JP2006341303A - Mixed sand for preventing burning - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide simple and efficient supply sand in an aggregate for a mold and an organic self-hardening closed method capable of preventing burning at a low cost. <P>SOLUTION: Mixed sand obtained by mixing the predetermined amount of artificial sand mainly consisting of coarse 2MgO-SiO<SB>2</SB>obtained by air-granulating nickel refining slag in silica sand in advance is applied as special sand for preventing burning or supply sand for an organic self-hardening closed method. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

Detailed Description of the Invention

Industrial application fields

  The present invention relates to foundry sand forming a casting mold. More specifically, the present invention provides a new structure of anti-seize mixed sand for preventing seizure in place of conventionally used chromite sand, zircon sand and mullite. Provide new mixed sand that can improve

  On the other hand, in the organic self-hardening closed method in which used sand is collected and reused, a new replenished mixed sand that improves the accumulation of these special sands and can reduce the seizure of the entire recovered and reclaimed sand is provided.

Problems to be solved by the prior art and the invention

  Conventional organic self-hardening closed, the furan self-hardening method is the most common in the world. In this furan self-hardening method, natural silica sand has been used. However, due to the large thermal expansion of silica sand, molten iron penetrates into places where thermal conditions are severe and seizure occurs and sand is generated. It takes time to drop. As a solution to this problem, it is a fact that expensive special low expansion sand such as fine chromite sand, zircon sand and mullite artificial sand of old JIS Nos. 6 to 7 are separately kneaded and applied partially. It is.

  Further, such special low expansion sand is expensive, but has a large specific gravity, so that it easily accumulates in the collected sand by the recycling method, and the properties of the collected sand change. For this reason, it cannot be used much and careful management of the collected sand is required.

On the other hand, in the furan self-hardening closed method, artificial sand mainly composed of 2MgO.SiO ₂ obtained from a molten slag of nickel ore has recently attracted attention. Coarse artificial sand is accumulated as supplementary sand and replenished until it reaches about 30 to 40% of the retained sand, improving the mold strength of recovered and remanufactured sand, reducing costs and reducing thermal expansion. A method of improving quality such as baking has been adopted.

  However, in this method, it is necessary that about 30 to 40% coarse artificial sand is contained in the entire sand holding. On the other hand, for cores and the like having severe thermal conditions, it is necessary to separately knead seizure-preventing sand in which the content of coarse artificial sand is further increased in addition to the retained sand. This is because increasing the proportion of coarse artificial sand in the entire sand holding is likely to cause an increase in mold costs and casting skin defects, which is inefficient including countermeasures. is there.

Further, even in the same furan self-hardening closed method, the sand is operated without containing artificial sand mainly composed of 2MgO · SiO ₂ obtained from molten slag of nickel ore (hereinafter referred to as Ni ore sand). There are many factories. In this case, chromite sand, zircon sand, and mullite artificial sand are separately kneaded to prevent seizure, but the amount of use is limited as much as possible due to the high cost and consideration of accumulation in sand. While using.

  It is a new method to mix this coarse Ni ore sand in advance with silica sand and use it as an anti-caking sand. The actual situation is that no seizure prevention sand containing a predetermined amount of sand has been developed and marketed. In order to reduce the cost, this method can be applied by purchasing silica sand and coarse Ni ore sand separately and weighing and mixing them to obtain the prescribed composition. Inefficient because it must be manufactured.

  In order to control the content of Ni ore slag in this recovered sand to 30-40%, the retained sand is analyzed to calculate the content, and the amount of silica sand and Ni slag is replenished alternately. I have to take a way to replenish. Since this method requires frequent analysis work, management is complicated. In addition, it is necessary to order and stock quartz sand and Ni ore sand separately, and it is difficult to manage inventory and secure a place for storage.

Means to be Solved by the Invention

  As described above, as a method for solving the problems described so far, by providing a dedicated mixed sand in which coarse Ni ore sand that cannot be applied alone to a mold and silica sand that has been conventionally used are mixed in a predetermined ratio, It has been found from long-term implementation results that various problems can be solved.

  For example, by providing dedicated mixed sand that has been mixed in advance at a predetermined ratio, it is possible to use the same method as conventional anti-seize sand, and it is possible to provide extremely low-cost anti-seize sand. This is because the unit price of the mixed sand is lower than that of the conventional special sand for preventing seizure and the specific gravity of the sand is small, so that double cost reduction is possible. As a comparative example, Table 1 shows a cost comparison between commercially available chromite sand and mixed sand having the same anti-seizure effect as chromite sand according to the present invention.

On the other hand, in the case of replenishing Ni ore sand with a purity of 100% when supplying the Ni ore sand with the organic self-hardening closed method while maintaining the Ni ore sand content of the retained sand at 30-40%, the replenishment amount Therefore, it is necessary to frequently carry out an analysis of Ni ore sand in the retained sand.
Therefore, if supplementary sand with a composition that takes into account the reduction of silica sand and Ni ore sand can be replenished, the Ni ore sand content rate close to the control value can be maintained, and can be covered by analysis once every several months for confirmation.

  On the other hand, when replenishing Ni ore sand, it is necessary to purchase and stock two types of sand, silica sand and Ni ore sand, which makes it difficult to balance storage warehouses and inventory quantities.

