Nano level cementing material in use for foundry sand, preparation method and usage

Abstract

An adhesive for the nano-class casting sand is prepared from phenol, aldehyde, clay, alkali catalyst and silane coupling agent through stirirng phenol while heating to 55 + / -2 deg.C, adding activated solid acetate of alkali metal, condensation reaction, adding alkali catalyst, polycondensation reaction, and intercalating the clay for nano-class dispersing.

Description

technical field [0001] The invention relates to a casting sand binder, in particular to a casting binder for self-hardening mold (core) sand, a preparation method and application thereof. The foundry binder of the present invention is not only applicable to the making of ordinary casting sand molds (cores), but also especially suitable for large and complex castings with special requirements for mold (core) sand, such as large nuclear power equipment, hydrogenation reactors, 200,000 Cylinder blocks of generator sets above kilowatts and gas turbines, large steel rolling mill archways, etc. Background technique [0002] In recent years, thermosetting phenolic resins, especially liquid alkaline phenolic resins prepared with alkaline catalysts and in the presence of strong alkaline media, have been widely used as mold (core) sand binders in the foundry industry and have developed rapidly. quick. However, there are still some shortcomings in existing products: one is that the t...

AI Technical Summary

Problems solved by technology

However, there are still some shortcomings in existing products: one is that the tensile strength of the basic phenolic resin used in these binders is too low, especially for sand molds (cores) made at low temperatures (such as below 10°C), the strength cannot meet the requirements. The needs of production; the second is that after the prepared resin sand is placed for a long time, such as more than 100 minutes, the strength of the sand mold (core) mixed with these resins will drop a lot. Finally, its strength is only about 0.40Mpa, which cannot meet the production needs; third, the stability of the resin is poor, and the shelf life of the resin is no longer than three months. According to actual measurements, after one month of storage at 25°C, the initial performance drops by 30%. The above; Fourth, the surface stability of the sand mold (core) made in summer is not good, which may easily cause defects such as sand washing and internal sand inclusions during casting, and the pass rate of MT and UT flaw detection is low

[0003] ---The basic phenolic resin used has low activity and high viscosity. When making sand molds (cores), the fluidity of the sand is not good, and the internal structure of the sand molds (cores) is uneven and dense, resulting in low overall performance; Low utilization

[0004] ---The molecular structure of the curing agent matched with these resins is unreasonable, the curing rate is too fast, and the curing time (when the tensile strength of the sand mold drops by 20%) is measured to be less than 80 minutes (25°C); the prepared resin sand has a short storage time, However, when making large and complex sand molds (cores), it takes a long time, causing the sand molds (cores) to be easily delaminated, unable to form a solid whole, and have low strength.

[0005] Due to the above reasons, the existing foundry sand binders cannot meet the needs of large castings in terms of products or use, such as large nuclear power equipment, hydrogenation reactors, generator sets above 200,000 kilowatts, and cylinder blocks of gas turbines. , large rolling mill archway, etc. The molten steel casting temperature of these castings is as high as 1500 ° C, the weight is 700 tons, the size changes greatly, and the wall thickness is from 10 mm to ≥ 1000 mm. The use time of resin sand, the strength and stability of sand mold (core) Sex and other quality indicators have high requirements

[0006] In addition, the harmful components in the existing alkaline phenolic resin are too high: for example, the content of free formaldehyde and free phenol is 0.10%-3.5% and 0.20%-5%, respectively. During the process of boxing, baking, and casting, the site emits a strong irritating odor, and the operators have adverse reactions such as teary eyes, sore throat, dizziness, and nausea.

[0007] Except these problems that above-mentioned commercially available goods exist, according to the resin introduced in Chinese patents such as application publication number CN1385264A, when adopting its recommended curing agent to make large sand mold (core) at lower temperature, its strength, smell, usable Time is also a very prominent problem, especially the curing agent used in these patent application publications contains nitrogen, phosphorus, sulfur and other elements harmful to castings, such as hexamethylenetetramine or p-toluenesulfonic acid, etc., the intrinsic quality of castings Not high; and as the Chinese patent of application publication number CN1392196A, realize intercalation with existing technology and use is phenolic resin 2123, 2124 etc., simultaneously the curing agent that these resins are used is still aforementioned hexamethylenetetramines The foundry resin sand prepared with these resins has poor fluidity, poor sand mold (core) quality, low strength, high gas generation, and short service life, especially not suitable for making large and complex sand molds (cores).