JP2002501437A - Metal strip casting - Google Patents

Abstract

Twin roll casting has been applied with some success to non-ferrous metals, which solidify rapidly on cooling. The same, however, is not true for ferrous metals, as it has not been possible to achieve sufficiently rapid and even cooling of metal over the casting surfaces of the rolls. This problem has been overcome by utilising a metallic surface for the rolls, which has a high affinity for the molten steel of the casting pool and a melting temperature greater than the temperature of the casting surface. The molten steel produces extremely good wetting of the casting surface of the roll, resulting in a wetting angle of the molten steel on the casting surface of less than 40 DEG . Preferably, this wetting angle is less than 20 DEG and the casting surface has an Arithmetic Mean Roughness Value (Ra) of less than 10 microns. These desirable properties on the roll surface are achieved by selecting an at least partially amorphous alloy of two constituents. Preferably, the alloy is a fully amorphous alloy of the nickel-phosphorus systemcontaining about 10 % phosphorus and the balance nickel, which may be applied by eletroless coating. This roll surface prevents the build-up of iron oxide on the casting surfaces of the rolls, which build-up interferes with the uniform conduction of heat away from the molten steel, resulting in simultaneous solidification of the delta and gamma iron phases (0.01-0.18 %C), which causes a surface defect, known as "crocodile-skin". The net effect of utilising this amorphous alloy for the surface of the casting roll is a superior and uniform conduction of heat away from the molten steel, rapid transformation of the steel's microstructure into the wholly austenitic ( gamma ) region, exhibited by fine prior austenite grain boundaries conforming to dendritic grain boundaries and absence of "crocodile-skin" surface defects on the cast strip.

Description

DETAILED DESCRIPTION OF THE INVENTION                           Metal strip casting Technical field   The present invention relates to casting of metal strip. Especially for iron-based metal strip casting Related to, but not limited to, the application.   It is public to cast metal strip by continuous casting with twin roll caster. Is knowledge. In this technology, a pair of horizontal casting rolls that are cooled and rotate in Introduce the molten metal in between, solidify the metal shell on the moving roll surface, and The metal shells are combined and sent downward from the roll gap as a solidified strip product. Pay. In this document, the term "roll gap" refers to the area where rolls are closest to each other. Used to refer to The molten metal is poured from the ladle into a small container, from where it is Flows to the metal supply nozzle located above the roll gap, and then to the roll gap. As a result, the molten metal supported on the roll casting surface immediately above the roll gap and extending in the roll gap length direction A casting pool of molten metal can be formed. Usually, this casting pool is Side plates or weirs held in sliding engagement with the pool to prevent overflow from both ends of the casting pool Although defined in between, alternatives such as electromagnetic barriers have been proposed.   Twin roll casting has achieved some success with non-ferrous metals that solidify rapidly upon cooling However, there is a problem in applying it to the ferrous metal casting technology. One special The problem is to achieve sufficiently rapid and uniform cooling of the metal on the roll casting surface. is there.   US Patent No. 5,520,243 (International Patent Application No. PCT / AU9) No. 3/00593) describes the relative movement between the molten metal in the casting pool and the roll casting surface. In this regard, measures should be taken to ensure that the roll surface has some smoothness. Can dramatically improve metal cooling on roll casting surfaces. Discloses the development that has been completed. In particular, the patent describes vibrations of selected frequency and amplitude. If you add it, you will achieve a completely new effect on the metal solidification process, Heat transfer can be dramatically improved, and the improvement can reduce the metal thickness cast at the same casting speed. To increase significantly or significantly increase the casting speed for the same metal thickness It discloses that it can be. Improving heat transfer can improve the surface structure of the cast metal. Very relevant to being scoured.   Our U.S. Patent No. 5,584,338 also applies sound waves to the molten metal in the casting pool. The effective relative vibration between the molten metal in the casting pool and the casting surface. The heat transfer can be increased simply by applying sound waves of very low power level. Disclosed is a further development wherein purification of the added and solidified structures can be achieved.   Our further US Pat. No. 5,720,336 discloses a casting surface and casting pool. It discloses the results of research on the heat transfer mechanism that occurs at the interface with the molten metal, Ensure that each casting surface is covered with a layer of material that is at least partially liquid Can control and increase the heat flux during solidification, so that the casting pool Heat transfer can be achieved without necessarily generating relative vibration between the roller and the roll It is disclosed that.   In the following description, reference should be made to a quantitative measure of the smoothness of the roll surface. I One particular measure used in various experimental tasks and useful in limiting the scope of the invention Is generally the symbol R_aArithmetical Mean Roughness Value The standard measure known as. This value is measured from the profile centerline Length l_mIt is defined as the arithmetic mean of the total absolute distances of the roughness profiles within. The center line of the profile is the line around which the roughness is measured, And the profile parts on both sides And the roughness-width cut-off (roughness- A line parallel to the general direction of the profile within the limits of width cut-off). Arithmetic The operative mean roughness can be defined as follows.   With the above developments, a high solidification rate can be achieved in the casting of ferrous metal strip. However, trees that do not exhibit surface defects known as `` crocodile skin '' It has proven to be very difficult to manufacture the tips. This defect is In the shell of the roll casting surface of a twin roll casting machine in an environment where the heat flux through the Occurs when the δ- and γ-iron phases solidify simultaneously. δ iron phase and γ iron phase have different heights It has a temperature strength characteristic, and therefore, due to heat flux fluctuations, Local distortions occur in the solidified shells that are brought together by the gaps, resulting in Crocodile skin defects occur. Traditionally, this problem has been solved Attempts have been made to keep the above oxide formation within strict limits.   Controls uniform flux during solidification of metal on the surface of the casting roll if oxide deposition is mild Can be beneficial to secure. When the roll surface enters the molten metal casting pool The oxidized deposits melt, creating a thin liquid interface layer between the casting surface and the molten metal in the casting pool. Helps establish and promotes good heat flux. However, not much When the oxides are formed, melting of the oxides produces a very high heat flux, The heat flux then decreases sharply as the oxide resolidifies. As a result, solidification Fluctuations in the heat flux in the shell cause local distortion, resulting in crocodile skin defects.   