FR2473379A1 - PROCESS FOR PRODUCING PLATE STEEL PLATE BY HOT ROLLING WITH INTERPOSITION OF INTERMEDIATE LAYER - Google Patents

Abstract

A method for producing a plated steel plate is disclosed. According to the invention, a contact surface of a bearing steel and a plating metal (at 1) is cleaned, the bearing steel and the plating metal are superposed with an intermediate layer interposed between their contact surfaces (in 2), the backing steel and the cladding metal are welded along the contact lines between them to form a composite slab, leaving at least part of the contact lines not welded to form a vent hole for the air (at 3), a slight reduction is applied to the composite slab to cause any air remaining between the contact surfaces to escape through the vent hole (at 4), then close by welding the vent hole of the slightly reduced slab to isolate the contact surfaces from the internal atmosphere (at 5), the composed and welded slab is introduced into a heating oven and heated to a rolling temperature (in 6), and the composite and heated slab is hot-rolled (at 7). The invention applies in particular to metallurgy. (CF DRAWING IN BOPI)

Description

The present invention generally relates to a production process

  a plated steel plate, and more particularly to a method of producing a plated steel plate having a high bond strength, at a very good efficiency. Plated steel plates have been widely

  used to date in various fields.

  Recently, however, there has been a strong demand especially for plated steel plates having

  a strong binding strength and a very good quality.

  Of the various methods of producing clad steel plates used to date, the most typical methods used at industrial scales are cold-pressure plating, hot-pressure plating and explosive cladding. In each of these traditional processes, however, there is frequently a poor bond between the support steel and the plating metal, due to the oxidation of these materials to the contact surfaces, with the result that

  a decrease in the rate of production of products.

  In order to obtain a better bond between the support steel and the plating metal in the traditional hot-press welding process, various means as described below have been used: A. Support plate and the The acides are welded to each other on all contact lines between their periphery edges in one slab, and any air remaining between the contact surfaces is forced to escape through a vent hole provided in part of the contact lines using a vacuum pump; b. the support steel and the plating metal are superimposed in a vacuum chamber and welded on all the lines of contact between their peripheral edges by an electron beam; and c. a space is intentionally provided between the support wire and the plating metal, where an inert gas such as argon is closed, and then the gas is forced

2473379 -

  inert to escape from the space through a vent hole

  during the hot rolling process.

  However, in each of these ways it is difficult.

  to produce the escape of air between the contact surfaces at a substantially effective extent, and the support steel and the plating metal oxidize on the contact surfaces during heating, by the small amount of the air still remaining between these contact surfaces, with the result that the Croatians formed therein pocket the formation of a satisfactory metallurgical bond and this insufficient metallurgical bond can appear in the form of a defect in an inspection

  ultrasound. The weak link seems easy to

  particularly close contact lines securely welded between the peripheral edges of the slab, and presents a serious problem to ultrasonic inspection. In another means currently put into practice,

  to prevent the reduction of shear strength

  In the plated interface, a metal such as nickel is plated on the contact surface of the support steel and the plating metal, and the plated metal diffuses along the contact surfaces of the support steel. and plating metal to form a strong bonding alloy layer. However, this other means has the drawbacks of an increase in the production price and an inability to completely prevent oxidation in the contact surfaces. Accordingly, the subject of the present invention is a method for producing a plate. plated steel having a significant bond strength at a very good yield. The process for producing a plated steel plate according to the invention comprises the steps of cleaning a contact surface of a supporting steel and a plating metal, of superimposing the steel of support and the plating metal with an intermediate layer interposed between the contact surfaces of the bearing steel and the plating metal, to weld the bearing steel and the plating metal along contact lines between them to form a compound slab by leaving at least a portion of the non-welded contact lines to form a vent port for air, to apply a slight reduction to the composite slab to escape any remaining air between them contact surfaces through the vent hole, to close the vent orifice of the reduced composite slab, by welding, to isolate the contact surfaces of the external atmosphere, to load the compound slab and welded in a furnace heating and heat it up

  a rolling temperature, and hot rolling.

  The intermediate layer may be a metal sheet or a metal plating layer. The metal plating layer may be provided on the support steel or the plating metal or both. The metal sheet

  can be used in one or more kinds.

  Insufficient binding resulting in

  decrease in the production rate of products, is mainly

  caused by oxidation in the contact surfaces. In the process according to the present invention, it is possible to prevent oxidation in the contact surfaces during hot rolling and accordingly, to greatly increase the bonding ratio because the final weld is accomplished after exhaust air between the contact surfaces, which makes them

  brings in very tight contact with each other.

  Furthermore, in the process according to the invention, the intermediate layer provided between the support steel and the plating metal diffuse in both during hot rolling to thereby form a strong metallurgical bond and prevent carbon migration. of

  occur from the plating metal backing plate.

