JPH0447920A - Method, apparatus and controlling method for extruding semi-molten metal - Google Patents

Abstract

PURPOSE:To make it possible to produce extrudate having longitudinally uniform material characteristics irrespective of the material of a plunger tip by a method wherein solid-state metal material is pressurized through an extrusion plunger and the plunger tip, which is provided at the tip of the extrusion plunger, and, at the same time, heated with a heat generating body. CONSTITUTION:In the container 6 of an extruder, a heat generating body or induction coil 4 is arranged adjacent to a die 3 so as to heat stock precedent inserted in the interior of the container 6 just before the die 3. In addition, in a die holder 2, cooling device, with stock 5 just after extrusion molding is cooled and solidified, is annexed. The stock 5 made of solid-state metal material is inserted in the container 6 of the extruder and pressurized through an extrusion cylinder 7 and a plunger tip 7', which is provided at the tip of the extrusion cylinder by a set pressure loaded on an extrusion cylinder 7'' and, at the same time, heated by a heat generating body 4. Since the heat generating body 4 is arranged just before a die 3, the temperature of the portion, which comes into contact with the plunger tip 7, of the stock does not become higher, resulting in facilitating the selection of the material of the plunger tip 7' and, in addition, shortening the heating time of the respective portions of the stock and consequently preventing crystal grains from growing.

Description

[Detailed Description of the Invention] (Industrial Application Field) Related to extrusion processing methods, extrusion processing devices, and extrusion processing control methods using metals, alloy materials, and metal matrix composites such as cermets as raw materials. In particular, the results of research and development on the advantageous realization of extrusion processing of the above-mentioned materials in a semi-molten state, that is, in a solid-liquid coexistence region, are disclosed herein.

(Conventional technology) The objects processed by conventional extruders are exclusively solid phase materials.
Extrusion of metal in a coexisting solid-liquid state is not considered at all.

Generally, extruded materials (whole parts are heated in a recessed heat furnace,
For this reason, even in the hot extrusion of solid-phase materials, the material of the extrusion plunger tip that comes into contact with the material has been considered a problem due to the high temperature, but even more so in a solid-liquid coexistence state, the high temperature is even higher, making this an even more troublesome problem. There are no materials with high melting points such as iron-based materials that can withstand sufficient use and can be used economically.

In conventional solid phase material extrusion, extrusion processing in which the solid phase rate is kept constant as a processing condition has never been considered in the first place, and there is no solid phase rate sensor that can be used industrially.

Furthermore, since the conventional technology is solid-phase extrusion, there is no attempt to cool the molded product at the exit of the die to solidify it.

(Problem to be solved by the invention) The problems to be solved by this invention in relation to the conventional technology are as follows.

■ Regarding the material of the plunger tip, since the material becomes hotter than during hot processing, the conventional method of uniformly heating the entire material requires only the plunger tip, which contacts the end of the material and pressurizes it, to be exposed to high temperatures. . Therefore, the material of the plunger tip becomes an issue.

2. Regarding extrusion with a constant solid phase ratio and solid phase rate sensor: In order to obtain a homogeneous molded product by extrusion processing of a material in a semi-molten state, it is necessary to extrude at a constant solid phase rate. To this end, is there a way to detect the solid fraction during extrusion and feed it back to the heating device?The current method of measuring the solid fraction is to measure the temperature in a laboratory, This can only be done using a method of estimating from Since this method requires embedding a temperature sensor in the workpiece, it is not practical for industrial extrusion processing.

In addition, the method of controlling the solid phase ratio using a heating device has a slow response and can only be applied to extremely low-speed extrusion.

3. Concerning changes in the longitudinal direction of crystal grains, the crystal grains of a material in a solid-liquid coexistence state grow rapidly over time. Therefore, if the entire material is uniformly heated in advance, extrusion processing will be added to the leading and trailing ends of the material. The time required for this to occur is different, and as a result, the crystal grains at the leading end are small and those at the trailing end are large, making it impossible to obtain a homogeneous molded product.

4. Concerning crystal grain coarsening, one of the advantages of extrusion in the solid-liquid coexistence region is that the processing pressure is low, but as described in the previous section, when the crystal grains become large, it becomes difficult for them to pass through the die hole. As a result, the extrusion pressure increases. As a result, the crystals connect with each other in the die hole mold and in front of it, making it impossible to pass under small pressure, and eventually requiring pressure equivalent to hot working.

