JPH03277541A - Titanium clad steel sheet having austenitic stainless steel excellent in corrosion resistance as base material and production thereof - Google Patents

Abstract

PURPOSE:To enhance corrosion resistance of a cutting face and a rear by utilizing austenitic stainless steel wherein the components of C, Si, Mn, Cr, Ni and N are specified. CONSTITUTION:Titanium or titanium alloy is produced by utilizing austenitic stainless steel which contains <=0.03% C, <=1.0% Si, <=2.0% Mn, 15-27% Cr, 6-22% Ni, <=0.03% N and consists of the balance Fe and inevitable impurities as the base material and constituting the clad material. Si and Mn are regulated to 1.0% and 2.0% respectively as the upper limit because hot workability is deteriorated when these are added at large amounts. Cr is regulated to 15% as the lower limit from a point for securing corrosion resistance of the base material. Corrosion resistance of this base material is enhanced as the amount of Cr is made more plenty. However, Cr is regulated to 27% as the upper limit because toughness is deteriorated and moreover rise of cost is made large. Ni is regulated to 6% as the lower limit to secure the structure in austenite of stainless steel of the base material. N is regulated to 0.03% as the upper limit because nitride of Cr is deposited after hot rolling and corrosion resistance is deteriorated when N exceeds 0.03%. When <=4% Mo and <=1.5% Cu are added independently or compositely to stainless steel of the base material, enhancement of corrosion resistance is more obtained. Further when <=0.5% Ti and <=1.0% are added singly or compositely, corrosion resistance is further improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a titanium clad steel plate with excellent corrosion resistance and a method for manufacturing the same.

[Conventional technology]

Sea bream is inexpensive and has good mechanical, thermal, and electrical properties, so it has been used for a very wide range of purposes since ancient times.

However, steel has the fatal drawback of rusting and corroding in a short period of time if used as is. On the other hand, titanium has significantly better corrosion resistance than steel, so it almost solves the problem of corrosion and rust prevention, but it has other properties, such as thermal conductivity, magnetism, and bondability with steel, that are different from steel. In addition to having excellent characteristics, it also has the disadvantage of being extremely expensive. Therefore, it is not necessarily technically and economically easy to completely replace steel with titanium.

As a method to solve these problems, clad steel with a titanium surface and steel base material is used. Clad steel is a material that has excellent corrosion resistance and satisfies the desired characteristics by using steel that matches the desired characteristics as the base material and using titanium, which has excellent corrosion resistance, on the surface.

However, titanium clad steel has brittle F at the interface between titanium and steel.
If a thick layer of e-Ti intermetallic compound or TiC is formed, there is a risk of peeling at the interface, so the highly productive cast-in method, which is performed at the level of molten steel, cannot be applied, and it requires special equipment. It had to be manufactured by joining at the phase level. As a result, the material has to be expensive.
Its use was limited to chemical equipment such as heat exchangers and reactors.

In response to this, the present inventors have invented a method that makes it possible to manufacture clad steel in the atmosphere by actively utilizing intermetallic compounds of Ti and Cu (Japanese Patent Application Laid-Open No. 1122677).
Since this method has dramatically reduced costs compared to conventional methods, there has been an increasing demand for its application to daily necessities such as building materials, automobile parts, and even household appliance parts.

By the way, titanium clad steel sheets have excellent corrosion resistance, but the base material carbon steel is exposed on the back side (C steel surface) of single-sided titanium clad steel sheets, and on the cut end of double-sided titanium clad steel sheets. Corrosion is inevitable. In the case of thin steel sheets used as building materials or automobile parts, if corrosion prevention measures are taken on the cut edges and the back side (steel surface), the advantage of covering the surface with titanium to improve corrosion resistance will almost disappear. However, in the case of clad steel for thick plate applications such as chemical equipment, it is possible to take measures to prevent corrosion, such as designing the equipment so that the cut surface is not exposed, and painting the steel surface for single-sided clad steel. There was no need to consider the corrosion resistance of the parts. Therefore, simply rolling the titanium clad plate used in current chemical equipment and the like into a thin plate is not practical for use in thin plate applications due to cost considerations.

[Problem to be solved by the invention]

As described above, since titanium clad steel sheets, which are extremely expensive, have not been used for thin sheet applications, the corrosion resistance of cut edges and back surfaces has not been considered a problem. In other words, there was no titanium clad '111m board that took into consideration the corrosion resistance of the cut surface and back surface.

