JPS606734B2 - Anti-sulfurization coating for organic binder molds - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coating mold that prevents the dilution phenomenon that occurs near the surface of a casting when manufacturing a casting using an organic sticky mold, which is a type of casting mold. .

Organic binder molds are made by adding organic binders such as furan resin or phenol resin to foundry sand, organic acids such as paratoluene sulfonic acid, xylene sulfonic acid, benzene sulfonic acid, and phosphoric acid, sulfuric acid, etc. as hardening agents. This mold is used to harden the adhesive by adding an inorganic acid or S02 gas.

In this case, an organic acid containing S or S02 gas is generally used as a curing agent. Organic sticky molds have many advantages such as easy sand recycling, resource saving, reduction of industrial waste, and improved productivity, but on the other hand,
When the metal is injected into the mold, the organic curing agent contained in the mold and the sulfuric acid generated by the S02 gas are thermally decomposed by the heat of the metal, resulting in sulfur gases such as S02 and 2S. occurs.

S from these gases diffuses into the vicinity of the surface of the casting, creating a so-called sulfurization phenomenon in which a concentrated layer is formed. Usually, a small amount of S exists as an unavoidable element in metals.

S dissolves into the metal matrix to some extent, but it mainly combines with elements that have a strong tendency to form sulfides, such as Fe and Mn, and forms sulfides such as FeS and MnS, which often exist as nonmetallic inclusions. . Such sulfides generally do not have a positive effect on the properties of the metal, but when the amount of sulfides is small it is not a big problem. However, sulfides are intensively generated on the surface of a casting manufactured using an organic binder mold due to the sulfurization phenomenon, which significantly deteriorates the properties of the casting, resulting in various problems. The deterioration of various properties of castings due to sulfurization includes a decrease in weldability and gradeability for universal steel, a decrease in corrosion resistance for stainless steel, and a decrease in oxidation resistance and high-temperature cracking resistance for heat-resistant steel. An example of inferiority is given.

Furthermore, in spheroidal graphite cast iron, a phenomenon occurs in which the spheroidization rate of graphite decreases. Therefore, when producing castings using an organic* binder mold, it is necessary to take measures to prevent this sulfurization phenomenon. Currently, as a method to prevent sulfurization when manufacturing castings using an organic binder mold, it is possible to use an inorganic acid such as phosphoric acid that does not cause sulfurization as a hardening agent. However, when recycling sand, which has the advantage of sand recycling, problems arise such as phosphorus accumulation and slow hardening speed. Another possible method is to use a coating mold to which a substance having a strong affinity for S is added. From the above-mentioned viewpoint, the present invention provides a coating mold in which powder of a manganese alloy related metal is added as a substance having a strong affinity with S into a coating mold aggregate made of commonly used high-grade refractories such as zircon, chromite, and magnesia. The organic binder is applied to the surface of the mold to prevent sulfurization of the surface of the casting due to sulfidation gas generated when the gap metal is injected.

In this case, the amount of manganese alloy-related metal added to the coating aggregate is preferably 5 to 40% by weight. In addition, in relation to manganese alloys, the term "metal" refers to a material having a content of manganese as a main component of 5% by weight or more, such as ferromanganese, silicomanganese, and manganese metal. Conventionally, CaC039A○ is a substance added to coating molds for the purpose of preventing sulfurization.
, Si027Mn02, Mg○, etc. are used, but
Compared to these substances, manganese alloy-related metals are extremely effective in preventing sulfurization even when added in small amounts, so sulfurization can be prevented without impairing the heat resistance of the coating mold.

In addition, some of the above-mentioned additives that have traditionally been added to prevent sulfurization, such as Mn02, can cause pinholes and hot spots on the surface of castings when added to the extent that they alone can prevent sulfurization. Since wrinkles and the like often occur and the surface condition deteriorates significantly, adding a t-manganese alloy related metal is very effective in preventing sulfurization and not damaging the surface condition of the casting. Therefore, by using the coating mold to which the manganese alloy metal of the present invention is added, sulfurization of the surface of the casting can be prevented, and as a result, deterioration of various properties of the casting can be prevented. In addition, the above-mentioned CaC03, next ao, Si02
, Mn02, Mg○, etc. can also be used to obtain the same effect.

Example 100% Fremantle sand, 0.8% furan tree,
Diameter 5 with furan sand made of 0.4% xylene sulfonic acid.
A test piece with a height of 5 walls was prepared, and the first
The coating molds of Invention Examples 1 and 2 and Comparative Examples 3 and 4 shown in the table were applied with a brush to a thickness of 0.5 to 0.7, and placed in the cavity of the flan mold shown in Figure 1. A spacing metal having a composition of SCSI with an S content of 04014% was injected.

After the spacing metal was solidified, the amount of sulfurization of the casting on the surface of the test piece in contact with the coating mold was measured. The results are shown in Table 2. As is clear from Table 1 and Table 2, when the sulfurization prevention coating for organic binder molds of the present invention is used, sulfurization is significantly prevented compared to conventional coatings. It has been recognized to be effective and can prevent the deterioration of acidity, corrosion resistance, oxidation resistance, ballability, and other properties of the casting surface, which are problems when manufacturing castings using organic binder molds, so it has low industrial value. is large.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a test mold in which the present invention was compared with a conventional example. 1...? 50 x 5-item wiping test piece, 2...Cavity, 3...Coating mold of the present invention or conventional coating mold, 4...
・Heating sleeve ~ 5...Flan mold. hair figure

Claims (1)

[Claims] 1. A sulfurization-preventing coating mold for an organic binder mold, characterized in that a manganese alloy-related metal powder is added to the coating mold aggregate.