JPS6311420B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] This invention is particularly aimed at producing a material that has excellent corrosion resistance and heat resistance, and does not cause peeling or cracking in the plating layer even when subjected to bending, by hot-plating the surface of a steel material. This invention relates to a Zn alloy for hot-dip plating. [Prior Art] In general, as a cheap and simple method for improving the corrosion resistance of steel materials, it is known to hot-plate Zn or a Zn alloy on the surface of the steel material. As one,
Zn alloy previously proposed by the present inventors: Ti: 0.1-1.2%, Mn: 0.05-0.6%, Al: 0.1-1.6%, and Si: 0.01 as necessary.
~0.4%, with the remainder consisting of Zn and unavoidable impurities (wt%)
91143), the plating layer formed by melt plating on a steel plate is Ti.
When the Al content is high and the Al content is low (in the case of high corrosion resistance), minute peeling and cracking are likely to occur on the bent surface after bending tests based on JIS Z2248, and on the other hand, the occurrence of such peeling and cracking In order to avoid this, if the Al content is increased within the above range, the corrosion resistance of the plating layer will be extremely reduced. 30%, and the remainder is Zn and unavoidable impurities; Ti: 0.1 to 2%; one or two of Mn and Ni: 0.1 to 2%;
1.6%, Al: 0.05-0.4%, and the rest is Zn and inevitable impurities.
proposed coating a steel plate with a molten Zn alloy plating layer consisting of a double structure of
issue). [Problems to be Solved by the Invention] However, forming a melt-plated layer having such a double structure has the disadvantage that the number of steps increases and the operation becomes complicated. [Findings based on research] Therefore, the present inventors conducted various studies to solve these problems, and as a result, (1) Zr was conventionally added to improve the corrosion resistance of Zn plating layers. (2) Ti is an effective component for improving the corrosion resistance of the Zn plating layer, similar to Ti, which was used to improve the corrosion resistance of the Zn plating layer.
Or for hot-dip plating, in which Zr contains Zr and Al, which improves workability without causing peeling or cracking of the plating layer during bending.
In Zn alloys, when Ti and Zr oxidize, their potential becomes nobler than that of Ag, so
The potential difference between Ti and Al is large, and therefore Ti on the surface of the plating film made of such a Zn alloy
Or, since electrolytic corrosion is likely to occur between Zr and Al,
Although the addition of Al reduces the corrosion resistance of Zn alloys containing Ti or Zr, when the weight ratio of Ti or Zr to Al is 1:10 to 1:100, electrolytic corrosion occurs between Ti or Zr and Al. (3) Between Ti or Zr and Al, TiAl ₃ or
When an intermetallic compound represented by ZrAl ₃ (ratio of the number of atoms) is formed and exists in a finely dispersed form in Al, the above-mentioned electrolytic corrosion is completely prevented and the corrosion resistance of the plating film is dramatically improved. In other words, a plating film that is sufficiently corrosion resistant even when containing a large amount of Al, which is necessary to improve the workability of a plating film, that is, a plating film that has both excellent corrosion resistance and workability. (4) A conventional Zn-plated steel plate can be cut by melting, for example.
Alternatively, when spot welding was applied to this, the Zn in the plating film exposed to high temperatures evaporated, and the corrosion resistance of that part was extremely reduced. % by weight, the same applies hereinafter), especially when it is contained at 20 to 25%,
This Al oxidizes more preferentially than Zn, forming an alumina film with excellent heat resistance, and inhibiting oxygen from entering the plating film thereafter.
High temperature oxidation of the plating film is prevented, thus
In high Al content areas containing 10% or more of Al,
Combined with the findings in the previous section, it is possible to obtain a plating film that is not only corrosion resistant and processable, but also has excellent heat resistance.
contains Zn and has a large specific gravity difference with Zn, so it tends to separate from Zn in the molten state and tends to collect near the surface of the plating bath. This tends to result in the plating film becoming rough and its corrosion resistance decreasing, but when Zn alloys containing such intermetallic compounds are
When one or more of these metals are added, these metals have a large affinity for Ti and Zr, that is, they act as a solvent for Ti and Zr,
These high specific gravity metals combine with the intermetallic compounds and make them heavy, so that these intermetallic compounds are uniformly dispersed in the Zn, improving the stability of the plating bath, thereby reducing the roughness. (6) When Ti or Zr is added to a Zn plating bath, the viscosity of the plating bath increases and its fluidity decreases. In addition to reducing workability, pinholes are likely to occur in the plating film, and the corrosion resistance of the plating film decreases due to the pinholes.