  In the case where the metal foil is used as an intermediate layer, one or more kinds of metal foils are arranged on the support steel,

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  and above them is superimposed the plating metal.

  This does not require special equipment and as a result, no additional initial price. Since there is no limit to the size of the welded composite slab, the unit weight per unit weight of the slab is considerably low. It is quite easy to make the metal sheet quite thick, unlike the fact that it is

  difficult to make the veneer layer quite thick.

  As a result, by providing a metal foil

  thicker it becomes easier to prevent migra-

  the carbon of the support steel to the plating metal, which makes it possible to pocket the embrittlement of the interface and to roll the slab very efficiently during a hot rolling, thus greatly reducing the price per weight unitary slab. Moreover, from the point of view of the purchase price and handling of the metal foil, much lower than for the metal plating layer, the use of the metal foil in the process according to the present invention makes it possible to obtain a

  composite slab at a price equivalent to several percent

  price of the metal plating process.

  Heretofore, it has commonly been considered that a metal sheet interposed between the support steel and the plating metal would move freely between their contact surfaces during hot rolling and would not laminate with them uniformly. However, the present inventors have found experimentally that the diffusion of the constituents of the metal sheet having started in the support steel and the plating metal during heating, penetrates deeper into it with the progress of the hot rolling, so the support steel and plating metal are well rolled into one body, resulting in uniform rolling of the

metal foil.

  Moreover, until now, it has also been commonly considered that the metal foil can not be rolled to a sufficiently small thickness because of inclusions almost always present in the sheets. However, the present inventors have also found experimentally that the metal sheet can be rolled to a sufficiently small thickness of the order of 4 p without breaking between the support steel and the

metal plating.

  In the production method according to the invention, the ultrasonic inspection rate of hot-rolled steel plates increases strongly by about 70-80% in the conventional production process.

about 95-100%.

  In the production of plated steel plates by a process similar to that of the invention without using

  the intermediate layer, the rate of inbpection to the

  Hot-rolled plates may be quite increased in some cases. However, without the intermediate layer, the support steel and the plating metal generally diffuse into each other across the interface to forge an alloy layer, which layer

  alloy is, in most cases, brittle and brittle.

  Such a fragile alloy layer formed along the interface easily breaks in the following method of bending or bending and / or welding to make the plating metal separable from the supporting steel, and this can be

  detected as a defect in an ultrasonic inspection

  sounds, resulting in a decrease in the production rate. In general, in the widely used stainless steel clad steel produced without an intermediate layer, the diffusion produces a layer of martensite along the interface, a cemented layer on the stainless steel side and a decarburized layer on the steel side. support. Each of these layers is fragile and easily cracked in the following processes, which presents

  an important defect in an ultra-light inspection.

  sounds. In some special cases of such a combination of metals not giving a brittle diffusion alloy layer between the support steel and the plating metal (for example nickel-plated steel), the intermediate layer is not always necessary. On the other hand, a metal plate can be used as an intermediate layer to produce effects equivalent to the metal foil and the metal plating layer. The invention will be better understood and other purposes, features, details and advantages thereof

  will appear more clearly during the description

  explanatory text which will follow with reference to the accompanying schematic drawings given solely by way of example illustrating several embodiments of the invention and in which: - - Figure 1 gives a block diagram illustrating the process of the process according to the present invention; Figs. 2A and 2B are schematic illustrations of the soldering step of the method according to the present invention; FIG. 3 is a graph showing the results of the measurement of plated steel plates obtained by an example of practice of the method according to the invention, by an electron probe micro-analyzer (EPMA), supporting steel, B denoting the nickel-copper plating metal, and C denoting the metal foil, nickel); Fig. 4 is a microstructure of a section of a steel plate of Fig. 3; FIG. 5 is a graph showing the results of an EPMA measurement of a plated steel plate obtained by another example of practicing the method according to the invention; FIG. 6 is a microstructure of a section of a

steel plate of Figure 5; -

  FIG. 7 is a graph showing the results of an EPMA measurement of a plated steel plate obtained by another example of practicing the process according to the invention (D: metal plating, nickel); and - Figure 8 is a microstructure of a section

  of a steel plate of Figure 7.

  The method of producing a plated steel plate according to the present invention will now be described in detail with reference to FIG. 1. In the first step 1 of the method according to the invention, the support steel and the metal veneers are cleaned on their contact surfaces. In the second following step 2, the support steel and the plating metal are superimposed with a layer

  intermediate interposed between their contact surfaces.

  In the third step 3, the overlying support steel and the superposed cladding metal are welded together along the contact lines on the peripheral lugs leaving at least a portion of the non-welded contact lines to form vent holes, in order to form a composite slab. In the fourth step 4, the compound slab is

  subject to a slight reduction to cause the escape

  any air remaining between the mating surfaces, through the vent holes. In the fifth step 5, the vent holes of the slab after slight reduction are closed by welding. At sixth step 6, the compound slab which has been welded on all the nips is

  placed in a heated oven and heated to a

  rolling mill. Finally, in the seventh step 7, the compound and heated slab is hot rolled into a

plated steel plate.

