JPS6240417B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an ultra-high corrosion-resistant amorphous amorphous alloy, and in particular, the present invention relates to an ultra-high corrosion-resistant Fe-Cr-Mo amorphous alloy that has corrosion resistance in a corrosive environment of about 6NHCl or higher. Traditionally, common corrosion-resistant alloys that have been widely used include stainless steel alloys, such as 13% chromium steel, 18-8 stainless steel (304 steel), 17-14-2.5Mo stainless steel (316 steel), and nickel-based alloys. can be,
Excellent weather resistance and corrosion resistance. However, in even more corrosive environments, such as 1N aqueous hydrochloric acid, the passive film is destroyed and almost all conventional corrosion-resistant alloys suffer from pitting corrosion. On the other hand, one of the inventors previously filed a patent application for
74246 (Japanese Unexamined Patent Publication No. 51-4017), an amorphous iron alloy with high strength, fatigue resistance, general corrosion resistance, pitting corrosion resistance, crevice corrosion resistance, stress corrosion cracking resistance, and hydrogen embrittlement resistance, and patent application No. 53-10397 ( (Japanese Patent Application Laid-open No. 54-103730) invented carbon-based amorphous iron alloys and applied for a patent, but these amorphous iron alloys were treated with 1N hydrochloric acid,
It was disclosed that it shows a high degree of corrosion resistance even in sulfuric acid or 1N saline solution, and that no general corrosion or pitting corrosion occurs. The amorphous iron alloy disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 51-4017 contains 1 to 40% Cr, P, and C in terms of atomic percent.
and 7 to 35% of one or two or more of B
as a main component, and as a subcomponent: (1) Any one or both of Ni and Co 0.01 to 40
%. (2) 0.01 to 20% of one or more of Mo, Zr, Ti, Si, Al, Pt, Mn, and Pd. (3) 0.01 to 10% of one or more of V, Nb, Ta, W, Ge, and Be. (4) Au, Cu, Zn, Cd, Sn, As, Sb, Bi and S
0.01 to 5% of one or more of the following. The total amount of one or more selected from the group of 0.01 to 75% is contained, and the remainder is substantially composed of Fe. Further, the carbon-based amorphous iron alloy disclosed in JP-A-54-103730 is Fe a Cr b M c Q d (where Fea is a atomic % of Fe, Crb is Cr is b atomic %, and Mc is Any one or more selected from Cr, Mo, and W is c atomic %, and Qd is C d
Indicates that the content is atomic%. ), which has a component composition shown by the formula:
Among them, those with excellent corrosion resistance have a of 28 to 28,
It was disclosed that it is a carbon-based amorphous iron alloy in which b is in the range of 2 to 20, c is in the range of 4 to 26, and d is in the range of 12 to 26. As can be seen from the above invention, in amorphous iron alloys, as in crystalline alloys, chromium is the most effective alloy additive for improving corrosion resistance, and addition of molybdenum in addition to chromium includes chromium. Improves the corrosion resistance of iron-based amorphous alloys. By the way, the present inventors further investigated the corrosion resistance of the above-mentioned two invention alloys, and found that due to the difference in the component composition range, a component composition range showing extremely strong corrosion resistance against a hydrochloric acid aqueous solution with a higher concentration than a 1N hydrochloric acid aqueous solution, It has been discovered that there is a composition range that exhibits relatively weak corrosion resistance, and furthermore, it has been found that the invention alloy cannot exhibit sufficient corrosion resistance in the strongly corrosive environment found in the above-mentioned 1N aqueous hydrochloric acid solution or higher. I knew. As an example, 3N
Hydrochloric acid aqueous solution (room temperature), 6N nitric acid aqueous solution (room temperature) and
Table 1 shows the results of experiments on corrosion rates using 18N sulfuric acid aqueous solution (80℃).