(7) Of Ti and Zr, the addition of B reduces the viscosity of the plating bath and restores its fluidity, thereby avoiding the problems of reduced workability and pinhole formation. When Mg is added to a Zn alloy plating film containing one or two types and Al,
This Mg prevents intergranular corrosion, and due to interaction with Al, Fe-Zn, Fe-Ti and Fe-Zr
In addition to preventing the formation of a plating layer and preventing peeling and cracking of the plating layer caused by these alloy layers during bending, the viscosity of the plating bath is increased to increase the thickness of the plating film, and Since it has the effect of increasing the concentration of Ti and Zr dissolved in the coating and improving the corrosion resistance of the plating coating, the addition of Mg not only improves the workability and corrosion resistance as described above, but also improves the corrosion resistance of the plating coating.
It has been found that this method is effective for adjusting the thickness of the plating film. [Means for Solving the Problems] This invention was invented based on the above findings, and provides a Zn alloy for hot-dip plating that has excellent corrosion resistance and workability, and also has excellent heat resistance if necessary. The weight ratio of Ti or Zr to Al is 1:10 to 1:
100, one or two of Ti or Zr: 0.01~
1.0%, Al: 0.15 to 25.0%, one or more of Mn, Ni, Co, and Fe: 0.01 to 0.8%, and if necessary, one of Si or B or Type 2: 0.01-0.5
%, and Mg: 0.01 to 0.8%.
An intermetallic compound having a composition consisting of Zn and inevitable impurities and formed from Ti or Zr within the above range and Al also within the above range: one type of TiAl ₃ or ZrAl ₃ The invention relates to a Zn alloy for hot-dip plating, characterized in that it contains 0.02 to 2.6% (or more by weight) of the above two types. Next, the reason why the composition range and other conditions of the Zn alloy of the present invention are limited as described above will be described. (a) Ti and Zr Ti and Zr components have the effect of imparting excellent corrosion resistance to the plating film that satisfies even in severe corrosive environments.
Ti and Zr react with Al and are contained as intermetallic compounds of TiAl ₃ and ZrAl ₃ , respectively.
It shows particularly excellent corrosion resistance, but if the content of Ti and/or Zr is less than 0.01%, the desired corrosion resistance is not imparted to the plating film, while if the content exceeds 1.0%, the reaction of Ti and Zr Since it is difficult to dissolve TiAl ₃ and ZrAl ₃ respectively produced by
It was set at 0.01-1.0%. (b) Al The Al component suppresses the formation of hard and brittle Fe-Zn, Fe-Ti, and Fe-Zr alloys between the surface of the substrate and the plating layer during hot-dip plating.
During the bending process, the Fe-Zn, Fe-Ti and
In addition to preventing peeling and cracking of the plating layer caused by Fe-Zr alloy metals, Mn, Ni, Co,
The addition of Fe has the effect of mitigating the hardening of the plating layer, but if the Fe content is less than 0.15%, the desired effect cannot be obtained; on the other hand, if it exceeds 25.0%, the Fe-Al alloy Since a layer develops and processability deteriorates, its content was set at 0.15 to 25.0%. (c) Mn, Ni, Co, Fe As mentioned above, these components are made by dissolving TiAl ₃ and ZrAl ₃ and finely and uniformly dispersing these intermetallic compounds in the Zn matrix. It has the effect of stabilizing the plating bath and preventing the roughness of the plating film, and further improving its corrosion resistance.However, if its content is less than 0.01%, the desired effect of improving the above effect cannot be obtained; 0.8
If the content exceeds 0.01%, the workability of the plating film will decrease.
It was set at ~0.8%. (d) Si, B The Si and B components improve the fluidity of the plating bath and improve workability during plating, as well as form a smooth and glossy plating film.
These properties are especially required because it suppresses the formation of Fe-Zn, Fe-Ti, and Fe-Zr alloy layers, improves the workability of plating films, and dramatically improves corrosion resistance. If the content is less than 0.01%, the desired effect of improving the above action cannot be obtained;
Since plating properties will be impaired if the content exceeds 0.01 to 0.5%. (e) Mg As mentioned above, the Mg component prevents intergranular corrosion, and also has the ability to interact with Fe-Zn, Fe-
It prevents the formation of Ti and Fe-Zr alloy layers, prevents peeling and cracking of the plating layer caused by these alloy layers during bending, and increases the viscosity of the plating bath to reduce the thickness of the plating film. This Mg component has the effect of increasing the corrosion resistance of the plating film by increasing the concentration of Ti and Zr contained in the film, so this Mg component has the effect of improving the processability and the corrosion resistance of the plating film, especially when these properties are required. It is included as necessary not only to improve corrosion resistance but also to adjust the thickness of the plating film, but if the content is less than 0.01%, the desired effect cannot be obtained; If it is contained in excess of 0.8%,
Since the viscosity of the plating bath increases too much and the workability of plating is impaired, its content should be reduced.
