Manufacturing method for Cu-Sn containing steel

Abstract

Provided is a Cu-Sn-containing steel production method that, even during hot working using a heating furnace with low heating performance, prevents trouble in the heating furnace with no surface cracking of Cu-Sn-containing steel and makes stable production possible.　The present invention provides a Cu-Sn-containing steel production method, said method comprising: a hot heating step in which a first flux that at least contains one of the components B2O3, P2O5, K2O, PbO, Na2O-FeO, Na2O-SiO2, Na2O-TiO2, and Li2O-SiO2 and that has a liquid phase ratio of 10 mass% or higher at 1000°C is adhered to the surface of a Cu-Sn-containing cast slab such that the mass per unit area is in the range of 50 g / m2 to 5000 g / m2, a second flux that has a liquid phase ratio of 0 mass% at 1400°C or lower is adhered to the surface of the Cu-Sn-containing cast slab such that the mass per unit area is in the range of 50 g / m2 to 5000 g / m2, and then the Cu-Sn-containing cast slab is heated at a temperature of 1000-1400°C; and a hot working step in which the Cu-Sn-containing cast slab is subjected to hot working.

Description

[Technical Field]

[0001] The present invention relates to a method for producing Cu-Sn containing steel, which can suppress surface cracking of the steel and maintain stable transportation. [Background technology]

[0002] In recent years, the demand for reducing CO2 emissions has increased, and the use of electric furnaces in the steelmaking process has expanded. In order to reduce manufacturing costs in the steelmaking process, it is necessary to use scrap with a high content of tramp elements, especially scrap with a high content of Cu and Sn, as raw materials.

[0003] However, it is difficult to remove the tramp elements during the refining process, and the tramp elements inevitably remain in the steel. In a slab (hereinafter referred to as a "Cu-Sn-containing slab" or simply "slab") in which tramp elements (e.g., Cu, Sn) remain during the refining process, a Cu-Sn molten liquid is generated in the surface layer during the hot heating process, and red shortness caused by the Cu-Sn molten liquid occurs in the hot working process such as rolling, causing cracks (fractures) on the surface of the steel (hereinafter referred to as a "Cu-Sn-containing steel" or simply "slab") that has undergone the hot working process, making it difficult to produce a hot-rolled steel sheet with excellent surface quality.

[0004] It has also been known that adding a certain amount of Ni to Cu-Sn-containing slabs can suppress the precipitation of Cu-Sn-enriched molten metal on the slab surface during high-temperature oxidation of Cu-Sn-containing slabs, which causes surface defects in Cu-Sn-containing steel, and can prevent cracks on the slab surface. However, adding Ni is costly and does not allow for the benefits of using scrap with a high tramp element content to be fully utilized.

[0005] Therefore, since the Cu-Sn molten liquid that causes surface defects in Cu-Sn-containing steel occurs only in the surface layer of Cu-Sn-containing slabs, a method for preventing surface cracks by surface modification of the Cu-Sn-containing slabs has been proposed.

[0006] Patent Document 1 discloses a method of melting the slab surface by plasma heating using a DC arc plasma vibrated by an AC magnetic field, thereby adding Ni only to the surface layer. Patent Document 2 discloses a method of suppressing surface hot shortness by applying a flux containing SiO2 to the surface of a Cu- and Sn-containing continuously cast slab at a slab temperature of 1150°C or higher, thereby generating a scale of FeO-SiO2-based low-melting-point oxide liquid, and incorporating Cu-Sn molten liquid into it. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 5454132 [Patent Document 2] Japanese Patent Application Publication No. 6-297025 Summary of the Invention [Problem to be solved by the invention]

[0008] However, even if the cost of adding Ni can be reduced with the method disclosed in Patent Document 1, the initial investment costs for the AC magnetic field and arc plasma equipment are enormous. Also, the method disclosed in Patent Document 2 has problems such as not being applicable to hot working in a temperature range below 1150°C, and the flux peeling off during transportation, causing the peeled flux to adhere to the fixed and movable beams that transport the slab, making it impossible to maintain stable transportation.