5. Concerning cooling and solidification immediately after molding, the molded material that passes through the die hole in a solid-liquid coexistence state is still highly fluid at the exit of the die hole, so it is extremely easy to lose its shape. Extruders according to the prior art do not have such means for coagulating.

(Means for solving problems) This invention is based on the findings listed below.

■ Regarding the plunger tip material, since the material is deformed and formed by the large die, there is no need to heat and uniformly heat the entire material in the container, but the part just before it flows into the die hole mold. It suffices if they are in a solid-liquid coexistence state. Therefore, by disposing the heating element of the heating device or the induction heating coil just before the die, the part of the material that comes into contact with the plunger chip does not reach a high temperature, making it easy to select the material for the plunger chip.

2 Regarding extrusion with a constant solid phase ratio and means for solid phase rate sensors, the flow and deformation characteristics of metal in a solid-liquid coexistence state have a certain relationship with the solid phase rate, and the extrusion pressure also depends on the extrusion ratio and die hole shape. There is a certain relationship with the solid phase ratio as a parameter.

In other words, the solid phase ratio has a unique relationship with the extrusion pressure theoretically determined from the flow/deformation characteristics and processing conditions, or the extrusion pressure measured by trial extrusion, so the solid phase rate is determined by the extrusion pressure during processing. is required.

Furthermore, since there is a certain relationship between the solid phase ratio and the extrusion pressure, if extrusion is performed at a constant extrusion pressure, extrusion processing can be performed at a constant solid phase rate. Further, even if the extrusion pressure is kept constant, disturbances such as fluctuations in the output of the heating device or fluctuations in heat transfer due to uneven surface conditions of the material can be absorbed by changes in the extrusion speed.

3. As for measures against longitudinal grain non-uniformity, if the material is locally heated just before the die, a solid-liquid coexistence state occurs only just before the die, and grain growth is prevented at both the leading and trailing ends of the material. Since the conditions are the same, uniform molding in the longitudinal direction can be achieved.

4. Regarding measures to prevent grain coarsening, as mentioned in the previous section, local heating immediately before the die shortens the heating time of each part of the material and prevents grain growth.

25. Regarding cooling and solidification immediately after molding, a cooling device is installed immediately after the die (for example, a cooling water nozzle is placed on the die holder), and a strong solidified shell that does not easily lose its shape is formed in the molded product immediately after passing through the die. It can be allowed to solidify or completely solidify.

Based on the above, the present invention provides a method for inserting a material made of a solid metal material or a metal matrix composite material into an extruder container, and passing it through an extrusion plunger and a plunger tip at the tip of the extrusion cylinder. A method for extruding semi-molten metal characterized by pressurizing it at a set pressure (P0) loaded on the metal and heating it using a heating element or an induction coil. An extrusion processing device for semi-molten metal, characterized in that it is installed close to a die to enable heating in the immediate vicinity, and measures extrusion speed, extrusion pressure (P), and heating output during extrusion, and extrusion is measured. Set the pressure (P) and compare it with the pressure (P, ), increase the extrusion speed when (P) < (P0), and increase the extrusion speed when (P) > (
A method for controlling the extrusion process of semi-molten metal, characterized by increasing or decreasing the heating output by a heating element or an induction coil so as to maintain the extrusion speed while reducing the speed at P0);
and a method for controlling extrusion processing of semi-molten metal, characterized in that the cooling capacity of a cooling device provided at the die outlet is increased or decreased in proportion to the extrusion speed.

(Function) Regarding the method of determining the set extrusion pressure in this invention, as already stated, it is clear that the pressure P of the extrusion cylinder can be easily determined from the extrusion force F, and the method for determining the required extrusion force F is as follows. It is as follows.

The flow and deformation properties of metals in a solid-liquid coexistence state can be determined experimentally. An example is shown in FIG.

In FIG. 1, σ is called flow 5tress or one-dimensional deformation resistance.

From FIG. 1, σ for the solid phase ratio f can be found. Once σ is determined, the required extrusion force F for a simple die hole shape can be determined by using the upper bound method, the line field method, and for complex die hole shapes, a method such as the finite element method. I can do what I want.

Alternatively, it may be determined by trial extrusion as follows.

A material to be extruded with a temperature sensor embedded in the test material is inserted into an extruder container, heated and extruded.

Then, the temperature at the time when the temperature sensor reaches the die inlet (temperature and solid phase ratio have a 1:1 relationship) and the extrusion force F may be measured.

To apply this method to the extruder according to the present invention shown in FIG. If extrusion processing is performed with different solid phase ratios f,
The extrusion force F is determined, and the relationship between the solid fraction desired for processing and the extrusion force F is easily determined.