The reason why the corrosion resistance of the cut surface is poor is because carbon steel is used as the base material. Therefore, it is easy to consider using stainless steel, which has 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 soften and ensure corrosion resistance is difficult to achieve at the interface between titanium and the base metal or intermediate joint material. The corrosion resistance of the stainless steel part of the cut surface is not possible due to the coarse growth of intermetallic compounds.
It did not reach the corrosion resistance level of stainless steel alone.

The present invention provides a titanium clad steel plate whose base material is austenitic stainless steel, which has excellent corrosion resistance on the cut surface and the back surface, by carefully selecting the material and determining the manufacturing conditions, and a method for manufacturing the same.

[Means to solve the problem]

It is a common experience that the corrosion resistance of the stainless steel portion exposed at the cut end of titanium clad stainless steel does not reach the corrosion resistance level of the stainless steel alone. The present inventors believe that the cause of this is that the corrosion of stainless steel is accelerated due to the formation of local batteries due to the difference in ionization tendency between titanium and stainless steel, which has been previously stated, as well as the thermal process in the manufacturing process of clad steel sheets. It was found that the influence of

Hot rolling of metals, including titanium clad stainless steel, requires high temperature heating with low hot deformation resistance.

In addition, the base metal stainless steel (austenitic stainless steel) is usually made with
Solution treatment is performed at 000°C or higher.

Figure 1 shows the JIS Type 1 Ti laminated material, SOS 304.
The effect of the hot rolling heating temperature and the heat treatment temperature of the hot rolled sheet on the corrosion resistance of the stainless steel base material exposed at the cut surface of a titanium clad stainless steel sheet having steel as the base material was shown. In the figure, the ○ mark indicates the heating temperature, and the * mark indicates the heat treatment temperature of the hot-rolled sheet. The corrosion test was performed using 5% NaCl containing 0.2%) + 20□.
A salt water spray test was conducted in which water was sprayed for 2 hours under the conditions of JIS-Z2371, and the presence or absence of red rust was visually determined and evaluated. A rating of O indicates that no red rust has occurred, a rating of 2 indicates that rust has occurred in dots, and a rating of 2 indicates that rust has occurred in the form of streaks. As a result, it was found that corrosion resistance was improved by performing a compacting treatment at a temperature of 950°C or higher after hot rolling, or by increasing the hot rolling heating temperature to a temperature higher than 950°C, reaching a level similar to that of stainless steel alone. did. However, when hot-rolling is performed at temperatures exceeding 950°C, intermetallic compounds grow violently at the bonding surface between titanium and the base metal or intermediate welding material, making it impossible to manufacture titanium clad steel. If a hot-rolled sheet is heat-treated at a temperature that exceeds 150 degrees, the subsequent cold rolling or cold working will cause peeling from the titanium-steel interface, making it incompatible with producing clad steel and ensuring corrosion resistance on the cut surface. Ta.

Next, 8 pieces of titanium clad stainless steel plate that can be manufactured
The heating temperature is limited to 50-950℃, and the base material l8Cr
Titanium clad stainless steel plates were manufactured by changing the C content of 9Ni stainless steel. The influence of C content of stainless steel on the corrosion resistance of stainless steel at the cut surface was measured using the titanium clad stainless steel plate.
Shown in the figure.

As is clear from the figure, the amount of C in the base material stainless steel is 0.
It has been found that when it is 0.3% or less, the corrosion resistance of the cut surface does not deteriorate even when the hot rolling heating temperature is 950° C. or less. Moreover, if the C content of the base material stainless steel is 0.03% or less,
Even if the hot-rolling heating temperature is set to 950°C or less, the hot-rolling load is reduced, which not only makes hot-rolling easier, but also eliminates the need for heat treatment to soften the hot-rolled sheet after hot-rolling, leaving the hot-rolled sheet as it is. It was also found that cold rolling was possible. As a result, the chance of growth of intermetallic compounds at the interface between the laminate and the base material or intermediate joint material is reduced, and it is expected that workability will be improved.

It has also been found that when Ti and Nb are added singly or in combination to the base material stainless steel, the -layer corrosion resistance is improved.

The present invention has been achieved based on this knowledge.