[0009] The present invention has been made in view of the above circumstances, and aims to provide a method for producing Cu-Sn-containing steel that can maintain stable transportation without causing surface cracks in the Cu-Sn-containing steel even during hot working using a heating furnace with low heating capacity. [Means for solving the problem]

[0010] The gist and configuration of the present invention to solve the above problems are as follows. [1] A method for producing Cu-Sn-containing steel, comprising: applying a first flux containing at least any one of B2O3, P2O5, K2O, PbO, Na2O-FeO, Na2O-SiO2, Na2O-TiO2, and Li2O-SiO2, and having a liquid phase ratio of 10 mass% or more at 1000°C, to the surface of a Cu-Sn-containing slab in a manner that the mass per unit area is 50 g / m 2 More than 5000g / m 2 After that, a second flux having a liquid phase ratio of 0 mass% at 1400°C or less was applied to the surface of the Cu-Sn containing slab in a mass per unit area of ​​50 g / m 2 More than 5000g / m 2 a hot heating step of heating the Cu-Sn-containing slab at a temperature of 1000°C to 1400°C, and a hot working step of hot working the Cu-Sn-containing slab. [2] The method for producing a Cu-Sn-containing steel according to [1], wherein the second flux contains at least one of SiO2, MgO, Al2O3, and SiC. [Effects of the Invention]

[0011] According to the present invention, even in hot working using a heating furnace with low heating capacity, surface cracks of Cu-Sn containing steel do not occur and stable transportation can be maintained. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram illustrating the action of a flux on a Cu—Sn melt. [Figure 2] FIG. 2 is a schematic plan view showing the state of conveyance of Cu—Sn-containing slabs in a heating furnace. [Figure 3] FIG. 3 is a diagram showing a state in which the first flux and the second flux are attached to the surface of a Cu—Sn-containing cast piece. [Figure 4] FIG. 4 is a schematic diagram showing an outline of a flux spraying device. DETAILED DESCRIPTION OF THE INVENTION

[0013] A method for carrying out the present invention will be described below. In this embodiment, the term "flux" includes both the "first flux" and the "second flux." When the term "first flux" or "second flux" is used, it means the respective flux.

[0014] First, the behavior of the generation of Cu-Sn molten liquid in the surface layer of a Cu-Sn-containing slab and the flux attached to the surface of the Cu-Sn-containing slab when the Cu-Sn-containing slab is heated to a high temperature and the surface of the Cu-Sn-containing slab is oxidized (hereinafter referred to as a "high-temperature oxidized state") will be described with reference to FIG. 1.

[0015] Figure 1(a) shows a state in which no flux is applied to the surface of a Cu-Sn-containing slab. Figure 1(b) shows a state in which a flux that results in a liquid phase ratio of 80% in a high-temperature atmosphere is applied to the surface of a Cu-Sn-containing slab. Figure 1(c) shows a state in which a flux that results in a liquid phase ratio of 5% in a high-temperature atmosphere is applied to the surface of a Cu-Sn-containing slab.

[0016] Figure 1(a) shows a schematic diagram of the interface between Cu-Sn-containing slabs and scale under high-temperature oxidation conditions. As shown in Figure 1(a), Fe oxidizes more readily than Cu and Sn. Therefore, a scale layer forms on the slab surface, and Cu and Sn concentrate within the slab surface. The melting point of Cu is 1085°C, and the concentration of Sn further lowers this melting point. Therefore, in high-temperature environments above 1000°C, the Cu-Sn-enriched phase becomes liquid, and this liquid (hereinafter referred to as "Cu-Sn liquid") infiltrates the grain boundaries of the Cu-Sn-containing slabs. The Cu-Sn liquid acts as a starting point for embrittlement during hot processing such as rolling, and the greater the amount of liquid, the greater the depth of cracking.

