JPS59225875A - Heat insulating method for blind riser and heat insulating material for blind riser - Google Patents

Abstract

PURPOSE:To accelerate the feeding effect of a blind riser in casting of a sand mold casting by placing an exothermic compsn. in the recess of a casting mold having the blind riser and floating the same by the inflow of a molten metal so that exothermic heat insulation is effected by the same. CONSTITUTION:An exothermic compsn. 3 having the shape of a spherical body, ellipsoidal body of revolution, a polyhedron of a hexahedron or above or briquette is placed in the recess of a sand mold with a blind riser 2 of said mold. When a molten metal is poured through a sprue 1 into the mold, the compsn. 3 is easily floated by the molten metal and generates heat by firing from the part in contact with the molten metal until the comps. arrives at the top of the blinder riser where the compsn. stays still. The feeding effect to a casting body 5 is thus assisted.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a heat insulating method for a blind feeder and a heat insulating material for the blind feeder for the purpose of promoting the feeding effect of the blind feeder in the production of castings using sand molds. It is about provision.

In general, in the production of castings, in order to obtain internally sound casting products by preventing the formation of shrinkage cavities due to the solidification and shrinkage of molten metal poured into a mold, it is necessary to A feeder is installed nearby.

In addition, due to the relationship between the shape of the product casting and the mold flask in the mold, and the saving of molten metal, an open riser with the upper surface of the feeder opened on the upper surface of the mold flask, and a blind feeder that is also enclosed within the mold flask are selective. It is also well known that it is used in

Therefore, when using a blind feeder, the following measures are taken in order to fully demonstrate its effectiveness and to smoothly supply molten metal from the blind feeder in an amount equivalent to the amount of solidification shrinkage of the product body. ing. That is, (1) the blind feeder is kept warm so that it does not solidify faster than the product body. (2) In order to facilitate the movement of molten metal from the blind feeder to the product body, atmospheric pressure is introduced into the blind feeder.

Here, the former method includes a method of enclosing the blind feeder with a molded sleeve that has heat generation properties, heat insulation properties, or heat generation/insulation properties, and for the latter method, there is a method of enclosing the blind feeder with a molded sleeve. It is also well known that there is an "atmospheric pressure riser" in which the core is inserted from the top of the blind feeder toward the center thereof, and that a blind feeder sleeve that combines both is often used.

However, each of these conventional techniques has the following zoni. In other words, the method of using a molding sleeve has drawbacks such as the complexity of attaching it to the sand mold or model, deformation, breakage, or separation from the sand mold during the molding process, and the problems with atmospheric pressure risers. Problems include the complexity of inserting the core into the core and sand falling off due to friction during insertion. Furthermore, these drawbacks delay the cycle time of molding and cause internal defects in the cast product.

The present invention has been made in order to solve the problems of the prior art and to provide a method and product for simply and effectively promoting the function of a blind feeder. That is, the first aspect of the present invention is that, in the casting of sand molds, at least one exothermic composition in the form of a sphere, a rotating rod, a polyhedron of hexahedron or more, or a lump is added to the blind feeder before pouring into the mold. A heat retention method for a blind feeder, characterized in that the composition is placed in the inner mouth of the feeder, floats up as the molten metal flows in, and is positioned at the top of the feeder when pouring is completed to heat and keep the core of the feeder warm. , and the second one is
This is a heat insulating material for a blind feeder in sand casting, characterized in that the exothermic composition is in the form of a sphere, a rotating cylindrical body, a polyhedron of hexahedron or more, or a lump, and the bulk specific gravity is smaller than the specific gravity of the molten metal.

The exothermic composition used here can be one that has conventionally been used to keep casting feeders warm, and the composition that determines the calorific value depends on the capacity of the blind feeder and the desired It may be selected within a range that makes the bulk specific gravity smaller than that of the molten metal, depending on the exothermic reaction duration. Its shape is spherical,
The design of a rotating dowel, a hexahedron or larger polyhedron, or a nodular shape was taken into account the buffering effect on the sand mold wall when the molten metal floats up, and the sustaining effect of the exothermic reaction due to ignition after immersion. Next, the exothermic composition can be shaped into such a shape by conventional techniques such as adding a known binder and molding using a sieve or forming a block using a dish-type granulator.

