JPH0970604A - Manufacture of titanium-based seamless pipe excellent in prevention of occurrence of rolling flaw - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a titanium pipe at a low cost without making a rolling flaw occur on the outside surface of the pipe by Mannesmann rolling method. SOLUTION: After coating by thermal spraying or application of a metal containing 90% Al or over on the surface of a pipe material whose stock is a titanium-based alloy containing 0.2% class 1 or 2 of Pd, Ru or below respectively, if necessary, in either of pure titanium, α based-titanium alloy or α+β-based titanium alloy, the manufacture of a titanium-based seamless pipe excellent in prevention of the occurrence of a rolling flaw, by which the pipe is manufactured by an inclined rolling system, is attained.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a technique for producing a seamless pipe of pure titanium, α-based or α + β-based alloy titanium, Pd-alloyed titanium and Ru-alloyed titanium (hereinafter abbreviated as titanium) by a Mannesmann rolling method. .

[0002]

BACKGROUND OF THE INVENTION Titanium has been applied to various applications such as aircraft parts, oil, gas well, geothermal well drilling pipes or oil well pipes and cylinder members because of its light weight, excellent mechanical properties and corrosion resistance. It is a metal material that has been used and is expected to be expanded in the future. Above all, seamless pipes are indispensable for drill pipes, oil well pipes, cylinder members, etc., and the demand for them is increasing year by year.

Conventionally, a titanium seamless pipe is disclosed in Japanese Patent Laid-Open No. 63-1.
It has been produced by hot extrusion of the Eugene system as seen in Japanese Patent No. 26614. However, since hot pressing requires a hollow round billet as a material, there is a problem in that the yield is reduced when the material is machined. In producing an expensive material such as titanium, this reduction in yield has a great influence on the product cost. Therefore, in order to manufacture a low-cost titanium tube, it is necessary to rely on a manufacturing method (for example, the Mannesmann rolling method) which does not require machining of the billet.

[0004]

However, no attempt has been made so far to manufacture a titanium tube by an inclined rolling method, for example, a Mannesmann method in which perforation is performed by using an inclined roll and a plug. This is because even if titanium is rolled by the Mannesmann method to produce conventional steel pipes or stainless pipes, rolling flaws occur on the outer surface of the pipe as described below, and grinding is essential for making it a product. Therefore, the cost is increased in the end. Therefore, it is desired to develop a technology capable of manufacturing a titanium tube at a low cost by the Mannesmann method without causing a flaw.

In the fields of sheet rolling, forging, and slabbing, as a technique for preventing surface defects and skin roughness of titanium products, for example, as disclosed in Japanese Patent Publication No. 7-18018, Al and resin are applied to the surface of the material. A method is known in which an antioxidant composed of a solvent is applied and processed. However, since the tube processing by Mannesmann rolling is far more severe than the processing strains of plate rolling, forging, and slab rolling, such a technique does not provide sufficient effect, and when the same technique is applied. However, it is necessary to apply a material having a higher degree of antioxidant function.

In view of the above situation, an object of the present invention is to provide a technique for producing a titanium pipe at a low cost, and further, to produce a titanium pipe by the Mannesmann rolling method without causing a pipe outer surface rolling defect. To do.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted a study back to the mechanism of occurrence of outer surface rolling flaws of titanium pipes by the Mannesmann rolling method, and as a result, the rolling flaws of titanium pipes were subjected to a piercing or stretching rolling process. It was clarified that the cause is the oxygen-rich layer of high hardness and low ductility formed during heating. FIG. 1 is a cross section of a titanium pipe material after heating and before perforation, conceptually showing a state in which an oxygen-enriched layer 2 is formed on the surface layer of a titanium substrate 1 (3 in FIG. 1 indicates a scale). . It is said that the oxygen-enriched layer causes minute defects such as bald spots and rough skin even in strip rolling, but Mannesmann rolling adds excessive shear strain as compared with strip rolling, so defects due to the oxygen-enriched layer are caused. Is not limited to the minute ones found in sheet rolling, but also develops cracks with a depth of 2 mm. Therefore, in order to prevent this, it was important to suppress oxygen storage during heating of the surface of the pipe material, and it was found that it is better to coat the surface of the pipe material with a metal having a high Al content in order to achieve this. . Furthermore, we have found the conditions necessary for a coating layer that can effectively prevent defects.