[0017] Figure 1(b) shows a schematic diagram of the interface between a Cu-Sn-containing slab and scale when a flux with a liquid phase ratio of 80% is applied in a high-temperature atmosphere. The scale formed by oxidation reacts with and mixes with the liquid phase of the flux, resulting in a mixed state of flux and scale (mixed phase) on the slab surface, as shown in Figure 1(b). The Cu-Sn molten liquid present in the slab surface layer is then absorbed into the liquid phase of this mixed phase, allowing the Cu-Sn molten liquid to be removed without penetrating the grain boundaries of the Cu-Sn-containing slab.

[0018] Figure 1(c) shows a schematic diagram of the interface between Cu-Sn-containing slabs and scale when a flux with a liquid phase ratio of 5% is applied in a high-temperature atmosphere. In the state shown in Figure 1(c), the flux does not generate a sufficient liquid phase, so the scale that forms on the slab surface does not react sufficiently with the flux and does not mix, resulting in oxidation proceeding. As a result, the slab surface and the flux are separated by the scale, and the Cu-Sn molten liquid penetrates the grain boundaries of the Cu-Sn-containing slabs, similar to the high-temperature oxidation state shown in Figure 1(a).

[0019] 1(a) to 1(c), in order to remove the Cu-Sn molten liquid present in the surface layer of a slab under high-temperature oxidizing conditions, it is necessary to prevent the slab surface from being separated from the flux by scale. In other words, it is necessary to fully liquidize the flux in a high-temperature atmosphere such as a heating furnace.

[0020] Therefore, in the present invention, we focused on a flux (hereinafter referred to as "first flux") containing at least one of B2O3, PO5, KO, PbO, Na2O-FeO, Na2O-SiO2, Na2O-TiO2, and Li2O-SiO2 components, because the liquid phase ratio is 10 mass% or more in a high-temperature atmosphere of 1000°C. Here, "Na2O-FeO" means containing both Na2O and FeO components, "Na2O-SiO2" means containing both Na2O and SiO2 components, "Na2O-TiO2" means containing both Na2O and TiO2 components, and "Li2O-SiO2" means containing both Li2O and SiO2 components, respectively.

[0021] The liquid fraction of the flux may be confirmed using an equilibrium diagram obtained by experiment or thermodynamic calculation. Alternatively, the liquid fraction may be evaluated by holding the sample at a predetermined temperature to achieve thermodynamic equilibrium, then freezing the sample by water cooling or other methods to obtain a cross-section of the sample.

[0022] The composition of the first flux is such that the liquid phase ratio at 1000°C is 10 mass% or more, and in addition to containing at least any of the aforementioned components B2O3, PO5, KO, PbO, Na2O-FeO, Na2O-SiO2, Na2O-TiO2, and Li2O-SiO2, it may further contain unavoidably mixed oxides, fluorides, carbonates, and metal components.

[0023] Furthermore, even if the flux is primarily composed of SiO2, CaO, Li2O, Na2O, F, MgO, Al2O3, etc., and is known as a mold flux for continuous casting, it can be used as the first flux as long as the liquid phase ratio at 1000°C is 10 mass% or more.

[0024] The base material of the first flux containing at least any of the aforementioned components B2O3, P2O5, K2O, PbO, Na2O-FeO, Na2O-SiO2, Na2O-TiO2, and Li2O-SiO2 may be an oxide, carbonate, fluoride, etc. These base materials may be mixed, or the flux may be pre-melted and applied to the surface of the Cu-Sn-containing slab.

[0025] Next, the transport state of the Cu-Sn-containing slab will be described with reference to Fig. 2. Fig. 2 is a schematic plan view showing the transport state of the Cu-Sn-containing slab S in a heating furnace. As shown in Fig. 2, a fixed beam 11 and a movable beam 12 are provided in the heating furnace to transport the Cu-Sn-containing slab S in a transport direction A.

