JPS6317003B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to high-temperature isostatic extrusion in which a billet is hydrostatically extruded from a die at high temperature using an organic pressure medium. This product solves problems such as coarsening of crystal grains and surface oxidation caused by the oxidation of grains, and makes it possible to obtain high-quality extruded products.

High-temperature isostatic extrusion involves heating a billet made of steel or nonferrous metal to a high temperature, placing it in a container, filling the area around the billet with pressure medium, and extruding it from a die through a stem or mandrel to obtain the desired extruded material. It is well known that this method is widely used in various fields due to its advantages such as high-speed processing with a large extrusion ratio, but such high-temperature isostatic extrusion methods commonly have the following problems. A point exists. In other words, organic pressure medium and lubricant adhere to the surface of the extruded material by several micrometers, and during high-temperature extrusion, this becomes black or carbonized, staining the surface of the extruded material and causing poor surface condition. Furthermore, since items extruded at high temperatures require time to cool down, the crystal grains of the extruded material tend to become coarser during this time. For example, in the case of brass, which is a non-ferrous metal material, If such coarse grains are formed, the surface will become rough during drawing after extrusion, leading to a decrease in quality.Furthermore, if the extruded material is left in the atmosphere at high temperatures, the adhesion pressure medium on the surface of the extruded material and The lubricant turns black and then burns, which develops into surface oxidation, and this phenomenon is particularly noticeable in pure copper, nickel-copper alloys, and carbon steel.

The present invention has been made in order to solve such problems. Immediately after extrusion by such high-temperature isostatic pressure extrusion, a combustion aid is supplied to the exit side of the die to burn the adhering pressure medium, and then cooling is performed. This method prevents surface oxidation as well as grain growth by providing a region of the billet, which is characterized by the fact that the billet is diced at high temperature using an organic pressure medium. It is a method of hydrostatic extrusion, which consists in supplying a combustion aid to the outer surface of the extruded material on the exit side of the die to burn the pressure medium adhering to the outer surface of the extruded material, and then cooling the extruded material with water. Further, its characteristics are that the billet is made of copper or a copper alloy, the combustion improver is air, and the supply amount Q is Q=K・d ^m・R・vl/min.
(However, d is the outer diameter of the extruded material mm, R is the extrusion ratio, v is the extrusion speed mm/S, m is a constant of 1.4±0.1, and K is a constant of 0.00067
≦K≦0.0018).

The present invention will be described in detail below based on the illustrated examples. When a heated billet is charged into a container, the area around the billet is filled with an organic pressure medium, and the billet is extruded, the surface of the extruded material is Looking at the thickness of the adhering carbide (pressure medium), for example, when a copper alloy tube is extruded with an extrusion ratio of 100, a billet heating temperature of 800°C, and pressure medium heat-resistant grease, the thickness of the carbide is measured by EPMA. The maximum amount of adhesion was 1.4 μm. Therefore, in order to burn and remove such adhering carbides, it is sufficient to supply a combustion aid while the extruded material is at a high temperature and combust it through the heat of the extruded material itself.

For example, as shown in the experimental example shown in FIG. 1, a heated billet 2 charged into a container 1 is filled with a pressure medium 3 around the outside of the billet using the container 1, and the billet 2 is transferred to an extrusion stem ( The desired extruded material 5 is obtained by high-temperature isostatic extrusion using a die 4 (not shown), and a block 6 or the like loosely surrounding the extruded material 5 is used on the exit side of the die 4. Same block 6 and extruded material 5
A combustion improver circulation area A is formed in a spatial manner between the two, and a combustion improver such as air or other combustion agent is provided in this area A so that it flows to the outer periphery of the extruded material 5 through the supply port 7. be. At this time supply port 7
It may be supplied directly into the area A, or it may be supplied through a partition wall 8 made of a perforated plate as shown in the figure. However, when supplying a combustion improver to burn the adhering carbide, care should be taken to ensure that the combustion is insufficient and the adhering carbide does not remain.
It is also necessary to ensure that combustion is not too sufficient and oxidation does not occur too much. In the present invention, the supply time and supply amount of the combustion improver were variously changed, and the necessary or minimum conditions for obtaining an extruded material with a beautiful surface were studied. Since there is not much difference between
200mm, heating temperature 900℃, extrusion speed of extrusion stem
As a result of repeating various experiments under the conditions of 50 mm/sec, extrusion ratio of 51, 120, and using air as a combustion improver, the following was clarified.

That is, since the amount of air supplied is proportional to the amount that the surface of the extruded material passes through the combustion zone per unit time, the relational expression Q=K.d ^m.R.vl /min can be obtained for the amount of air supplied. However, in the above formula, K and m are constants, d is the outer diameter of the extruded material (mm), R is the extrusion ratio, and v
is the extrusion speed (stem mm/S), and the internal constant m of the above constant is determined by the die angle, extrusion speed, and viscosity of the pressure medium, and it was determined by experiment that m = 1.4 ± 0.1. It turns out that there is something.

According to the experimental results repeatedly conducted in this way, the relationship between the surface quality of the extruded material made of Cypronickel material and the extrusion conditions is as shown in the graph of Figure 2, where the vertical axis is the air supply amount Q, and the horizontal axis is the Extruded material d
However, as is clear from the figure, the boundary to prevent surface oxidation is (Q = 150 l/min, d = 6.2
mm), (Q=118l/min, d=9.5mm), and the values of constant K and constant m at this time are K=
0.0018, m=1.44, and similarly, in order for no unburned carbide to remain on the surface, the value of the constant K is
0.00067, and the value of the constant m is 1.14. In this case, the constant m should originally be m = 1, but since the thickness of the carbide adhering to the extruded material surface changes depending on the extrusion ratio, in reality m≠0, and generally m> It is 1.

When the results of the above experiments are organized in terms of the relationship between the air supply area passage time and the air supply amount, the graph shown in FIG. 3 is obtained. In other words, the figure is a graph showing the influence of air supply conditions on the external surface quality of extruded materials. The vertical axis is the combustion time, the horizontal axis is the air supply amount, and the passing time to obtain a beautiful surface is the It depends on the air supply amount, but for example, if the air supply amount is 140l/min, it will take 0.13 seconds, and if the air supply amount is 140l/min, it will take 70l/min.
In the case of min, it can be seen that 0.35 seconds or less is good. At this time, if the amount of air supplied is small, the passage time can be increased, but in this case there is a disadvantage that the temperature of the extruded material decreases less and coarse grains grow. The above-mentioned test material, Cypronickel, does not generate extremely coarse crystals even if it is left to cool in the air after extrusion, so the crystal grains grow quickly, and because of this, aluminum brass has a problem of rough skin during drawing. As a result of conducting repeated experiments and examining the length of the air supply region using the material as a test material, we came to the following conclusion regarding the length of the air supply region that can prevent coarsening of crystal grains. It was obtained. That is, as extrusion conditions, a billet made of aluminum brass material (68 mm × 200 mm) was used, the heating temperature was 800 ° C, the extrusion speed was 1.7 m/S, the extrusion ratio was 40, the extruded material size was 22.0 mm × DD × 1.5 mm, and as a combustion improver. air
20l/min, and its extrusion device is as illustrated in Figure 4, in which 1 is a container, 2 is a billet, 3 is a pressure medium, and 4 is a die.These structures were previously shown in Figure 1. This is the same as described above, but in this case, the length of the distribution area A with air supply similar to that shown in Fig. 1 provided on the exit side of the die 4 is 0.7 m.
Further, following the area A shown in FIG. 1, a water cooling area B, which surrounds the outer surface of the extruded material 5 and is supplied with cooling water from the supply port 9, is shown in FIG. In the device shown in , the length of area B is 1.2 m.

