JPS59225852A - Production of casting mold - Google Patents

Abstract

PURPOSE:To reduce man-hours for sand molding and to economize a material for facing sand by blowing quick-curable system sand formed by kneading refractory particles with a binder and a hardener added with a quick curing accelerator to the surface of a pattern thereby forming quickly a facing sand layer. CONSTITUTION:Zircon sand, chromite sand, etc. having high refractoriness are used for the refractory particles in order to prevent burning after casting. Furan, phenolic, phenol, furan resins are used for the binder and xylene sulfonic acid, paratoluene sulfonic acid, benzensulfonic acid and phosphoric acid curing agent added with a sulfuric acid as a quick curing accelerator are used for the curing agent. The system sand is used by changing the kind of the binder and curing agent and the amt. thereof to be added and the amt. of the curing accelerator to be added for spring, summer and winter in order to adjust the pot life of the system sand. The facing sand layer is formed on the surface of a pattern by a spray molding device.

Description

[Detailed description of the invention] The present invention relates to a method for manufacturing a mold.

Foundry sand spray molding device (Patent Application No. 57-067470)
When manufacturing molds with an as-cast weight of 1 ton or more for cast steel products using molds, baking may occur on the surface of the casting surface, so instead of crushed sand, a thin mold with high refractory properties such as zircon sand or chromite sand is used. A sandy layer is formed, but the method has already been proposed in a patent application filed in 1982-17.
It is proposed in No. 0788.

In this method, as shown in Figures 1 and 2, a wire mesh 2 such as expanded metal or tortoise shell wire mesh is stretched over the model surface 1, and supports 4 corresponding to the thickness of the skin sand layer 3 are attached to the wire mesh according to the model dimensions. A predetermined sand layer is formed using a blow molding device.

The present invention does not rely on the above-mentioned method, but instead sprays kneaded sand using a rapid hardening agent onto the model surface to rapidly form a predetermined skin sand layer, thereby reducing the number of man-hours required for sand filling and saving the material used for skin sand. It was done for that purpose.

That is, the present invention provides a mold characterized in that a quickly hardening kneaded sand prepared by kneading refractory particles with a binder and a hardening agent added with a rapid hardening accelerator is sprayed onto the model surface to rapidly form a surface sand layer. It concerns the manufacturing method.

The molding material used in the method of the present invention uses refractory particles such as zircon sand and chromite sand, which have high refractory properties, in order to prevent burning after casting. The binder used is furan-based, phenol-based, or phenol/furan-based resin, and the curing agent was xylene sulfone filament, para-toluene sulfonic acid, benzene sulfonic acid, or phosphoric acid, which promotes rapid curing. Use one with sulfuric acid added as an agent.

The addition ratio of the binder to the above fire-resistant particles is 0.5~
It is desirable that the weight ratio is 1.2, and the addition ratio of the curing agent is 0.1 to 0.5 weight ratio. If the binder is less than 0.5% by weight, the curing speed will be slow, depending on the amount of curing agent added, but if it is more than 1.2% by weight, the curing speed will be further accelerated. This is unfavorable from an economic point of view (binder cost).

Also, if the hardening agent is less than 0.1 weight ratio, the curing speed will be slow, depending on the amount of binder added.If the hardening agent is more than 0.1 weight ratio, the curing speed will be further accelerated. However, it is not economically viable.

In addition, sulfuric acid is added to the above curing agent as a rapid curing accelerator, but the amount is 5 to 10% by weight based on the curing agent.
is preferred.

If the amount of sulfuric acid is less than 3 parts by weight, the curing rate will be slow; if more than 10 parts by weight of sulfuric acid is added, the curing rate will be faster, but the desired mold strength will not be achieved.

In addition, in the present invention, in general, in order to adjust the pot life of the kneaded sand, the type and amount of the binder, curing agent, and amount of curing accelerator are changed for spring, winter, and winter use. .

The present inventors conducted basic tests to find molding conditions for forming a sand layer on the model surface using a spray molding device. The results of the study are shown below.

1. Test conditions 1.1 Test material (1) Fire-resistant particles: Zircon sand CA, F, S 11
0) (2) Rapid curing agent (applicable to the present invention) Binder: Phenol furan resin (Asahi Yokuzai Kogyo C Co., Ltd.), product name HP1000F) (0,
8% by weight/for sand) N-curing agent: Benzene sulfo/acid (Asahi Yokuzai Kogyo C Co., Ltd.), product name PB-20) (3% by weight/based on caking agent, but sulfuric acid 1-15% by weight/8% by weight) (For benzenesulfonic acid) 1.2 Blow molding apparatus The apparatus shown in FIG. 3 was used.

In FIG. 3, the zircon sand put into the sand tank 5 is continuously and quantitatively supplied to the kneading machine 7 by a continuous quantitative feeder 6. The 7Vi multi-blade type high-speed rotation mixer instantly removes the added binder, hardener, and zircon sand.
It flows out to booster 9 via chute 8. The kneaded sand is accelerated to the speed required for spray molding by booster 9 and spray molded via Plast hose 10. Amount of sand produced: 1. ' s ton / Hr Kneading injection speed ratio (the injection speed of the mixed sand divided by the limit speed that causes pulsation when the mixed sand is transported in the plast hose): arbitrary injection speed ratio (2) Model, other models and spray angle lf: flat plate model (500mm x 500
mX 50wt), and the angle with the horizontal plane is 9
It was installed and sprayed at 0° (vertical).