[0026] In a heating furnace, when a Cu-Sn-containing slab S is placed on the upper surface (skid) of the fixed beam 11 and the movable beam 12, the movable beam 12 periodically rotates relative to the fixed beam 11, whose position is fixed, within a movable range in the vertical direction and the transport direction A. Therefore, the Cu-Sn-containing slab S is moved (transported) along the transport direction A by the periodic rotation of the movable beam 12.

[0027] Here, when a Cu-Sn-containing slab S with a first flux attached to its surface is placed on the upper surface (skid) of the fixed beam 11 and the movable beam 12, in a heating furnace with a temperature range of 1000°C to 1400°C, the liquid phase first flux may peel off from the Cu-Sn-containing slab S and adhere to the surfaces of the fixed beam 11 and the movable beam 12. Then, when the number of times the Cu-Sn-containing slab S is transported increases, the amount of the first flux attached becomes non-uniform at each position on the fixed beam 11 and the movable beam 12, causing the Cu-Sn-containing slab S to tilt in the height direction.

[0028] For this reason, during transportation of the Cu-Sn-containing slab S, displacement occurs in the width direction B, which is a direction perpendicular to the transportation direction A, and stable transportation of the Cu-Sn-containing slab S may become difficult. Furthermore, if the displacement of the Cu-Sn-containing slab S in the width direction B becomes large, problems such as the Cu-Sn-containing slab S falling in the heating furnace may occur.

[0029] In the manufacturing method of Cu-Sn-containing steel according to this embodiment, in order to prevent the first flux from adhering to the fixed beam 11 and the movable beam 12, another flux (hereinafter referred to as "second flux") having a higher melting point than the first flux is applied on top of the first flux.

[0030] Specifically, by applying the second flux, which has a liquid phase ratio of 0 mass% at 1400°C or less, onto the first flux, it is possible to prevent the first flux from adhering to the fixed beam 11 and the movable beam 12 in a heating furnace with a temperature range of 1000°C to 1400°C. In addition, the second flux preferably contains at least one of SiO2, MgO, Al2O3, and SiC, because the second flux has low reactivity with the first flux and fluctuations in its composition as a flux are suppressed.

[0031] Here, the states of the first flux and the second flux in the hot heating step will be described with reference to Fig. 3. Fig. 3 is a diagram showing the behavior of the first flux and the second flux on the surface of a Cu-Sn-containing slab in the hot heating step.

[0032] In the hot heating process, the Cu-Sn-containing slab is heated at a temperature of 1000°C or higher and 1400°C or lower. The first flux, which has a liquid phase ratio of 10 mass% or higher at 1000°C, undergoes liquid phase transformation on the surface of the Cu-Sn-containing slab. As a result, scale formed by oxidation reacts with and mixes with the liquid phase of the first flux, resulting in a mixed state of the first flux and scale on the surface of the Cu-Sn-containing slab, as shown in FIG. 3. On the other hand, the second flux, which has a liquid phase ratio of 0 mass% at 1400°C or lower, does not undergo liquid phase transformation and remains in a flux state on the surface of the first flux where liquid phase transformation is progressing.

[0033] Therefore, the Cu-Sn molten liquid present in the surface layer of the Cu-Sn-containing slab is captured in the liquid phase of the mixed phase (first flux and scale), and can be removed without infiltrating the grain boundaries of the Cu-Sn-containing slab. As a result, surface cracking of the Cu-Sn-containing steel can be suppressed even during hot working using a heating furnace with low heating capacity.

[0034] Furthermore, the second flux is not liquefied and remains in a flux state on the surface of the first flux, preventing the first flux from adhering to the surfaces of the fixed beam 11 and the movable beam 12. Therefore, while the Cu-Sn-containing slab is being transported in the heating furnace, the first flux and the second flux are not peeled off and remain on the surface of the Cu-Sn-containing slab. As a result, during the transport of the Cu-Sn-containing slab, positional deviation in the width direction, which is the direction perpendicular to the transport direction, can be suppressed, and stable transport can be maintained.

