JP7118769B2 - Manufacturing method of plastic working material - Google Patents

Description

The present invention relates to a method of manufacturing a plastically worked material.

Extrusion for manufacturing metal pipes and bars processes metal materials by plastic deformation. For extrudability in the above-described extrusion process, it is important that the metal material not break due to cracks or the like during deformation, enhance the properties of the metal material, or be processed into a predetermined size and shape. Extrudability depends on many factors such as the temperature of the metal material, extrusion conditions such as the temperature and deformation speed of molds such as containers, dies, stems and mandrels, and the properties of the metal material such as composition and structure. In addition, one of the factors that affect the extrudability of metal materials is heat transfer, friction, and wear caused by the interaction between the mold surface and the metal material surface. Therefore, the heat insulation and lubricity between the metal material and the mold such as a container, die, stem, mandrel, etc. during extrusion are factors that affect extrudability.

For example, in extrusion processing, it is common to insert a billet into a billet hole in a die, apply an extrusion force to the billet in a container with a stem, and pass the billet through the gap of the die by this extrusion force to shape it. . In this extrusion process, the dies, mandrels, and the inner peripheral wall of the container often seize, and in a relatively short period of time, the degree of seizing becomes excessive, increasing the frictional force between the dies, mandrels, containers, and the billet. This may shorten the life of dies such as dies, mandrels and containers.

In the prior art, it is disclosed to apply a solid lubricant with excellent thermal stability and coating film formation to the mold for the purpose of reducing friction during processing and suppressing damage to the mold due to wear ( See JP-A-2001-240887).

JP-A-2001-240887

Use of the solid lubricant reduces friction during processing such as extrusion and forging. However, with conventional molds coated with solid lubricants, the durability of the coating film is not sufficient, and each time the extrusion process is repeated, the surface area of the metal material expands and the lubricant wears off, causing friction with the mold. Due to this, there is a risk that flaws due to seizure or the like may occur on the surface of the plastically worked material after working. These problems are particularly desired in the hot plastic working of heat-resistant and difficult-to-work metallic materials such as titanium, titanium alloys, nickel alloys, and zircaloys.

The present invention has been made in view of such circumstances, and provides a method for manufacturing a plastically worked material that can reduce friction during hot plastic working and suppress the occurrence of flaws due to seizure or the like on the surface of the plastically worked material. for the purpose of providing

In order to solve the above problems, the present inventors have studied a method for improving the plastic workability of difficult-to-work metal materials such as titanium, titanium alloys, nickel alloys, and zircaloys.

One aspect of the present invention, which has been made to solve the above problems, measures the arithmetic mean roughness (Ra) of the surface of a difficult-to-work metal material according to JIS-B0601 (2001) by shot blasting. A method for producing a plastically worked material, comprising the steps of adjusting the thickness to 1.5 μm or more and 25.0 μm or less, applying a solid lubricant to the surface of the metal material, and plastically working the metal material.

In the method of manufacturing the plastic working material, the arithmetic mean roughness (Ra) of the surface of the difficult-to-work metal material is adjusted to 1.5 μm or more and 25.0 μm or less by shot blasting as a pretreatment step for plastic working. The solid lubricant can be fixed on the surface of the metal material by applying the solid lubricant by pressing. As a result, it is possible to suppress the removal of the solid lubricant due to friction between the metal material and the mold, and improve the adherence of the solid lubricant to the surface of the difficult-to-work metal material. It is possible to suppress the occurrence of flaws due to seizure on the surface of the plastically worked material.

The method of manufacturing a plastically worked material according to the present invention can reduce friction during plastic working and suppress the occurrence of flaws due to seizure or the like on the surface of the plastically worked material.

1 is a cross-sectional view of a hollow billet, which is a metal material used in the method of manufacturing a plastically worked material of the present invention; FIG. 1 is a schematic cross-sectional view of an extrusion device during hot extrusion processing in one embodiment of the method for manufacturing a plastically worked material of the present invention. FIG.

A method of manufacturing a plastically worked material according to one embodiment of the present invention will be described below.

