JPH02179802A - Metal powder clad tube extruded billet and heat insulating steel tube - Google Patents

Abstract

PURPOSE:To provide an extruded billet for high deforming resistant metal powder clad tube without any surface defect by making multi-layered heat insulating structure of a metal plate covering outer surface of metal powder having high deforming resistance. CONSTITUTION:The high deforming resistant metal powder 3, which becomes one layer and high density after extruding, is packed into space composed of an outer cylinder 1 of thick steel pipe and inner cylinder 2 and an upper and lower cover plates 4, 5 to form the billet. In this billet, the inner cylinder 2 is made of heat insulating steel pipe, for example, composed of outer layer pipe 2-1, inner layer pipe 2-2 and the heat insulating layer 2-3. By this method, even if the whole thickness of the inner cylinder 2 is thin, the effect of restraining cooling of the metal powder 3 is large and the development of the surface defect of crack and break-off at the metal powder layer 3 side at the time of hot-extrusion working is prevented and also the inner cylinder 2 is easily removed after extruding. Then, the inner and outer cylinders 2, 1 may be used in reverse.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a metal powder clad pipe extrusion billet with high deformation resistance and members used therefor, and more specifically to a cylindrical billet composed of a plurality of concentric material layers. and the insulated steel pipes that make up it.

Conventional technology For pipes used in usage environments that require strength and corrosion resistance, there are clad pipes that provide strength with steel pipes and corrosion resistance with expensive highly corrosion-resistant metals, but highly corrosion-resistant metals are difficult to process. For this reason, there are metal powder clad pipes using powder metallurgy.

For example, as shown in FIG. 4, a metal powder clad pipe is manufactured by disposing a metal powder layer (13) between a thick-walled metal cylinder (11) and a thin-walled metal cylinder (12). respectively above 14) and below! A method of making a billet with a closed structure using (15) and hot extruding it (Special Publications No. 6)
0-37162), a thin intermediate wall is provided in a cylindrical capsule, and the inside and outside of this intermediate wall are filled with different metal powders, and then the billet from which the intermediate wall is removed is hot extruded. A method (Japanese Patent Publication No. 55-10643) is known.

The thin side cylinder of the extruded billet used in these methods is removed after extrusion. That is, these cylinders form the walls of the capsule into which the powder is placed.

Problems to be Solved by the Invention When using such conventional extruded billets, it is possible to manufacture the desired product without any particular problem if there is no large difference in hot deformation resistance between the dissimilar metals that make up the clad pipe. However, when hot-extruding materials with large differences in deformation resistance between dissimilar metals, such as alloy powders with high deformation resistance, microcracks and roughness may occur on the surface of the metal with high deformation resistance. In severe cases, this metal layer may be missing, resulting in a large defect.

These quality defects occur because the temperature of the alloy powder surface, which has high deformation resistance, decreases due to local cooling from the outside due to the thin capsule wall material, causing an increase in deformation resistance and a decrease in ductility. It is thought that this occurs due to shear deformation during hot extrusion processing. Although cooling can be alleviated by increasing the thickness of the capsule wall material, it is not preferable because it requires a large amount of expense in the removal step after extrusion.

As described above, in the conventional methods for manufacturing metal powder clad tubes, defects occur on the tube surface after hot working in the case of clad tubes made of metal materials with significantly different deformation resistances.

This invention was made in view of these conventional problems, and by making the metal plate that covers the outer surface of metal powder with high deformation resistance into a multilayer insulation structure, it is possible to reduce the overall thickness of the metal powder even though the total wall thickness is small. First, the present invention provides an extruded billet and an insulating steel pipe for producing a high-quality, high-deformation-resistant metal powder clad pipe that is highly effective in suppressing cooling of metal powder and has no surface defects.

Means for Solving the Problems The gist of the present invention is to provide an extrusion billet for use in producing a clad pipe made of two layers, one layer of high deformation resistance metal and the other layer of steel, by hot extrusion. The space consisting of the cylinder, the inner cylinder, and the upper and lower cover plates is filled with the densified high deformation resistance metal powder that becomes one layer after extrusion, and the outer cylinder is a thick-walled steel pipe that becomes the extruded layer. The inner cylinder is an insulated steel pipe that is removed after extrusion, and the metal powder clad pipe extruded billet is characterized in that the outer cylinder is an insulated steel pipe that is removed after extrusion, and the inner cylinder is an insulated steel pipe that is removed after extrusion. It is characterized by being a thick-walled steel tube that forms another layer, and on the outer periphery of the space consisting of the outer cylinder, inner cylinder, and upper and lower lids, there is a high-density, high-deformation-resistance metal powder that forms a single layer after extrusion. The inner peripheral side of the space is filled with densified high powder that will become another layer after extrusion, the outer cylinder is an insulated steel pipe that is removed after extrusion, and the inner cylinder is is characterized by a metal covering that is to be removed after extrusion,
In addition, the inner circumferential side of the space is filled with highly densified high deformation resistance metal powder that will form one layer after extrusion, and roughly the outer circumferential side of the space is filled with highly densified metal powder that will form another layer after extrusion. This is a metal powder clad pipe extrusion billet characterized by being filled with copper powder.

Briefly, the present invention provides an insulated steel pipe for extruded billet metal powder clad pipe, characterized in that a heat insulating material is filled between each layer of at least two or more thin-walled steel pipes.

Here, high deformation resistance metals are Fe-based alloys, NL-based alloys, C
Refers to O-based alloys, especially those whose deformation resistance at 1ooo'c is 20
refers to alloys with f/- or more. In addition, the deformation resistance is
This refers to the high-temperature tensile strength of a material after sintering powder or an ingot material.

For production Next, the reasons for limiting each component will be explained.

The annular billet is placed inside the container of the extrusion equipment,
A mandrel is inserted into the inner diameter portion and extruded from the die.

Barrel: The barrel is a component of the capsule that confines the powder. However, when the outer layer of the extruded clad pipe is made of steel manufactured by a melting method, it is also a component of the product. The wall thickness and material should be selected according to the required strength of the product. The outer diameter is the size that fits into the billet container of the extrusion equipment.

If it is not used as a component of a product and does not come into contact with high deformation resistant metal powder, the thickness and material should be selected so that it can function as a capsule and be easily removed after extrusion. For example, the material is mild steel.

If it is not used as a component of a product and comes into contact with high deformation resistant metal powder, use an insulated steel pipe.

Inner cylinder: The inner cylinder is also a component of the capsule to confine the powder. However, when the inner layer of the extruded clad pipe is made of steel manufactured by a melting method, it is also a component of the product. The wall thickness and material should be selected according to the required strength of the product.

If it is not used as a component of a product and does not come into contact with high deformation resistant metal powder, the thickness and material should be selected so that it can function as a capsule and be easily removed after extrusion. For example, the material is mild steel.

If it is not used as a component of a product and comes into contact with high deformation resistant metal powder, use an insulated steel pipe.

Upper and lower lid plates: Both are constituent members of the capsule to confine the powder. These are assembled with an inner cylinder and an outer cylinder concentrically. One or both of these may be fitted with tubes for filling the powder, for adding powder to the colander after it has been filled, or for removing any gas remaining in the capsule. good.

The material should be selected to be easy to assemble with the outer cylinder and inner cylinder. The wall thickness should be appropriate so that the side that will become the tip during extrusion also serves as a dummy member, and its shape should be appropriate as a dummy. During extrusion, the side that will become the rear end should have an appropriate thickness and shape so that it also serves as a push plate.

Densified high deformation resistant metal powder: This powder is a component of the product after extrusion. This side of the product is used for corrosive environments. Therefore, the material must be highly corrosion resistant to the environment. The wall thickness of the product after extrusion is selected depending on the usage conditions, but generally it can be thinner than the cladding steel member. The thickness of the powder layer during billeting may correspond to the thickness of the product.

The powder may have the components of the final product, or it may be mixed in a powder state and the components may be adjusted. This powder must be encapsulated and densified. By densifying the powder, the uniformity of the wall thickness distribution and productivity (product length relative to billet length) of the product after extrusion can be significantly improved. It is possible to extremely easily design the dimensions of the billet that roughly correspond to the dimension ratio of the cladding layer of the product.

Steel powder: This steel powder is a component of the finished product after extrusion.

This method is effective in manufacturing clad pipes made of steel materials and high deformation resistance metals, which are difficult to manufacture using the melting method. The thickness and material of this powder layer should correspond to the product.

Insulated steel pipe: The insulated steel pipe is also a component of the capsule for confining the powder, especially the capsule wall material on the side that contacts the high deformation resistant metal.

Since the product after extrusion has one layer made of high deformation resistance metal and the other layer made of steel, there is a large difference in deformation resistance at the same temperature, and therefore extrusion processing is usually extremely difficult.

Roughly, after heating before extrusion, a slight temperature drop occurs in the inner and outer surface layers of the billet while the billet is carried into the container of the extrusion equipment, and during the extrusion process after being carried into the container and inserting the mandrel, the billet is transferred to the container and mandrel. Pressed with high pressure.

Although the container and mandrel are preheated, the temperature is generally very low compared to the billet temperature. For example, these tool temperatures are about 250-300°C and billet temperatures are about 1200'C.

Therefore, the temperature of the outer and inner surfaces of the billet decreases rapidly. Since the high deformation resistance metal powder has higher deformation resistance than the steel in other layers even at the same temperature, the difference becomes even larger, making normal extrusion extremely difficult.

This insulated steel pipe has a very large effect in preventing the temperature of the high deformation resistant metal powder from decreasing.

The reason why the insulated steel pipe is made into a multi-layered pipe with two or more layers is to reduce the thickness so that it can be easily removed by, for example, pickling after extrusion. The wall thickness and material may be of any material as long as it can withstand the wall thickness range due to oxidation during heating and maintain the capsule function.

Insulating material: Insulating material has the effect of reducing the heat transfer performance of insulated steel pipes and improving their insulation performance.

The material may be metal oxides, metal nitrides, mixtures thereof, other refractory bricks or heat-insulating brick materials, etc., as long as they have a sufficient heat insulating effect. These substances may be filled between the laminated layers of the insulating steel pipes, or may be formed on the laminated surfaces.

EXAMPLE Billets having the structure shown in FIGS. 1 to 3 were manufactured, and their effects were compared with those of the conventional billet shown in FIG. 4.

Figure 1 shows a case where the high deformation resistance metal is the inner layer of the product and the steel pipe is the outer layer. Therefore, the outer cylinder (1) is a thick-walled steel pipe, and the inner cylinder (2) is a heat-insulating steel pipe. A high deformation resistance metal powder layer (3) is formed between the outer cylinder and the inner cylinder. At the top and bottom, there are an upper M (4) and a lower M (5), respectively. The insulated steel pipe (2) - for example, an outer layer pipe (2-1) and an inner layer pipe (2-1)
-2) and a heat insulating material layer (2-3).

FIG. 2 is an example in which the inner and outer cylinders are opposite to those in FIG. 1.

FIG. 3 shows a case where the high deformation resistance metal is the inner layer of the product and the sintered steel pipe is the outer layer. Therefore, the outer cylinder (1) is a thin-walled steel tube that is removed after extrusion, and inside this there is a steel powder layer (sword), and further inside that there is a high deformation resistance metal powder layer (3), and the inner cylinder is an insulated steel tube ( 2).

The dimensions of each of these billets are 1000mm in total length.
, an outer diameter of 180 mm and an inner diameter of 86 mm. Table 1 shows the billet structure, dimensions, materials, and pipe manufacturing results.

The material of the upper and lower lids is mild steel, and the extruded tip is made thick to create a dummy material effect. The metal members of the insulated steel pipe are low carbon steel.

The insulated steel pipe of Example 1 had two layers, and the inner layer and outer layer of this tube were oxidized in the atmosphere at 850° C. for 1 hr, and then stacked and lightly drawn. Therefore, in this case the insulation material is iron oxide.

The insulated steel pipes of Examples 2, 3, and 4.5 also have two layers, and after applying a predetermined heat insulating material to a predetermined thickness on the surface of the inner layer pipe, as shown in Table 1, It was manufactured by stacking it with a tube and drawing it lightly.

In the case of the billet shown in FIG. 1, the inner diameter of the heat-insulating tube corresponding to the example was 78 mm, and after cutting to a length of about 1000° C., the tube was expanded by a well-known method until the inner diameter of both tube ends became 86 mm. After this tube was welded to the lower lid, the annular gap was filled with the powder shown in Table 1, and the upper lid was welded.

This assembly was subjected to isostatic hydrostatic pressure treatment (CIPffi process) at 4300 atmospheres and maintained for 2 minutes. After the CIP treatment, the billet had an inner diameter of approximately 86 mm and was approximately in the shape of a right cylinder.

Through this process, the density of the powder is approximately 7% of the true density at the time of filling.
While it was 2%, it increased to about 81% after CIP treatment.

In the case of the billet shown in Fig. 2, the outer diameter of the insulated pipe corresponding to the example was 198 mm, and after cutting it to a length of about 1000 mm, the pipe was drawn by a spinning method until the outer diameter of both pipe ends became 180 mm. Ta. After this tube was welded to the lower cover, the upper cover to which two exhaust pipes were attached was welded.

After injecting the powder from one side of this tube, one tube is sealed,
After exhausting residual marsh air from the other tube using a vacuum device, it was sealed.

This assembly was subjected to CIP treatment at 4300 atmospheres for 2 minutes. This treatment increased the density of the powder to about 80% of the true density, and the outside diameter of the billet was about 180 mm.

In the case of the billet shown in FIG. 3, a container was created by a method that combined FIGS. 1 and 2. In this case, the powder is filled by inserting a metal cylinder concentrically into the space of the capsule to form a partition wall, the outer space of this partition wall is filled with carbon steel (CIM) powder, and the inner space is filled with HF. After filling the base alloy,
The partition wall was removed and the top cover was welded.

The above billet is heated to 1100 to 1220 by high frequency heating.
It was heated to 0.degree. C. and a tube with an outer diameter of 102 mm and an inner diameter of 86 mm was extruded. The preheating temperature of the container and mandrel is approximately 270℃.
It is °C.

After extrusion, the inner and outer tubes, which are not product constituents, were removed by pickling to produce a product.

From Table 1, it is clear that in the case of the present invention, the presence of the heat insulating tube prevents the temperature drop of the high deformation resistant metal powder, and the extrusion process is good, which is better than when using the conventional billet. I'll go.

As described below in detail of the margin invention, according to the method of this invention, 1ooo℃
Even with high deformation resistance metal powder whose deformation resistance exceeds 20 kq 4J, it is possible to prevent the temperature of the metal powder layer from decreasing, which is the main cause of tube surface defects.
It has become possible to manufacture high-quality metal powder clad tubes without surface defects, which has been considered difficult in the manufacture of clad tubes made of metal materials with significantly different deformation resistance, and it is now possible to manufacture hot extruded clad tubes using powder metallurgy. It has great effects.

[Brief explanation of the drawing]

Figures 1 to 3 illustrate billets of metal powder clad pipes according to the present invention. Figure 1 shows high deformation resistance metal powder arranged inside a thick-walled cylinder, and the inner cylinder of the billet is connected to a heat-insulating tube. Figure 2 is a vertical cross-sectional view showing a billet with a billet outer cylinder made of a heat-insulating tube placed outside a highly deformable metal powder cylinder, and Figure 3 is a billet outer cylinder. is a thin-walled steel tube, a carbon steel powder layer and a high deformation resistance metal powder layer are arranged inside this outer tube, and the inner tube of the billet is made of an insulating steel tube. Figure 4 is a vertical cross-sectional view showing a billet made of a heat-insulating steel tube. Required for longitudinal sectional views showing examples.

Claims (1)

[Claims] 1. An extrusion billet used in the production of a two-layer clad tube, one layer of high deformation resistance metal and the other layer of steel, by hot extrusion, the billet comprising an outer tube and an inner tube. The space formed by the cylinder and the upper and lower lid plates is filled with the densified powder of the high deformation resistance metal that becomes the single layer after extrusion, and the outer cylinder is a thick-walled steel pipe that becomes the other layer after extrusion. A metal powder clad pipe extrusion billet, wherein the inner cylinder is an insulated steel pipe that is removed after extrusion. 2. The metal powder clad pipe extrusion billet according to claim 1, wherein the outer cylinder is an insulated steel pipe that is removed after extrusion, and the inner cylinder is a thick-walled steel pipe that becomes the other layer after extrusion. 3. An extrusion billet used when manufacturing a clad tube consisting of two layers, one layer of high deformation resistance metal and the other layer of steel, by hot extrusion, and the billet consists of an outer cylinder, an inner cylinder, and upper and lower cover plates. The outer periphery of the space is filled with the highly densified high deformation resistance metal powder that becomes the one layer after extrusion, and the inner periphery of the space is filled with the densified powder that becomes the other layer after extrusion. An extruded metal powder clad pipe billet, characterized in that the outer tube is an insulated steel tube that is removed after extrusion, and the inner tube is a metal that is removed after extrusion. . 4 The inner periphery of the space in claim 3 is filled with the densified powder of the high deformation resistance metal that becomes the single layer after extrusion, and the outer periphery of the space is filled with the other layer after extrusion. A metal powder clad pipe extrusion billet characterized by being filled with highly densified steel powder. 5. An insulated steel pipe for an extruded billet of metal powder clad pipe, characterized in that a heat insulating material is filled between each layer of at least two or more thin-walled steel pipes.