[0035] Although the present embodiment has described a method of applying the second flux onto the first flux to prevent the first flux from adhering to the fixed beam 11 and the movable beam 12 in the heating furnace, the same effect can be obtained for the Cu-Sn-containing slab S after it has been extracted from the heating furnace. That is, even when the Cu-Sn-containing slab S that has been subjected to the hot heating step is extracted from the heating furnace and then transported by transport rollers or the like, the first flux can be prevented from adhering to the transport rollers.

[0036] As shown in Fig. 3, in the hot heating step, the first flux, which has turned into a liquid phase, and the second flux, which has not turned into a liquid phase, are adhered to the surface of the Cu-Sn-containing slab. Therefore, after the hot heating step, an oxide removal step for descaling the scale on the surface of the Cu-Sn-containing slab may be performed to remove the scale and the first flux and the second flux that have absorbed the Cu-Sn molten liquid. Thereafter, a hot working step for hot working the Cu-Sn-containing slab may be performed.

[0037] The method for applying (supplying) the flux to the Cu-Sn-containing slab does not necessarily need to be limited to a specific method, and may be carried out by any suitable method such as coating or spraying. The flux may be in the form of a powder or a slurry. It may be dissolved or suspended in water or other liquid and then applied. It may also be mixed with an inorganic or organic mixed polymer or solvent, as in common coating agents.

[0038] Next, the flux supply device 10 will be described with reference to FIG. 4. FIG. 4 is a schematic diagram showing an overview of the flux supply device 10. As shown in FIG. 4, to supply flux 4, a slab 1 is placed on rollers 3 for placement or transport. The flux supply device 10 has spray guns 2 arranged above and below the slab 1 placed on the rollers 3 to uniformly supply flux 4 to the surface of the slab 1. Flux powder 5 and spray air 6 are mixed and supplied to the spray gun 2 through a supply pipe 7. The amount of flux 4 adhered to the surface of the slab 1 can be adjusted by controlling the supply amount of flux 4 and the transport speed through the supply pipe 7.

[0039] The flux 4 may be applied to the underside of the slab 1 that comes into contact with the rollers 3 by using a slab turnover device to turn the slab 1 over and then applying the flux 4 to the upper surface, or by supplying the flux from a spray gun 2 provided on the underside of the slab 1 while the slab 1 is moving on the rollers 3. The flux 4 may be in powder form when applied as a paint. When applied in a flocculent form, it may be applied using an adhesive.

[0040] The application (supply) of flux to the slab 1 may be performed by applying a first flux to the slab 1 and then applying a second flux on top of the first flux. The application of the first and second fluxes to the slab 1 may also be performed before a hot heating step in which the slab 1 is hot heated.

[0041] The amount of the first flux applied to the slab surface was set to 50 g / m2 on the surface of the Cu-Sn-containing slab. 2 More than 5000g / m 2 The amount of the first flux applied is preferably 50 g / m or less. 2 If the coating weight of the first flux is less than 5000 g / m, the first flux cannot sufficiently take in the Cu-Sn melt, which is undesirable because cracks occur on the surface of the steel billet after hot working. 2If the amount exceeds this, the excessively supplied first flux will adhere to the roller 3 and the like, causing early deterioration of the flux supply device 10, and economic problems such as increased costs will also occur due to the excessive supply of the first flux, which is not preferable.

[0042] The amount of second flux applied was set to 50 g / m2 on the surface of the Cu-Sn-containing slab. 2 More than 5000g / m 2 The amount of the second flux applied is preferably 50 g / m or less. 2 If the amount of the second flux is less than 5000 g / m, it is not possible to reliably prevent the liquefied first flux from adhering to the fixed beam 11 and the movable beam 12, which is not preferable. 2 If the amount exceeds 100%, the excessively supplied second flux will adhere to the roller 3 and the like, causing early deterioration of the flux supply device 10, and economic problems such as increased costs will also occur due to the excessive supply of the second flux, which is not preferable.

