JPH062384B2 - Titanium clad steel sheet using austenitic stainless steel having excellent corrosion resistance as a base material and method for producing the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a titanium clad steel sheet having excellent corrosion resistance and a method for producing the same.

[Conventional technology]

Steel has long been used for a very wide range of applications because it is inexpensive and has good mechanical, thermal and electrical properties.
However, steel has a fatal defect that it rusts or corrodes in a short time when used as it is. Titanium, on the other hand, has significantly better corrosion resistance than steel, so it almost solves the problems of corrosion and rust prevention, but other properties such as thermal conductivity, magnetism, and bondability with steel differ from steel. In addition to having the characteristics described above, it has the drawback of being extremely expensive.
Therefore, it is not always technically and economically easy to completely replace steel with titanium.

As a method for solving these problems, clad steel having titanium as the surface and steel as the base material is used. The clad steel is a material that has excellent corrosion resistance and satisfies the desired characteristics by using a steel that matches the desired characteristics as the base material and using titanium that has excellent corrosion resistance on the surface.

However, the titanium clad steel has a brittle Fe at the interface between titanium and steel.
-Ti intermetallic compound and TiC, if a thick layer is formed, may cause delamination at the interface.Therefore, the highly productive cast-in method performed at the molten steel level cannot be applied, and solid phase that requires special equipment is not applicable. It had to be manufactured by level bonding. As a result, it is inevitably a high cost material, and it has been used only in chemical devices such as heat exchangers and reactors.

On the other hand, the inventors of the present invention have invented a method capable of producing a clad steel in the air by positively utilizing an intermetallic compound of Ti and Cu (JP-A-1-122677). Since this method drastically reduces the cost as compared with the conventional method, there is an increasing demand for application to daily necessities such as building materials, automobile parts, and even home electric appliance parts.

By the way, although the titanium clad steel sheet has excellent corrosion resistance, the carbon steel of the base metal is exposed on the back surface (steel surface) of the single-sided titanium clad steel sheet and on the cut end surface of the double-sided titanium clad steel sheet. Corrosion is inevitable. In the case of thin steel sheets such as building materials and automobile parts,
If the cut end surface or the back surface (steel surface) is taken as a countermeasure against corrosion, the advantage of covering the surface with titanium to improve the corrosion resistance will almost disappear. However, in the case of clad steel for thick plate applications such as chemical equipment, the design of the equipment is such that the cut surface is not exposed, and with single-sided clad steel, corrosion protection measures such as painting the steel surface are possible. It was not necessary to consider the corrosion resistance of the part. Therefore, it is impossible to apply the titanium clad steel thick plate used in the present chemical equipment to a thin plate by rolling it into a thin plate for practical use in terms of cost.

[Problems to be Solved by the Invention]

As described above, the titanium clad steel plate, which is extremely expensive in the past, has not been used for thin plate applications, and therefore the corrosion resistance of the cut end surface and the back surface has not been a problem. That is, there was no titanium clad thin steel sheet that considered the corrosion resistance of the cut surface and the back surface.

The corrosion resistance of the cut surface is poor because carbon steel is used as the base material. Therefore, it is easily conceivable to use stainless steel having excellent corrosion resistance as the base material. However, in the case of titanium-clad stainless steel that uses stainless steel as the base material, the heat treatment that is performed on ordinary stainless steel alone to ensure softening and corrosion resistance does not affect the interface between titanium and the base material or intermediate contact material. Corrosion resistance of the stainless steel part of the cut surface is not possible due to coarse growth of intermetallic compounds.
The corrosion resistance level of stainless steel alone was not reached.

The present invention provides a titanium clad steel sheet using an austenitic stainless steel as a base material, which has excellent corrosion resistance of the cut surface and the back surface, and a manufacturing method thereof, by carefully selecting materials and determining manufacturing conditions.

[Means for Solving the Problems]

It is often experienced that the corrosion resistance of the stainless steel portion exposed at the cut end of titanium clad stainless steel does not reach the level of corrosion resistance of the stainless steel alone. As a cause of this, the inventors of the present invention have not only promoted corrosion of stainless steel due to the formation of a local battery due to the difference in ionization tendency between titanium and stainless steel, which has been conventionally described, but also the thermal process of the clad steel plate manufacturing process. It was found that the influence of

Not only titanium clad stainless steel but also metal hot rolling is directed to high temperature heating with low hot deformation resistance. The base material stainless steel (austenitic stainless steel) is usually subjected to solution treatment at 1000 ° C or higher in order to maintain softening and corrosion resistance after hot rolling.