[0008] The present invention is based on this finding,
The main points are pure titanium, α-based titanium alloy,
Excellent in preventing rolling flaws, which is characterized by coating the surface of a tube made of any one of α + β titanium alloys with a metal containing 90% by weight or more of Al, and then making the tube by a tilt rolling method. There is a seamless pipe manufacturing method. In the above manufacturing method, the material of the pipe material is pure titanium,
In addition to α-based titanium-based alloys and α + β-based titanium-based alloys, titanium-based alloys containing 0.2% or less of Pd and / or Ru in these alloys can be selected. Furthermore, as a coating method, a thermal spray method,
Alternatively, it is possible to select any of the methods of applying a metal powder containing 90% or more of Al as well as a coating consisting of a resin and a solvent, in which the Al content in the dry coating film exceeds 75% by weight.

[0009]

The present invention will be described in detail below. Titanium targeted by the present invention is JIS H 4600, 4607,
Pure titanium specified in 4630, 4631, 4635, 4636, etc., α-based alloy titanium added with Al or Sn, or α + β-based alloy titanium added with Al, V, Cr, Mo, Fe, Si, etc., Pd or Ru alloy Titanium oxide is a titanium that has hot workability and can be produced by a normal Mannesmann rolling method. Pd
And Ru have the effect of improving the corrosion resistance of titanium or titanium-based alloys, and are contained as necessary. However, if over 0.2%, the effect is saturated, and since it is an expensive metal and large addition is uneconomical. The upper limit is 0.2%.

The Mannesmann rolling method referred to here is a pipe manufacturing method including a step of piercing or stretching by a rolling machine having an inclined roll, and for example, press roll piercing-inclined rolling (elongator) as shown in FIG. rolling)
-Plug mill rolling method is also included. In this method, a tubular material having a rectangular cross-sectional shape is used, but when a punching method using an inclined punching machine is adopted, a tubular material having a circular cross-sectional shape is used.

As a function of the coating applied to the surface of the titanium pipe material, since the coating material (metal) covers the titanium surface and oxygen is blocked at the surface of the coating layer, the oxygen does not diffuse inside the titanium, resulting in rolling defects. It is possible to prevent the formation of a harmful oxygen-enriched layer. The reason why the main component of the coating material is Al is to utilize the strong oxygen affinity of Al, and the content of Al is 9% by weight.
0% or more is required. This is 9 as shown in FIG.
This is because if it is less than 0%, a good oxygen barrier function cannot be obtained and rolling defects cannot be sufficiently prevented.

As a coating method, thermal spraying or coating is the most suitable in terms of workability. Compared with the coating method, the thermal spraying method tends to have a better effect of preventing flaws because the adhesion of Al to the material is more reliable, and the thermal spraying method is more preferable than the coating method. If satisfied, it is possible to obtain a certain degree of flaw prevention effect.

As the thermal spraying method, it is not necessary to use vacuum or the like, and the ordinary thermal spraying method in the atmosphere is sufficient. The sprayed thickness is not particularly specified, but a sufficient effect can be obtained at about 0.1 mm. In addition, a blast treatment may be performed as a pretreatment to improve the adhesion.

In the case of application, a coating material containing a metal powder containing 90% or more of Al as a main component, a resin as a binder for adhering the metal powders or the metal powder and the surface of the pipe material, and a solvent for adjusting the viscosity. As the coating material. It is necessary that the Al content in the coating material exceeds 75% in terms of dry weight. This is because, as shown in FIG. 4, when the content is 75% or less, a sufficient oxygen barrier function cannot be exhibited and rolling defects cannot be sufficiently prevented. The shape of the metal powder is not particularly limited and may be spherical or scaly, but the size is preferably as small as possible from the viewpoint of the contact area with oxygen, and the average particle size is preferably 0.1 mm or less.