Roll casting surface to create very good wetting of the casting surface by the molten metal If it is made of a material that has a high affinity for the molten metal in the casting pool, We now know that the detrimental effects of products can be avoided and very fast solidification rates can be achieved. Decided times. Solidification proceeds very quickly with sufficient good wetting by the molten metal Thus, there is insufficient time for a significant amount of oxide to form. In case of molten steel Effectively eliminates the possibility of crocodile defects because molten steel rapidly solidifies into a single-layer solid structure. can avoid.Disclosure of the invention   In accordance with the present invention, a casting pool of molten metal is provided where metal is transferred from the pool onto a moving casting surface. Continuous casting of metal strip of the type formed in contact with a moving casting surface to solidify In a fabrication method, a casting surface is provided with a solid coating on a heat transfer body, the coating comprising a casting table. The casting surface during metal solidification, such that the wet angle of the molten metal on the surface is 40 ° or less Metal strip consisting of a material having a melting temperature higher than the temperature A continuous casting method is provided.   More preferably, the coating has a wetting angle of the molten metal on the casting surface of 20 ° or less. It is formed of a certain material.   Preferably, the coated surface has an arithmetic average roughness (R_a).   The coating material is chosen so that it does not dissolve in the molten metal at the casting surface temperature during solidification Should.   Preferably, the coating material is at least partially amorphous. For example, 2 It can be composed of a metal amorphous alloy. One of these metals is phosphorus May be included.   More specifically, the coating material is an amorphous nickel-phosphorous compound containing about 10% phosphorus. Can be made of gold.   The heat transfer body may be a copper or copper alloy body.   The molten metal can be an iron-based metal.   More specifically, the molten metal can be molten steel. In this case, the molten steel Solidification of the steel into a single-phase solid structure on the casting surface by choosing a coating material with a horn angle Can be done.   According to the present invention, the casting pool of molten steel is also free of steel from the pool and onto the moving casting surface. A continuous casting method of steel strip of the type formed in contact with a moving casting surface to solidify In the method, the casting surface is provided with a solid coating on the heat transfer body, and the coating is provided on the casting surface. The casting surface temperature at the time of metal solidification, such that the wet angle of the molten steel is 40 ° or less. Is formed of a material that also has a high melting temperature, Solidifies to a solid structure, the phase of which does not transform before the strip leaves the casting surface. A continuous metal strip continuous casting method is provided.   The method of the present invention may be performed on a twin roll caster.   According to the invention, furthermore, the molten metal is introduced into a roll gap between a pair of parallel casting rolls. And introduced through a metal supply nozzle arranged above the roll gap, A type of metal strike that creates a casting pool of molten metal supported on the upper roll casting surface In the continuous lip casting method, the casting surface of the roll has a solid coating on the heat transfer roll. Wherein the coating has a wetting angle of less than 40 ° of the molten metal on the roll casting surface. Some materials made with a melting temperature higher than the casting surface temperature during solidification of the metal Provided is a method of continuously casting a metal strip.BRIEF DESCRIPTION OF THE FIGURES   In order to more fully explain the invention, we attach the results of experimental work performed to date. This will be described with reference to the drawings.   Figure 1 shows the measurement of the solidification rate of a metal in a state simulating the state of a twin-roll caster. Fig. 1 shows an experimental device to be determined.   FIG. 2 shows an immersion paddle incorporated in the experimental apparatus of FIG.   FIG. 3 shows the thermal resistance values obtained during solidification of a typical steel swatch in an experimental setup.   Figure 4 shows the relationship between the wettability of the interfacial layer, the measured heat flux and the interfacial resistance. Show the person in charge.   FIG. 5 shows the effect of wettability on nucleation resistance.   FIG. 6 shows the shell surface temperature that occurs on a steel shell deposited on a chromium substrate.   FIG. 7 shows heat flux measurements for steel shells deposited on nickel-phosphorous and chromium substrates. This is a graph that shows the results of the experiment.   FIG. 8 shows steel shells deposited in an immersion test using a nickel-phosphorus alloy substrate and a chromium substrate. Is a graph of the measured value of K value.   9 and 10 are photomicrographs of the steel shell deposited in the immersion test referred to in FIG. .   FIG. 11 shows the steel shells deposited in further immersion tests using various substrates and molten steel compositions. It is a drawing of the measured K value on a graph.   12 to 16 are micrographs of the steel shell deposited during the immersion test referred to in FIG. It is.   FIG. 17 is a plan view of a continuous strip caster operable according to the present invention.   FIG. 18 is a side elevational view of the strip casting machine shown in FIG.   FIG. 19 is a longitudinal sectional view taken along line 19-19 in FIG.   FIG. 20 is a longitudinal sectional view taken along line 20-20 in FIG.   FIG. 21 is a longitudinal sectional view taken along line 21-21 of FIG.DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS   Figures 1 and 2 show that a block to be cooled of 40 mm x 40 mm was placed in a bath of molten steel. Gold advanced at a speed that closely simulates the state of the casting surface of the roll casting machine 1 shows a genus coagulation test tool. As the cooled block moves through the molten bath, the steel Solidifies on the cooling block to create a layer of solidified steel on the block surface. Adjust the thickness of this layer Measurement at various points in the area of Effective speed can be mapped. Therefore, total solidification rate and total heat flux can be measured It is. The microstructure of the strip surface was examined to determine the change in coagulated microstructure. It is also possible to relate to changes in the solid velocity and the heat transfer value.   The introduction furnace 1 constituting the experimental tool shown in FIGS. 1 and 2 is, for example, argon or Includes a melt of molten metal 2 in an inert atmosphere that can be provided by nitrogen gas. Overall The slider 4 to which the immersion paddle 3 is attached advances into the molten metal 2 at a selected speed. Can be retracted later by the operation of motor 5 controlled by computer. Can be.   The steel body 6 constituting the immersion paddle 3 is a chrome metal having a diameter of 46 mm and a thickness of 18 mm. Includes a substrate 7 which is a plugged copper plate. The substrate is a copper disc. This involves measuring the heat flux A thermocouple is instrumented to monitor the temperature rise of the substrate providing a constant value.   Tests performed with the experimental tool shown in FIGS. 1 and 2 have demonstrated that The observed solidification rate and heat flux values and the microstructure of the solidified shell are reduced by the shell / matrix interface during solidification. It is greatly influenced by the condition of the surface. Testing has shown that High heat flux and solidification rate can be achieved by a smooth substrate surface, which A refined grain structure can result.   During solidification, the total resistance to flow from the melt to the substrate (heat sink) is It is governed by the thermal resistance of the hardened shell and the shell / substrate interface. Coagulation is completed in about 30 minutes Under the conditions of conventional continuous casting sections (slabs, blooms or billets) The heat transfer resistance is governed by the solidification shell resistance. However, from our experimental work Under the conditions of thin strip casting where solidification is completed in less than 1 second, heat transfer resistance is It has been proved that it is governed by the interfacial thermal resistance at the surface.   