JPS63212036A - Treatment of mold surface - Google Patents

Abstract

PURPOSE:To improve the heat resistance and corrosion resistance of a casting mold and to improve working environment by mixing sodium silicate with a standard liquid consisting of lignin sulfonate as a chief material to prepare a treating liquid for the mold surface and coating such treating liquid on the mold surface. CONSTITUTION:The standard liquid is prepd. by using the sodium silicate as the chief material and adding an alkaline soln. thereto and further, the sodium silicate is mixed at a prescribed ratio to this standard liquid to prepare the treating liquid for the mold surface. The treatment of the mold surface is executed by coating such treating liquid on the mold surface which is a surface to be poured with a molten metal and drying the coating. The treating liquid penetrates down to an adequate depth from the mold surface at this time and bonds among the particles of the molding sand to fix the surface layer part on drying, thereby forming the mold surface having high smoothness. The burn of the casting mold is thereby prevented and the casting surface is smoothed. The heat resistance and corrosion resistance of the casting mold are, therefore, improved and since no carbonaceous materials are used, the working environment is improved.

Description

[Detailed description of the invention] Industrial applications: The present invention relates to injected molten metal (hereinafter referred to as molten metal).

), and is cooled and solidified to form a casting of a predetermined shape, it is related to a mold surface treatment method that maintains a good working surface and improves the finish of the casting surface.

Background of the Invention: In casting, metal molds, sand molds, and special molds are used depending on the purpose of the four types of metals or the cast products to be cast. In particular, sand molds are most often used through various operations such as green molds and dry molds, and the majority of castings are produced by sand mold casting.

Cast steel, cast iron, copper alloy intermediates, and nickel alloys are almost all sand-cast, and aluminum alloys and magnesium alloys are also sand-cast in large quantities.

Conventional technology: To make a casting, a mold with a sprue, runner, riser base, necessary core, etc. is made according to each casting method.
Pour hot water into the raw mold or after drying. Next, the casting is removed from the mold, sand is removed, flash is removed, and the casting product is made into a cast product through inspection and finishing.

In such operations, heat resistance that is suitable for the properties of the molten metal is required in order to obtain castings of the original size without causing sand burning on the casting surface of the castings. In order to achieve this purpose, increase the durability of the mold, and make it easier to take out the casting, it is common practice to cover the nine cavities of the mold, the so-called mold surface, with a refractory slurry. There is. This refractory slurry has the function of preventing heat dissipation and controlling the cooling rate ft of intermediate materials, and is made of carbonaceous material. In particular, graphite has excellent heat resistance, thermal shock resistance, and corrosion resistance, and has a layered structure that satisfies the above conditions, and is widely used as a coating agent for mold surfaces such as sand molds. It is applied by applying it to the mold surface using a casting brush or the like.

Problems to be solved: Sand molds are economical and advantageous because they are easy to create a casting plan and can cast relatively large objects, but they do not have the equipment to prepare and recover suitable molding sand. This requires a lot of work, and the work area is often polluted by the unruly sand, and there is a lot of dust, making the work site likely to be in poor condition. Furthermore, the graphite used as a mold coating agent is suspended in a solution or applied to the mold surface in the form of a colloid, so after drying, it forms a layer of fine powder that gets entangled in the fine pores of the mold surface and covers it. The dust was easily peeled off, which, together with the molding sand, further encouraged the generation of dust.

Problems and means for eliminating them: The present invention was made to solve the above problems, and it was decided not to use graphite, which is a difficult point on the work platform and easily peeled off, as a coating agent. That is, it has the function of suppressing the peeling and disturbance of the surface structure of the mold surface, and also makes it possible to impart all the properties of heat resistance, thermal shock resistance, and corrosion resistance to the mold in terms of functions for molten metal. The purpose is to provide a method for processing the SIa surface.

Effect of the invention: A mold whose mold surface that comes in contact with pouring metal is treated by the method of the present invention has excellent heat resistance and improves the durability of the mold.

In addition, by forming a compacted structure on the mold surface without impairing air permeability, it is possible to prevent sand from burning on the casting surface of the casting, and to obtain a casting with a smooth surface finish.

Example: The casting method of the present invention involves applying a specific solution to the surface, placing it on the surface layer where fine and J-grained foundry sand gathers, and caking it with heating and drying to form fine particles. This creates pound functions between the grains.

The specific solution used in the present invention, namely the mold surface treatment solution (
Hereinafter, F1 will be simply referred to as treatment liquid. ] is based on lignin sulfonate such as calcium or sodium salt of lignin sulfonic acid, to which an alkaline solution such as NaOH aqueous solution is added to prepare a standard solution, and then sodium silicate is mixed with this standard solution. This can be obtained by

The lignin sulfonate used in this example preferably has a solid concentration of about 50%, a specific gravity of about 1.265 at 20° CVC, and a pH of 5 to 6 when made into an aqueous solution. Risa Co., Ltd./Product name Sunextract C
etc. can be used. Sodium silicate is a 0-C1N substance with a composition of Na20・n5i02, which is called water glass.
It is preferable that the molar ratio of a2t) and StO is in the range of 2.8 to 8-1, and the aqueous solution has a Baume degree of 42 to 53 degrees.

The method of the invention was applied to a dry sand mold. Add 10% NaO,H aqueous solution to i part of the above Sun Extract C100]
A standard solution was prepared by removing tt and tm. In this standard solution, the solid content concentration of Sunextract C was 85% or more. Next, the reference solution was mixed in 8 stages of 20, 80:p and 400:p with 100 parts of the liquid sodium silicate as described above, and treatment solutions (a), (b), and (c) were prepared. I got it. The treatment solutions (a), (b), and (c) thus obtained were applied to the mold surface in the same manner as a conventionally used graphite mold coating agent. As a result, the treatment liquid was 0.5 to 2.5 J from the mold surface.
The molding sand was impregnated to a depth of EIIa degree, and as it dried, the molding sand was bonded to each other to solidify the surface layer, resulting in a mold surface with rich smoothness. If the standard liquid mixed with 100 parts of IJIl is less than 20 parts by weight, the caking properties of the surface layer will be poor and the function to prevent the molding sand from flaking will be insufficient, and the amount of 4OjIL will be less than 20 parts by weight. If it exceeds 100 mm, the fine particles will not only be bonded to each other, but will also fill in between the particles, which will impede air permeability and tend to make the casting surface IfJ coarse.

Effect of the invention: It is well known to be used as a binder for water glass, pulp waste sand, or refractory materials, but it is necessary to mix and prepare all of these under predetermined conditions and apply only to the surface layer of the mold surface. There are no examples of this.

A mold whose entire S plate surface has been treated by the method of the present invention exhibits the same heat resistance during pouring as when a conventional coating agent containing graphite as the main ingredient is applied. Furthermore, the mold has excellent heat resistance, 4R shock resistance, and corrosion resistance, and in particular, the surface structure of the mold surface is prevented from peeling off or collapsing before and after pouring. In addition, fine dust is not generated not only when treating the mold surface but also when dismantling the mold, improving the occupational hygiene and environment of the foundry workplace, and having great industrial applicability.

Claims (1)

[Claims] The main ingredient is lignin sulfonate, an alkaline solution is added to it to make a standard solution, sodium silicate is mixed with this standard solution to prepare a mold surface treatment solution, and the mold surface in contact with the pouring surface is treated as described above. A mold surface treatment method characterized by applying a liquid and drying it.