JPH0542352A - Raw material for die-casting iron series alloy containing carbon and method for producing it and method for using it - Google Patents

Abstract

PURPOSE:To execute the suitable die casting without melting surface layer part of a raw material and to improve the yield and the productivity by executing surface decarbonizing treatment under the specific atmosphere. CONSTITUTION:To an iron series alloy containing carbon, the surface decarbonizing treatment for >=20min under heating in the temp. range of 700-1000 deg.C in the air or for >=10 min under heating in the temp. range of 700-1200 deg.C in reducing atmosphere containing moisture, is executed. Further, this is heated to the temp., by which the surface decarbonized coating layer is held to solid-phase condition and the inner part becomes at least solid-liquid coexisting condition, and in succession to this heating, injection forming is executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention proposes a material for die casting which is advantageously suitable for die casting of an iron-based alloy containing carbon, a method for preparing the same, and a method for using the same.

[0002]

2. Description of the Related Art As a conventional die-casting method, there is a method widely used, in which a material is melted, and the molten metal is poured into a sleeve by ladleing and then injected into a mold. In addition, by heating the material to melt a part of it and making it into a solid-liquid coexisting state, it behaves like a solid as a whole at the time of heating and transferring, but when deformed, it behaves like a liquid as a whole. In this way, there is also a method in which the material is transferred to the mold gate portion in a solid state and is made to have the same fluidity as a liquid at the time of injection, and the material is injected into the mold.

[0003]

In the above-mentioned conventional die casting method, the molten metal is injected into the sleeve by ladle or the like, that is, the amount of molten metal required for one injection from the melting furnace is injected for each injection. In the method of drawing out with a dipper etc. and injecting it into the sleeve, moving it to the mold with the plunger and injecting it, There is gas entrainment due to flow, which deteriorates the product characteristics. -It is difficult to pump out an accurate amount of molten metal, and in order to prevent the lack of molten metal amount, the amount of molten metal that is larger than that required for injection molding is pumped out, resulting in a decrease in yield.・ When the molten metal in the ladle is transferred from the melting furnace to the sleeve, it cannot be transported at high speed to prevent the molten metal from spilling. There are problems such as.

On the other hand, in the method of injecting in a solid-liquid coexisting state by melting a part of the material, the solid phase is connected like a net during heating and transfer, and behaves like a solid as a whole. At times,
In order to break the solid phase that was connected in a mesh due to deformation and the solid phase particles to float in the liquid, and to exhibit the same behavior as the liquid as a whole, the preferred range of the amount of liquid phase (50 ~ (70 wt%)
And it is difficult to control this. That is, in order to secure the above-mentioned suitable amount of liquid phase, it is sufficient to read the temperature range in which the amount of liquid phase is within the suitable range from the state diagram of the material and heat within the temperature range. Carbon steel,
In the case of an iron-based material such as cast iron, the temperature difference between the solidus line and the liquidus line is small depending on the component composition thereof, so that the above temperature range becomes extremely narrow, and it becomes difficult to control the temperature within this range. There is a problem.

When the amount of liquid phase is out of the preferable range, it behaves as a liquid during heating, and phenomena such as deformation and melting occur during heating, making it impossible to transfer to the mold.
On the contrary, if it is small, it behaves as a solid during injection molding,
The deformation resistance increases, and the material is destroyed, making injection molding impossible.

Therefore, the present invention advantageously solves the above-mentioned problems, and based on a new idea that die casting can be performed without trouble, a material for die casting of an iron-based alloy containing carbon, a method for preparing the same, and a method for preparing the same. The purpose is to suggest a usage method.

[0007]

SUMMARY OF THE INVENTION According to the present invention, by covering the surface of a raw material with a component composition having a high melting point, that is, by forming a surface decarburizing coating layer, even if the internal substance is in a molten state, it is as if it were liquid. It is intended to make it possible to carry out the transfer and the injection without any trouble by putting the raw material into the container of the surface decarburized coating layer.

That is, the gist of the present invention is a material for die casting (first invention) of an iron-based alloy containing carbon, which is in the form of a lump and has a surface decarburizing coating layer formed around it.

[0009] Further, the iron-based alloy containing carbon is
Perform surface decarburization treatment for 20 minutes or longer under heating in the temperature range of 00 ℃ or more and 1000 ℃ or less, or in the temperature range of 700 ℃ or more and 1200 ℃ or less in a reducing atmosphere containing water. A method for preparing a material for die-casting an iron-based alloy containing carbon, which is subjected to surface decarburization treatment for 10 minutes or more under heating (second, third
The invention), further, the material for die casting of iron-based alloys containing carbon, the surface decarburized coating layer is held in a solid state, but heated to a temperature at which at least solid-liquid coexistence state in the internal matter, A method of using the above-mentioned material for die casting, which is injection-molded into a mold following this heating (the fourth invention).

Here, the surface decarburizing treatment may be carried out alone, or the surface decarburizing treatment and heating for injection may be continued.

[0011]

The present invention will be described in more detail below. The greatest feature of this invention is to form a surface decarburizing coating layer with a high melting point and a low carbon content on the surface of a lumpy material, and even if the internal substance is in a molten state, the liquid material is a surface decarburizing coating layer. It is to be put in the container of.

