JPH0583638B2 - - Google Patents

Description

[Detailed description of the invention]

(a) Industrial Application Field The present invention relates to a method for descaling a single-sided titanium clad steel plate. Titanium-clad steel sheets, which use carbon steel or stainless steel that matches the desired strength characteristics as the base material and titanium, which has excellent corrosion resistance, on the surface, are manufactured by explosion bonding methods, rolling methods, etc. In this case, depending on the purpose, one with titanium bonded on both sides and one with titanium bonded on only one side are used. An object of the present invention is to provide a method for efficiently descaling a single-sided titanium-clad steel sheet without causing roughening of the steel surface. (b) Conventional technology Titanium clad steel sheets are inexpensive, have good mechanical properties,
It is a material that takes advantage of the characteristics of both steel, which has thermal and electrical properties, and titanium, which has extremely excellent corrosion resistance, and is suitable for use in harsh environments such as chemical industrial plants such as heat exchangers and marine structures. It is a composite material that is also used in fields such as roofing materials and home appliances. This titanium clad steel sheet has a hard and brittle intermetallic compound layer formed at the interface between titanium and steel at high temperatures, and a thin oxide film (passive film) that is extremely difficult to remove at room temperature. Since it is difficult to manufacture by bonding, special bonding methods such as the explosion bonding method (Japanese Patent Publication No. 43-432 of 1973) have been used. However, with such a special manufacturing method, the manufacturing cost is extremely high and the applications are limited. On the other hand, the growth of intermetallic compounds at the interface can be prevented (Japanese Unexamined Patent Publication No. 63-63585), and the hot rolling method that uses molten intermetallic compounds and does not require a vacuum for bonding (Japanese Unexamined Patent Publication No. 63-63585) −144881 Publication, Patent Application 1983−
No. 277826) was disclosed, and the cost of titanium clad steel sheets has been rapidly decreasing. Titanium clad steel plates that are hot-bonded in this way need to have the thick oxide film formed during the manufacturing process removed, but as overall costs have been reduced, there has been an increasing demand for cost reductions in the descaling process. . Conventionally, descaling of titanium clad steel sheets has been done by polishing (Masahide Shimazaki et al., "Titanium and Zirconium", Vol. 34, Vol. 3).
(No. 157) or the descaling process for stainless steel and titanium (Ichiro Iitaka and Masayoshi Hasegawa, "Metallic Titanium" Nikkan Kogyo Shimbun S30 Luminescence P109). It had not been done. That is, for example, a process of pickling by immersion in a mixed acid of HNO ₃ and HF for a long time, or a process of performing H ₂ SO ₄ pickling after shot projection and then performing a mixed acid pickling of HNO ₃ and HF has been used as is. The reason for this is that it is assumed that titanium, which is extremely difficult to descale, must be reliably descaled, so the pickling process for stainless steel and titanium is
This is because HNO ₃ and HF pickling processes are used. However, although HNO ₃ and HF pickling are effective for descaling titanium, the dissolution rate of steel is extremely high, so by the time descaling of titanium is completed, the dissolution of the steel has progressed rapidly, and the steel side The disadvantage was that the surface roughness progressed and the surface roughness deteriorated. This disadvantage is not a problem in the case of double-sided cladding, but in the case of single-sided cladding, not only does the commercial value decrease considerably, but also the yield of the steel side is greatly reduced, and the acid melts due to excessive melting of the steel. This was a major factor in increasing costs, as it led to rapid deterioration. (c) Problems to be Solved by the Invention The present invention aims to alleviate the large difference in the dissolution rate of titanium and steel in acid in the descaling process of single-sided titanium clad steel sheets, and to achieve a descaling process that matches the respective descaling rates. The present invention provides a method. (d) Means to solve the problem The conventional pickling and descaling process for stainless steel involves first removing most of the scale with inexpensive H ₂ SO ₄ or HCl, and then using expensive HNO ₃ and HCl. This pickling process aims to remove scale left by the HF mixed acid and smut, which is a dissolved product during pickling. Therefore, most of the scale will have been removed by the time of HNO ₃ and HF pickling. When this process is applied to a single-sided titanium clad steel plate, most of the scale on the steel side is removed as in the conventional method, but the titanium side dissolves in H ₂ SO ₄ and HCl very little, so a considerable amount of scale is removed. It will be immersed in a mixed acid of HNO ₃ and HF with some remaining residue. For this reason, the steel will melt at a much higher rate than the dissolution rate of titanium until the descaling of titanium is completed. In addition, conventional descaling of titanium mainly involves HNO ₃ and HF pickling, so if steel is immersed under the same conditions as titanium (concentration, temperature, time), the dissolution rate of steel will be lower than that of titanium. It will be much faster. From the above points, the present inventors have determined that in order to alleviate the large difference in the dissolution rate of titanium and steel in acid and to balance their respective descaling rates, the dissolution rate of steel in a mixed acid of _HNO3 and HF can be reduced. The present invention was developed based on the belief that it is important to reduce the Conventionally, in the development of descaling methods, it has been important to find a way to increase the dissolution rate, and many efforts have been made to this end. It was an act of direction. In order to reduce the dissolution rate of steel by simultaneously immersing titanium and steel in a mixed acid of HNO ₃ and HF, it is conceivable to coat the steel surface with a film that prevents contact with the acid. However, if an organic film or the like is applied for this purpose, it will not only complicate the process but also stop the desired descaling, making it impossible to apply. For this purpose, the present invention has devised the idea of using the scale to be descaled as a dissolution inhibiting film, and descaling only one side by spraying an acid solution, and then descaling the other side. . For this purpose, we reversed the order of first pickling with a cheap acid and then pickling with an expensive acid, which is used in the conventional descaling process for stainless steel. Although it is hardened first, it is easier to descale the titanium. HNO ₃ and HF