Fig. 1 shows the hot rolling heating temperature and the heat treatment temperature of the hot rolled sheet that affect the corrosion resistance of the base stainless steel exposed on the cut surface of the titanium clad stainless steel sheet with JIS Class 1 Ti as the composite material and SUS304 steel as the base material. Showed the effect. In the figure, ○ indicates heating temperature and ● indicates heat treatment temperature of the hot rolled sheet. Corrosion test is 0.
2% 5% NaCl water containing 2% H ₂ O ₂ under the conditions of JIS-Z2371
A salt spray test in which spraying was performed for an hour was performed, and the presence or absence of red rust was visually evaluated and evaluated. Rating 0 means no red rust, rating 1
Indicates a dot-like appearance, and a rating of 2 indicates a flow-like rust-like appearance. As a result, it was found that the corrosion resistance is improved and reaches the same level as the stainless steel single material if the heat treatment is performed at a temperature of 950 ° C or higher after hot rolling or the hot rolling heating temperature is set to a temperature higher than 950 ° C. . However, if heating is performed at over 950 ° C and hot rolling is performed, the intermetallic compound grows violently at the joint surface between titanium and the base metal or intermediate contact material, making it impossible to manufacture titanium clad steel. When the heat treatment of the hot-rolled sheet was carried out, the phenomenon of peeling from the interface between titanium and steel occurred during the subsequent cold rolling or cold working, and the production of clad steel and the securing of corrosion resistance of the cut surface were not compatible.

Then, titanium clad stainless steel sheet can be manufactured 85
The heating temperature was limited to 0 to 950 ° C., the C content of the base material 18Cr-9Ni stainless steel was changed, and a titanium clad stainless steel sheet was produced. The effect of the C content of the stainless steel on the corrosion resistance of the stainless steel on the cut surface, measured using the titanium clad stainless steel plate, is shown in FIG.

As is clear from the figure, the C content of the base material stainless steel was 0.03
It was found that when the content is less than 100%, the corrosion resistance of the cut surface does not deteriorate even when the hot rolling heating temperature is set to 950 ° C or less. Moreover, when the C content of the base material stainless steel is 0.03% or less, the hot rolling load is reduced even if the hot rolling heating temperature is 950 ° C. or lower, and not only the hot rolling becomes easy, but also the hot rolled sheet after hot rolling is It was also found that there is no need for heat treatment for softening, and cold rolling can be performed as hot rolled. As a result, the chance of intermetallic compound growth at the interface between the bonding material and the base material or intermediate contact material is reduced,
It was also possible to expect improvement in workability.

It was also found that the addition of Ti and Nb alone or in combination to the base material stainless steel further improves the corrosion resistance.

The present invention has been accomplished based on this finding.

That is, the steel sheet of the present invention is (1) C: 0.03% or less, Si: 1.0% or less, Mn: 2.0% or less, C
r: 15% to 27%, Ni: 6% to 22%, N: 0.0
Titanium clad stainless steel sheet containing austenitic stainless steel containing 3% or less and the balance Fe and unavoidable impurities as a base material, and the composite material is titanium or titanium alloy, (2) C: 0.03% or less, Si: 1.0% or less , Mn: 2.0% or less, C
r: 15% to 27%, Ni: 6% to 22%, N: 0.0
Austenitic stainless steel with 1% or 2% of Mo: 4% or less and Cu: 1.5% or less, balance Fe and inevitable impurities as a base material, and a composite material of titanium or titanium alloy A titanium clad stainless steel plate, (3) C: 0.03% or less, Si: 1.0% or less, Mn: 2.0% or less, C
r: 15% or more and 27% or less, Ni 6% or more and 22% or less, N: 0.03
% Or less, Ti: 0.5% or less, Nb: 1.0% or less, 1 or 2 types, the balance Fe and unavoidable impurities are used as the base material, and the alloy is titanium or titanium alloy. Titanium clad stainless steel plate, (4) C: 0.03% or less, Si: 1.0% or less, Mn: 2.0% or less, C
r: 15% to 27%, Ni: 6% to 22%, N: 0.0
3% or less, 1 or 2 kinds of Mo: 4% or less, Cu: 1.5% or less and 1 or 2 kinds of Ti: 0.5% or less, Nb: 1.0% or less, balance Fe and unavoidable impurities Is a titanium-clad stainless steel plate in which the austenitic stainless steel consisting of is a base material and the joining material is titanium or a titanium alloy.