It was set at 0.01-0.8%. (f) Weight ratio of Ti or Zr to Al Both Ti and Zr are components that are contained in Zn alloys in the form of TiAl ₃ and ZrAl ₃ that have reacted with Al and exhibit excellent corrosion resistance. If the weight ratio of Ti or Zr to Al is less than 1:100, the proportion of Ti and Zr that provides corrosion resistance will be small, and
On the other hand, if the ratio of Al, which reduces corrosion resistance, becomes too large, the desired corrosion resistance cannot be obtained, and on the other hand, if it exceeds 1:10, the ratio of Ti or Zr becomes too large, and these Ti or Zr The content ratio of Ti or Zr to Al was determined to be 1:10 to 1:100 since the electrolytic corrosion that occurs with Al becomes noticeable. (g) TiAl ₃ , ZrAl ₃ As mentioned above, since Ti and Zr are dispersed and contained in the Zn alloy in the form of TiAl ₃ and ZrAl ₃ , respectively, they do not cause electrolytic corrosion with Al. , and has the effect of imparting excellent corrosion resistance to the plating film, but if the content of these compounds is less than 0.02%, the amount of these compounds is insufficient and the desired corrosion resistance cannot be obtained; Since these intermetallic compounds will not be completely dissolved in the Zn alloy if the content exceeds this content, the content is set at 0.02 to 2.6%. In addition, the Zn alloy of this invention can be melted and
In addition to being used as a molten plating bath, this Zn alloy, melted with a blowpipe flame or electric arc, is sprayed as an extremely fine mist onto metal surfaces using high-pressure gas to form a plating film, in the form of so-called metallicon. Alternatively, the Zn alloy may be homogeneously mixed in a paint or vehicle in the form of a fine powder and applied to the metal surface to form a coating particularly corrosion resistant. You can also use it by folding it. [Example] Next, the Zn alloy of the present invention will be explained using Examples and in comparison with Comparative Examples. Melt plating baths of Zn alloys 1 to 15 of the present invention, comparative Zn alloys 1 to 4, and conventional Zn alloys 1 to 2, each having the composition shown in Table 1, were prepared, and then the plating bath temperature was adjusted to 460 to 460°C, respectively. In the melt plating bath maintained at a predetermined temperature within a temperature range of 500°C,
The Zn alloy of the present invention was prepared by immersing a steel plate having a thickness of 0.4 mm pretreated with a ZnCl ₂ -NH ₄ Cl flux for 5 seconds to form a plating layer with a thickness of 13 μm on one side on the surface of the steel plate. Plated steel plate 1 to 15,
Comparative Zn alloy plated steel plates 1 to 4 and conventional Zn alloy plated steel plates 1 to 2 were manufactured, respectively. Comparative Zn alloys 1 to 4 all have compositions in which the content of any of their constituent components (those marked with * in Table 1) is outside the scope of the present invention. be. Next, for each of these steel plates, JIS/
Salt spray test based on Z2371 and JIS/
A bending test was conducted based on Z2248, and in the spray test, the time until red rust appeared on the plated surface of the steel plate was measured, and in the bending test, the state of the plated layer on the bent surface was observed, and there was no peeling or cracking in the plated layer. A case where no occurrence of peeling and cracking is observed is evaluated with a mark ◎, and a case where peeling and cracking are clearly observed in the plating layer is evaluated with an x mark. In order to confirm that these Zn alloys of the present invention have excellent corrosion resistance especially during melt cutting and spot welding,
15, a heat resistance test was conducted at 800℃ for 5 minutes, and the case where no abnormality was observed on the plating surface was marked with ◎, and the case where abnormality due to high temperature oxidation was observed on the plating surface was marked with ×. The results of these measurements are shown in Table 1. Further, the Zn alloy of the present invention is manufactured as follows, for example, taking the Zn alloy used in manufacturing the Zn alloy plated steel sheet 13 of the present invention as an example. (i) Production of Ti master alloy Ti: 59.51g, Mn: 25.76 in an alumina crucible
g, Al: 9.82 g, and Si: 491 g, and arc melted in an argon gas atmosphere. 163 g of Ti master alloy produced by cooling the molten metal had the following composition. Ti Mn Al Si 59.51 25.76 9.82 4.91% (ii) Production of Zn-Ti intermediate alloy Place 2812.5 g of Zn in a graphite crucible, heat it to 500°C in a high-frequency melting furnace to melt the Zn, and melt the Zn. Place 163 g of the previously produced Ti master alloy on top, cover with a carbon lid, raise the temperature to 830-850°C in an argon gas atmosphere, maintain this temperature for 60 minutes, and then cool to 600°C. After this, the molten metal was poured into an ingot case, thereby preparing 2975.5 g of a Zn--Ti intermediate alloy having the following composition. Ti Mn Al Si Zn 2.0 0.87 0.33 0.17% Remaining (iii) Production of Zn-Ti blended alloy Take 2514.5 g of Zn in a graphite crucible and add 480

〔Effect of the invention〕

From the results shown in Table 1, the present invention Zn alloy 1
Each of the present invention was melt-plated by ~15
Zn alloy plated steel sheets 1 to 15 all exhibit excellent corrosion resistance, and while inventive alloys 1 to 15 form a plated layer with excellent adhesion that does not peel or crack at all even during bending. Comparative Zn alloys 1 to 1 have compositions in which the content of any one of the constituent components is outside the scope of the present invention.