By doing so, the surface decarburized coating layer functions as a container for the molten material, can be transferred from the heating device to the gate part of the mold in the same manner as a solid, and the internal content can be oxidized,
Protects from gas entrapment and contamination by foreign matter. Then, this surface decarburized coating layer is destroyed by injection force during injection, and exhibits the same fluidity as a liquid as a whole to facilitate injection molding.

The surface decarburized coating layer is destroyed when it passes through the gate portion during injection and is mixed with the product. However, the decarburized layer itself is rich in toughness and adheres to the internal non-decarburized portion. Has little effect on the material.

Therefore, it has been difficult to control the amount of liquid phase within a suitable range as described above in the conventional methods of injection molding in the solid-liquid coexisting state. More than the lower limit of the preferred range of phase amount (50 wt% or more)
Since it is not necessary to regulate the upper limit, control becomes easy, and suitable injection molding can be performed.

Next, a surface decarburization treatment method for forming the surface decarburization coating layer will be described. At room temperature, a round bar cut into a size necessary for one injection is used to perform surface decarburization by heating in the atmosphere prior to heating for injection. If the heating temperature is less than 700 ° C, a sufficient thickness of the surface decarburized layer will not be formed, and if it exceeds 1000 ° C, the surface will be significantly oxidized, which is not suitable. Further, if the holding time is less than 20 minutes, the surface decarburized layer having a sufficient thickness cannot be formed. Therefore, the surface decarburization treatment in the atmosphere should be performed at temperatures above 700 ° C
The temperature should be kept below ℃ and the holding time should be 20 minutes or longer.

In the above surface decarburization treatment, it is needless to say that the surface decarburization treatment is performed once and then cooled and then heated again for injection, and that the surface decarburization treatment and heating for injection are continuously performed. Good. That is, 700 ℃
It may be heated in the temperature range of 1000 ° C. for 20 minutes or more, and subsequently heated to the injection temperature for injection.

On the other hand, when heated in the atmosphere, a slight oxide layer is formed on the outside of the decarburized layer even at a temperature of 1000 ° C. or lower. However, when it is desired to prevent the formation of this oxide layer, in a reducing atmosphere containing water. It may be heated.

In this case, a surface decarburized layer having a sufficient thickness is not formed at a temperature of less than 700 ° C, and a deformation of the material during heating becomes large at a temperature of more than 1200 ° C, which is not suitable.
If the time is less than 10 minutes, the surface decarburized layer having a sufficient thickness cannot be formed. Therefore, in the surface decarburization treatment in a reducing atmosphere containing water, the temperature range is 700 ° C or higher and 1200 ° C or lower, and the holding time is 10 minutes or longer.

[0019]

EXAMPLES The results of trial die casting for the conforming examples and comparative examples of the present invention are listed below.

The main specifications of the die casting machine used above are as follows. Mold clamping force: 425t Die stroke: 560mm Radiation output: 3 to 53t Plunger stroke: 595mm Injection speed: 0.01 to 5.00m / sec

Conformance Example 1 A cast iron round bar (length: 70 mm, diameter: 60 mm) containing C: 3 wt%, Si: 2 wt% and Mn: 0.5 wt% was heated at a temperature of 800 ° C. in the atmosphere. After heating for 120 minutes, a surface decarburization treatment of cooling to room temperature was performed. Then, the surface-decarburized material was subjected to high frequency at room temperature to 1230 ° C (liquid phase amount 82wt%).
It was heated for 15 minutes, grabbed with a flame and loaded into the sleeve, and was pushed into the mold gate section with a plunger to try injection molding into the mold. As a result, the material could be grabbed with a firestick and successfully ejected.

Conformance Example 2 Using a round bar similar to the above, from room temperature to 1230 ° C. in the atmosphere.
(Liquid amount 82wt%) in 30 minutes (700 ℃ to 1000 ℃)
(Heat up to 25 ° C for 25 minutes), grabbed it with a flame and loaded it into the sleeve, pushed it into the mold gate part with a plunger and tried injection molding into the mold (heating for surface decarburization and injection). It went continuously). As a result, the material could be grabbed with a firestick and successfully ejected.

Application Example 3 Using the same round bar as in Application Example 1, nitrogen: 80 Vol%, hydrogen
: 15 Vol% and water: 1100 in 5 Vol% gas atmosphere
After heating at a temperature of ° C for 20 minutes, a surface decarburization treatment of cooling to room temperature was performed. Then, the surface-decarburized material is heated at high frequency from room temperature to 1230 ° C (liquid phase amount 82wt%) in 15 minutes, grabbed with a flame and inserted into the sleeve, and then the mold gate is used with a plunger. Injection molding was attempted by pushing into the mold. As a result, the material could be grasped and the normal injection could be performed.