In general, hot-rolled austenitic stainless steel is required to be heat treated at a temperature of 1000 ° C or higher to soften and maintain corrosion resistance. A hot rolled material of titanium clad stainless steel also needs a heat treatment for the same purpose, but as described above, it is impossible to carry out the heat treatment under the same conditions for growing an intermetallic compound at the interface. Therefore, even if the titanium-clad stainless steel conventionally manufactured for thick plates such as chemical equipment is made into a thin plate by hot rolling, the corrosion resistance of the base material stainless steel exposed on the end face and the back face because the heat treatment is not performed, Only stainless steel that was significantly inferior could be produced.

The inventors of the present invention have completed the method of the present invention because the use of the titanium clad stainless steel according to the present invention maintains the corrosion resistance of the base material stainless steel even if the heat treatment is omitted.

That is, the production method of the present invention, (5) in the production of titanium clad stainless steel produced by rolling the assembly slab hot and cold, the hot rolling heating temperature is 950 ° C. or less, hot rolled sheet annealing A cold rolling without performing, and then performing a final annealing.
A method for producing a titanium clad stainless steel sheet according to item (1), (2), (3) or (4).

[Action]

Next, the operation will be described together with the limiting conditions of the present invention.

Based on the results of FIG. 2, the upper limit of C in the base material stainless steel was 0.03%.

Si and Mn in the base material stainless steel are necessary as deoxidizing agents for the base material itself, but if added in large amounts, the hot workability deteriorates, so 1.0% and 2.0% were made the upper limits, respectively.

Cr in the base material stainless steel is used to secure the corrosion resistance of the base material.
The lower limit was 15%. The corrosion resistance of the base material improves as the amount of Cr increases, but the toughness deteriorates and the cost increases significantly, and it becomes more expensive than the thin plate of titanium alone and the meaning of clad formation greatly decreases, so the upper limit is 27%. And

The lower limit of Ni in the base material stainless steel was 6% in order to secure the austenite structure of the base material stainless steel. The addition of a large amount of Ni stabilizes the austenite phase and also improves the corrosion resistance, but the cost increase is large and it is more expensive than a thin plate of titanium alone, and the meaning of clad formation is greatly reduced.
The upper limit was 22%.

N in the base material stainless steel may be added in a large amount from the viewpoint of stabilizing the austenite phase, but if it exceeds 0.03%, it may precipitate Cr nitrides after hot rolling to deteriorate the corrosion resistance. % Was set as the upper limit.

The addition of Mo or Cu alone or in combination to the base material stainless steel can further improve the corrosion resistance, but the addition of a large amount leads to a large increase in cost and is more expensive than a thin plate of titanium alone, and the meaning of clad formation is significant. In order to reduce, the upper limits were 4% and 1.5%, respectively.

Further, addition of Ti or Nb alone or in combination to the base material stainless steel can further improve the corrosion resistance, but even if added in a large amount, the effect of improving the corrosion resistance does not change, only the cost increases and it is more expensive than the thin plate of titanium alone. Therefore, the meaning of clad formation is greatly reduced, so the upper limits were 0.5 and 1.0%, respectively.

Further, in the production of titanium clad stainless steel sheet, if the hot rolling heating temperature exceeds 950 ° C, intermetallic compounds at the interface between titanium and the base material or the intermediate contact material will grow, resulting in deterioration of workability and production of clad steel. 950 ℃ to become impossible
Was set as the upper limit.

As described above, the titanium clad stainless steel sheet according to the present invention can be manufactured without deteriorating the corrosion resistance of the end surface and the back surface, and can be manufactured without the need for a corrosion resistance maintaining means that hinders the manufacturability. became. In the manufactured titanium-clad stainless steel sheet according to the present invention, the stainless steel portion exposed on the end face has the same corrosion resistance as the single stainless steel, and deterioration of the corrosion resistance of the stainless steel due to the titanium and the clad is not observed. .

〔Example〕

Pure titanium plate is used as the joining material, and single-sided titanium clad stainless steel plate using the stainless steel whose chemical composition is shown in Table 1 as the base material (total thickness: 1.0 mm, clad ratio:
5-10%). On the back surface of the produced clad steel plate, 5% NaCl water containing 0.2% H ₂ O ₂ was sprayed for 2 hours under the conditions specified in JIS-Z2371. For comparison with the corrosion resistance of the base material, the surface of a thin plate of the base material alone was simultaneously sprayed.
The degree of occurrence of red rust after the test is shown in Table 2. In the table, a score of 0 indicates that red rust did not occur, a score of 1 indicates that it occurred on the ceiling, and a score of 2 indicates that it occurred in the form of flow rust.

In each of the invention examples according to the method of the present invention, no red rust was generated from the back surface base metal portion in this test, and it was equivalent to the corrosion resistance of the base metal stainless steel alone. On the other hand, in the single-sided titanium clad stainless steel shown in the comparison, although red rust did not occur from the thin plate of the base material alone, red rust occurred from the back surface of the clad steel and the corrosion resistance was poor.

If the hot rolling heating temperature exceeds 950 ℃, peeling during hot rolling,
It was impossible to manufacture a clad steel plate. When the annealing temperature of the hot-rolled sheet exceeded 950 ° C, the corrosion resistance of the backside base metal part evaluated by the hot-rolled sheet was equivalent to that of the stainless steel alone as the base material, but peeled off during cold rolling and It was impossible to manufacture a thin sheet.

〔The invention's effect〕

As described above, according to the present invention, it is possible to use a titanium clad stainless steel sheet having excellent corrosion resistance on the end surface and the back surface. As a result, it can be used as a material for building materials, home electric appliances, etc. without fear of deterioration of the corrosion resistance of the back surface or the end surface, and can enjoy the excellent corrosion resistance of titanium. Further, the use of the clad has a large economic advantage as compared with the use of the titanium thin plate alone.

[Brief description of drawings]

FIG. 1 is a drawing showing the effects of hot rolling heating temperature and heat treatment temperature of hot rolled sheet on the corrosion resistance of base material stainless steel on the cut surface of titanium clad steel sheet, and FIG. It is the drawing which showed the influence of the carbon content of stainless steel which acts on the corrosion resistance of steel.

Claims (5)

[Claims] 1. C: 0.03% or less, Si: 1.0% or less, Mn: 2.0
% Or less, Cr: 15% or more and 27% or less, Ni: 6% or more and 22% or less, N: 0.03% or less, with the balance being austenitic stainless steel consisting of Fe and unavoidable impurities, with titanium or titanium A titanium clad steel plate whose base material is austenitic stainless steel, which is a titanium alloy and has excellent corrosion resistance. 2. C: 0.03% or less, Si: 1.0% or less, Mn: 2.0
% Or less, Cr: 15% or more and 27% or less, Ni: 6% or more and 22% or less, N: 0.03% or less, and Mo: 4% or less, Cu: 1.5
% Or less of 1 or 2 with the balance Fe and unavoidable impurities as the base material, and a titanium alloy or titanium alloy as the base material, which has excellent corrosion resistance, and titanium as the base material. Clad steel plate. 3. C: 0.03% or less, Si: 1.0% or less, Mn: 2.0
% Or less, Cr: 15% to 27%, Ni: 6% to 22%, N: 0.03% or less, Ti: 0.5% or less, Nb: 1.0
% Or less, and titanium as the base material, which is an austenitic stainless steel with a balance of Fe and unavoidable impurities and whose main component is titanium or a titanium alloy. Clad steel plate. 4. C: 0.03% or less, Si: 1.0% or less, Mn: 2.0
% Or less, Cr: 15% or more and 27% or less, Ni: 6% or more and 22% or less, N: 0.03% or less, and Mo: 4% or less, Cu: 1.5
% Or less 1 type or 2 types, Ti: 0.5% or less, Nb: 1.0%
Austenitic stainless steel containing the following 1 or 2 and the balance Fe and unavoidable impurities as a base material,
A titanium clad steel plate whose base material is austenitic stainless steel, which has excellent corrosion resistance and whose composite material is titanium or a titanium alloy. 5. A titanium clad stainless steel sheet produced by rolling an assembled slab hot and cold,
The hot rolling heating temperature is set to 950 ° C or lower, cold rolling is performed without performing hot rolled sheet annealing, and then final annealing is performed, (1), (2), (3) or (4). A method for producing a titanium clad steel sheet using, as a base material, an austenitic stainless steel having excellent corrosion resistance.