The present invention was completed as a descaling process in which pickling is carried out with a mixed acid of 100% and then pickling with an acid that is hardly expected to descale titanium but is effective for descaling steel. That is, the gist of the present invention is as follows. (1) In the descaling process of a single-sided clad steel plate where the base material is steel and the mating material is titanium or titanium alloy, a shot is shot only on one side of the titanium or titanium alloy side, and then both sides are treated with HNO ₃ and HF.
A method for descaling a single-sided titanium clad steel sheet, the method comprising pickling by immersing it in a mixed acid solution. (2) The single-sided titanium cladding according to the preceding item 1, which is pickled with a mixed acid of HNO ₃ and HF, and then subsequently pickled by spraying HCl or/and H ₂ SO ₄ solution or by immersing it in the acid or the mixed acid solution. Method for descaling steel plates. (3) In the descaling process of a single-sided clad steel plate where the base material is steel and the mating material is titanium or titanium alloy, only one side of the titanium or titanium alloy side is
A method for descaling a single-sided titanium clad steel sheet, which comprises spraying a mixed acid of HNO ₃ and HF for pickling, and then spraying a mixed acid of HNO ₃ and HF on both sides or immersing it in a solution of the mixed acid for pickling. . (4) Only on one side of titanium or titanium alloy side.
Before pickling by spraying a mixed acid of HNO ₃ and HF,
The preceding item 3 of projecting a shot onto one or both sides.
The described method for descaling a single-sided titanium clad steel plate. (5) In the descaling process of a single-sided clad steel plate where the base material is steel and the cladding material is titanium or titanium alloy, only one side of the titanium or titanium alloy side is
One side characterized by pickling by spraying a mixed acid of HNO ₃ and HF, followed by spraying HCl or/and H ₂ SO ₄ on both sides, or by immersing it in the acid or mixed acid solution. A method for descaling titanium clad steel sheets. (6) Only on one side of titanium or titanium alloy side.
Before pickling by spraying a mixed acid of HNO ₃ and HF,
The preceding item 5 of projecting a shot on one or both sides
The described method for descaling a single-sided titanium clad steel plate. (7) After pickling with HCl or/and H ₂ SO ₄ , spray HNO ₃ or a mixed acid of HNO ₃ and HF on both sides, or immerse them in the acid or mixed acid solution for pickling. Method for descaling a single-sided titanium clad steel sheet according to 6. The present invention is most effective when applied to a single-sided titanium clad steel sheet after hot rolling. In some cases, it is also effective to apply it to the subsequent descaling step. Next, the limiting conditions of the present invention are shown. Although the shot projection conditions have an influence on the absolute descaling speed depending on the size of the shot grains and the shot projection density, the effects of the present invention can be seen in any case, and the descaling properties of titanium and steel surfaces are Depending on the difference between the two conditions, it is possible to select shot projection conditions with a slow absolute descaling rate. For titanium descaling, a mixed acid of HNO ₃ and HF is most effective, so it is limited to a mixed acid of these. After aiming at descaling steel, HCl or H ₂ SO ₄ , which is a conventionally proposed descaling acid for steel, and a mixed acid of these are suitable.
Limited to H ₂ SO ₄ and mixed acids thereof. Pickling to be carried out after descaling if necessary Pickling for removing smut is limited to a mixed acid of HNO ₃ and HF, which is most effective for removing smut. (e) Effect In the method according to claims 1 and 2, descaling is progressed only on the titanium surface by shot projection. During the subsequent pickling in a mixed acid of HNO ₃ and HF, dissolution of the steel side is suppressed because the scale remains in the form of a film on the steel side. In the methods described in claims 3, 4, 5, and 6, melting of the steel side is suppressed by injecting a mixed acid of HNO ₃ and HF only to one side of the titanium side. In the methods described in claims 2, 5, and 6, it is possible to descale the steel side using H ₂ SO ₄ or HCl, which hardly causes dissolution of titanium. This process makes it possible to reliably perform descaling on both sides even if the descaling results on the titanium side and the steel side are different. In the methods described in claims 3 and 5, mechanical descaling such as shot projection may be used in combination before pickling, and also the method of shot projection for only one side according to the methods described in claims 1 and 2 may be applied. is possible. Furthermore, claims 2 and 5
In the method described in 6 and 6, after pickling with HCl or/and H ₂ SO ₄ aiming at descaling the steel side,
Pickling It is also possible to pickle with a mixed acid of HNO ₃ and HF to remove smut. In this way, in pickling descaling of a single-sided titanium clad steel sheet, it is possible to promote descaling on the titanium side and to suppress descaling by leaving a film-like scale on the steel side that suppresses descaling. Ta. Further, as a matter of course, the method of the present invention did not have any adverse effect on the quality of titanium clad steel sheets. In addition, the concentration, concentration ratio, or temperature of the mixed acid of HNO ₃ and HF, the acid of HCl or/and H ₂ SO ₄ ,
The higher the concentration and the higher the temperature, the greater the effect;
Since the effect is recognized even at low temperatures, it may be determined appropriately depending on the descaling situation depending on the steel type and conditions such as pickling immersion and spraying. (F) Example After hot-rolling a 2.5 mm thick single-sided titanium clad steel plate with a base material of carbon steel containing 0.112% C and a JIS-1 class pure titanium plate with a thickness of 80 μm as the laminating material,
Descaling was carried out under various conditions. The results are shown in Table 1. Note that shot projection is based on the average particle size.
Shot grains of 200 μm were used. As is clear from the results in Table 1, descaling is completed in all methods of the present invention, and the surface roughness of the steel surface is less than 10 μm in Rmax without shot projection, and 15 μm even with shot projection. It can be seen that the surface is smooth and has no surface defects such as roughness.