【table】

[Table] Therefore, the present inventors have determined that the severe corrosive environment
After selecting a 6N hydrochloric acid aqueous solution and conducting various studies on the corrosion resistance of the invention alloy, we finally discovered that the amorphous alloy of the invention has excellent corrosion resistance within the composition range, and completed the invention. The present invention was made for these reasons.
The purpose is to provide an ultra-high corrosion-resistant Fe-Cr-Mo amorphous alloy that can maintain corrosion resistance in strongly corrosive environments such as 6N hydrochloric acid or hot hydrochloric acid. That is, the present invention provides an amorphous amorphous alloy consisting of Fe, Cr, Mo, and a semimetal, in which Cr is 5 atomic % or more and Mo 20 atomic % or less, and the total of Cr and Mo is 15 to 35 atomic %.
ultra-high corrosion resistance within the range of atomic%, the metalloid element is composed of P-Si system, P10 atomic% or more, Si 5 atomic% or more, and the total is within the range of 20 to 25 atomic%
It is a Fe-Cr-Mo based amorphous alloy. The present invention will be explained in detail below. First, the reason for adding the constituent elements of the alloy according to the present invention and the reason for limiting the range of addition will be explained. It is generally known that amorphous amorphous alloys are more susceptible to corrosion due to their higher activity than crystalline alloys of the same composition, but iron-based amorphous alloys containing chromium have higher corrosion resistance than crystalline alloys of the same composition and conventional It is known to exhibit higher corrosion resistance than alloys. The present inventors investigated the cause of the corrosion resistance of the iron-based amorphous amorphous alloy containing chromium, and found that the cause is the chemical uniformity and high activity of the amorphous amorphous alloy itself, and the chemical uniformity is due to uniform unevenness. It was found that the high activity helps to form a dynamic film, and the high activity helps to form the passive film rapidly and make it strong and dense. The passive film mainly consists of hydrated chromium hydroxide, and the enrichment of chromium hydroxide in the passive film is an important factor for the high protective properties of the passive film. Molybdenum has a great effect on enriching the passive film. Therefore,
The addition of chromium is essential for corrosion resistance, and the addition of molybdenum promotes the formation of a passive film. Therefore, we selected the Fe-Cr-Mo alloy system,
We investigated the composition range of components that self-passivate by measuring polarization curves using the potentiostat method in various strongly corrosive environments such as room temperature or 6N hydrochloric acid aqueous solution at 80°C. Next, the composition range of the above self-passivating components will be explained using research data. As shown in Figure 1, in the Fe-Cr-Mo-15P-5Si amorphous alloy, Cr5
Those containing atomic% or more are Mo10 atomic%.
The above results in self-passivation, and for those containing 10 atomic % or more of Cr, addition of 5 atomic % of Mo is sufficient to self-passivate. In FIG. 1, the shaded areas above and below the series of lines connecting each point are the self-passivation regions for 6NHCl, and below each of the series of lines is the active region. Therefore,
The content of Cr must be 5 atomic % or more, and the total of Cr and Mo must be 15 atomic % or more. Increasing the Cr content reduces the amount of Mo required to self-passivate.
The amount added decreases, for example Fe−25Cr−2Mo−15P
The figure shows that -5Si alloy self-passivates in 6N hydrochloric acid aqueous solution. Furthermore, although the addition of a large amount of Mo has the effect of increasing the corrosion potential, as can be seen from FIG. 2, above a certain amount of Mo, the corrosion rate becomes constant and no particular effect is found. Therefore
It is not a good idea to add Mo in an amount of 20 atomic % or more, especially since Mo is an expensive element. In addition, Mo is 20 atomic% or more or the total of Cr and Mo is
When the content exceeds 35 atomic %, the amorphous amorphous formation ability deteriorates. Next, under even more severe corrosion conditions, the first
As can be seen from the figure, as a result of polarization curve measurement in 6N hydrochloric acid aqueous solution (80℃), in 15P-5Si alloy, when Cr5 at% and Mo15 at% or more, or Cr10 at% and Mo10 at% or more, Self-passivation occurs in the above cases, but it was found that the amount of Mo required for self-passivation does not decrease even if Cr increases to 10 atomic % or more. Next, the reason for selecting the metalloid and its concentration range will be explained. In order to manufacture amorphous iron alloys, it is necessary to add metalloid elements, and generally P, C, B, and Si are used, and the properties of the amorphous iron alloys produced by the addition of these elements have different characteristics. It will be done. The effect is JP-A-54-103730
raw material cost, solubility, ability to form amorphous, crystallization temperature,
Hardness, strength, corrosion resistance, and embrittlement were shown in detail, and the results showed that P-C system, P-B system, P-Si
As a result of experiments on B, Si-B, and C systems, some of which are shown in Table 1, those containing B and metalloids other than B and B have poor corrosion resistance, and also have high raw material costs. Yes, P- as a metalloid
C system, P-Si system, and C system were selected. Regarding the amount of these metalloid elements added, as shown in Figure 3, when the total of P and Si is 20 atomic % or more in the Fe-10Cr-5Mo-P-Si system, at room temperature,
Self-passivate in 6N aqueous hydrochloric acid. Further P
Cr and Mo can be saved by increasing the sum of Si and Si. For example, as shown in Figure 1, P and
Total Si content is 25 atomic% (P15 atomic%, Si 10 atomic%)
When the total content of Cr and Mo exceeds 10 atomic %, self-passivation occurs in room temperature 6N hydrochloric acid aqueous solution. This is economically very important when considering it as a practical alloy because Mo is expensive, but