The type of binder is not particularly limited as long as it can be dissolved in a solvent such as hydrocarbon or water and air-dried, but a water-soluble binder such as sodium polyacrylate or the like can be used as long as these conditions are satisfied. Examples include alkyd resins, phenolic resins, vinyl resins, and other resins that are soluble in organic solvents. The amount of the binder or solvent added is not particularly specified, and the Al content in the dry coating film is 75
As long as the condition that the content exceeds 10% is satisfied, it may be arbitrarily adjusted within the range in which sufficient spreadability of the paint and adhesion of the coating film are obtained. The coating thickness is required to be about twice the average particle diameter of the metal, but if it is too thick, the effect will be saturated, so about 0.05 to 0.3 mm is preferable.

[0016]

EXAMPLES The present invention will be further described with reference to examples.
Test rolling of titanium was performed using an actual machine of the process shown in FIG. The components of the test material are pure titanium, α-based alloy, α + β-based alloy, Pd alloy, and Ru alloy shown in Table 1. After forging, the ingot was formed into a bloom having a cross section of 215 × 215 mm, and a metal having the composition shown in Table 2 was formed on the surface of the pipe material by a thermal spraying method and a coating method, and then subjected to rolling. The film thickness was 0.1 to 0.15 mm in the thermal spraying method and 0.1 to 0.3 mm in the dry state in the coating method. The metal powder used in the coating method had an average particle size of 0.03 to 0.06 mm. Alkyd resin was used as a binder and toluene was used as a solvent. Table 3 shows the details of the test conditions. The test results were obtained by pickling the rolled material, visually observing the outer surface of the pipe, and then determining the maximum flaw depth by observing the cross section with a light microscope.

As is clear from Table 3, No. 3 to 6,9
According to the present invention of ~ 12, 15-21, good quality can be obtained. On the other hand, No. In Nos. 13 and 14, the Al content in the coating metal was No. In Nos. 7 and 8, the Al content in the coating film was No. In Nos. 1 and 2, the content of Al in the coating metal and the content of Al in the coating film are outside the scope of the present invention, and therefore, sufficient effects of preventing flaws are not obtained. In addition, No. In Nos. 22 to 26, an oxygen-enriched layer was formed because no coating was applied, and this was broken during perforation or stretching, and many defects starting from that and reaching a depth of 2 mm or more occurred frequently.

[0018]

[Table 1]

[0019]

[Table 2]

[0020]

[Table 3]

[0021]

As described above, according to the present invention, it becomes possible to significantly suppress the outer surface rolling defects of the pipe and manufacture the pipe by the Mannesmann rolling method.

[Brief description of drawings]

FIG. 1 shows a cross section of a titanium pipe material after heating and before perforation.

FIG. 2 shows an example of a Mannesmann rolling process for producing a seamless pipe.

FIG. 3 shows the relationship between the Al content in the coating metal and the maximum rolling flaw depth.

FIG. 4 shows the relationship between the Al content in a dried coating film and the maximum depth of rolling flaw.

[Explanation of symbols]

 1: Titanium base 2: Oxygen enriched layer 3: Scale

Claims (4)

[Claims] 1. A pipe material made of pure titanium, an α-type titanium alloy or an α + β-type titanium alloy, coated with a metal containing 90% or more of Al on the surface of the pipe material, and then produced by an inclined rolling method. A method for producing a titanium-based seamless pipe excellent in preventing rolling flaws, characterized by: 2. A pipe material made of a titanium-based alloy containing pure titanium, an α-type titanium alloy, or an α + β-type titanium alloy and 0.2% or less of one or two of Pd and Ru, respectively. A method for producing a titanium-based seamless tube excellent in preventing rolling flaws, characterized in that the surface of the tube is coated with a metal containing 90% or more of Al, and then the tube is manufactured by an inclined rolling method. 3. The method for producing a titanium-based seamless pipe excellent in preventing rolling flaws according to claim 1 or 2, wherein a metal containing 90% or more of Al is coated by a thermal spraying method. 4. Coating by a coating method with a coating material comprising a metal powder containing 90% or more of Al, a resin and a solvent, and having an Al content in the dry coating film of more than 75% by weight. The method for producing a titanium-based seamless pipe excellent in preventing rolling flaws according to claim 1 or 2.