Heat transfer resistance is defined as follows.         R_(t)= ΔT_(t)/ ΔQ_(t) Here, Q, ΔT and t are the heat flux, the temperature difference between the molten metal and the substrate, and the time, respectively. It is.   FIG. 3 shows the solidification of a typical manganese-killed low carbon steel sample in a laboratory tool. It shows the thermal resistance value obtained when This shows that the shell thermal resistance is the total thermal resistance Contribute only to a small part of the total, and the total thermal resistance is controlled by the interfacial thermal resistance That is. The interfacial resistance is initially determined by the melt / substrate interfacial resistance and later by the shell / Determined by the substrate interface resistance. Furthermore, interfacial thermal resistance varies greatly with time. It can be seen that there is no interfacial thermal resistance at the initial melt / substrate contact It shows that it is governed by thermal resistance.   In a two component system (melt and substrate), the melt / substrate interface resistance and heat flux are It depends on the wettability of the molten metal on the substrate. This is shown in FIG. How the interfacial resistance increases with increasing wetting angle, which corresponds to a decrease in wettability, It shows whether the heat flux is reduced.   The importance of wetting the substrate by the molten metal was described above, which discloses the application of vibration. US Patent No. 5,520,243 (International Patent Application PCT / AU93 / This is demonstrated in the development work described in 00593). Applying vibration promotes substrate wetting and increases nucleation density for melt solidification It is for the purpose of letting them. The mathematical model described on page 8 of the case is complete Based on the fact that a high degree of wetting is required and vibration energy is taken into account to achieve this. Progressed. In experimental work demonstrating this analysis, a significant improvement in heat flux was not It was shown that it could not be obtained unless it was clear. More specifically, even if the vibration energy The substrate must be 5 microns to obtain complete wetting of the substrate, even when applying The following arithmetic average roughness (R_aNeed to have). These results indicate that molten steel is suitable. Suitable for chromium substrates with very good wettability. However, According to Ming, the roll casting surface is made of a material with much higher affinity for molten steel. Can be made to achieve much better wetting than can be achieved with a chrome surface You. In these situations, the smoothness of the substrate is not particularly important. However, moderately To produce a strip with good surface finish and refined microstructure In practice, the casting surface has an arithmetic average roughness (R_a) No.   When solidifying metal on a smooth substrate, the solidification occurs at the heterogeneous nucleation sites throughout the substrate. It can be assumed that it will proceed. No nucleation according to such classical heterogeneous nucleation theory The effect of the wetting angle on the dimensional free energy is shown in FIG. FIG. 5 shows the increase in the wetting angle. In other words, as the wetting efficiency decreases, the dimensionless free energy barrier factor increases. Shows how. A wetting angle of less than 40 ° shows very good wetting effect, The energy barrier for it is negligible. Wetting angles greater than 75 ° exhibit inadequate wetting There is a significant energy barrier against metal solidification.   Twin roll strip casters for casting ferrous metals are generally manufactured by plating. Casting rolls with a chrome or nickel casting surface Have been. Such surfaces are robust and generally subject to the thermal stresses associated with strip casting. Can withstand. Furthermore, the molten steel is reasonably good on chromium and nickel surfaces Because of the high wettability, an effective heat flux value can be achieved. we, The metal oxide deposited from the typical molten steel used for strip casting is chromium. And has a high affinity for nickel, so that it has good wettability on such cast surfaces Properties, ie, exhibiting a very low wetting angle. This is because as the casting progresses And the oxide coating has a very strong tendency to spread and establish over the casting surface That is to say.   FIG. 6 shows diagrams for both a clean substrate surface and a surface with a large amount of oxide deposited. Shell table occurring on steel shell deposited on chromium surface in immersion test shown in 1 and 2 The surface temperature measurement is shown. Solidification shell surface as solidification progresses on smooth substrate surface It can be seen that the surface temperature decreases. If the substrate has a large amount of oxide coating, the shell Initially, the temperature decreases to around 1200 ° C, at which stage a sharp reversal occurs, and the shell temperature rises. The degree rises. The temperature drops while the oxide is in a liquid state, It is believed that the oxide solidifies to provide a nucleation site for metal solidification. But However, solid oxides then provide a barrier to heat flux, and consequently The effectiveness of cooling is impaired and the shell surface temperature increases. Previously, this effect included: Careful cleaning of rolls during casting to keep oxide levels within very tight limits It was thought that it could only be overcome by doing. However, we According to the measurements this time, an alternative that causes very good wetting by molten steel Forming the casting surface with the material can result in a significant temperature drop below the liquidus temperature. It is possible to cause the solidification of the molten steel without any help. Such cooling is very rapid And there is not enough time for oxides to form on the casting surface, Do not suffer significant interference from accumulated oxide Coagulation progresses. In particular, these results are based on nickel-phosphorus containing 10% phosphorus. Proven by immersion tests in the apparatus shown in FIGS. 1 and 2 using a cooled substrate of the alloy Was done. This alloy can be coated on chill rolls by an electroless metal deposition process, Promotes very good wetting by molten steel. For most molten steel, this coating The wetting angle is about 25 ° or less.   FIG. 7 shows the heat flux measurements obtained during solidification of carbon steel on a nickel-phosphorus alloy substrate. Values compared to heat flux measurements obtained when the same steel is solidified on a chromium substrate Is drawn on the graph. The carbon steels in these tests have the following composition, Calls it MO6 steel.   FIG. 8 shows the results obtained by using a molten carbon steel having the above-mentioned composition and using a nickel-phosphorus alloy substrate and a chromium substrate. 5 provides the results of measuring the K value (indicative of heat flux) in the multiple immersion test. 7 and 8 From both results, the nickel-phosphorus alloy has a higher heat flux than a normal chromium substrate. It can be seen that this result is proved. For nickel-phosphorous alloy substrates, the phase The heat flux varied in different tests, and in particular, the results shown in FIG. The K value has decreased in the experiment. These fluctuations are due to nickel as the test progresses. Due to melting of the phosphorus alloy; Therefore, cast steel strip at high melting temperature Increase the melting temperature to achieve long life coating on commercial strip casters It is desirable to modify this particular alloy composition to achieve this. However, testing Have demonstrated dramatically improved results that can be achieved at low wetting angles, and Kel- It has been proven that phosphorus alloys are perfectly suitable for casting other metals such as copper.   