Comparative Zn alloy plated steel sheets 1 to 4, each of which was hot-dipped by No. 4, showed inferior results in at least one of corrosion resistance, heat resistance, and bending evaluation. Further, in the conventional Zn alloy plated steel sheets 1 and 2, a Fe--Zn alloy layer was formed, and the corrosion resistance and adhesion of the plated layer were significantly deteriorated. Furthermore, as seen in Zn alloy plated steel sheets 2 to 5 and 7 to 15 of the present invention, it contains a predetermined amount of one or two of Si and B, and one or more of Mg. The corrosion resistance of the Zn alloy plated steel sheets of the present invention tends to be further improved.
It can be seen that in No. 15, the Al content is high, so the heat resistance is particularly excellent. In addition, in addition to hot-plating with the Zn alloy of the present invention,
It was confirmed that corrosion resistance was further improved by further applying chromate treatment. As mentioned above, according to the highly corrosion-resistant Zn alloy for hot-dip plating of the present invention, excellent corrosion resistance can be ensured even under severe usage conditions, especially by hot-plating the surface of steel materials. It also has extremely good adhesion to the steel material surface, and has excellent adhesion to the brittle Fe.
- Since there is almost no formation of Zn, Fe-Ti or Fe-Zr alloy layers, there is no peeling or cracking of the plating layer during bending, and it is possible to obtain products with excellent heat resistance. Furthermore, the thickness of the plating film can be easily adjusted, making it possible to apply a sufficiently thick plating layer with the above characteristics even to shapes such as angles, which generally require a thicker plating layer than plate materials. Various industrially useful effects are brought about.

Claims (1)

[Claims] 1. One or two of Ti or Zr: 0.01 to 1, provided that the weight ratio of Ti or Zr to Al is 1:10 to 1:100.
1.0%, Al: 0.15 to 25.0%, one or more of Mn, Ni, Co, and Fe: 0.01 to 0.8%, with the remainder consisting of Zn and inevitable impurities, and Ti or Zr within the above range
and an intermetallic compound formed from Al also within the above range: 0.02 to 2.6% (or more by weight) of one or two of TiAl ₃ or ZrAl ₃
A Zn alloy for hot-dip plating, characterized by comprising: 2 One or two of Ti or Zr: 0.01 to 2, provided that the weight ratio of Ti or Zr to Al is 1:10 to 1:100.
1.0%, Al: 0.15-25.0%, One or more of Mn, Ni, Co, Fe: 0.01-0.8%, One or two of Si or B: 0.01-0.5
%, with the remainder consisting of Zn and unavoidable impurities, and within the above range Ti or Zr
and an intermetallic compound formed from Al also within the above range: 0.02 to 2.6% (or more by weight) of one or two of TiAl ₃ or ZrAl ₃
A Zn alloy for hot-dip plating, characterized by comprising: 3 One or two of Ti or Zr: 0.01 to 1, provided that the weight ratio of Ti or Zr to Al is 1:10 to 1:100.
Contains 1.0%, Al: 0.15-25.0%, one or more of Mn, Ni, Co, and Fe: 0.01-0.8%, Mg: 0.01-0.8%, and the rest is Zn and unavoidable impurities. Ti or Zr having the composition and within the above range
and an intermetallic compound formed from Al also within the above range: 0.02 to 2.6% (or more by weight) of one or two of TiAl ₃ or ZrAl ₃
A Zn alloy for hot-dip plating, characterized by comprising: 4 One or two of Ti or Zr: 0.01 to 1, provided that the weight ratio of Ti or Zr to Al is 1:10 to 1:100.
1.0%, Al: 0.15-25.0%, One or more of Mn, Ni, Co, Fe: 0.01-0.8%, One or two of Si or B: 0.01-0.5
%, Mg: 0.01~0.8%, with the remainder consisting of Zn and unavoidable impurities, and Ti or Zr within the above range.
and an intermetallic compound formed from Al also within the above range: 0.02 to 2.6% (or more by weight) of one or two of TiAl ₃ or ZrAl ₃
A Zn alloy for hot-dip plating, characterized by comprising: