JP2000317573A - Method for preventing defect in casting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a preventing method of the peculiar defect in a casting in the case of casting by a mold containing phosphorus atom, and a coating agent used to this method. SOLUTION: This preventing method of the defect due to phosphorus in the casting, is executed by applying the coating agent containing 5-30 pts.wt. at least one kind among magnesium oxide, titanium oxide, chronium oxide, manganese oxide, iron oxide, nickel oxide, zinc oxide and zirconium oxide to 100 pts.wt. refractory aggregate on the mold containing >=0.05 wt.% phosphorus atom and casting. In this way, while receiving such merit as to reduce the odor in the case of casting by the mold using the phosphorus containing compound such as phosphoric acid as a hardening agent, the defect in the casting caused by the phosphorus atom can efficiently be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preventing defects in a casting when casting with a mold containing a phosphorus atom, and a mold wash used therefor.

[0002]

2. Description of the Related Art Self-hardening molds are produced by mixing, kneading and curing a binder and a curing agent made of an acid-curable resin with a refractory granular material such as silica sand. As one of the curing agents, there is a phosphorus-containing compound such as phosphoric acid, and the curing speed is slow but the odor during casting is improved. In recent years, especially with a curing accelerator such as 2,5-bishydroxymethylfuran. It has been proposed to use them together (JP-A-6-2977072).

[0003]

However, when a phosphorus-containing compound is used as a curing agent, phosphorus is concentrated in the reclaimed sand, and pinholes and seizure defects are likely to occur.

For various purposes, such as preventing surface defects of castings and improving casting surfaces, mold wash agents have conventionally been used. It has been proposed to coat iron oxide, chromium oxide, and manganese oxide to prevent porosity defects due to nitrogen (Japanese Patent Application Laid-Open No. 54-147127-9). There were no effective measures for impact. An object of the present invention is to provide a method for preventing a defect in a casting which is peculiar to the case of casting with a mold containing a phosphorus atom, and to provide a coating agent used for the method.

[0005]

DISCLOSURE OF THE INVENTION The present invention relates to a mold wash containing a refractory aggregate in a mold having a phosphorus atom content of 0.05% by weight or more, comprising magnesium oxide, titanium oxide and chromium oxide. , A manganese oxide, an iron oxide, a nickel oxide, a zinc oxide, and a zirconium oxide, a casting agent containing 5 to 30 parts by weight based on 100 parts by weight of the refractory aggregate is coated and cast. This is a method for preventing casting defects by phosphorus. Thereby, while enjoying the advantage of odor reduction when casting with a mold containing a phosphorus-containing compound such as phosphoric acid as a curing agent,
Casting defects caused by phosphorus atoms can be effectively prevented.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION A template is formed by using a curing agent composed of a single or a mixture of phosphorus-containing compounds such as phosphoric acid, condensed phosphoric acid, potassium phosphate, and potassium hydrogen phosphate, thereby forming a phosphorus atom. It contains. Even if the curing agent is a sulfonic acid compound or sulfuric acid and does not contain phosphoric acid,
In some cases, the recycled sand contains phosphorus atoms due to the movement from the casting surface. When the phosphorus atom content of the mold is 0.05% by weight or more, the content of phosphorus on the surface of the casting to be cast increases, and casting defects such as baking occur as described above. Usually the upper limit is 0.
It is about 8% by weight.

As the refractory granular material used for the mold, in addition to quartz sand containing quartz as a main component, new sand or recycled sand such as chromite sand, zircon sand, olivine sand, alumina sand and artificial ceramic sand can be used. Examples of the acid curable resin of the binder include furfuryl alcohol, furfuryl alcohol polymer, furfuryl alcohol / urea polycondensate, furfuryl alcohol / aldehyde polycondensate,
Furfuryl alcohol / aldehydes / urea polycondensate,
Furfuryl alcohol / melamine polycondensate, furfuryl alcohol / aldehydes / melamine polycondensate, furfuryl alcohol / phenol polycondensate furan resin, urea / aldehyde polycondensate, phenol / aldehyde polycondensation One or more of the objects can be used. As aldehydes, formaldehyde, glyoxal, furfural and the like can be used, and as phenols, phenol, resorcinol, bisphenol A and the like can be used. Preferably, the acid-curable resin is at least one selected from furfuryl alcohol, urea / formaldehyde polycondensate, phenol / formaldehyde polycondensate, and furfuryl alcohol / formaldehyde polycondensate.