9 and 10 show the nickel-phosphorus alloy substrate in FIG. 9 and the nickel-phosphorus alloy substrate in FIG. Is a micrograph of an MO6 steel shell deposited on a traditional chromium substrate. The photograph is also shown at a magnification of x100. The shell deposited on the nickel-phosphorus alloy About twice the thickness of the shell deposited on the nickel-phosphorus substrate Reflecting a much higher heat flux and more rapid solidification. This is very High solidification rate can be obtained and, thus, it is possible with the present invention That strip casting can proceed at dramatically higher production speeds than has been considered Prove that. Furthermore, the microstructure of the shell deposited on the nickel-phosphorus alloy substrate is transmitted. Much finer than that deposited on conventional chromium substrates, and also It can be seen that it is extremely uniform over This microstructure is precisely later dendritic The liquid carbon steel solidifies and exhibits direct austenite grain boundaries Proving to be a stainite. In this coagulation process, the development of crocodile skin defects There is no possibility to do it. This is because these defects have δ and γ phases in the solidified steel shell. It happens only in certain cases.   High wettability of nickel-phosphorus alloy is due to its amorphous structure Is known. Liquids generally have a high surface affinity for other liquids Because the body does not have a preferred orientation, when wetting an amorphous solid We have now found that a similar effect can occur. Therefore, wetting of the liquid metal on the casting surface Degradability can increase dramatically if the coating material is completely amorphous. 8 and 9 Nickel-phosphorus alloys with a 10% phosphorus content as used in the tests relating to Non-electrodepositable metal deposition to obtain a virtually amorphous structure with a molten composition It can be easily deposited by the process. It deviates significantly from the eutectic composition Change the phosphorus component If the deposited bimetallic alloy coating is not completely amorphous but partially crystalline, Will have a weave. Furthermore, crystalline structures can be annealed at elevated temperatures after depositing the coating. It can also be made by doing To increase the hardness when applying any coating This phenomenon is used for   According to the present invention, the amorphous coating has the effect of increasing the wettability and the heat flux. To prove, we have performed a series of further tests to determine the nickel composition with different phosphorus compositions. On a phosphorus alloy substrate, on a nickel-phosphorus alloy substrate annealed at high temperature before testing, Freezing the molten steel even on a smooth nickel substrate providing standard or control data Hardened. Furthermore, according to the present invention, the steel is directly solidified to form austenite dendrites. In order to further prove that this is the case, peritectic grade s teel). In the peritectic grade steel, during solidification, it simultaneously forms δ and γ phases This is because the solidification usually causes significant distortion. The results of this further test are 11 to 16 are shown.   FIG. 11 provides the measurement results of the K value in the multiple immersion test. In immersion tests 1-27 All the steel melts having the above MO6 composition were used. In tests 1 to 9, the steel shell was R_avalue Is 5.6 and the average roughness (R_a) Is 8.7 And a nickel-phosphorus substrate.   The nickel-phosphorous substrates used in tests 1-9 were deposited by a non-electrodepositable metal deposition process. Was not annealed. In this substrate, a smooth two-piece Very high K values are achieved compared to the Huckel substrate. These results are shown in FIG. It was exactly the same as the one.   In Tests 10 to 15, in which FIG. 8 shows further results, the nickel substrate is Arithmetic mean roughness (R_aSolidification on a nickel-phosphorus alloy substrate having 6.6) The results were retained as a control comparison. 5% phosphorous alloy The K value produced was 10% of tests 1-9, even though relatively smooth substrates were used. Partial crystals inevitable in 5% phosphorus alloys, much smaller than those in phosphorus alloys It has been demonstrated that quality tissue reduces wettability and total heat flux.   In tests 16 to 23, in which FIG. 11 shows further results, the MO6 steel shell was Deposited on a nickel-phosphorous alloy substrate, each of which has a 10% phosphorus content. But one of the substrates is 1.5 hours at 400 ° C. after deposition of the non-electrodeposited metal deposit. Annealed, other substrates not annealed It was. Substrates that have not been annealed are as already experienced in Tests 1-9 Annealed substrate is achieved with plain nickel substrate, resulting in high K values It produced a much lower K value than the one. FIG. 12 shows the nickel substrate of Test No. 11. FIG. 13 is a photomicrograph of the deposited shells, FIG. FIG. 14 is a photomicrograph of the shell deposited on the substrate, FIG. 4 is a photomicrograph of a shell deposited on an unfavorable nickel-phosphorous alloy. Test 11 The microstructure of the shell deposited on the nickel substrate and the annealed substrate of test 18 was similar. You can see that there is. In each case, the shell is relatively thin and has a coarse microstructure. In addition, it shows that it is initially solidified into ferrite. Not annealed The shell of FIG. 14 deposited on the gold substrate is very thick and the initial solidification is directly austenite. Exhibit a fine microstructure associated with the very high solidification rates achievable with the present invention.   FIG. 8 also shows a comparison with the reference nickel substrate previously used in Tests 1-15. With 10% phosphorus content but only partially annealed at 400 ° C for 45 minutes 7 provides the results of tests 24-27 in which shells were deposited on nickel-phosphorous alloys. Partially baked Annealed substrate is generally annealed with non-annealed substrates of tests 16-23 It was found that the K value was between In addition, the effect of amorphous coating depending on the degree of the crystalline structure in the coating, the K value and the heat Shows a gradual decrease in flux.   FIG. 11 also shows that a shell was formed from a peritectic steel composition having a carbon content of 0.13% and a nickel content having a phosphorus content of 10%. 9 provides results obtained from tests 29-31 deposited on a Kel-phosphorus alloy substrate . Normally, steels of such a composition have good surface quality by direct sheet strip casting technology. Cannot be cast in quality. Because steel has δ ferrite phase and γ ferrite This is because it solidifies simultaneously with the phase and causes significant distortion of the solidified shell. However, In this test, the peritectic steel composition was previously achieved with MO6 steel on a nickel-phosphorus alloy substrate. Produces a shell with the same microstructure and the same K value as formed, and a similar heat flux during solidification Prove that.   The solidification structure of the peritectic steel shell made in test number 30 is shown in FIG. 15 and textured. The solidification structure of the same steel shell deposited on the (textured) chromium substrate is shown in FIG. FIG. 5 is exactly the same as shown in FIGS. And demonstrate that liquid carbon steel solidifies directly to austenite. ing. Furthermore, even after the solidification progresses and the cooling rate is reduced, There are no signs that the site will grow. This is a feature of the present invention in the strip casting method. As more austenite solidification begins, it is completely transformed into austenite. Does not return to ferrite growth. Of course, the strip is a casting surface After leaving, there is post-transformation at low temperature.   