JPS62107041A - Highly corrosion resistant titanium alloy - Google Patents

Abstract

PURPOSE:To improve workability as well as corrosion resistance by incorporating prescribed percentage of platinum group elements, Ni, Co, Mo, W and V. CONSTITUTION:The titled titanium alloy has a composition consisting of, by weight, 0.01-0.12%, in total, of one or more kinds among platinum group elements, 0.05-2% Ni and/or Co and the balance Ti, or further containing besides the above, 0.05-2%, in total, of one or more elements among Mo, W and V. This alloy is excellent in corrosion resistance and workability, so that performance and reliability of facilities and equipments used under a corrosive environment can be improved on application of this alloy.

Description

[Detailed Description of the Invention] <Industrial Application Field> This invention not only has good corrosion resistance when worn, but also has general corrosion resistance such as acid resistance, and is equivalent to pure titanium. This invention relates to a low-cost titanium alloy that exhibits good workability.

Background technology When titanium first began to be produced on an industrial scale, its light and strong characteristics were utilized, and titanium was mainly used in the aeronautical industry. Recently, it has been widely used as materials for industrial equipment, thermal and nuclear power generation equipment, and materials for seawater and freshwater equipment.
It has come to be used once. However, although titanium generally has excellent corrosion resistance, it exhibits its high corrosion resistance only in oxidizing acid environments such as nitric acid or neutral chloride environments such as seawater. Corrosion resistance in a non-oxidizing acid environment (hydrochloric acid, sulfuric acid, etc.), which is relatively common in the environment, and plow-spread corrosion resistance in a high-temperature chloride environment F were extremely unsatisfactory.

Therefore, CTi-Pd alloy was developed for use in such non-acid (arsenic acid environments and environments where splitting is a concern), and has come to be used particularly in environments containing hydrochloric acid. This is based on the phenomenon that when a small amount (approximately 0.2 weight 111) of Pd is added to titanium, its hydrogen supernatant decreases significantly and the natural potential is maintained in the passive region. be.

However, corrosion resistance (: the well-established Ti-Pd
Alloys are expensive because they contain precious metals that are relatively hyperactive, and there is a problem in that their use must be restricted.

On the other hand, apart from this, a titanium alloy with a small amount of combined addition of Ni and Mo has also been proposed (Japanese Patent Application Laid-Open No. 130614/1983), with the main purpose of improving the same resistance to plow corrosion.
This alloy has poor acid resistance and poor workability, so its widespread adoption has been discouraged.

<Means for Solving the Problems> From the above-mentioned viewpoints, the present inventors have developed not only excellent leg-leg eating properties, but also acid resistance in non-acid and arsenic acid environments. , provides an inexpensive titanium alloy that is resistant to general corrosion and exhibits good workability comparable to that of industrially pure Tedan.
As a result of extensive research, the following findings were obtained.

That is, a) In order to significantly improve the corrosion resistance of titanium without impairing its workability, platinum group elements (Ru*Rh*Pd
*Os, Ir and Pt) are indispensable, but in addition to these platinum group elements, slight addition of Ni and C is essential.
When one type of o or type h is added in combination, the hydrogen overpower reduction effect of platinum group elements CNi or '! The corrosion resistance of the titanium alloy is maintained even if the content of expensive platinum group elements is reduced due to the superimposed hydrogen overvoltage reduction effect of Co. b) The above titanium alloy C2 containing a trace amount of platinum group elements and a small amount of Ni or Co, as well as Mo, W and V,
When more than one species is added in combination, the combined effect of the platinum group element and Ni or Co; resulting in a remarkable hydrogen overvoltage reduction effect, and the above-mentioned Mo*W or V being dissolved in the environmental liquid. The resulting molybdate ions, tungstate ions, or vanadate ions stabilize the formed passive film on the titanium surface and further improve corrosion resistance, especially resistance to splitting corrosion. is combined, and the corrosion resistance of the core titanium alloy, mainly in the case of assembling spread corrosion, is further improved without deterioration of workability.

This invention was made based on the above findings (2).Titanium alloy.

Platinum group elements (Ru, Rh5Pd*0s-Ir and Pt)
One or more of: 0.01 to 0.12'fb in total One or more of sNi and Co: 0.05 to 2.00 in total, or if necessary further Mo + W and One or more types of V: 0.05 in total
2.004 and the remainder is substantially Ti, it not only improves general corrosion resistance such as plow corrosion resistance and acid resistance, but also provides good corrosion resistance. It is characterized by the fact that it also ensures workability.

Here, in the titanium alloy of the present invention, the reason why the component ratio is limited to two numerical values of C as described above will be explained.

(al platinum group element (Ru * Rh @ Pd,
(Os, Ir, and Pt) These components have the same effect of improving the corrosion resistance of titanium alloys (including the spread corrosion resistance and acid resistance, etc.), and their corrosion resistance improvement effect is similar to that of one of the platinum group elements. If 0.014 or more of the above are contained in total (-The more they appear, the more pronounced the problem becomes, but Ni or C
In coexistence with o, the total content of platinum group elements is 0.12
If the content exceeds 0.9%, the above effect will be saturated, and the price of the alloy will rise. Therefore, the total content of one or more platinum group elements is set at 0.01 to 0.12%. Ta.