Application Example 4 Using the same round bar as in Application Example 1, after heating in air at a temperature of 700 ° C. for 20 minutes, the surface was decarburized by cooling to room temperature. Then, the surface-decarburized material is heated from room temperature to 1230 ° C (liquid phase amount 82wt%) for 10 minutes at high frequency, grabbed with a flame and inserted into the sleeve, and then the mold gate is used with a plunger. Injection molding was attempted by pushing into the mold. As a result, the material could be grabbed with a firestick and successfully ejected.

Application Example 5 Using the same round bar as in Application Example 1, the surface was decarburized by heating in air at a temperature of 1000 ° C. for 60 minutes and then cooling to room temperature. Then, the surface-decarburized material is heated from room temperature to 1230 ° C (liquid phase amount 82wt%) for 10 minutes at high frequency, grabbed with a flame and inserted into the sleeve, and then the mold gate is used with a plunger. Injection molding was attempted by pushing into the mold. As a result, the material could be grabbed with a firestick and successfully ejected.

Application Example 6 Using a round bar similar to Application Example 1, in a gas atmosphere of nitrogen: 80 Vol%, hydrogen: 15 Vol% and water: 5 Vol%, 700
After heating at a temperature of ° C for 10 minutes, a surface decarburization treatment of cooling to room temperature was performed. Then, the surface-decarburized material is heated at high frequency from room temperature to 1230 ° C (liquid phase amount 82wt%) for 10 minutes, grabbed with a flame and loaded into the sleeve, and then the mold gate is used with a plunger. Injection molding was attempted by pushing into the mold. As a result, the material could be grabbed with a firestick and successfully ejected.

Application Example 7 Using a round bar similar to Application Example 1, in a gas atmosphere of nitrogen: 80 Vol%, hydrogen: 15 Vol% and water: 5 Vol%, 1200
After heating at a temperature of ° C for 60 minutes, a surface decarburization treatment of cooling to room temperature was performed. Then, the surface-decarburized material is heated at high frequency from room temperature to 1230 ° C (liquid phase amount 82wt%) for 10 minutes, grabbed with a flame and loaded into the sleeve, and then the mold gate is used with a plunger. Injection molding was attempted by pushing into the mold. As a result, the material could be grabbed with a firestick and successfully ejected.

Adaptation Example 8 A round bar (length: 70 mm, diameter: 60 mm) containing C: 4 wt% and Si: 2 wt%, which is almost eutectic composition, was
After heating at a temperature of 800 ° C. for 60 minutes, a surface decarburization treatment of cooling to room temperature was performed. Then, the surface-decarburized material is heated at high temperature from room temperature to 1160 ° C (liquid phase amount 100wt%) for 10 minutes, put into a sleeve with a flame, and use a plunger to reach the mold gate. An injection molding was tried into a push mold. As a result, the material could be grabbed with a firestick and successfully ejected.

Comparative Example 1 The same round bar as in Comparative Example 1 was used without surface decarburization treatment.
At high frequency, it was heated from room temperature to 1230 ° C (liquid phase amount 82wt%) for 10 minutes, and I tried to load it into the grab sleeve with a fire flame, but the material was too soft to catch with the fire flame.

As described above, the conforming example of the present invention in which the surface decarburized coating layer is formed, even if the internal liquid phase ratio exceeds 70 wt% (including the molten state), the sleeve is blown by the flame and the sleeve is mounted. It is shown that it can be inserted and transferred to the mold gate section, and normal injection can be performed.

[0031]

Industrial Applicability According to the present invention, it is possible to control the amount of liquid phase typified by eutectic cast iron by forming a surface decarburizing coating layer having a high melting point on the surface of a material for die casting of an iron-based alloy containing massive carbon. Even if it has a particularly difficult component composition, it makes it possible to perform a suitable die casting without melting the surface layer of the material, compared to a method of performing the die casting by melting the entire material, a. Since no foreign matter is mixed into the molten metal and no gas is entrained, the quality characteristics of the product are improved. b. The method of cutting a round bar, compared with the method of drawing molten metal with a dipper, can obtain an accurate amount of raw material and thus improve the yield. c. Since the material can be handled in a solid state immediately before it is put into the mold, automation is easy and productivity can be improved. It has features such as the following and can be advantageously applied to die casting of iron-based alloys containing carbon.

Claims (4)

[Claims] 1. A material for die-casting an iron-based alloy containing carbon, which is in the form of a lump and has a surface decarburizing coating layer formed around it. 2. An iron-based alloy containing carbon, at 700 ° C. in the atmosphere.
As described above, the method for preparing a material for die casting of an iron-based alloy containing carbon, which comprises subjecting the surface to decarburization for 20 minutes or longer under heating in a temperature range of 1000 ° C or lower. 3. An iron-based alloy containing carbon is subjected to a surface decarburizing treatment for 10 minutes or more under heating in a temperature range of 700 ° C. or more and 1200 ° C. or less in a reducing atmosphere containing water. A method for preparing a material for die-casting an iron-based alloy containing carbon, which is characterized. 4. A material for die casting of an iron-based alloy containing carbon is heated to a temperature at which the surface decarburized coating layer is kept in a solid state but at least in a solid-liquid coexisting state in the interior, and this heating is performed. A method of using a material for die casting of an iron-based alloy containing carbon, characterized by performing injection molding into a mold.