  In the first step 1, the cleaning of the contact surfaces of the support steel and the plating metal is accomplished by any conventional means such as machining.

  and / or grinding.In the second step 2, the inner layer

  medium is formed by either plating a metal or

having a metal sheet.

  In the case of metal plating, a layer of the metal plating is formed on the support steel or the plating metal or both, each having its contact surface cleaned. The metal to be plated is preferably

nickel or pure iron.

  In the case of the arrangement of a metal foil, one or more kinds of foils are disposed on the cleaned contact surfaces of the support steel and the plating metal, and then the plating metal or the steel of support is superimposed on the metal sheets, with its contact surface downwards. The sheet is preferably made of a metal such as titanium, aluminum, nickel, chromium and

  pure iron, on a thickness of 20-200i.

  In the third step, welding of the supporting steel and the superposed plating metal along the edges of the contact surfaces is accomplished by any conventional means such as arc welding. In this step, the vent holes are formed by welding the support steel and the plating metal along the lines of contact therebetween, leaving a non-welded portion at the center of the lower edge of the slab. (As can be seen in Figure 2A), or several non-welded parts, one at the center of the lower edge and some on the side edges (as can be seen in Figure 2B). In FIGS. 2A and 2B, the reference 10 generally designates the slab, the mark 11 indicating weld beads, the mark 12 indicating the vent holes, and the mark 13 indicating the direction of advance of the rolling.

or pressure.

  In the fourth step 4, the slight reduction of the slab is accomplished either by a current rolling mill or a

press, without heating the slab.

  In the sixth step 6, the slab is introduced into a heating furnace, where it is heated to an ordinary rolling temperature of the plating metal (for example in the case of steel-clad steel

stainless, at 1000-12500C).

  In the seventh step 7, the heated slab is rolled

  by a hot rolling mill, plated steel plate.

  Specific examples will now be described

  of practicing the method according to the invention.

Example 1

  (1) Support steel Name: welded structure steel plate (Japanese standard JIS G3106 SM 41) Chemical composition (% by weight) C If Mn Fe 0, 20 0.30 0.80 remains Dimension (mm) : length 1500 x width 1000 x thickness 77 (2) Veneer metal Name: cupro-nickel plate Chemical composition (% by weight): Cu Ni

90 10

  Dimension (mm): length 1500 x width 1000 x thickness 17.5 (3) intermediate layer: 56 p thick nickel sheet (4) Production condition The supporting steel and the plating metal are finished at their contact surfaces by grinding, are superimposed with the nickel sheet interposed between their contact surfaces vis-à-vis, are welded together along the contact lines in the peripheral edges, into a compound slab leaving a portion of 100 mm long at the center of the lower edge of the slab along the non-welded contact line, as a vent hole,

  are cold-rolled under a slight reduction in the thickness

  total origin of bearing steel and ml

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  up to 94.5 mm, to cause the escape of any air remaining between the mating surfaces through the vent hole, are still welded to close the vent in the slab having a thickness of 94.5 mm and are heated to a temperature of 10000C then hot-rolled into plated steel plates having a total thickness of 13.5mm, where the thickness of the supporting steel, the plating metal and the nickel sheet are 2.5 mm, 11.0mm

and 8 p, respectively.

  (5) Plated steel plate Ultrasonic inspection of the plated steel plate thus produced results in a yield of almost 100%. This shows that the air remaining between the contact surfaces completely escapes during cold rolling and that consequently the lack of bonding of the contact surfaces is

perfectly pocketed.

  Then, the diffusion state in the bonding zone between the support steel and the plating metal is inspected by an electron probe microanalyzer (EPMA). The results of the inspections are shown in Figure 3 and the microstructure of a section of the plate

  plated steel is shown in Figure 4.

  As can be seen in FIGS. 3 and 4, the nickel of the sheet interposed as an intermediate layer

  diffuses satisfactorily into the support steel.

  and in the plating metal to produce between them a

strong metallurgical bond.

  Angle welding tests performed on this

  plated steel plate have shown that the metallurgical bond

  that so produced was so strong that there was no detachment of the interface by a stress of the weld.

Example 2

  The bearing steel, the plating metal and the metal foil are the same as in Example 1. A compound slab is formed in the same way as in Example 1 and the exhaust is evoked. any air remaining between the contact surfaces, through the vent port by cold pressim. Next, the compound slab is formed of a plated steel plate in the same manner as in Example 1 where the plating metal, the backing steel and the sheet

  are 2.5 mm, 11 mm and 8 mm thick, respec-

  tively. Ultrasonic inspections of the plated steel plate thus produced showed

  almost 100%, as in Example 1.

Example 3

  (1) Support steel Name: Welding structure steel plate (Japanese standard JIS SM 41) Chemical composition (% by weight) | C If Mn Fe 0.20 0, 30 0.80 remains Dimension (mm) : length 1500 x width 1000 x

thickness 56.

  (2) Veneer metal Name: Stainless steel plate (SUS 316L) Chemical composition (% by weight) C If Mn Ni Cr Mo Fe 0.02 0.70 1.60 13 17 2.5 Remaining Dimension (mm) : length 1500 x width 1000 x thickness 21 (3) Intermediate layer: 56 i thick nickel sheet (4) Production condition A composite slab is formed in the same way as in Example 1. The slab is heated to 1200 C and then hot-rolled into a plated steel plate having a total thickness of 11 mm, where the thicknesses of the plating metal, the supporting steel and the metal foil are respectively 3 mm, 8 mm and 8 M.

  The results of the EPMA inspections and the micro-

  Photograph of a section of the plated steel plate thus produced are indicated respectively in FIGS. 5 and 6. As can be seen in FIGS. 5 and 6, the nickel of the sheet interposed as an intermediate layer diffuses satisfactorily in the supporting steel and in the plating metal to produce a strong metallurgical bond between them. Fillet weld tests performed on this plated steel plate showed that the metallurgical bond thus produced was so strong that there was no detachment of the interface by a stress of the weld. Moreover, it has been confirmed that the important cementation

  of the supporting steel in the plating metal was perfectly

  pocketed in this area by the interposed nickel foil.

Example 4

  (1) Supporting steel: as in example 3.

  (2) Veneer metal Name: Cupro-nickel plate Chemical composition (% by weight) Cu Ni

| 10 |

  Dimension (mm) length 1500 x width 1000 x

thickness 21.

  (3) intermediate layer: nickel plating of a

thickness of 28) -

  (4) Production condition After having formed a layer of nickel plating with a thickness of 28 μm on the contact surface of the plating metal, a composite slab was formed under the same conditions as in Example 1. The slab is heated to 10000C and then hot-rolled into a plated steel plate having a total thickness of 11mm, where the thicknesses of the plating metal, the supporting steel and the nickel plating layer are respectively 3 mm, 8 mm and 4 ii. Ultrasonic inspections of this plated steel plate gave a yield of almost 100%. This shows that the very small amount of air remaining between the contact surfaces escapes completely through the vent port during the cold rolling step and that insufficient bonding due to oxidation in the surfaces

  contact is perfectly prevented.

  The results of EPMA inspections and a micro-

  Photograph of a section of the plated steel plate thus produced are shown in Figures 7 and 8, respectively. As can be seen in FIGS. 7 and 8, the nickel component of the intermediate layer diffuses satisfactorily in the support steel and in the plating metal to produce a strong metallurgical bond between them. Furthermore, the fillet weld tests performed on this plated steel plate have shown that the metallurgical bond thus produced

  was so strong that there was no detachment from

face by a welding stress.

  Of course, the invention is not limited to the embodiments described and shown which have been given by way of example. In particular, it includes all means constituting equivalents

  described techniques, as well as their combinations.

  if they are executed according to his spirit and implemented in the context of protection as claimed.

Claims (6)

R E V E N D I C A T I 0 N S   A method of producing a plated steel plate, characterized in that it comprises the steps of cleaning a contact surface of a support steel and a plating metal (at 1); superimpose support steel and veneer   with an intermediate layer interposed between leuis sur-   contact faces (in 2); welding the support steel and the plating metal along the lines of contact therebetween to form a compound slab, leaving at least a portion of the non-welded contact lines. to form an air vent (at 3); applying a slight reduction to the composite slab to cause any remaining air entering the contact surfaces to escape through said vent port (at 4); closing, by welding, said slightly reduced slab vent orifice to isolate the contact surfaces from the outside atmosphere (at 5); introducing the compound and welded slab into a heating furnace and heating it to a rolling temperature (at 6); and hot rolling said compound and heated slab (in 7).   2. Method according to claim 1, characterized in that the aforementioned intermediate layer is formed   at least one kind of a metal sheet.   3. Method according to claim 1, characterized in that said intermediate layer is formed by applying metal plating to at least one of the contact surfaces of the supporting steel or plating metal.   4. Method according to any one of the claims   2 or 3, characterized in that the composite slab mentioned above-   receives the aforementioned slight reduction by cold rolling.   5. Process according to any one of the claims   2 or 3, characterized in that the aforementioned compound slab   receives the aforementioned slight reduction by cold pressure.   6. Process according to any one of the claims   2 or 3, characterized in that the aforementioned vent orifice   is formed at the lower edge of the aforementioned slab.