In the practice of the present invention, the material of the roll casting surface is that of the casting surface during metal solidification. Must have a melting temperature higher than the temperature. The temperature of the casting surface is above the casting surface It depends on the wetting angle of the molten metal. More specifically, the temperature experienced by casting surface coatings The degree increases as the wetting angle decreases. Therefore, the coating material has high heat flux and rapid From the balance with rapid solidification and the melting temperature of the coating Arguably, it can be selected to provide maintenance of a low coating temperature.   The results shown in FIGS. 8 and 11 for the unannealed nickel-phosphorus substrate Shows a gradual loss of performance due to coating erosion. For hot steel casting, According to the invention, two other metallic amorphous coatings can be used. Appropriate To select a coating, the melting temperature of the coating, the interface temperature during casting, and the annealing of the coating Temperature must be taken into account. Table 1 shows the results of the casting of thin strip steel. Illustrates the relative criteria of a number of possible alloy coatings that can be used You.   In Table 1, before the steel metal is in full contact at 1650 ° C. with a coating at 25 ° C. By the way, the interface temperature is calculated.   17 to 21 show twin roll continuous strip casters operable according to the invention. ing. The casting machine has a main machine frame 11 rising from a factory floor 12. . The casting roll carriage 13 supported by the frame 11 is connected to an assembly station 14. It can be moved horizontally between the casting station 15. A pair carried by the cart 13 Are supplied from a ladle 17 to a parallel casting roll 16 during casting. Molten metal is supplied through a nozzle 19 to create a casting reservoir 30. Casting roll Since 16 is water-cooled, the metal shell solidifies on the moving roll surface 16A and At the roll exit, the coagulated strip 20 is produced. Mark this item It can be sent to the semi-coiler 21 and then to the second coiler 22. Container 23 is cast Attached to the main machine frame adjacent to the station, the molten metal flows into this container, Significant deformation of the product through the overflow 24 of the tundish or during casting. If a serious inconvenience occurs, pull out the emergency plug 25 on one side of the tundish. Can be transferred.   A bogie frame 31 that constitutes the roll bogie 13 is formed by rails 33 with wheels 32. And the rail 33 extends along a part of the main machine frame 11, so that The entire vehicle 13 is movably mounted on the rail 33. Trolley frame The roll 16 is rotatably mounted on a pair of roll cradles 34 carried by the base 31. It is. Roll cradle 34 interconnects complementary sliding members 35,36. As a result, the hydraulic cylinder units 37 and 38 It is possible to adjust the roll gap between the casting rolls 16 by moving on a bogie under the influence. Form a transversal line under the strip as possible and as described in more detail below Rolls can be quickly and quickly reciprocated when needed I do. Double-acting that operates so that the entire carriage can be moved along the rails 33 Hydraulic pin The stone cylinder device 39 is provided between the drive bracket 40 of the roll carriage and the main frame. Between the assembly station 14 and the casting station. It is operable to be able to move to and from the housing 15 and vice versa.   The casting roll 16 is driven by a drive shaft 41 from an electric motor and a transformer on the bogie frame 31. Rotated in mutually directions via the mission. On the copper peripheral wall of the roll 16 A series of water cooling passages formed and extending in the longitudinal direction and separated in the circumferential direction are provided with a rotating gland 4. 3 through a water supply conduit in a roll drive shaft 41 connected to a supply hose 42. Cooling water is supplied through the end of the cooling water. Can produce 2000mm width strip products To achieve this, the rolls typically have a diameter of about 500 mm and a length of 20 mm. It can be up to 00 mm.   The ladle 17 has a completely conventional configuration, and is supported by an overhead crane via a yoke 45. And can be moved from the hot metal receiving station to a fixed location. On the ladle By operating the provided stopper rod 46 with a servo cylinder, the molten metal The tundish 1 from the ladle via the outlet nozzle 47 and the refractory shroud 48 8 can flow.   The tundish 18 also has a conventional configuration, and is resistant to magnesium oxide (MgO) or the like. It is formed into a wide dish made of fire. One side of the tundish is molten gold from a ladle And an overflow plug 24 and an emergency plug 25 are provided. Tandy On the other side of the mesh are a series of longitudinally spaced metal outlet openings 52. . The mounting bracket 53 carried by the lower part of the tundish rolls the tundish An opening provided in the mounting bracket for mounting on the bogie frame 31 Position the tundish accurately by receiving the positioning pegs 54 on the bogie frame It is supposed to.   The supply nozzle 19 is an elongated body made of a refractory material such as alumina graphite. Because the lower part is tapered and narrows inward, , Can enter the gap between the casting rolls 16. The nozzle has a mounting bracket 60 It is equipped and supports the nozzle on the roll carriage frame, and the nozzle is mounted on the upper part An outwardly projecting side flange 55 located on the bracket is formed.   Nozzle 19 has a series of horizontally spaced channels that extend generally vertically To produce an appropriate slow release flow of metal over the entire width of the roll, Molten metal can be fed into the roll gap without directly hitting the roll surface where it occurs it can. Or, if the nozzle has a single continuous slot outlet, a low speed curtain The molten metal may be fed directly to the nip and / or May be immersed in the molten metal reservoir.   A pair of side closing plates 56 that bound the reservoir at the end of the roll are formed by a roll carriage and a casting stay. The roller is held at the stepped end 57 of the roll. The side closing plate 56 is Scallop made of a strong refractory material such as iodine and matching the curved surface of the stepped end 57 of the roll It has a side end 81. A plate holder 82 in which the side plates can be mounted is located at the casting station. Is movable by the operation of the pair of hydraulic cylinder units 83, and the side plate is Of the molten pool formed on the casting roll during the casting operation Construct an end closure.   During the casting operation, the ladle stopper rod 46 is operated, and the molten metal is removed from the ladle. Pour into a dish and flow through a metal feed nozzle to a casting roll. Story The clean head of the finished product 20 is moved to the coiler 21 by the operation of the apron table 96. Guided to the jaw. The apron table 96 is mounted on a pivot mount 97 on the main frame. From the hydraulic cylinder unit 9 after a clean head end is formed. By the operation of 8, it is possible to turn toward the coiler. For piston cylinder unit 101 Actuated by upper strip The apron table 96 can be operated with respect to the guide flap 99, and a strip product Can be confined between the pair of vertical side rolls 102. Head end of coiler jaw Is rotated, the coiler is rotated to take up the strip product 20, and the apron The table is turned in the opposite direction to return to the non-operation position, and is wound directly on the coiler 21. Simply suspended from the main engine frame, separated from the strip product being taken State. The resulting strip product 20 is later sent to a coiler 22 for casting. It can be the final rolled product that is carried out of the machine.   Full details of a twin roll caster of the type shown in FIGS. Patent Nos. 5,184,668 and 5,277,243 and International Patent Application PC It is described in more detail in T / AU93 / 00573.

[Procedure for Amendment] Article 184-8, Paragraph 1 of the Patent Act [Date of Submission] March 23, 1999 (Feb. We have now determined that a fast solidification rate can be achieved. With sufficient good wetting by the molten metal, solidification proceeds very rapidly, and not enough time is available to form a significant amount of oxide. In the case of molten steel, the possibility of crocodile skin defects can be effectively avoided since the molten steel solidifies rapidly to form a single-layer solid structure. DISCLOSURE OF THE INVENTION According to the present invention, a continuous casting method of metal strip of the type wherein a casting pool of molten metal is formed in contact with a moving casting surface such that the metal solidifies from the pool onto the moving casting surface. The surface is provided with a solid coating on the heat transfer body, the coating having a melting temperature higher than the casting surface temperature during solidification of the metal, such that the wetting angle of the molten metal on the casting surface is 40 ° or less. A metal strip continuous casting method comprising forming a material is provided. More preferably, the coating is formed of a material such that the molten metal has a wetting angle of 20 ° or less at the casting surface. Preferably, the coated surface has an arithmetic average roughness ( _Ra ) of 10 microns or less. The coating material should be chosen so that it does not dissolve in the molten metal at the casting surface temperature during solidification. Preferably, the coating material is at least partially amorphous. For example, it can be composed of an amorphous alloy. One of these metals can include phosphorus. More specifically, the coating material can be comprised of an amorphous nickel-phosphorous alloy containing about 10% phosphorus. The heat transfer body may be a copper or copper alloy body. The molten metal can be an iron-based metal. More specifically, the molten metal can be molten steel. In this case, by selecting a coating material in which the molten steel has a low wetting angle, the steel can be solidified on the casting surface into a single-phase solid structure. According to the present invention, there is also provided a method of continuous casting of steel strip of the type wherein a casting pool of molten steel is formed in contact with a moving casting surface such that the steel solidifies from the pool onto the moving casting surface. Provided with a solid coating on a heat transfer body, the coating formed from a material having a melting temperature higher than the casting surface temperature during solidification of the metal, such that the wet angle of the molten steel on the casting surface is 40 ° or less. Wherein the steel solidifies on the casting surface into a single-phase solid structure, the phase of which does not transform before the strip leaves the casting surface. The method of the present invention may be performed on a twin roll caster. According to the present invention, further, the molten metal is introduced into the roll gap between the pair of parallel casting rolls via the metal supply nozzle arranged above the roll gap, and the result of the flux measurement is graphically drawn. Things. FIG. 8 graphically depicts the measured K value of a steel shell deposited in an immersion test using a nickel-phosphorous alloy substrate and a chromium substrate. 9 and 10 are photomicrographs of the steel shell deposited in the immersion test referred to in FIG. FIG. 11 graphically depicts K value measurements of steel shells deposited in further immersion tests using various substrates and molten steel compositions. 12 to 16 are micrographs of the steel shell deposited during the immersion test referred to in FIG. FIG. 17 is a plan view of a continuous strip caster operable according to the present invention. FIG. 18 is a side elevational view of the strip casting machine shown in FIG. FIG. 19 is a longitudinal sectional view taken along line 19-19 in FIG. FIG. 20 is a longitudinal sectional view taken along line 20-20 in FIG. FIG. 21 is a longitudinal sectional view taken along line 21-21 of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS . 1 and 2 illustrate the speed of a 40 mm × 40 mm block to be cooled into a bath of molten steel so as to closely simulate the condition at the casting surface of a twin roll caster. Shows a metal coagulation test tool to be advanced in the above. As the cooled block moves through the molten bath, the steel solidifies on the cooled block, creating a layer of solidified steel on the block surface. The thickness of this layer was measured at various points in the area and was verified experimentally. This alloy can be coated on chill rolls by an electroless metal deposition process and promotes very good wetting by the molten steel. For most molten steels, the wetting angle with this coating is about 25 ° or less. FIG. 7 is a graph comparing heat flux measurements obtained when solidifying carbon steel on a nickel-phosphorus alloy substrate with heat flux measurements obtained when solidifying the same steel on a chromium substrate. I'm drawing. The carbon steel in these tests has the following composition, which we refer to as MO6 steel. FIG. 8 provides the measurement results of the K value (indicative of heat flux) in a multiple immersion test using a molten carbon steel having the above composition and a nickel-phosphorus alloy substrate and a chromium substrate. It can be seen from the results of both FIGS. 7 and 8 that the nickel-phosphorous alloy results in a higher heat flux than a conventional chromium substrate. In the case of the nickel-phosphorus alloy substrate, the heat flux varies in different tests, and in particular, the results shown in FIG. 8 show that the K value decreases in the continuous immersion test. These variations were due to melting of the nickel-phosphorous alloy as the test progressed. Therefore, to achieve long life coatings on commercial strip casters that cast steel strip at high melting temperatures, it is desirable to modify this particular alloy composition to increase the melting temperature. However, tests have demonstrated dramatically improved results that can be achieved at low wetting angles, and demonstrate that the nickel-phosphorus alloys tested are perfectly suitable for casting other metals such as copper. 9 and 10 are MO6 steel shell micrographs deposited on a nickel-phosphorous alloy substrate in the case of FIG. 9 and on a traditional chromium substrate in the case of FIG. 10, both micrographs at x100 magnification. Is shown. The shell deposited on the nickel-phosphorous alloy substrate is almost twice as thick as the shell deposited on the chromium substrate, reflecting the much higher heat flux and more rapid solidification obtained with the nickel-phosphorous alloy substrate. I have. This demonstrates that very high solidification rates can be obtained, and thus that the present invention allows strip casting to proceed at dramatically higher production rates than previously thought possible. Furthermore, it can be seen that the microstructure of the shell deposited on the nickel-phosphorous alloy substrate is much finer than that deposited on a traditional chromium substrate, and is also significantly more uniform throughout the shell. This microstructure exhibits a predecessor austenite grain boundary that later becomes a dendritic grain boundary, proving that the liquid carbon steel solidifies directly into austenite. In this coagulation process, there is no possibility of developing crocodile defects. This is because these defects occur only when there are δ and γ phases in the solidified steel shell. It has been found that the high wettability of the nickel-phosphorus alloy is due to its amorphous structure. Liquids have a generally high surface affinity for other liquids because liquids have no preferential orientation, and we have now found that similar effects can occur when wetting amorphous solids. . Thus, the wettability of the liquid metal to the casting surface can increase dramatically if the coating material is quite amorphous. Nickel-phosphorus alloys with a 10% phosphorus content as used in the tests relating to FIGS. 8 and 9 are essentially eutectic and have a non-electrodepositable metal deposition to obtain a substantially completely amorphous structure. It can be easily deposited by the process. If the phosphorus component is varied so as to deviate significantly from the eutectic composition, the deposited nickel-phosphorous alloy coating will have a partially crystalline structure rather than a completely amorphous one. Furthermore, crystalline structures can be created by annealing the coating at an elevated temperature after deposition. A phenomenon used to increase hardness when applying any coating. To demonstrate that the amorphous coating has the effect of enhancing wettability and heat flux in accordance with the present invention, we have performed a series of further tests on nickel-phosphorus alloy substrates with different phosphorus compositions before testing. The molten steel was solidified on a nickel-phosphorous alloy substrate annealed at a high temperature and on a smooth nickel substrate providing standard or control data. Furthermore, further tests included the deposition of shells from peritectic grade steel to further demonstrate that the steel solidifies directly into austenite dendrites according to the present invention. This is because peritectic grade steel usually solidifies to a 6-phase and a γ-phase at the time of solidification, which usually causes significant distortion. The results of this further test are shown in FIGS. FIG. 11 provides the measurement results of the K value in the multiple immersion test. In all of the immersion tests 1 to 27, the molten steel having the above MO6 composition was used. In tests 1 to 9, steel shells were deposited on both a smooth nickel substrate with an R _a value of 5.6 and a nickel-phosphorus substrate with a 10% phosphorus content and an average roughness (R _a ) of 8.7. . The nickel-phosphorous substrates used in tests 1-9 were deposited in a non-electrodepositable metal deposition process and were not annealed. Very high K values are achieved with this substrate compared to the smooth nickel substrate used as a control. These results were exactly the same as those shown in FIG. In tests 10 to 15, where FIG. 8 shows further results, the nickel substrate was compared to the solidification result on a nickel-phosphorus alloy substrate having a phosphorus content of 5% and an arithmetic mean roughness ( _Ra ) of 6.6. Retained as control reference comparison. The K value achieved with the 5% phosphor alloy was much smaller than that with the 10% phosphor alloy of Tests 1-9, even though a relatively smooth substrate was used, and was avoided in the 5% phosphor alloy. No partial crystalline structure has been demonstrated to reduce wettability and total heat flux. In tests 16-23, FIG. 11 shows further results, MO6 steel shells were deposited on a smooth nickel-phosphorous alloy substrate, each of which had 10% phosphorus content, one of which was It had been annealed at 400 ° C. for 1.5 hours after deposition of the non-electrodeposited metal deposit, and the other substrates had not been annealed. Unannealed substrates yielded high K values as already experienced in trials 1-9, while annealed substrates yielded much lower K values than those achieved with plain nickel substrates. 