The thus obtained heat insulating material for a blind feeder of the present invention can be used by simply placing it in the recess of a sand mold. This can be easily done at any time before mold matching during the mold making process. It can be placed even after mold matching.

The placement position can be arbitrarily selected as long as it can be placed at the top of the blind feeder when pouring is completed after the heat insulating material floats due to the inflow of molten metal. It is preferable to use a recess forming the bottom of the blind feeder because it is the shortest distance to the feeder. At least one of them may be used for one blind feeder, and a plurality of the feeders may be used in consideration of the volume of the blind feeder.

Next, when pouring the metal into the mold, the heat insulating material easily floats in the flow of the molten metal, ignites from the immersion part, generates heat, reaches the top of the blind riser, and comes to rest. During the floating process, the heat insulating material is not damaged either by itself or others when it comes into dynamic contact with the sand mold wall due to its shape, and therefore does not induce casting defects related to the casting surface or internal material. As mentioned above, the heat generation of the heat insulating material starts with the immersion, so the hot water surface surrounding it is kept warm and reaches the top of the blind feeder together with the heat insulating material. Since the heat generation continues for a predetermined period of time depending on the composition, shape, size, etc. of the heat insulating material, the solidification of the blind feeder becomes slow, which promotes the repair effect on the casting body. Furthermore, due to the air permeability of the heat insulating material, atmospheric pressure can be introduced into the blind feeder without being hindered, and the feeder effect is enhanced.

In the cast product according to the present invention, the blind riser after solidification is as a result of the heat retention effect of the heat insulating material and sufficient repair of the casting body.
A contraction cavity remains from the top to the core, and within the contraction cavity at the top, the heat insulating material of the present invention, which has been sintered after the heat generation is finished, remains in its original shape. Therefore, the heat insulating material after use does not become mixed with the recovered sand after the mold is dismantled as a residue and impede its separation.

Next, examples of the present invention will be described.

Metal aluminum 25% by weight, ferrous oxide 5% by weight,
Ferric oxide 20% by weight, barium nitrate 5 times Mi-chi, butt) IJum 3 times 1 year, expanded obsidian 27% by weight
, silica sand 5% by weight, phenol formaldehyde resin 1
After molding the exothermic composition consisting of 0% by weight in a mold, the exothermic composition is heat-cured into spheres, and one piece each is placed at the bottom of a blind riser provided in a sand mold made of ductile cast iron or ordinary cast steel. The results of casting each molten metal after combining are as follows.

Example 1 Example 2 Casting Material Tasotile cast iron Ordinary cast steel Insulating material dimensions (tomo) 30' 45
'Same as above ratio 0.9 0.9 Blind feeder dimensions (tomo) 55'X90 10♂×150
Casting temperature (made by Q 1390 1520)
Product No internal defects No internal defects Here, the internal quality of the product was inspected on specimens cut 10 fins thick in the direction of the center line, and no defects were found in any of the specimens. At this time, for comparison, in a blind feeder made only by a sand mold in which the present invention was not implemented, shrinkage pits were found here and there in the center of the wall thickness and in the vicinity of the weir for the same test piece.

[Brief explanation of the drawing]

The figure is a radial cross-sectional view of a sand mold showing an embodiment of the present invention. 1. Sprue, 2. Blind feeder, 3.4. Heat insulating material for blind feeder of the present invention (3 indicates the position before pouring, and 4 indicates the position after pouring. ), 5...Casting body.

Claims (2)

[Claims] (1) In sand casting, at least one exothermic composition in the form of a sphere, a rotating solid, a polyhedron of hexahedron or more, or a lump is placed in the recess in the casting head on the pouring surface of the blind feeder. A method for keeping warm a blind feeder, characterized in that the composition floats up with the inflow of molten metal and is positioned at the top of the blind feeder when pouring is completed to heat and keep the core part warm. (2) Heat insulation for blind feeder in sand casting, characterized in that the exothermic composition is in the form of a sphere, a rotating solid, a polyhedron of hexahedron or more, or a nodule, and the bulk specific gravity is smaller than the specific gravity of the molten metal. Material.