[Table] Results column ○: Descaling completed, ×: Scale remaining
(G) Effects of the Invention According to the present invention, in the pickling and descaling of a single-sided titanium clad steel plate, the phenomenon in which dissolution progresses rapidly only on the steel side is eliminated, and the surface quality after pickling is improved. In addition, the yield of steel has been significantly improved, and precise design control of the cladding ratio has become possible. As a result, it has become possible to make the titanium layer thinner, and the cost of titanium clad steel sheets has been reduced. On the other hand, because the excessive melting of steel in the expensive mixed acid of HNO ₃ and HF was significantly reduced, the acid consumption rate was also significantly reduced, which in turn contributed greatly to the cost reduction of titanium clad steel sheets. As shown above, the present invention not only reduces the manufacturing cost of titanium clad steel sheets, but also provides inexpensive titanium clad steel sheets, making it possible to enjoy titanium's excellent corrosion resistance at a low cost, resulting in resource and economic benefits. is a big one.

Claims (1)

[Claims] 1. In the descaling process of a single-sided clad steel plate in which the base material is steel and the cladding material is titanium or titanium alloy, a shot is projected only on one side of the titanium or titanium alloy side, and then both surfaces are treated with HNO ₃ . A method for descaling a single-sided titanium clad steel sheet, characterized by immersing it in a mixed HF acid solution and pickling it. 2. The single-sided titanium clad steel sheet according to claim 1, wherein after pickling with a mixed acid of HNO ₃ and HF, both sides are subsequently pickled by spraying an HCl or/and H ₂ SO ₄ solution or by immersing the plate in the acid or the mixed acid solution. Descaling method. 3. In the descaling process for single-sided clad steel plates where the base material is steel and the cladding material is titanium or titanium alloy, only one side of the titanium or titanium alloy side is
A method for descaling a single-sided titanium clad steel sheet, which comprises spraying a mixed acid of HNO ₃ and HF for pickling, and then spraying a mixed acid of HNO ₃ and HF on both sides or immersing it in a solution of the mixed acid for pickling. . 4 Only on one side of titanium or titanium alloy side
4. The method for descaling a single-sided titanium clad steel sheet according to claim 3, wherein a shot is projected onto one or both surfaces of the sheet before pickling by jetting a mixed acid of HNO ₃ and HF. 5. In the descaling process of single-sided clad steel plates where the base material is steel and the cladding material is titanium or titanium alloy, only one side of the titanium or titanium alloy side is
One side characterized by pickling by spraying a mixed acid of HNO ₃ and HF, followed by spraying HCl or/and H ₂ SO ₄ on both sides, or by immersing it in the acid or mixed acid solution. A method for descaling titanium clad steel plates. 6 Only on one side of titanium or titanium alloy side
6. The method for descaling a single-sided titanium clad steel sheet according to claim 5, wherein a shot is projected onto one or both surfaces of the sheet before pickling by jetting a mixed acid of HNO ₃ and HF. 7. After pickling with HCl or/and H ₂ SO ₄ , both sides are further pickled by spraying HNO ₃ or a mixed acid of HNO ₃ and HF or by immersing them in the acid or mixed acid solution. The described method for descaling a single-sided titanium clad steel plate.