<Method for manufacturing plastically worked material>
The manufacturing method of the plastically worked material relates to heat-resistant alloys such as titanium and titanium alloy materials, and manufacturing methods thereof. In the method for producing the plastic work material, the arithmetic average roughness (Ra) measured according to JIS-B0601 (2001) of the surface of the difficult-to-work metal material is shot blasted to 1.5 μm or more and 25.0 μm. a step of applying a solid lubricant to the surface of the metal material; and a step of plastic working the metal material. Moreover, it is preferable that the method for manufacturing the plastically worked material includes a step of heating the metal material. The heating step may be performed either before or after the solid lubricant application step.

In the method for producing the plastically worked material, the surface of a difficult-to-work metal material (billet) is adjusted to a predetermined arithmetic mean roughness by shot blasting, and then the surface of the metal material is coated with a solid lubricant to perform plastic working. It is possible to secure the lubricity at the time and suppress the outer surface defects of the plastically worked material. More specifically, according to the method for producing a plastically worked material, even in the plastic working of a difficult-to-work metal material, there is good adhesion between the metal material and a mold such as a die, container, stem, or mandrel. lubricity can be ensured. As a result, the friction between the mold and the metal material can be reduced, and defects such as seizure and galling (abnormal wear of the sliding surface) that tend to occur during plastic working can be suppressed, and the surface quality is excellent. It is possible to manufacture plastic processed materials with good dimensional accuracy. In addition, the release between the metal material being processed and the mold or the like becomes smooth, and the life of the mold or the like can be extended. In addition, since the surface defects of plastically worked materials can be reduced, it is possible to reduce costs and improve quality by improving the yield and productivity of plastically worked metal materials such as titanium, titanium alloys, nickel alloys, and zircaloy, which are difficult to work. Become.

Specific examples of the plastic working include free forging, closed forging, forward extrusion, backward extrusion, radial forging, upset forging, and draw forging.

[Arithmetic Mean Roughness Adjustment Step]
In this step, the arithmetic mean roughness (Ra) of the surface of the hard-to-work metal material measured according to JIS-B0601 (2001) is adjusted to 1.5 μm or more and 25.0 μm or less by shot blasting. This step can improve the fixability of the solid lubricant on the surface of the hard-to-work metal material.

Hard-to-work metal materials such as ingots and billets used in the present invention are suitable for hard-to-work metal materials such as titanium, titanium alloys, nickel alloys, and heat-resistant alloys such as zircaloy.

Alumina, steel, stainless steel, ceramic, and the like are preferable as the material of the shot for shot blasting, which is the means for adjusting the arithmetic mean roughness. Among these, steel is preferable from the viewpoint of improving the fixability of the solid lubricant to the surface of the metal material.

The lower limit of the arithmetic mean roughness (Ra) measured in accordance with JIS-B0601 (2001) of the surface of the difficult-to-work metal material after adjusting the arithmetic mean roughness is 1.5 μm. If the average roughness is less than 1.5 μm, the solid lubricant may not sufficiently adhere to the surface of the metal material. The upper limit of the arithmetic mean roughness (Ra) is 25.0 μm, and if the arithmetic mean roughness exceeds 25.0 μm, the surface properties of the plastically worked material may be affected.

[Solid Lubricant Application Process]
In this step, a solid lubricant is applied to the surface of the difficult-to-work metal material whose arithmetic mean roughness has been adjusted in the arithmetic mean roughness adjusting step. Through this process, a solid lubricant intervenes on the contact surface between the metal mold and the metal material (billet) during plastic working, thereby reducing the frictional force generated between the plastic working tool such as the metal mold and the metal material. In addition, it is possible to suppress the occurrence of defects such as seizure and galling on the contact surface between the plastic working tool and the metal material.

(solid lubricant)
The solid lubricant is not particularly limited. Examples include graphite-based lubricants.

Examples of graphite-based lubricants include graphite powder. Natural graphite powder or the like can be used as the graphite powder. As the graphite powder, a mixture of different types of graphite can be used.

A solid lubricant may be dispersed in a solvent in order to improve coating layer formability. Solvents include water.

(Application method)
As a method of applying the solid lubricant, for example, after preheating in the range of 80° C. to 120° C., application by brush coating or the like can be mentioned.

[Heating process]
In the heating step, the hard-to-work metal material is heated to a predetermined temperature. The metal material is heated by a heating furnace or an induction heater (high-frequency induction heating device) to a temperature in the range of 600° C. or higher and 1300° C. or lower. By this process, the structure of the plastically worked material can be homogenized, and the plastic workability is further improved.

The heating step may be performed after the solid lubricant application step or before the solid lubricant application step.

The lower limit of the heating temperature in the heating step is preferably 600° C. or higher, more preferably 650° C. or higher, from the viewpoint of deformability of the metal material at high temperatures. The upper limit of the heating temperature is preferably 900° C. or lower, more preferably 850° C. or lower, from the viewpoint of retention of the solid lubricant at high temperatures.

[Plastic working process]
The plastic working process plastically works the metal material after the arithmetic mean roughness adjusting process, the solid lubricant applying process and the heating process.

In the present embodiment, as an example of the plastic working process of the metal material, a case of manufacturing a metal pipe by hot extrusion using a hollow billet having a through hole in the center as the metal material will be described.

FIG. 1 is a cross-sectional view of a hollow billet 1, which is a metal material used in the method of manufacturing the plastically worked material. FIG. 2 is a schematic cross-sectional view of an extrusion device during hot extrusion processing in one embodiment of the method for manufacturing the plastically worked material. A hollow billet 1, which is a metal material used in the method of manufacturing the plastically worked material, is manufactured from a difficult-to-work metal material 11, and has solid lubricant coating layers 12 on the outer and inner peripheral surfaces. A die 2 is attached to one end side of a container 3 in an extrusion device 10 used for manufacturing a pipe material. Also, the temperature of the extruder 10, which serves as a mold, is raised from room temperature to 900°C.

In the extrusion apparatus 10 configured as described above, hot extrusion of the metal material is performed as follows. First, as shown in FIG. 2, the hollow billet 1 is mounted in the billet hole of the container 3 . A mandrel 9 is inserted into the through hole of the hollow billet 1 via a pressure medium 13 , and a seal piston 7 is arranged on the rear end surface of the hollow billet 1 via a pressure medium 13 .

In such a configuration, when the stem 8 is actuated to push the sealing piston 7 in the extrusion direction F of the hollow billet 1 , the hollow billet 1 is extruded from the annular space formed by the die 2 and the mandrel 9 . Then, a tube member 15 having an outer diameter corresponding to the inner diameter of the die 2 and an inner diameter corresponding to the outer diameter of the tip of the mandrel 9 on the die side is manufactured.

At the time of extrusion, the coating layer 12 of the solid lubricant is interposed between the inner peripheral surface of the die 2 and the hollow billet 1 and between the outer peripheral surface of the mandrel 9 and the hollow billet 1, so that good lubrication is achieved. can ensure the integrity of the As a result, the friction between the inner peripheral surface of the die 2 and the hollow billet 1 and between the outer peripheral surface of the mandrel 9 and the hollow billet 1 can be reduced to suppress surface defects of the tube material 15, resulting in excellent surface quality and dimensional accuracy. can do well. In addition, the release between the plastically worked material and the mold after working becomes smooth, and the life of the mold can be extended.

(advantage)
In the method for manufacturing a plastically worked material, friction during plastic working can be reduced, and the occurrence of flaws due to seizure, etc. on the surface of the plastically worked material can be suppressed. It is possible to reduce costs and improve quality by improving yield and productivity.

(Other embodiments)
The present invention is not limited by the following examples, and appropriate modifications can be made within the scope of the gist of the present invention.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited by the following examples, and can be carried out with appropriate modifications within the scope of the gist of the present invention. All of them are included in the technical scope of the present invention.

[Test No. 1 to No. 11]
The hollow billet was subjected to the following steps, and test no. 1 to No. Eleven plastic worked materials were produced.

[Arithmetic Mean Roughness Adjustment Step]
(hard-to-work metal material)
A hollow billet made of titanium was used as a hard-to-work metal material (billet).

(Shot blast)
Shot blasting was performed on the outer peripheral surface and the inner peripheral surface of the hollow billet. Alumina (Grit size: F46 and F80 specified in JIS-R6001 (1998)) or steel grid (No. 100) was used as the shot material.

