JPS6155580B2 - - 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 amorphous alloy that has corrosion resistance in a corrosive environment of about 6NHCl or more. 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. It has 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 present inventors previously applied for a patent application in 1973-
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 No. 53-10397) 103730) invented carbon-based amorphous iron alloys and applied for a patent.
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 and P, C as atomic %.
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, A1, 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 the above-mentioned Japanese Patent Application Laid-Open No. 54-103730 is Fea Crb Mc Qd (where Fe a is a atomic % of Fe, Cr b is b Cr
atomic %, Mc is c atomic % of one or more selected from Cr, Mo, and W, and Qd is C
It shows that the content is d atomic %. ), which has a component composition shown by the formula:
Among them, those with excellent corrosion resistance have a of 28 to 82,
It is disclosed that the carbon-based amorphous iron alloy has b in the range of 2 to 20, c in the range of 4 to 26, and d 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 an effective alloy additive to improve corrosion resistance, and addition of molybdenum in addition to chromium improves chromium. Improves the corrosion resistance of iron-based amorphous alloys. By the way, the present inventors further investigated the corrosion resistance of the two invention alloys, and found that the composition range showed extremely strong corrosion resistance against a hydrochloric acid aqueous solution with a higher concentration than that of a 1N hydrochloric acid aqueous solution due to the difference in the integral composition range. It was discovered that there is a component composition range that exhibits relatively weak corrosion resistance, and that the invention alloy cannot exhibit sufficient corrosion resistance in the strong corrosive environment found in the above-mentioned 1N hydrochloric acid aqueous solution or higher. I learned. As an example, 6N
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 selected a 6N hydrochloric acid aqueous solution as a more severe corrosive environment, and after repeated various studies regarding the corrosion resistance of the above-mentioned inventive alloy, finally found that the amorphous alloy of the present invention has excellent corrosion resistance within the composition range. The present invention was completed based on the new finding that The present invention was made for these reasons.
The objective 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 is 20 atomic % or less, and the total of Cr and Mo is 15 to 35 atomic %.
ultra-high corrosion resistance, with the metalloid element consisting of the P-C system, with P and C each at 5 at% or more, and the total being within the range of 20 to 25 at%.
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 reason why the iron-based amorphous amorphous alloy containing chromium exhibits corrosion resistance, and found that the cause is due to the chemical uniformity and high activity of the amorphous amorphous alloy itself, and the chemical uniformity is due to uniform unevenness. It has been 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-13P-7C 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 area above the series of lines connecting each point is the self-passivation region 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―20Cr―2Mo―
The figure shows that the 13P-7C alloy self-passivates in a 6N aqueous hydrochloric acid solution at room temperature. Also a large amount of Mo
Although the addition of Mo has the effect of increasing the corrosion potential, as can be seen from Figure 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 increase the amount of Mo added to 20 atomic % or more, especially since Mo is an expensive element. In addition, when Mo is 20 atomic % or more or the total of Cr and Mo is 35 atomic % or more, the ability to form amorphous assemblies deteriorates. Next, under even more severe corrosion conditions, as shown in Figure 1, polarization curve measurements in a 6N hydrochloric acid aqueous solution (80°C) revealed that 13P-7C alloys had 5 at.% of Cr.
when Mo15 atomic% or more, or
It was found that self-passivation occurs when Cr is 10 atomic % and Mo is 10 atomic % or more, but even if Cr increases to 10 atomic % or more, the amount of Mo required for self-passivation does not decrease. Next, the reason for selecting the metalloid and its concentration range will be explained. In order to produce amorphous iron alloys, it is necessary to add semimetallic 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 in addition, raw material costs may be high. Yes, as a metalloid P-
We selected C system, P-Si, and C system. Regarding the amount of these metalloid elements added, as shown in Figure 3, when the total of P and C is 20 at% or more in the Fe-10Cr-5Mo-P-C system, at room temperature,
Self-passivate in 6N aqueous hydrochloric acid. Further P
By increasing the sum of Cr and C, Cr and Mo can be saved. For example, as shown in Figure 1, P and C
When the total of Cr and Mo is 22 at% (P10 at%, C12 at%) and the total of Cr and Mo is 10 at% or more, self-passivation occurs in a 6N aqueous hydrochloric acid solution at room temperature. This is economically very important when considering it as a practical alloy because Mo is expensive, but P and C
If the total of P and C exceeds 25 at%, the amorphous amorphous forming ability of the alloy deteriorates, so the total of P and C should be 25 at%.
It is necessary to do the following. 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--C based. In addition, the C system can use cheaper raw materials than the P-C system, and Fe-(25-35)Cr-Mo
The corrosion resistance of -18C series was measured in 6N hydrochloric acid aqueous solution at 80℃. As a result, as shown in Figure 1, it was found that materials containing 10 atomic % or more of Mo self-passivated. But the same amount
Compared to the PC system containing Cr and Mo, it has a lower corrosion potential and a higher anodic current density, so it is inferior in corrosion resistance. In other words, in the Fe-10Cr-5Mo system, C alone as a non-metallic element does not provide the desired high corrosion resistance, and it is necessary to coexist P. can get. Similarly, since corrosion resistance is poor even when P alone is used, the content of C needs to be 5 at % or more. 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 blended 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 metalloid 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 is already 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 alloy consisting of 10 atomic% Cr, 2, 5, 7, 10, 15 atomic% Mo, 13 atomic% P, 7 atomic% C, and the balance Fe was rolled using a single roll method (roll diameter 30 cm).
This amorphous alloy was immersed in 6NHCl at room temperature to examine the corrosion rate. Above Fe―10Cr―Mo―13P―
7C amorphous alloy is based on polarization curve measurement results.
At Mo5 atomic % or more, self-passivation occurs, but as shown in Figure 2, the corrosion rate was significantly reduced at Mo 5 atomic % or more, and the corrosion resistance was extremely excellent. Example 2 The above Fe-10Cr-Mo-13P-7C amorphous alloy was immersed in 6NHCl at 80°C and the corrosion rate was measured in the same manner. Under these conditions, Mo becomes self-passivated at 10 atomic % or more, but as shown in Figure 2, a significant decrease in corrosion rate is observed, indicating excellent corrosion resistance. Example 3 An amorphous alloy consisting of 25 atomic % of Cr, 2,5,7,10,15 atomic % of Mo, 13 atomic % of P, 7 atomic % of C, and the balance Fe was manufactured by the same method as in Example 1. It was immersed in 6NHCl at 80°C and the corrosion rate was measured. The result is as shown in Figure 2.
When Mo is 10 atomic % or more, the corrosion rate decreases significantly, and it has excellent corrosion resistance. Further, from Examples 1, 2, and 3, it can be seen that even if Mo is increased more than necessary, the corrosion rate does not change, and that increasing Cr decreases the corrosion rate and increases corrosion resistance. 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 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. An amorphous alloy consisting of Fe, Cr and Mo and a metalloid, in which Cr is 5 atomic % or more and Mo 20 atomic % or less, and the total of Cr and Mo is within the range of 15 to 35 atomic %, and Ultra-high corrosion resistance characterized by the metal element consisting of the PC system, with P and C each containing 5 at% or more and the total being within the range of 20 to 25 at%.
Fe-Cr-Mo based amorphous alloy. 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.