  In addition, when replenishing Ni ore sand, normally, Ni ore sand is discharged and replenished at a stroke from the bottom of the 1t flexible container bag. In this case, Ni ore sand tends to segregate, and Ni in the recovered sand is replenished. Mineral sand content is likely to fluctuate.

Therefore, if the exclusive replenishing mixed sand in which the Ni ore sand is appropriately mixed is supplied, these problems can be solved quickly.

  Thus, according to the present invention, instead of the conventional special sand for preventing seizure and the supplementary sand of the organic self-hardening closed method, a new refractory aggregate for casting that can solve the problem, that is, the conventional silica sand for casting, is used in advance. There is provided a new refractory aggregate for castings, characterized in that it is composed of a special mixed sand in which coarse Ni ore sand is mixed at a predetermined ratio.

  The mixed aggregate of the present invention is mainly composed of a mixture of silica sand and Ni ore sand. The grain size of silica sand is composed of old JIS Nos. 5 to 6, and the grain size of Ni ore sand is usually composed of old JIS Nos. 1 to 3 which cannot be applied as casting sand alone. Table 2 shows a typical particle size distribution.

  As the weight mixing ratio of the present invention, the predetermined problem can be solved at a ratio of old JIS No. 5 silica sand: old No. 3 Ni ore sand = 90:10 to 30:70 depending on the product to be applied. No. quartz sand: old No. 3 Ni ore sand = 70: 30 to 55:45 is desirable.

The artificial sand mixed with the silica sand of the present invention can be similarly applied as long as it is artificial sand having an equivalent particle size structure made of mullite spherical sand mainly composed of AL ₂ O _{3 in} addition to Ni ore sand.

  In the present invention, when the thermal expansion of the mixed sand of quartz sand and Ni ore sand and the mixed sand of quartz sand and mullite sand is measured, the thermal expansion coefficient decreases as the mixing ratio with respect to the quartz sand increases. This indicates that it is possible to reduce the occurrence of seizure defects due to baining that is likely to occur in organic self-hardening sand. Table 3 shows the results of the measurement of rapid expansion coefficient measured according to JACT test method M-2.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, this invention is not limited to these.

  Using the blended sand shown in Table 4, a wedge-shaped core test piece was cured with a furan resin, and a core baking test was performed in a cast shape as shown in FIG. After casting and cooling, the volume of the core sand was measured, and the superiority or inferiority was evaluated by the volume of the sand deposited. The measurement of the deposited sand volume was obtained by filling the concave portion with fresh sand after the completion of sand removal by shot blasting and calculating the volume of the filling amount.

  As shown in Table 5, 100% Ni ore sand and domestic silica sand are alternately replenished as supplementary sand, and the content of Ni ore sand in the retained sand is controlled at about 30% and 45%, respectively. As a result of testing for about 2 years for B2 company, if the replenishment sand mixed at a specific ratio is replenished, rationalization such as improvement of workability, omission of sand storage place, reduction of container bag processing, reduction of inventory, etc. is achieved. It was. The results are shown in Table 5.

  From the above results survey, the ratio of Ni ores and sands to be mixed with the replenishment sands will be maintained if the foundry sets the ratio of replenishment sands at the ratio of the target values that determined the content ratio of Ni ores and sands. it can. Therefore, frequent analysis can be performed and managed without cost.

The invention's effect

By using mixed sand obtained by mixing a predetermined amount of Ni ore sand with silica sand in advance as anti-seizure sand for casting production or supplementary sand for organic self-hardening closed method, the following effects can be obtained.
(1) It can be adequately applied in place of seizing prevention sand such as chromite sand, and the cost can be significantly reduced.
(2) By using it as supplementary sand for the organic self-hardening closed method, the content of Ni ore dredged sand in the recovered recycled sand can be maintained substantially constant, so the number of analyzes can be greatly reduced.
(3) By using it as supplementary sand for the organic self-hardening closed method, the disposal of flexible container bags can be greatly reduced, and the waste treatment can be rationalized.
(4) The amount of sand stock decreases and the sand storage area can be reduced.

The draft test method for casting is shown. The shape of the core used for the seizure test is shown. Photograph of the casting test result.

Explanation of symbols

1 Core for evaluation of seizure test 2 Cylindrical casting (FC300)
3 Runway 4 Silica sand 100% after core shot plasting 5 Silica sand 90%: Ni ore sand 10% after core shot blasting 6 Silica sand 70%: Ni ore sand 30% after core shot blasting 7 Silica sand 50%: Ni ore sand After 50% core shot blasting

Claims (3)

A molten slag composed mainly of 2MgO · SiO ₂ generated during Ni refining is a refractory produced by air crushing, having a particle size in the range of 0.08 to 3.50 mm and an AFS particle size index of 8 to 35. Spherical coarse refractories composed in the range of 10 to 70% by weight in advance are mixed with silica sand in a weight ratio, and blended so that it can be applied to mold making as it is. sand. The mixed sand for preventing seizure according to claim 1, which is a mullite-type spherical artificial sand produced by air crushing or sintering with Al ₂ O ₃ as a main component. The mixed sand according to claim 1 or 2, which is replenished as supplementary sand in a closed method in which the sand used in the organic self-hardening method is repeatedly collected, regenerated and reused.

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