, and has low local loss. It has high strength, low breakage rate, is durable, and has a high regeneration and recycling rate of up to 98%. It has a low thermal expansion coefficient, reducing defects such as casting veins. It has environmental advantages, generating less waste and exhaust gas, and is a green casting material. Core sand has high thermal conductivity, good permeability, and good collapsibility.

II. Comparison of Several Situations

1. Alkaline phenolic resin recycled sand

Ratio: Sand 100% + Resin 1.5% (by weight of sand) + Curing agent 20% (by weight of resin)

Gas evolution: 24h: 34

Compressive strength sample: 139

2. New silica sand

Ratio: Sand 100% + Resin 1.5% (by weight of sand) + Curing agent 20% (by weight of resin)

Gas evolution: 24h: 14.4

Compressive strength sample: 145

3. Baizhu sand (30/70)

Ratio: Sand 100% + Resin 0.9% (by weight of sand) + Curing agent 20% (by weight of resin)

Gas evolution: 24h: 9.8

Compressive strength sample: 183

4. Baizhu sand (40/70)

Ratio: Sand 100% + Resin 0.9% (by weight of sand) + Curing agent 20% (by weight of resin)

Gas evolution: 24h: 9.6

Compressive strength sample: 189

 

The results show that:

1. When the resin addition is reduced by 40%, the final strength increases by 39%; under the same strength, the resin addition can be reduced by 45 - 50%.

2. Compared with new sand, the gas evolution of the sand is reduced by 32%, which is equivalent to the proportion of resin addition.

3. The gas evolution of the recycled old sand mixture is very high, indicating poor recycling effect and more residual resin.

4. Based on the weight of the standard compressive strength sample, it is calculated that the weight of each cubic meter of Baizhu sand mixture is 30% heavier than that of quartz sand mixture.

 

Section Three: Points to Note

 

1. The main chemical components of zircon sand include Al₂O₃, SiO₂, etc. Among them, Fe₂O₃ and others can reduce the refractoriness and other properties. Al₂O₃ is the key component, and the higher its content, the fewer the harmful components. Practice shows that for alkaline phenolic resin self-hardening sand with zircon sand, the Al₂O₃ content is preferably above 75%.

2. The particle size of zircon sand: when using alkaline phenolic resin self-hardening sand with silica sand, high-silicon quartz sand with AFS 30 - 40 is generally used. If zircon sand with a similar particle size is used, the strength will be low. There are also cases where AFS 60 - 70 zircon sand is used. For the process of alkaline phenolic resin self-hardening sand with zircon sand, it is advisable to select raw sand with a finer particle size and a wider distribution.

3. Regeneration of zircon sand alkaline phenolic resin self-hardening sand: The regeneration of old sand is the key to the development of this process. The alkaline phenolic resin film is tough and difficult to regenerate. Mechanical regeneration is the mainstream process. Equipment regeneration has a good effect, and the reuse rate of zircon sand is high. The reuse rate of silica sand can reach 90%, and that of zircon sand can exceed 96%, generally around 98%.

 

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