JPH01122677A - Manufacture of titanium clad steel plate with copper or copper alloy as intermediate joining medium - Google Patents

Abstract

PURPOSE:To remove the oxide of a mating face under atmosphere and to join without forming the oxide as well by using a copper metal as the intermediate joining medium interposed in the mating face and rolling it by its melting under the specified conditions. CONSTITUTION:The Ti or Ti alloy 1 of a clad plate and the copper or copper alloy 2 contg. >=30% copper used as an intermediate joining medium are superposed in a sandwich shape on the steel 3 of a base metal and the end part is fixed by welding, etc. The alloy of copper and Ti is formed and simultaneously melted with a diffused reaction by heating at the temp. of 850 deg.C min. 1000 deg.C max. in this state and the rolling reduction of >= one pass is applied at the rolling reduction rate of >=10% prior to the solidification of this alloy. The alloy layer of the melted Ti and copper is then joined by bulging it. In this method the copper alloy 2 is taken at >=30% copper contg. rate and >=850 deg.C temp. due to the need for its diffused solution with Ti, but a slippage is caused without joining with the viscosity being reduced at the temp. >=1000 deg.C. Also in case of the rolling reduction rate being <=10% the bulging of the intermediate joining medium becomes insufficient.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing a titanium clad steel plate.

Steel has long been used in a wide range of applications because it is inexpensive and has good mechanical, thermal, and electrical properties.

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 solves the problem of corrosion and rust prevention, but titanium has other properties, such as thermal conductivity, that are quite different from steel. It is not necessarily easy to completely replace them.

Furthermore, since titanium is significantly more expensive than steel, the reality is that titanium is difficult in terms of resources and economy.

As a method to solve these problems, clad steel is used, which has a titanium surface and a steel core. Clad steel is a material that has excellent corrosion resistance and satisfies the desired characteristics by using carbon steel or stainless steel as the base material and using titanium, which has excellent corrosion resistance, on the surface. Because of this, it is widely used in chemical equipment such as heat exchangers.

The present invention provides a method for producing such titanium clad steel technically easily and inexpensively.

[Conventional technology]

There are roughly two types of manufacturing methods for so-called clad steel plates. In other words, there is a so-called cast-in method that performs composite formation at the molten steel level, and a method that joins at the solid phase level.

In the case of titanium clad steel, there is brittle Fe at the interface between titanium and steel.
When a layer of -Ti intermetallic compound or TiC is formed, it peels off at the interface. Therefore, the cast-in method performed at the molten steel level cannot be applied, and joining at the solid phase level is adopted. Among these, the explosive bonding method is currently the most widely used method because it does not use an intermediate bonding material and has high reliability in terms of bonding strength. However, because the explosive attachment method uses the power of a powerful explosion, it cannot be carried out everywhere, and usually has to be carried out in remote areas such as in the mountains. Moreover, it is a very expensive material as it is not suitable for mass production. In addition, the size is limited by the explosion bonding method, making it particularly difficult to manufacture thin plates.

The pressure welding method is more advantageous than the explosion bonding method because it has high productivity, allows a relatively flexible plate thickness, and can be applied to conventional manufacturing processes. However, in the pressure welding method, there is a very high possibility that a brittle layer such as an intermetallic compound will be formed at the bonding interface, and in addition, if Vcr11 compound or the like exists at the interface, bonding becomes impossible. In particular, in the case of hot welding, the diffusion rate and oxidation rate are rapid, so these risks are high.

As a method for bonding while suppressing the formation of a brittle intermediate layer at the interface, Japanese Patent Laid-Open No. 62-6783 describes limitations on hot rolling heating conditions; Publication No. 109588, JP 57-11298
No. 5 and Japanese Unexamined Patent Publication No. 57-192256 propose a method in which a plate or foil of pure iron, nickel, copper, or the like is sandwiched as an intermediate bonding material at the cladding interface.

On the other hand, in order to prevent oxidation at the bonding interface, there is no suitable method other than to at least make the bonding surfaces a vacuum or an inert atmosphere. The essential condition is to create a vacuum. For this reason, it is not possible to reduce costs, and it is not always easy to take advantage of the characteristic of clad steel that it is inexpensive. Therefore, titanium clad steel plates are usually used only as thick plates for chemical equipment such as heat exchangers where the corrosion resistance of titanium is essential.

In the case of clad steel plates such as stainless steel, methods such as rolling after welding the mating surfaces have been proposed, but this method cannot be applied to titanium clad steel plates because Fe-Ti intermetallic compounds are generated. .

In addition, as a method for preventing oxidation of the bonding interface, Japanese Patent Laid-Open No. 112985/1985 proposes covering the interface with flux. However, since special equipment is required, the cost cannot be reduced.

[Problem that the invention seeks to solve]

A common drawback of the conventional methods listed above is that they require treatments such as covering the mating surfaces with vacuum or inert gas in order to prevent oxidation of the interface, which inevitably increases costs. It is.