[0043] The slab (Cu-Sn-containing slab) to which the flux is supplied is heat-treated at a temperature of 1000°C or higher and 1400°C or lower, and then subjected to hot rolling (hot working). A heating temperature lower than 1000°C is undesirable because it increases the deformation resistance during hot working, resulting in a decrease in rolling efficiency. A heating temperature higher than 1400°C is undesirable because it may not be possible to obtain the desired steel material properties. The heating temperature for the slab (Cu-Sn-containing slab) is more preferably 1000°C or higher and 1300°C or lower. [Example]

[0044] Hereinafter, an example in which a Cu-Sn containing steel was produced based on the method for producing a Cu-Sn containing steel according to this embodiment will be described.

[0045] As an example of the invention, first, the first flux and the second flux were applied 50,000 times to the surface of a Cu-Sn-containing cast slab (carbon steel) having a Cu content of 1.0 mass% and an Sn content of 0.1 mass%, and then the slab was charged into a heating furnace and heated (hot heating) for 1 to 5 hours at an atmospheric temperature of 1000°C to 1400°C. Next, as hot processing, the heated Cu-Sn-containing cast slab was subjected to rough rolling and finish rolling to produce a Cu-Sn-containing steel (hot-rolled steel plate) with a plate thickness of 2.3 mm.

[0046] As comparative examples, a case was conducted in which only the first flux was applied to the surface of a similar Cu-Sn-containing cast slab (carbon steel) and hot heating and hot working were performed, and a case was conducted in which hot heating and hot working were performed to the surface of a similar Cu-Sn-containing cast slab (carbon steel) without applying a flux.

[0047] The components and liquid fraction of the first flux used in the examples are shown in Table 1. The components and liquid fraction of the second flux are shown in Table 2. The liquid fraction of the flux was confirmed by the following method. First, 10 g of a sample obtained by mixing the components of the first flux shown in Table 1 was added to a platinum crucible and melted in an electric resistance furnace at 1600°C for 1 hour, and then held at 1000°C for 48 hours. The sample was then frozen by water-cooling the side of the platinum crucible holding the sample. The sample was cut so that it was semicircular when viewed from above the platinum crucible, and the cross-section of the frozen sample was observed with an optical microscope and the cross-sectional liquid fraction was measured by image analysis. The liquid fraction of the second flux was also measured in the same manner, except for the mixing of the components.

[0048] [Table 1]

[0049] [Table 2]

[0050] In the inventive and comparative examples, the transport state of the Cu-Sn-containing slab after hot heating was evaluated. The transport state was evaluated by evaluating the state of the heated Cu-Sn-containing slab after it was extracted from the heating furnace and then transported on multiple rollers. Specifically, the Cu-Sn-containing slab extracted from the heating furnace was placed on multiple rollers and transported on the multiple rollers at a transport speed of 100 mm / s, and the arrival time at a predetermined position on the transport path was measured. Arrival of the Cu-Sn-containing slab at the predetermined position was determined by detection using a laser rangefinder installed at the predetermined position. The arrival time of the Cu-Sn-containing slab was measured by measuring the time between the start time of transport on the multiple rollers and the time of arrival at the predetermined position. For each example, transport on the rollers was performed 10 times, and the average value was used as the time length for that example.

[0051] The conveying condition was evaluated by comparing the time length when a Cu-Sn-containing slab without flux coating on its surface was conveyed with the time length in the example in which flux was applied to the Cu-Sn-containing slab. A time difference of less than 1 second was evaluated as "good," and a time difference of 1 second or more was evaluated as "poor." A time difference of 1 second or more corresponds to a positional deviation (100 mm) of the Cu-Sn-containing slab in the width direction perpendicular to the conveying direction.