(Measurement of arithmetic mean roughness (Ra) of hollow billet)
The arithmetic average roughness (Ra) of the outer peripheral surface and the inner peripheral surface of the hollow billet after shot blasting was measured according to JIS-B0601 (2001). Table 2 shows the arithmetic mean roughness (Ra) of each hollow billet.

[Solid Lubricant Application Process]
After preheating the outer and inner peripheral surfaces of the hollow billet after shot blasting in the range of 80 to 120° C., graphite lubricant A and graphite lubricant B were applied as solid lubricants by brushing.

The following two types were used as the composition of the solid lubricant.
(1) Graphite lubricant A
Fine graphite particles were used by dispersing them in water. The viscosity was adjusted in the range of 1200 Pa·s to 3500 Pa·s.
(2) Graphite lubricant B
Ultrafine graphite particles and fine graphite particles were used by dispersing them in water. The viscosity was adjusted in the range of 1200 Pa·s to 3500 Pa·s.

[Heating process]
The hollow billet was then heated at 750° C. for 7 minutes with an induction heater.

[Plastic working process]
Next, after mounting the heated hollow billet on a hot extruder, it was hot extruded at a ram processing speed of 5 mm/sec to 10 mm/sec to produce a tubular material as a plastically worked material. Table 1 shows the external dimensions of each hollow billet, the dimensions and mass of the tube material after extrusion, and the extrusion ratio. The extrusion ratio refers to the cross-sectional area ratio of the tube material after extrusion to the cross-sectional area of the hollow billet.

[evaluation]
(Surface flaw depth)
Test no. 1 to No. A test piece was sampled from 500 mm to 1000 mm at the tip of the plastically worked material of No. 11, and the cross section of the portion where the outer surface of the flaw was visually the deepest was cut out, and the relevant portion was photographed. The depth of the flaw was directly measured. . Test no. 1 to No. The surface flaw depth due to seizure on the outer peripheral surface of the plastically worked material No. 11 was measured. These measurement results are shown in Table 2.

(Surface texture)
Test no. 1 to No. Appearance evaluation was performed on the surface properties of 11 plastically worked materials. The evaluation criteria were as follows. These evaluation results are shown in Table 2.
A: Although it is a flaw that can be caught when touched with a fingernail, secondary processing such as cold working is possible without repair.
B: Slight streak-like flaws are seen when the outer surface is illuminated with light, but secondary processing is possible by partial repair.
C: Streak-like flaws are observed in the axial direction, and galling occurs. Secondary processing can be performed by removing flaws from the entire surface by grinding or the like corresponding to the depth of the flaw.

As shown in Table 2, test no. 1 to test No. The depth of surface flaws of No. 8 was 70 μm or less. On the other hand, the depth of the surface flaws in the comparative examples was in the range of 196 μm to 538 μm. From the above results, the method for manufacturing the plastic working material can reduce friction during plastic working even if a difficult-to-work metal material is used, and can suppress the occurrence of flaws due to seizure on the surface of the plastic working material. It was found that it is possible to reduce costs and improve quality by improving the yield and productivity of materials and their processed products.

As described above, the method for producing a plastically worked material of the present invention can reduce friction during plastic working and suppress the occurrence of flaws due to seizure on the surface of the plastically worked material. It can be suitably used when processing.

1 Hollow billet (metal material)
2 Die 3 Container 7 Seal piston 8 Stem 9 Mandrel 10 Extrusion device 11 Difficult-to-work metal material 12 Coated layer of solid lubricant 13 Pressure medium 15 Tube member F Extrusion direction of hollow billet

Claims (2)

A step of adjusting the arithmetic mean roughness (Ra) of the titanium or titanium alloy surface measured according to JIS-B0601 (2001) to 1.5 μm or more and 25.0 μm or less by shot blasting;
applying a solid lubricant to the surface of the titanium or titanium alloy ;
and a step of plastic working the titanium or titanium alloy .
2. The method of manufacturing a plastically worked material according to claim 1, wherein the material of the shot for said shot blasting is steel.

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