In addition, in the experiment using the apparatus shown in Figure 4, the water volume was varied from 0 to 36 liters to see the effect of water cooling.
This is a comparison between the min and the aquarium. Regarding the experimental results, firstly, the relationship between the amount of cooling water and the grain size is as shown in Figure 5, which shows the effect of the amount of cooling water on the grain size of the extruded material (extruded raw tube obtained in Figure 4). In this graph, the vertical axis shows the crystal grain size and the horizontal axis shows the amount of cooling water.As is clear from the figure, when the amount of cooling water is 0 l/min, the average grain size is 0.07 mm, but the cooling It can be seen that as the amount of water increases, the grain size becomes finer, and when the water flow is 20 l/min or more, the grain size becomes 0.040 mm or less.

In other words, when extruding a billet made of aluminum brass material to make a blank tube and drawing it after extrusion, the smaller the crystal grain size, the more beautiful the surface texture will be.
Considering what is clear from the graph of the relationship between cold working rate and crystal grain size illustrated in Figure 6, if the grain size is 0.04 mm or less, the surface texture is sufficiently good even with one or two passes of extrusion. You can get something,
Therefore, if an air circulation area A of 0.7 m is provided on the exit side of the die, the extrusion speed is 1.7 m/S, so
The passage time of this air supply area is 0.41 seconds, which is sufficient time to completely burn out the adhering carbide (organic pressure medium) on the surface of the extruded material, judging from the results shown in Figure 3 above. It turns out that there is something.

The present invention has been comprehensively obtained from the above experimental results, and is based on the fact that a combustion improver (air or other) is supplied to the surface of the extruded material immediately after extrusion on the exit side of the die, and the pressure medium that is the attached carbide is supplied to the surface of the extruded material immediately after extrusion. By completely combusting the extruded material and then cooling it with water, the adhering carbides are first removed by combustion, thereby eliminating stains on the surface of the extruded material and making it beautiful.
The subsequent water cooling can prevent coarsening of crystal grains due to delayed cooling time and also prevent surface oxidation, thereby eliminating the problems of the conventional method. At this time, crystal grain growth of copper-based metals progresses when the temperature exceeds 500°C, so it is preferable to rapidly cool the metal in the shortest possible time. As in the present invention, after the combustion zone is started and then cooled with water, the adhered carbides are burned off and the purified product is cooled, thereby preventing the coarsening of crystal grains. This makes it easy to obtain an extruded material with a beautiful surface texture, and this is very effective as it prevents the roughness that tends to occur during the drawing process after extrusion. Furthermore, surface oxidation caused by extruded material extruded at high temperature is left in the atmosphere, which can be reliably prevented by burning off adhering carbides immediately after extrusion and subsequently cooling with water. It is particularly effective for ferrous metal materials, and is excellent for accurately preventing deterioration of the surface of extruded materials caused by high-temperature isostatic extrusion and improving the quality thereof.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of an example of the method of the present invention, Fig. 2 is a graph showing the relationship between the surface quality of the extruded material and extrusion conditions, Fig. 3 is a graph showing the relationship between the same surface quality and air supply conditions, and Fig. 4 5 is a graph showing the relationship between the grain size and the amount of cooling water, and FIG. 6 is a graph showing the relationship between the cold working rate and the grain size. 1... Container, 2... Billet, 3... Pressure medium,
4... Dice, A... Combustion aid distribution area, B... Water cooling area.

Claims (1)

[Claims] 1. A method of isostatically extruding a billet from a die at high temperature using an organic pressure medium, in which a combustion improver is supplied to the outer surface of the extruded material on the exit side of the die to improve the quality of the extruded material. A method for high-temperature isostatic extrusion of metals, characterized in that the pressure medium adhering to the outer surface is combusted, followed by water cooling of the extruded material. 2 A method of isostatically extruding a billet from a die at high temperature using an organic pressure medium, in which a combustion improver is supplied to the outer surface of the extruded material on the exit side of the die, and the pressure is applied so that it adheres to the outer surface of the extruded material. When the medium is combusted and the extruded material is subsequently cooled with water, the billet is copper or copper alloy, the combustion improver is air, and the supply amount Q is Q=K・d ^m・R・Vl/min.
(However, d is the outer diameter of the extruded material mm, R is the extrusion ratio, V is the extrusion speed mm/s, m is the constant 1.4±0.1, and K is the constant 0.00067
≦K≦0.0018).