(bl　Ni, and C.

All of these components, like the platinum group elements, have the same effect of reducing the hydrogen overvoltage of the alloy, and therefore have the effect of improving the corrosion resistance of titanium alloys, but this effect is weaker than that of platinum. Even more noticeable when coexisting with group elements 1
Hi. The above-mentioned corrosion resistance improvement effect is caused by Ni and Co
If one or more of the above is contained in a total of 0.05% or more, it will be recognized as C; however, if it is contained in excess of 2.00'1, the coexistence with platinum group metals will result in poor processability. Since deterioration becomes noticeable, the content of one or more of Ni and Co was determined to be 0.05 to 2.001. In addition, when assuming a cold-finished product, it is preferable to adjust it to about 0.1 to 0.5.

fcJ Mo, W, and V These components are dissolved in the environmental solution of the alloy and added to the acid 1
It generates molybdate ions, dangunutate ions, vanadate ions, etc., which have an arsenic effect, and stabilizes the passive film formed on the surface of the titanium alloy, thereby increasing its resistance to corrosion, especially between gaps. Since it has the same effect as improving the properties, one or more of them are added when it is necessary to improve corrosion resistance, especially interlayer corrosion. However, if the total content of one or more of Mo, W, and V is less than 0.054, the effect of improving corrosion resistance centered on crevice corrosion resistance due to the above action is insufficient. In this case, the effect of improving acid resistance will be more pronounced, but since it will have a negative effect on workability, the content of one or more of Mo + W and V should be 0.05 to 2.00 mm. Established.

As mentioned above, in addition to containing a small amount of platinum group elements in C and titanium, one or more of Ni and Co is added, or one or more of Mo + W and V is also added. When a Ti alloy is constructed, the alloy is relatively inexpensive (secondly, it exhibits excellent overall corrosion resistance, including deep crevice corrosion resistance and acid resistance, without impairing workability). However, from the perspective of corrosion resistance and IPI7D workability,
F'e, 0. The less impurities such as C, N, and H, the better.
Particular attention should be paid to the Fe and O contents. However, with the titanium alloy of the present invention, no particular problem will occur if each amount is suppressed to 0.3 mm or less.

Next, the present invention will be explained using examples and comparing with comparative examples.

<Example> First, commercially available industrial titanium plates (JI 82 type) and Ti
-0.2% Pd alloy number (A S TM Grade
7), and further add the ingredients l! as shown in Table 1!
A four-component titanium alloy plate material was prepared. The titanium alloy plate material is a small ingot made by blending titanium with pure metal powder as an alloy component and melting it by button melting using an argon arc furnace, followed by hot forging, hot rolling, and scale removal treatment. (sand branut + pickling) and cold rolling to a thickness of 4 mm, followed by heat treatment (holding in vacuum at 700° C. for 30 minutes and then releasing).

Next, test pieces were taken from each of these materials and subjected to an "acid resistance test" and a "single leg eating test".

In addition, the acid resistance test was conducted using the sampled 3m thickness x 10M width x 40
After polishing a mm-long rectangular corrosion test piece with No. 600 emery paper, it was immersed in a boiling@54 IC/aqueous solution for 6 hours, and the amount of corrosion on the entire surface was measured. Acid resistance is evaluated by calculating the corrosion rate from the corrosion deposits for each two test pieces and comparing the average values.

In addition, for the plow-spread eating test, the sample specimens of 3 thickness x 30 width x 30 length (with a hole of 7 mm diameter in the center) were polished with No. 600 emery paper, and then two sheets of After applying dimethacrylate resin (anaerobic adhesive) between the test pieces, tighten them with titanium bolts and nuts through Teflon bushings. After completing the test, three pairs of test pieces for each material were immersed in boiling NaCA water for 100 hours in the middle of the night, and the condition of the test pieces was examined.

The test results conducted in this manner are shown in Table 1 (Table 2).

As is clear from the results shown in Table 1, the alloy of the present invention has a low price (despite the high price of Ti-〇2 winter P).
It is known that it has acid resistance and interstitial corrosion resistance that are different from that of D alloy, and it is clear that its corrosion resistance is worthy of special mention.

In addition, in a workability test bag conducted separately from this, it was confirmed that the alloy of the present invention exhibits excellent workability without any particular problems in practical use.

<Overall Effects> As described above, it is possible to provide titanium alloys that have both the 5 and 1-I eating properties and workability at a low cost. This will bring about significant benefits to the TB industry, such as making it possible to further improve the performance and reliability of equipment and mirrors used in corrosive environments.

Claims (2)

[Claims] (1) In terms of weight percentage, one or more of the platinum group elements: 0.01 to 0.12% in total, one or more of Ni and Co: 0.05 to 2.00% in total A titanium alloy with excellent corrosion resistance, characterized in that the remainder is substantially composed of Ti. (2) In terms of superposition ratio, one or more of the platinum group elements: 0.01 to 0.12% in total; one or more of Ni and Co: 0.05 to 2.00% in total , Mo, W, and V: a total of 0.05 to 2.00%, and the remainder substantially consists of Ti. A titanium alloy having excellent corrosion resistance.