Alternatively, the solid fraction may be determined by rapidly solidifying at the die hole exit without using a temperature sensor. The method of determining the solid fraction from the rapidly solidified metal structure is well known.

(Example) The main components for realizing the semi-molten metal extrusion method and extrusion control method according to the present invention are illustrated in FIG.

In the figure, 1 is a molded product obtained by the method of the present invention, 2 is a die holder having cooling means for the molded product 1, 3 is a die, 4 is a heating element or induction coil installed near the die 3, 5,
5' is a material, 6 is an extruder container into which the materials 5 and 5' are inserted in a solid state, and 7 is an extrusion plunger 7
' is a plunger tip, 7' is an extrusion cylinder, 8 is a pressure detector, 9 is a hydraulic pipe, 10 is an extrusion speed detector, 11 is a hydraulic device, 12 is a control/operation panel with a heating power source, 13 is a power detector, and 14 is a cooling control device including a cooling water source.

The extruder container 6 has a heating element or four induction coils installed adjacent to the die 3 so as to heat the preceding material inserted therein just before the die 3.

The die presser 2 is also equipped with a cooling device for cooling and solidifying the material 5 immediately after extrusion molding. In FIG. 2, the speed detector IO measures the speed of the extrusion plunger 7, but the speed of the molded body 1 or other material 5 may be measured.

FIG. 3 shows an example of the extruder operation/control sequence.

First, the extrusion force P0 is set as described above.

Setting Po here means determining the solid phase ratio f, so the temperature ΔT (=T-T0) to be heated can be found.

From this and the physical property values of specific heat, heat of fusion, and specific gravity, the amount of heat Q (J/m?) per unit volume can be determined.

Here, assuming the initial extrusion speed Vo (m/s),
If the cross-sectional area of the workpiece is S (m), the amount of heat that should be given to the workpiece is QSV per second (J/s), so the initial heating output of the heating element or induction coil is W, = ・Q
The output of the heating device is set so that SV, [:J/s). Here, K is called a coupling coefficient, and is a constant determined by the specific resistance, relative magnetic permeability, frequency of the induced current, and diameter of the heated object if it is a cylinder.

Insert the workpiece into the container 6, and press Pa and W.

Load. It can be operated and controlled according to the sequence shown in FIG. 4 below.

(Effects of the Invention) By the method of the present invention, regardless of the material of the plunger tip and without using a solid phase rate sensor, it is possible to obtain an extruded material whose material is like - in the longitudinal direction, I can make appropriate decisions.

[Brief explanation of drawings]

Figure 1 shows the solid phase ratio f of semi-molten metal and the flow stress (flow
FIG. 2 is an explanatory diagram showing the procedure for extruding semi-molten metal according to the present invention, and FIGS. 3 and 4 are initial and steady operation control sequence diagrams of the extruder. l...Molded body 2...Dice holder with cooling means 3...Dice 4...Heating element or induction coil 5.5" material 6...Extruder container 7.
...Extrusion plunger 8...Plunger tip Fig. 1 Fig. 3

Claims (1)

[Claims] 1. A material made of a solid metal material or a metal matrix composite material is inserted into an extruder container and loaded onto an extrusion cylinder via an extrusion plunger and a plunger tip at its tip. A method for extruding semi-molten metal, characterized by applying pressure at a set pressure (P_0) and heating using a heating element or an induction coil. 2. The set pressure (P_0) to be applied to the extrusion cylinder is determined by the flow or deformation characteristics of the material in the solid-liquid coexistence state, the extrusion ratio, and the hole type.Theoretical calculation is performed from the processing conditions or trial extrusion is performed in the material's solid-liquid coexistence state. The extrusion processing method according to claim 1, which is obtained in accordance with the above. 3. Place the heating element or induction coil inside the extruder container;
A semi-molten metal extrusion processing device characterized by being installed close to a die to enable heating of the material in the vicinity of the die. 4. Measure the extrusion speed, extrusion pressure (P) and heating output during extrusion, set the measured extrusion pressure (P) and compare it with the pressure (P_0), and set the extrusion speed to (P) < (P_0).
) and decelerates when (P)>(P_0), while increasing/decreasing the heating output by a heating element or induction coil to ensure the extrusion speed. Control method. 5. A method for controlling the extrusion process of semi-molten metal, characterized by increasing or decreasing the cooling capacity of a cooling device provided at the die outlet in proportion to the extrusion speed.