If the total amount of Si exceeds 25 atomic percent, the amorphous amorphous forming ability of the alloy deteriorates, so the total amount of P and Si must be 25 atomic percent or less. In addition, the desired high corrosion resistance cannot be obtained by using P or Si alone as semimetallic elements, and it is necessary to coexist P with Si.
As can be seen from the figure, P needs to be at least 10 atomic % and Si needs to be at 5 atomic % or more. Although it is stated in JP-A-54-103730 that the addition of Si impairs corrosion resistance more than B, the present inventors have newly discovered that when combined with P, corrosion resistance is exhibited. When the Cr content is 25 at% or more, Fe-Cr
In the case of -Mo-based amorphous alloys, C-based amorphous alloys are easier to manufacture than P-Si-based. In addition, C-based materials can use cheaper raw materials than P-Si-based materials, and Fe-(25-35)Cr-Mo-
The corrosion resistance of 18C series was measured in 6N hydrochloric acid aqueous solution at 80°C. The result is as shown in Figure 1.
It was found that materials containing 10 atomic % or more of Mo self-passivate. But the same amount of Cr
Compared to the P-Si system containing Mo, the corrosion potential is lower and the anode current density is higher, resulting in inferior corrosion resistance. The method for producing the Fe-Cr-Mo amorphous alloy according to the present invention is based on a commonly used ultra-quenching method of liquid metal. In other words, the compounded materials include pig iron or pure iron as the iron source, chromium or molybdenum as the alloying element, commercially available pure metals or ferrochrome or ferromolybdenum, and commercially available pure substances as the semimetal source, ferroboron, ferrophosphor,
The alloy of the present invention can be produced by using ferrosilicon or cementite, heating and melting after blending, injecting the molten alloy from a nozzle onto the moving cooling surface of a cooling body, and rapidly solidifying it. In the alloy of the present invention, the ability to use ferroalloy as an alloying element source is extremely advantageous in terms of economy and productivity. In other words, as a source of chromium or molybdenum, ferrochrome or ferromolybdenum is a cheap raw material today, and ferrochrome has already been used as a Fe-Cr-
It is a C-based alloy and has a low melting point, and ferromolybdenum also has a significantly lower melting point than pure molybdenum, making it suitable for producing a uniform molten alloy in large quantities. Furthermore, since the impurities in these ferroalloys are mainly P and Si, they are elements that have a rather favorable effect on the production of the alloy of the present invention. Next, the present invention will be explained with reference to examples. Example 1 An amorphous amorphous alloy consisting of 10 atomic% Cr, 2, 5, 7, 10 atomic% Mo, 15 atomic% P, 5 atomic% Si, and the balance Fe was processed using a single roll method (roll diameter 30 cm).
This amorphous alloy was immersed in 6NHCl at room temperature to examine its corrosion rate. Above Fe−10Cr−Mo−15P−5Si
The polarization curve measurement results show that the amorphous alloy self-passivates when Mo is 5 atomic % or more, and the corrosion rate is significantly reduced when Mo is 5 atomic % or more, as shown in Figure 2, indicating that it has extremely excellent corrosion resistance. Example 2 Cr25 atomic%, Mo10 atomic%, P15 atomic%, Si10
An amorphous amorphous alloy consisting of atomic percent and balance Fe was manufactured by the same method as in Example 1. it at room temperature
6NHCl and 6NHNO ₃ and 6NHCl and 18NH ₂ SO ₄ at 80 °C
The corrosion rate was measured by immersing it in the water. As a result, the corrosion rate was extremely low and excellent corrosion resistance was demonstrated. Figure 2 is a diagram plotting the corrosion rate in 6NHCl at 80°C against Mo atomic %.
The corrosion rate of Mo-rich alloys was significantly reduced. As a comparative example, Figure 2 shows the results of an immersion test in 6NHCl at 80°C using 18-8 stainless steel, pure titanium, and pure tantalum. In a highly corrosive environment, the Fe-Cr-Mo amorphous alloy according to the present invention is slightly inferior to pure tantalum, but has a 18-8
It was found that this alloy is far superior in corrosion resistance to stainless steel, titanium, etc. As described above, the amorphous alloy of the present invention can be manufactured as a thin strip or thin plate, has corrosion resistance that cannot be obtained with conventional practical materials, and is extremely inexpensive compared to conventional practical materials. Further, as already disclosed, the amorphous amorphous alloy having the composition of the present invention has high strength and hardness, with a breaking strength of 380 Kg/mm ² and a hardness of about HV950. Therefore, the amorphous amorphous alloy of the present invention has superior characteristics compared to conventional corrosion-resistant materials as a structural material and component material that require strength and high corrosion resistance for chemical plants, nuclear reactors, seawater-resistant equipment, etc.

[Brief explanation of the drawing]

Figure 1 shows the influence of the amounts of Cr and Mo on the formation of a passive film, Figure 2 shows the relationship between the Cr and Mo contents and the corrosion rate, and Figure 3 shows the effect of P on the formation of a passive film. and C, as well as the influence of P and Si.

Claims (1)

[Claims] 1. In an amorphous alloy consisting of Fe, Cr and Mo and a metalloid, Cr is 5 atomic % or more and Mo 20 atomic % or less, and the total of Cr and Mo is in the range of 15 to 35 atomic %, The metal element consists of P-Si system, P10
atomic% or more, Si5 atomic% or more, and the total is 20 to 25
An ultra-high corrosion resistant Fe-Cr-Mo amorphous alloy characterized by a corrosion resistance within the range of atomic %. 2. The ultra-high corrosion-resistant Fe according to claim 1, in which the content of Cr is 5 atomic % or more, the Mo content is within the range of 10 to 20 atomic %, and the total of Cr and Mo is within the range of 20 to 35 atomic %.
-Cr-Mo based amorphous alloy.