The present invention is directed to performing solid-phase bonding in the atmosphere or forming a double bond in order to reduce costs. The point of the present invention is to have completed a technology that removes oxides at the interface and does not generate oxides during bonding in the atmosphere.

[Means for solving problems]

The present inventors believed that in order to prevent the formation of oxides on the mating surfaces, it is important to remove the atmosphere from the interface, and that this can be achieved by filling the mating surface with a non-oxidizing substance other than the atmosphere. Based on this idea, we investigated various non-oxidizing substances and found that this could be achieved with low-melting-point substances such as molten metals. That is, strictly speaking, the mating surfaces are not completely smooth surfaces, so even if an intermediate bonding material is inserted, if it is solid, air will always remain if the materials are simply mated.

However, if it is filled with a liquid substance, it is possible to expel air even if there are non-contact areas on the mating surfaces. As an intermediate bonding material that is sandwiched between mating surfaces,
Although various alloys and compounds are possible, copper or a copper alloy was used in the present invention. That is, when copper or copper alloy is sandwiched between mating surfaces, the eutectic temperature of copper and titanium is reached at about 850° C. and melting begins. On the other hand, on the steel side, a portion of the copper begins to penetrate into the grain boundaries, resulting in a strong bond without becoming brittle at low temperatures.

However, if the mating surfaces remain in a molten state forever, joining is impossible, and even if the temperature drops and the molten copper-titanium alloy phase solidifies, the purpose cannot be achieved. Therefore, in the present invention, reduction is performed in a temperature range where the molten layer of copper and titanium is melted, and at the same time, the excess molten alloy and the slight remaining air layer are made to protrude from the end.

Next, the behavior of the titanium clad steel manufacturing process according to the present invention will be explained using FIG.

In manufacturing titanium clad steel by the method of the present invention, first, as shown in Fig. 1, titanium or titanium alloy 1, which is a mating plate, and copper or copper alloy 2, which is used as an intermediate welding material, are placed on steel 3, which is a base material. Stack them in a sandwich-like manner and fix the ends partially by welding, etc. In this state, it is heated to a temperature higher than the melting point of the alloy of copper and titanium, forming an alloy through a diffusion reaction and simultaneously melting it. Then, before the alloy solidifies, at least one bath of reduction is applied to force excess alloy, air, etc. out of the ends. As a result, a minimum amount of copper or copper alloy remains on the mating surfaces to fill in the unevenness of the surfaces, and titanium or titanium alloy and steel are joined by pressure welding. Also, because air remained at the interface, the thin oxide layer that had formed on the surface of the titanium or steel before the copper or copper alloy formed was largely extruded at the same time as the molten copper and titanium alloy. . Further, since the remaining oxide becomes very small, it is reduced by the titanium of the laminate by further rolling, and the oxygen diffuses into the titanium and becomes a solid solution.

Next, in order to examine the possibility of bonding, we stacked titanium and steel rods of 10 f/10 V4 f/lJ with a copper plate sandwiched in the atmosphere.
It was pressed with a load of I. Figure 2 shows the relationship between the bonding temperature and the tensile strength of the bonded surface after cooling. 650℃
In the following example, the copper plate was simply deformed without being joined.
Bonding was performed at 700°C or higher. However, at temperatures below 850° C., the fracture strength of the joint surface was several Kff/lJ or less, and the bond easily broke.

At temperatures exceeding 850° C., a molten layer of titanium and copper alloy was formed at the interface, and the fracture strength of the bonded surface was also improved to 10 Kff/mj or more. Further, when the temperature exceeds 1050° C., the molten layer of the alloy becomes thick, and the titanium and steel are bonded in such a way that they shift or bend at the bonding surface.Next, the limiting conditions of the present invention will be explained.

Copper or copper alloy as an intermediate welding material needs to be diffused into a solid solution and melted with titanium as a bonding material, so the copper content should be 30%.
% or more.

In order for the extra intermediate layer melted by rolling to protrude from the edge, it needs to be melted, so from Figure 2 we can see that the temperature range in which the titanium and copper alloy melts is 85°C.
Application of pressure at temperatures above 0°C was limited. However, if the bonding temperature is too high, the solid phase reaction between titanium and copper will proceed too much, which will not only reduce the thickness of the titanium, but also reduce the viscosity of the molten layer, causing slippage without bonding. Again, from FIG. 2, the upper limit temperature was set to 1000°C.

This reduction can be achieved with just one bus, and two
There is no problem even if the reduction is more than 1 bath, but if it is not applied, it will not be joined, or even if it is joined, sufficient quality as clad steel will not be obtained, so it was limited to applying a reduction of 1 bath or more.

Furthermore, if the rolling reduction ratio is less than 10 inches, the protrusion of the intermediate welding material is insufficient, so the rolling reduction is limited to 10% or more.

[Effect]

As shown above, the present invention has made it possible to manufacture titanium clad steel without using a vacuum. By not requiring a vacuum, for example, expensive equipment such as a vacuum pump or vacuum chamber is no longer required, and there is no need to create a vacuum, and manufacturing can be significantly simplified as work can be performed in an atmospheric environment. Become.

Further, the titanium clad steel according to the present invention has no difference in quality from the titanium clad steel manufactured using a conventional vacuum method. However, Cu in titanium and steel near the interface
A layer with a high content was observed, and it is presumed that Cu was dissolved and diffused into both the base material steel and the bonding material titanium.

However, no deterioration in quality as a clad steel, including interface bondability, was observed.

〔Example〕

A 3.0m thick JISI type pure titanium plate is used as a laminate material, and a 0.7mm thick JISI type pure titanium plate with a purity of 99.9% or more is used as an intermediate bonding material.
A copper plate with a thickness of ms was used as a base material of 19.24 Cr, Q,
4q6 Cu, 0.6% Nb and o, ooschi C
30cm thick stainless steel slabs containing titanium are layered in a sandwich-like manner, and then covered with a 1.0m thick steel plate with the same composition as the base material with a Hato08 release material on top of the titanium. Approximately half of the sides of the base metal were welded and fixed. The surface roughness (Hmt) of these materials was set to 5 μm or less, and the materials were mechanically finished and then assembled. Thereafter, it was heated to 980°C and one bath of 14% and 18 inch reduction was carried out at 870-950°C, and then the total plate thickness was reduced to 4 mm between 850°C and 730°C.
Hot rolled until smooth.

As a result, the molten copper and titanium alloy protruded from the parts that were not fixed by welding in the first bath.

However, rolling was completed without peeling. The manufactured titanium clad steel had no problems in terms of interface bondability, quality as a titanium clad steel, and mechanical properties of the corrosion-resistant base material of the laminated material.

For comparison, when titanium was simply placed on stainless steel without using copper and the steel pieces were assembled and rolled in the same manner as above, the parts that were not welded and fixed peeled off in the first bus, and in the third bus. It completely peeled off, making it impossible to manufacture clad steel.

When the partially bonded portion was bent back after cooling, it easily peeled off, and the bondability was poor.

Furthermore, a 4.0 m thick JIS Class 1 pure titanium plate was used as a laminate material, and a 1.0 mm thick copper plate with a purity of 99.9% or more was used as an intermediate bonding material with 0. 50cm thick carbon steel slabs containing carbon are layered in a sandwich fashion, and the same combination of titanium, copper and carbon steel is layered on top of the titanium via a kOx release material, and ZOm thick slabs are layered on the end and side surfaces. A steel plate with the same composition as the base material was applied and fixed by welding approximately half of each of the end and side surfaces.

The surface roughness (Hhxdr) of these materials was set to 5 μm or less, and the materials were mechanically finished and then assembled. Thereafter, it was heated to 920°C and subjected to one bath of 13 inches of pressure reduction at 880-920°C. At this time, molten copper and titanium alloy protruded from the end and side surfaces that were not fixed by welding. Thereafter, it was cooled, peeled vertically at the U and Os-based release material, and hot-rolled between 850°C and 730°C until the total plate thickness became 3fi. The manufactured titanium clad steel had no problems in terms of interface bondability, quality as a titanium clad steel, and mechanical properties of the corrosion-resistant base material of the laminated material.

〔Effect of the invention〕

The present invention has made it possible to produce titanium clad steel without physically creating a vacuum. As a result,
The production of titanium clad steel is technologically easier and less expensive, so the excellent corrosion resistance of titanium can be enjoyed at a lower cost, and the resource and economic benefits are significant. .

[Brief explanation of the drawing]

Fig. 1 is a diagram illustrating the assembly of pre-rolled materials for manufacturing titanium clad steel by the method of the present invention, and Fig. 2 is a diagram illustrating the relationship between the welding temperature and the fracture strength of the joint surface due to tension after cooling. It is. 1... Titanium or titanium alloy as a bonding material 2... Copper or copper alloy as an intermediate welding material 3... Carbon steel or stainless steel as a base material. In Koji Shinbe 1.-, “1: Titanium or titanium alloy as composite material 2 = Copper or copper alloy as intermediate welding material

Claims (1)

[Claims] In the production of clad steel sheets where the base material is steel and the cladding material is titanium or titanium alloy, copper or a copper alloy containing 30% or more of copper is sandwiched between the base material and the cladding material as an intermediate welding material, and the temperature is 850℃. A method for producing a titanium clad steel sheet, which comprises rolling the steel sheet at least once at a temperature of 1,000° C. or lower with a rolling reduction of 10% or more, and joining the steel sheet with a molten titanium and copper alloy layer protruding.