In order to improve the curing speed, 2,5-bishydroxymethylfuran, 2,5-bismethoxymethylfuran,
2,5-bisethoxymethylfuran, 2-hydroxymethyl-5
It is preferable to use a curing accelerator such as -methoxymethylfuran, 2-hydroxymethyl-5-ethoxymethylfuran, or 2-methoxymethyl-5-ethoxymethylfuran, preferably 2,5-bishydroxymethylfuran.

[0009] The mold wash used in the present invention is a mold wash containing a refractory aggregate, such as magnesium oxide, titanium oxide, chromium oxide, manganese oxide, iron oxide,
At least one of nickel oxide, zinc oxide and zirconium oxide is contained in an amount of 5 to 30 parts by weight based on 100 parts by weight of the refractory aggregate. Among these oxides, titanium oxide, chromium oxide, iron oxide, and nickel oxide are preferred from the viewpoint of the ability to prevent casting defects, and iron oxide is more preferred. The addition amount is also preferably 10 from the viewpoint of casting defect prevention ability.
-30 parts by weight, more preferably 15-30 parts by weight. As the refractory aggregate, graphite, magnesia, zircon, alumina and the like are appropriately selected according to the purpose of cast iron, cast steel and the like. The solvent may be either water or alcohol, penetrating the mold,
Various known additives can be included for thickening and the like.

The coating agent is applied to the wall of the mold by a known technique such as brushing, dipping, splashing, spraying, etc., and dried. Thereafter, pouring is performed and casting is performed.

[0011]

EXAMPLES Examples 1 to 12 and Comparative Examples 1 to 2 Fremantle silica sand (5%) was used at 55 ° C. and 55% RH.
Phosphoric acid as a hardening agent was mixed with the fresh sand of No. 3) so that the phosphorus atom content in the mold was 0.5% by weight. 1% by weight of furan resin containing 10% by weight of 2,5-bishydroxymethylfuran was added to Fremantle silica sand and mixed. The test piece shown in Fig. 1 was filled into a moldable mold and cured to form a mold. did. The mold was applied to the surface of the mold by brushing and dried. This mold wash is silica 60
It is based on a general graphite-based coating composition which is composed of parts by weight, 25 parts by weight of magnesia, and 15 parts by weight of graphite and diluted with alcohol, and further contains oxides in the types and amounts shown in Table 1.

After coating, FCD500 was poured at 1380 ° C. to cast a test piece having the shape shown in FIG. The test piece was cut from the bottom by 0.3 mm, and the cutting powder was wet-analyzed by a molybphosphoric acid blue absorption spectrophotometer (JIS G1214) to measure the phosphorus atom content%. In addition, the presence or absence of a seizure defect on the test piece surface was visually confirmed. The results are shown in Table 1.

Examples 13 to 22 and Comparative Examples 3 to 4 Molds were prepared in the same manner as above except that the base coating agent consisted of 60 parts by weight of zirconium silicate and 40 parts by weight of silica. And then cast. Analysis and confirmation of defects were performed in the same manner. Table 2 shows the results.

[0014]

[Table 1]

[0015]

[Table 2]

[0016]

In particular, when casting is performed using a mold containing a phosphorus-containing compound such as phosphoric acid as a curing agent, casting defects due to phosphorus atoms can be effectively prevented while enjoying the advantage of reducing odor.

[Brief description of the drawings]

FIG. 1 is an elevation view schematically showing a test piece casting used in an embodiment of the present invention.

Claims (4)

[Claims] 1. A coating composition containing a refractory aggregate in a mold having a phosphorus atom content of 0.05% by weight or more, comprising a magnesium oxide, a titanium oxide, a chromium oxide, a manganese oxide, and an iron oxide. A method for preventing casting defects by applying and casting a mold wash containing at least one of nickel oxide, zinc oxide and zirconium oxide in an amount of 5 to 30 parts by weight per 100 parts by weight of the refractory aggregate. 2. The method according to claim 1, wherein iron oxide is used. 3. The method according to claim 1, wherein the mold is formed using an acid-curable binder and a curing agent containing a phosphorus-containing compound. 4. A refractory aggregate comprising at least one of iron oxide, titanium oxide, chromium oxide and nickel oxide.
5 to 30 parts by weight with respect to parts by weight, the phosphorus atom content is 0.
A coating agent for preventing defects in castings caused by phosphorus used in molds of 05% by weight or more.