That is, the steel plate of the present invention has: (1) C: 0.03% or less, Si: 1.0% or less, Mn: 2.0% or less, Cr: 15% or more and 27% or less,
A titanium clad stainless steel plate whose base material is an austenitic stainless steel containing Ni: 6% or more and 22% or less, N: 0.03% or less, and the balance consisting of Fe and unavoidable impurities, and the bonding material is titanium or a titanium alloy. 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: A titanium clad stainless steel plate containing one or two types of 1.5% or less, with the balance being Fe and unavoidable impurities, the base material being austenitic stainless steel, and the bonding material being titanium or titanium alloy; (3)
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 Tj
Contains one or two types: 0.5% or less, Nb: 1.0% or less.

A titanium clad stainless steel plate in which the base material is austenitic stainless steel with the remainder being Fe and unavoidable impurities, and the bonding material is titanium or a titanium alloy, (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 or 2 types of 1.5% or less, and Ti
: 0.5% or less, Nb: 1.0% or less, the base material is austenitic stainless steel with the balance being Pa and inevitable impurities, and the titanium cladding material is titanium or titanium alloy. It is a stainless steel plate.

Normally, hot-rolled austenitic stainless steel materials must be subjected to compaction treatment at a temperature of 1000° C. or higher in order to soften them and maintain corrosion resistance. Hot rolled titanium clad stainless steel also requires compaction treatment for the same purpose, but as mentioned above, it is impossible to carry out compaction treatment under the same conditions due to the growth of intermetallic compounds at the interface. For this reason, even if titanium clad stainless steel, which was conventionally manufactured as a thick plate for chemical equipment, is hot-rolled into a thin plate, the corrosion resistance of the base material stainless steel, which is exposed on the end and back surfaces because no compaction treatment is performed, is Only materials that were extremely inferior to stainless steel could be produced.

The present inventors have completed the method of the present invention because when the titanium clad stainless steel according to the present invention is used, the corrosion resistance of the base material stainless steel is maintained even if the containerization treatment is omitted.

That is, the manufacturing method of the present invention is as follows: (5) In manufacturing a titanium clad stainless steel sheet by hot and cold rolling an assembled slab, the hot rolling heating temperature is set to 950"C or less, and the hot rolled sheet annealing is performed. The method for producing a titanium clad stainless steel sheet according to item (1), (2), (3) or (4) above, characterized in that the titanium clad stainless steel sheet is cold rolled without further annealing, and then final annealing is performed.

[For production]

Next, the limiting conditions and effects of the present invention will be explained.

Based on the results shown in Figure 2, C in the base material stainless steel is 0.03.
The upper limit was %.

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, hot workability deteriorates, so the upper limits are 1.0% and 2.0%, respectively. did.

The lower limit of Cr in the base material stainless steel was set at 15% from the viewpoint of ensuring the corrosion resistance of the base material. Corrosion resistance of the base material improves as the amount of Cr increases, but the toughness deteriorates and the cost increases significantly, making it more expensive than a thin sheet made of titanium alone, and the meaning of cladding is greatly reduced, so the upper limit is set at 27. And so.

The lower limit of Ni in the base material stainless steel was set to 6% in order to ensure the austenitic structure of the base material stainless steel. N
Addition of a large amount of i stabilizes the austenite phase and improves corrosion resistance, but the cost increases significantly, making it more expensive than a thin plate made of titanium alone, and the meaning of cladding is greatly reduced, so the upper limit was set at 22%.

It is acceptable to add a large amount of N to the base material stainless steel from the standpoint of stabilizing the austenite phase, but if it exceeds 0.03%, nitrides of Cr will precipitate after hot rolling and the corrosion resistance will deteriorate. The upper limit was set at 0.03%.

Adding Mo or Cu alone or in combination to the base material stainless steel can further improve corrosion resistance, but adding a large amount leads to a significant increase in cost, making it more expensive than a thin plate made of titanium alone, and making it a clad material becomes more important. In order to reduce the amount, the upper limits were set at 4% and 1.5%, respectively.

Further, corrosion resistance can be further improved by adding Ti or Nb alone or in combination to the base material stainless steel, but even if large amounts are added, the corrosion resistance improvement effect will not change, and the cost will simply increase, making it more expensive than a thin sheet made of titanium alone. 0.5% and 1.0% respectively.
The upper limit was %.

In addition, in the production of titanium clad stainless steel plates, if the hot rolling heating temperature exceeds 950°C, intermetallic compounds will grow at the interface between titanium and the base metal or intermediate welding material, resulting in poor workability and production of clad steel. 95 to become impossible
The upper limit was 0″C.