12 is a micrograph of the shell deposited on the nickel substrate of test number 11, FIG. 13 is a micrograph of the shell deposited on the annealed substrate of immersion test number 18, and FIG. 4 is a photomicrograph of a shell deposited on an unannealed nickel-phosphorous alloy. It can be seen that the microstructure of the shell deposited on the nickel substrate of test 11 and the annealed substrate of test 18 are similar. In each case, the shell is relatively thin, has a coarse microstructure, and exhibits initial solidification to ferrite. The shell of FIG. 14 deposited on an unannealed alloy substrate is very thick and exhibits a fine microstructure associated with the very high solidification rate achievable with the present invention, where the initial solidification is directly austenite. FIG. 8 further shows a nickel-phosphorus alloy having 10% phosphorus content, but only partially annealed at 400 ° C. for 45 minutes, compared to the reference nickel substrate previously used in Tests 1-15. 14 provides the results of tests 24-27 with shell deposition. It can be seen that the partially annealed substrate generally has a K value between the unannealed and annealed substrates of Tests 16-23, and furthermore, the degree of amorphous structure of the amorphous coating in the coating. It shows the effect and the gradual reduction of the K value and the heat flux. FIG. 11 also provides the results obtained from tests 29-31 in which shells were deposited from a peritectic steel composition with 0.13% carbon content on a nickel-phosphorous alloy substrate with 10% phosphorus content. Normally, steels of such composition cannot be cast with good surface quality by direct sheet strip casting techniques. This is because the steel solidifies simultaneously into the δ ferrite phase and the γ ferrite phase, and causes significant distortion in the solidified shell. However, in this study, the peritectic steel composition produced a shell with the same microstructure, the same K value previously achieved with MO6 steel on a nickel-phosphorous alloy substrate, and a similar heat flux during solidification. Has proved. The solidification structure of the shell of the peritectic steel made in test number 30 is shown in FIG. 15, and the solidification structure of the same steel shell deposited on a textured chromium substrate is shown in FIG. The structure of FIG. 15 is exactly the same as that shown in FIGS. 9 and 14, showing a preceding austenite grain boundary, demonstrating that the liquid carbon steel solidifies directly to austenite. Furthermore, there is no sign of ferrite growth even after solidification proceeds and the cooling rate is reduced. This indicates that when austenite solidification is initiated according to the invention in a strip casting process, it is a complete transformation to austenite and does not return to ferrite growth. Of course, after the strip leaves the casting surface, there is post-transformation at low temperatures. In the practice of the present invention, the material of the roll casting surface must have a melting temperature that is higher than the temperature of the casting surface during metal solidification. The temperature of the casting surface depends on the wetting angle of the molten metal on the casting surface. More specifically, the temperature experienced by the casting surface coating increases as the wetting angle decreases. Thus, the coating material can be selected to provide a balance between high heat flux and rapid solidification and to maintain a coating temperature that is arguably lower than the melting temperature of the coating. The results shown in FIGS. 8 and 11 for the unannealed nickel-phosphorous substrate show a gradual loss of performance due to coating erosion. For high temperature steel casting, two other metallic amorphous coatings can be used according to the present invention. In selecting an appropriate coating, it is necessary to take into account the melting temperature of the coating, the interface temperature during casting and the annealing temperature of the coating. Table 1 shows the relative criteria of a number of possible alloy coatings that can be used according to the invention in the casting of thin strip steel. Claims 1. In a continuous metal strip casting method of the type where a casting pool of molten metal is formed in contact with a moving casting surface such that the metal solidifies from the pool onto the moving casting surface, the casting surface is solid on the heat transfer body. A metal provided with a coating, wherein the coating is formed of a material having a melting temperature higher than the casting surface temperature during solidification of the metal such that the wetting angle of the molten metal at the casting surface is 40 ° or less. Strip continuous casting method. 2. The method of claim 1 wherein the coating is formed of a material such that the molten metal has a wetting angle of 20 ° or less at the casting surface. 3. 3. The method of claim 1 or claim 2, wherein the coated surface has an arithmetic average roughness ( _Ra ) of 10 microns or less. 4. A method according to any of the preceding claims, wherein the molten metal is molten steel. 5. 5. The method of claim 4, wherein the steel solidifies on the casting surface into a single phase solid structure. 6. A method according to any of the preceding claims, wherein the coating material is at least partially amorphous. 7. 7. The method of claim 6, wherein the coating material is essentially completely amorphous. 8. A method according to any of the preceding claims, wherein the coating material is comprised of a binary alloy. 9. 9. The method of claim 8, wherein one of the components of the alloy comprises phosphorus. 10. The method of claim 9 wherein the other component of the alloy is nickel. 11. The method according to any of claims 8 to 10, wherein the alloy is essentially a eutectic alloy. 12. A method as claimed in any of the preceding claims, wherein the molten metal has an essentially eutectic composition. 13. A method according to any of the preceding claims, wherein the heat transfer body is a copper or copper alloy body. 14． A continuous casting method of steel strip of the type in which a molten steel casting pool is formed in contact with a moving casting surface such that the steel solidifies from the pool onto the moving casting surface, wherein the casting surface has a solid coating on the heat transfer body. Wherein the coating is formed of a material having a melting temperature higher than the casting surface temperature during solidification of the metal, such that the wetting angle of the molten metal at the casting surface is 40 ° or less; A continuous metal strip casting process wherein the solidifies on the casting surface into a single phase solid structure, the phase does not transform before the strip leaves the casting surface. 15. 15. The method of claim 14, wherein the steel has a carbon equivalent component of 0.13 wt% or less and the single phase structure comprises dendrites of solid austenite. 16. The method of claim 15 wherein the steel has an essentially peritectic composition. 17. 17. The method of claim 16, wherein the steel has a carbon content of about 0.13% by weight. 18. 18. The method according to any of claims 14 to 17, wherein the coating material comprises a binary amorphous alloy. 19. 19. The method of claim 18, wherein one of the components of the alloy comprises phosphorus. 20. 20. The method of claim 19, wherein the coating is a nickel-phosphorous alloy containing about 10% phosphorus. 21. 21. The method according to any of claims 14 to 20, wherein the heat transfer body is a copper or copper alloy body. 22. The moving casting surface is one of a pair of such surfaces, the surfaces of the pair of casting rolls forming a roll gap therebetween, the casting pool is supported on the casting roll above the roll gap, and the strip is 22. A method as claimed in any of claims 14 to 21, wherein the solid tissue is fed down from a roll gap. 23. In a method of continuously casting metal strip of the type formed by contact with a moving casting surface such that the casting pool of molten metal solidifies from the pool onto the moving casting surface, the metal has a peritectic composition and the casting surface Is provided as a solid coating on the heat transfer body, the coating comprising a material having a melting temperature higher than the casting surface temperature during solidification of the metal, such that the wetting angle of the molten metal at the casting surface is 40 ° or less. Wherein the metal solidifies into a single-phase solid structure on the casting surface, the phase not transforming before the strip leaves the casting surface. 24. A casting roll having a casting surface in contact with the casting pool of molten metal, and means for cooling the casting surface of the casting roll to solidify the metal thereon, wherein the roll surface is formed by solid coating of the heat transfer body of the roll Metal strip continuous casting apparatus, wherein the coating comprises a two-component essentially amorphous alloy. 25. 25. The apparatus of claim 24, wherein one of the components of the alloy comprises phosphorus. 26. 26. The apparatus of claim 25, wherein the coating alloy is a nickel-phosphorous alloy. 27. 27. The apparatus of claim 26, wherein the coating alloy comprises about 10% phosphorus. 28. A casting roll comprising a heat transfer cylindrical roll body covered with a solid coating defining a cylindrical metal casting surface, the coating comprising a two-component essentially amorphous alloy. 29. 29. The casting roll of claim 28, wherein one of the components of the alloy comprises phosphorus. 30. 30. The casting roll of claim 29, wherein the casting alloy is a nickel-phosphorous alloy. 31. 30. The casting roll of claim 29, wherein the coating alloy comprises about 10% phosphorus. 32. Cast steel strip made from continuous casting from steel having a carbon equivalent component of 0.13% by weight or less and having a microstructure resulting from the direct solidification of molten metal into austenite prior to subsequent low temperature transformation. 33. 33. The cast steel strip of claim 32, wherein the steel has an essentially peritectic composition. 34. 34. The cast steel strip of claim 33, wherein the steel has a carbon content of about 0.13% by weight.