Spraying distance: 1 m 2, Test method The conditions for forming a sand layer are that when the refractory particles are sprayed onto the model surface, they simultaneously undergo a rapid hardening reaction and harden, and the subsequent spraying is continuous. It is required not to be scattered by refractory particles. As a result of repeated tests to find forming conditions that met this requirement, we found that the model surface 9
The appropriate spraying conditions for forming a sand layer of 50 degrees or less with respect to 0° are as shown in Table 10. First, we arbitrarily changed the injection speed ratio and observed the scattering of refractory particles on the model surface. As a result, the optimum injection speed ratio Vi2.5-5.3
Next, the refractory particles on the model surface caused a rapid hardening reaction and solidified, forming a sandy layer.In order to achieve the optimum hardening agent distribution conditions, the binder was made of the same type of phenol-furan resin. year,
When the curing agent was repeatedly sprayed with different amounts of sulfuric acid in benzenesulfonic acid and under the optimum injection speed ratio of 2.5 to 3.3, it was found that the optimum curing agent mixing ratio was sulfuric acid in benzenesulfonic acid. It was found that this is the case when 3 to 10% by weight is added.

Table 17 Results of investigation of spraying conditions for skin sand layer (97 parts by weight of benzenesulfonic acid + 3 parts by weight of sulfuric acid) Note) ○: A sand layer of a specified thickness can be formed on the model surface, and the packing density is also high, under optimal conditions.

Δ: A sand layer of a specified thickness can be formed on the model, but the packing density is low (in this case, burning occurs during casting), and the conditions are poor.

×: Conditions in which almost no sand layer could be formed on the model surface.

As shown in Table 1, when the common agent is applied, the kneading sand that is sprayed onto the model surface is loose, so there is no risk of forming a skin sand layer at all. On the other hand, in the case of applying the rapid curing agent according to the method of the present invention, the kneaded sand sprayed onto the model surface undergoes a rapid curing reaction, and the viscosity increases, resulting in an increase in the curing effect.
A sandy layer is formed. However, in this case, by setting the optimum injection speed ratio (2.5 to 3.3) and the optimum curing agent blending ratio (3 to 10% by weight of sulfuric acid in benzenesulfonic acid) as the spraying conditions, the mold It was found that a sand layer of good quality could be obtained. In addition, in Table 1, the model surface 90
A sand layer with a thickness of about 50 mm was formed for 100 °C, but under these conditions, when the thickness was about 60 mm, the sand layer fell off due to its own weight. Although it is possible to form a thicker sand layer by further reducing the angle of inclination of the model surface, the thickness of the sand layer is approximately 50 tons for practical purposes due to the air permeability of the mold. Incidentally, when the thickness of the sand layer becomes thick, the air permeability of the mold becomes poor, which becomes a cause of surface defects (gas defects) in the casting.

In addition, in order to confirm the validity of the conditions for forming a skin sand layer using the rapid hardening agent that was clamped in the basic test, the present inventors used a test product model to spray mold the skin sand and back sand, and then cast them. A test was conducted to evaluate sand performance. The test conditions are as follows.

1. Test material (1) Refractory particle surface sand: Zircon sand (A, F, S 110) back sand
: Recovered silica sand (A, F, s 45) (2) Rapid curing agent Binder: Phenol-furan resin (Asahi Yokuzai Kogyo Co., Ltd. (Split Product Name: HP1000F)) (0
Hardening agent: Benzene sulfonic acid (Asahi Yokuzai Kohata C Co., Ltd.) dehiscence product name PB-20) + sulfuric acid (30% by weight/to binder, however, sulfuric acid 5 to 1) / benzenesulfonic acid) 2. Shot molding device A spray molding device shown in Fig. 3 was used.

3. Blow molding conditions Dimensions of hose 10: 32 mm x 6 m Sand
tf, : 1.5 ton,/Hr
Mixed sand injection speed ratio = 2.5-3.3 Spraying angle: 30-90° Spraying distance = 0.5-1. o
,.

4. Test product model A square model (10o) with a product weight of approximately 2 tons.

250 cm) was used.

5. For the molding test lower mold, set the flask 15 on the surface plate 14 as shown in Fig. 4,
Model 01 and runner 16 were placed within the frame.

Under the above conditions, using a blow molding apparatus, according to the method of the present invention, first about 20 layers of skin sand 13 are molded, and then back sand 17 is poured and solidified. After solidifying, invert the lower mold,
As shown in Fig. 5, a casting flask 15' is installed on the upper part, and an upper model 01' and a sprue 16 are placed at the same position as the lower model 01 and the runner 16.
′ is installed. Molding was carried out in the same procedure as for upper model 01, and after solidification, upper and lower models 01.01' were released from the mold to complete a test mold.

Using this test mold, we conducted a casting test on cast steel (SC46) (casting source If 1540°C, @ mold drying temperature approximately 80°C). As a result, there were no casting defects such as scum defects on the casting surface.
We were able to manufacture high-quality cast iron products.

[Brief explanation of drawings]

Figures 1 and 2 are diagrams for explaining the models used in the conventional mold manufacturing method, Figure 3 is a diagram showing an example of the spray molding apparatus used in the method of the present invention, and Figures 4 and 5 are diagrams for explaining the model used in the conventional mold manufacturing method. It is a figure showing an example of the mold made by the invention method. Sub-Agents 1) Meifuku Agent Ryo Hagiwara - Figure 1

Claims (1)

[Claims] A mold making method characterized by rapidly forming a surface sand layer by spraying fast-hardening kneaded sand prepared by kneading fire-resistant particles with a binder and a hardening agent added with a rapid hardening accelerator onto the model surface.