As shown above, the titanium clad stainless steel sheet according to the present invention can be manufactured without deteriorating the corrosion resistance of the end surface or the back surface, and can be manufactured without requiring any means for maintaining corrosion resistance that would impede 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 corrosion resistance equivalent to that of stainless steel alone, and no deterioration in the corrosion resistance of stainless steel due to the use of titanium and crund is observed. .

〔Example〕

A single-sided titanium clad stainless steel plate (total thickness = 1.0%, cladding ratio: 5 to 10%) was used as the laminating material, and the base material was stainless steel whose chemical composition is shown in Table 1. Manufactured. 5% NaCl water containing 0.2% H, O
Spraying was carried out for 2 hours under the conditions specified in IS-Z2371.

In order to compare the corrosion resistance of the base material, the surface of a thin plate of the base material alone was also sprayed at the same time. The degree of red rust generation after the test is shown in Table 2. A rating of O in the table indicates that no red rust occurred, a rating of 1 indicates that rust occurred on the ceiling, and a rating of 2 indicates that rust occurred in the form of flowing rust.

Table 2: Using 5% NaCl water containing 0.2% + 1□Ot under the conditions of JIS-Z2371. a! In all of the invention examples produced by the method of the present invention, red rust did not occur from the back base material, and the corrosion resistance was equivalent to that of the case where the base material was stainless steel alone. The single-sided titanium clad steelless steel shown in comparison with Nio had poor corrosion resistance, with red rust forming on the back side of the clad steel, although red rust did not occur from the thin base plate alone. .

When the hot rolling heating temperature exceeded 950° C., peeling occurred during hot rolling, making it impossible to manufacture a clad steel sheet.

In addition, when the annealing temperature of the hot-rolled sheet exceeded 950°C, the corrosion resistance of the back base material evaluated with the hot-rolled sheet was equivalent to that of the base material stainless steel alone, but it peeled off during cold rolling and It was not possible to manufacture rolled sheets.

〔Effect of the invention〕

As explained above, according to the present invention, it has become possible to use a titanium clad stainless steel plate with excellent corrosion resistance on the end and back surfaces. As a result, it can be used as a material for building materials, home appliances, etc. without worrying about deterioration of corrosion resistance on the back side or end face, and the excellent corrosion resistance of titanium can be enjoyed. Furthermore, the use of crunds provides greater economic benefits than using a titanium thin plate alone.

[Brief explanation of the drawing]

Figure 1 shows the effects of hot rolling heating temperature and heat treatment temperature on the corrosion resistance of the base material stainless steel on the cut surface of a titanium clad steel plate, and Figure 2 shows the effect of the base material stainless steel on the cut surface of a titanium clad steel plate. 1 is a diagram showing the influence of carbon content of stainless steel on 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:
An austenitic stainless steel with excellent corrosion resistance, in which the base material is an austenitic stainless steel containing 6% or more and 22% or less, N: 0.03% or less, and the balance is Fe and unavoidable impurities, and the bonding material is titanium or titanium alloy. Titanium clad steel plate with base material. (2) C: 0.03% or less, Si: 1.0% or less, nn
: 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 M
The base material is austenitic stainless steel containing one or two of the following: o: 4% or less, Cu: 1.5% or less, and the balance is Fe and unavoidable impurities, and the bonding material is titanium or titanium alloy. Excellent corrosion resistance. A titanium clad steel sheet whose base material is austenitic stainless steel. (3) 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 T
1 or 2 of i: 0.5% or less, Nb: 1.0% or less
A titanium clad steel sheet whose base material is an austenitic stainless steel that contains seeds and the balance is Fe and unavoidable impurities, and whose base material is an austenitic stainless steel with excellent corrosion resistance that is made of titanium or a titanium alloy. (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 M
o: 4% or less, Cu: 1.5% or less, and Ti: 0.5% or less, Nb: 1.0% or less, the remainder being Fe and unavoidable impurities. A titanium clad steel sheet whose base material is an austenitic stainless steel consisting of , and whose base material is an austenitic stainless steel with excellent corrosion resistance, whose cladding material is titanium or a titanium alloy. (5) In the production of titanium clad stainless steel sheets manufactured by hot and cold rolling assembled slabs, the hot rolling heating temperature is set to 950°C or lower, cold rolling is performed without hot rolling sheet annealing, and then final annealing is performed. A method for manufacturing a titanium clad steel sheet using an austenitic stainless steel having excellent corrosion resistance as a base material according to claim 1, (2), (3) or (4).