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Claims (1)

[Claims] 1. In a continuous metal strip casting method of the type where a casting pool of molten metal is formed in contact with a moving casting surface such that the metal solidifies from the pool onto the moving casting surface, the casting surface is solid on the heat transfer body. A metal provided with a coating, wherein the coating is formed of a material having a melting temperature higher than the casting surface temperature during solidification of the metal such that the wetting angle of the molten metal at the casting surface is 40 ° or less. Strip continuous casting method. 2. The method of claim 1 wherein the coating is formed of a material such that the molten metal has a wetting angle of 20 ° or less at the casting surface. 3. 3. The method of claim 1 or claim 2, wherein the coated surface has an arithmetic average roughness ( _Ra ) of 10 microns or less. 4. A method according to any of the preceding claims, wherein the molten metal is molten steel. 5. 5. The method of claim 4, wherein the steel solidifies on the casting surface into a single phase solid structure. 6. A method according to any of the preceding claims, wherein the coating material is at least partially amorphous. 7. 7. The method of claim 6, wherein the coating material is essentially completely amorphous. 8. A method according to any of the preceding claims, wherein the coating material comprises a bimetallic alloy. 9. 9. The method of claim 8, wherein one of said two metals comprises phosphorus. 10. The method of claim 9, wherein the other of the two metals is nickel. 11. The method according to any of claims 8 to 10, wherein the alloy is essentially a eutectic alloy. 12. A method as claimed in any of the preceding claims, wherein the molten metal has an essentially eutectic composition. 13. A method according to any of the preceding claims, wherein the heat transfer body is a copper or copper alloy body. 14． A continuous casting method of steel strip of the type in which a molten steel casting pool is formed in contact with a moving casting surface such that the steel solidifies from the pool onto the moving casting surface, wherein the casting surface has a solid coating on the heat transfer body. Wherein the coating is formed of a material having a melting temperature higher than the casting surface temperature during solidification of the metal, such that the wetting angle of the molten metal at the casting surface is 40 ° or less; A continuous metal strip casting process wherein the solidifies on the casting surface into a single phase solid structure, the phase does not transform before the strip leaves the casting surface. 15. 15. The method of claim 14, wherein the steel has a carbon equivalent component of 0.53 wt% or less and the single phase structure comprises dendrites of solid austenite. 16. The method of claim 15 wherein the steel has an essentially peritectic composition. 17. 17. The method of claim 16, wherein the steel has a carbon content of about 0.13% by weight. 18. The method of any of claims 14 to 17, wherein the coating material comprises a bimetallic amorphous alloy. 19. 20. The method of claim 18, wherein one of the two metals comprises phosphorus. 20. 20. The method of claim 19, wherein the coating is a nickel-phosphorous alloy containing about 10% phosphorus. 21. 21. The method according to any of claims 14 to 20, wherein the heat transfer body is a copper or copper alloy body. 22. The moving casting surface is one of a pair of such surfaces, the surfaces of the pair of casting rolls forming a roll gap therebetween, the casting pool is supported on the casting roll above the roll gap, and the strip is 22. A method as claimed in any of claims 14 to 21, wherein the solid tissue is fed down from a roll gap. 23. In a method of continuously casting metal strip of the type formed by contact with a moving casting surface such that the casting pool of molten metal solidifies from the pool onto the moving casting surface, the metal has a peritectic composition and the casting surface Is provided as a solid coating on the heat transfer body, the coating comprising a material having a melting temperature higher than the casting surface temperature during solidification of the metal, such that the wetting angle of the molten metal at the casting surface is 40 ° or less. Wherein the metal solidifies into a single-phase solid structure on the casting surface, the phase not transforming before the strip leaves the casting surface. 24. A casting roll having a casting surface in contact with the casting pool of molten metal, and means for cooling the casting surface of the casting roll to solidify the metal thereon, wherein the roll surface is formed by solid coating of the heat transfer body of the roll Metal strip continuous casting apparatus, wherein the coating comprises an essentially amorphous alloy of two metals. 25. 25. The device of claim 24, wherein one of the two metals comprises phosphorus. 26. 26. The apparatus of claim 25, wherein the coating alloy is a nickel-phosphorous alloy. 27. 27. The apparatus of claim 26, wherein the coating alloy comprises about 10% phosphorus. 28. A casting roll comprising a heat transfer cylindrical roll body covered with a solid coating defining a cylindrical metal casting surface, wherein the coating comprises an essentially amorphous alloy of two metals. 29. 29. The casting roll of claim 28, wherein one of the two metals comprises phosphorus. 30. 30. The casting roll of claim 29, wherein the casting alloy is a nickel-phosphorous alloy. 31. 30. The casting roll of claim 29, wherein the coating alloy comprises about 10% phosphorus. 32. Cast steel strip made from continuous casting from steel having a carbon equivalent content of 0.53 wt% or less and having a microstructure resulting from the direct solidification of molten metal into austenite prior to subsequent low temperature transformation. 33. 33. The cast steel strip of claim 32, wherein the steel has an essentially peritectic composition. 34. 34. The cast steel strip of claim 33, wherein the steel has a carbon content of about 0.13% by weight.