[0052] The Cu-Sn containing steel produced in this example was also investigated (evaluated) for surface cracks. The investigation (evaluation) of surface cracks was confirmed by the following method. First, 10 pieces of Cu-Sn containing steel, each 1 m wide and 1 m long, were sampled at random in the rolling direction, and the 1 m x 1 m area (surface) of each sheet was divided into 100 equal squares every 100 mm. Next, the number of squares where cracks occurred was counted, and the 1 m 2 The number of hits was calculated and the results of 10 pieces were averaged. The crack occurrence frequency was 0.3 pieces / m 2 A crack occurrence frequency of 0.3 pieces / m or less is evaluated as "good." 2 When the value exceeded 100%, the sample was evaluated as "poor." The results of the examples are shown in Table 3.

[0053] [Table 3]

[0054] As shown in Table 3, Comparative Example 2 is an example in which transportation and hot working were performed without applying flux to the surface of the Cu-Sn-containing slab. As the "transportation state" was evaluated as "good," it was confirmed that the liquid phase flux did not adhere to the transport rollers, and transportation was performed smoothly so that the time length between the start of transportation and the arrival time at the designated position was minimized. That is, the transportation state was evaluated based on this example (Comparative Example 2), and the transportation states of the other examples were evaluated. Since Comparative Example 2 did not apply the first flux, the "crack occurrence state" was evaluated as "poor."

[0055] As shown in Table 3, the first flux was applied to the surface of the Cu-Sn containing slab in Examples 1 to 3 and Comparative Example 1. The applied amount of the first flux was 400 g / m per unit area on the surface of the Cu-Sn containing slab. 2 The amount of adhesion was determined as follows. In Comparative Example 1, the first flux was applied, but the second flux was not applied. As a result, the liquidized first flux adhered to the transport roller, and the time length between the start of transport and the arrival at the specified position was longer than that in Comparative Example 2, resulting in the evaluation of the transport state being "poor." On the other hand, in Comparative Example 1, the first flux was applied, so the "occurrence of cracks" was evaluated as "good."

[0056] Inventive Examples 1 to 3, a first flux was applied to a Cu-Sn containing slab, and a second flux was then applied on top of the first flux. In Inventive Examples 1 to 3, the amount of the second flux applied was 100 to 4000 g / m per unit area on the surface of the Cu-Sn containing slab. 2Therefore, during the hot heating stage, the first flux liquefied and absorbed the Cu-Sn melt, while the second flux did not liquefy, preventing the first flux from adhering to the transport rollers. Therefore, the transport condition was evaluated as "good," and Cu-Sn-containing steel could be stably manufactured without any trouble during transport. In addition, since the first flux was applied to invention examples 1 to 3, the "occurrence of cracks" was also evaluated as "good." [Explanation of symbols]

[0057] 1. Castings 2 spray guns 3 Rollers 4. Flux 5 Flux powder 6. Injection air 7 Supply piping 10 Flux supply device 11 Fixed beam 12 Movable beam A Conveying direction S Cu-Sn containing slab

Claims

1. A method for producing a Cu—Sn-containing steel, comprising: B ２ O ３ , P ２ O ５ , K. ２ O, PbO, Na ２ O—FeO, Na ２ O—SiO ２ , Na ２ O-TiO ２ , Li ２ O—SiO ２ The first flux containing at least any one of the components and having a liquid phase ratio of 10 mass% or more at 1000 ° C. is applied to the surface of the Cu-Sn-containing slab in such a manner that the mass per unit area is 50 g / m ２ More than 5000g / m ２ After that, a second flux having a liquid phase ratio of 0 mass% at 1400°C or less was applied to the surface of the Cu-Sn-containing slab in a mass per unit area of ​​50 g / m ２ More than 5000g / m ２ a hot heating step of heating the Cu—Sn-containing slab at a temperature of 1000° C. or higher and 1400° C. or lower; a hot working step of hot working the Cu—Sn-containing slab; A method for producing a Cu—Sn-containing steel having the above formula.

2. The second flux is SiO ２ , MgO, Al ２ O ３ 2. The method for producing a Cu-Sn-containing steel according to claim 1, wherein the Cu-Sn-containing steel contains at least one of the components SiC and SiC.

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