Retort manufacturing method, retort, and rotary kiln

Abstract

Provided are a method for manufacturing a retort using an Ni-based alloy containing 2.0% by weight or more of Al, a retort employing the Ni-based alloy, and a rotary kiln provided with the retort. A retort manufacturing method according to the present invention is a method for manufacturing a retort by plasma-welding a joint part of a base material made of an Ni-based alloy, without using a filler. The retort of the present invention comprises a base material made of an Ni-based alloy containing 90.0 % by weight or more of Ni and 2.0 % by weight or more of Al, and a weld metal portion generated at a joint part of the base material, wherein the base material comprises a heat affected zone generated around the weld metal portion, and a base material portion, which is the part of the base material other than the heat affected zone, and a value obtained by (formula 1) (average crystal grain size of heat affected zone / average crystal grain size of base material portion) × 100 is 100 to 300%, and / or the average crystal grain size of the heat affected zone is less than 250 μm. The rotary kiln of the present invention is provided with the retort of the present invention.

Description

Retort manufacturing method, retort and rotary kiln

[0001] The present invention relates to a retort manufacturing method, a retort, and a rotary kiln.

[0002] A rotary kiln equipped with a retort (heating furnace) (see, for example, Patent Document 1) is used to heat treat various materials to be treated, including powder.

[0003] Among the materials that are heat-treated using a rotary kiln, there are some that are sintered in an oxidizing atmosphere, such as the positive electrode material of lithium-ion batteries, and there is a demand for the development of a retort that has excellent oxidation resistance at high temperatures (hereinafter referred to as "high-temperature oxidation resistance").

[0004] Known materials with excellent high-temperature oxidation resistance include nickel-based alloys (Ni-based alloys) containing, by weight, 2.0 to 5.0% aluminum (Al), 0.1 to 2.5% silicon (Si), 0.8 to 4.0% chromium (Cr), 0.1 to 1.5% manganese (Mn), 0.001 to 0.01% boron (B), 0.001 to 0.1% zirconium (Zr), with the remainder being nickel (Ni) and unavoidable impurities (Patent Document 2).

[0005] Another known material having excellent high-temperature oxidation resistance is a Ni-based alloy containing, by weight, 2.0 to 5.0% Al, 0.1 to 2.5% Si, 0.1 to 1.5% Mn, 0.001 to 0.01% B, 0.001 to 0.1% Zr, with the remainder being Ni and unavoidable impurities (Patent Document 3).

[0006] JP 2011-080740 A JP 2014-080675 A JP 2015-045035 A

[0007] However, since Al has a lower melting point than other contained components, Ni-based alloys containing a large amount of Al (2.0 wt % or more), such as the Ni-based alloys of Patent Documents 2 and 3, are difficult to weld, and the reality is that retorts using such Ni-based alloys are not distributed on the market.

[0008] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for manufacturing a retort using a Ni-based alloy containing 2.0% by weight or more of Al, a retort using a Ni-based alloy containing 2.0% by weight or more of Al, and a rotary kiln equipped with the retort.

[0009] [Retort Manufacturing Method] The retort manufacturing method of the present invention is a method for manufacturing a retort for a rotary kiln, in which a retort is manufactured by plasma welding, without using a filler, joints of a base material made of a Ni-based alloy containing 90.0 wt % or more of Ni and 2.0 wt % or more of Al (aluminum).

[0010] [Retort] The retort of the present invention is a retort for a rotary kiln, and comprises a base material made of a Ni-based alloy containing 90.0% by weight or more of Ni and 2.0% by weight or more of Al, and a weld metal zone formed at a joining point of the base material, wherein the base material comprises a heat-affected zone formed around the weld metal zone and a base material portion which is a portion of the base material other than the heat-affected zone, and the value obtained by (Equation 1) (average crystal grain size in the heat-affected zone / average crystal grain size in the base material portion) × 100 is 100 to 300%, and / or the average crystal grain size in the heat-affected zone is less than 250 μm.

[0011] In the present invention, a Ni-based alloy containing 2.0 to 5.0 wt % of Al can be used as the base material.

[0012] In the present application, a Ni-based alloy containing 90.0 wt % or more of Ni and 2.0 wt % or more of Al, as well as 0.1 to 2.5 wt % of Si, 0.1 to 1.5 wt % of Mn, 0.001 to 0.01 wt % of B, and 0.001 to 0.1 wt % of Zr can also be used as the base material.

[0013] In the present application, as the base material, a Ni-based alloy containing 90.0 wt% or more of Ni and 2.0 wt% or more of Al, as well as 0.1 to 2.5 wt% of Si, 0.8 to 4.0 wt% of Cr, 0.1 to 1.5 wt% of Mn, 0.001 to 0.01 wt% of B, and 0.001 to 0.1 wt% of Zr can also be used.

[0014] [Rotary Kiln] The rotary kiln of the present invention is equipped with the retort of the present invention.

[0015] According to the present invention, a retort using a Ni-based alloy having excellent high-temperature oxidation resistance can be provided.

[0016] (a) to (c) show an example of a manufacturing process for cylindrical parts. (a) to (d) show an example of a manufacturing process for retorts. (a) to (d) show an example of a rotary kiln. (b) A conceptual diagram of the joints of a retort.

[0017] (Definitions of Terms Used in the Present Application) Prior to describing the embodiments of the present invention, definitions of major terms used in the present application will be explained. In the present application, the term "weld" refers to a portion including a weld metal portion and a heat-affected zone. Here, the term "weld metal portion" refers to a fusion zone and a weld metal portion, and the term "heat-affected zone" refers to an unmelted portion of the base material where changes in structure, metallurgical properties, mechanical properties, etc. have occurred due to heat from welding, cutting, etc.

[0018] The term "fused zone" refers to the melted portion of the base material, and the term "welded metal zone" refers to the metal transferred from the filler metal to the weld zone. In this application, the term "base metal zone" refers to the portion of the base material other than the heat-affected zone.

[0019] In addition, in this application, the term "crystal" refers to a solid substance in which atoms or ions are arranged in a periodic three-dimensional lattice pattern, the term "crystal grain" refers to an individual crystal in a substance made up of a collection of fine crystals, such as a crystalline solid such as a metal or ceramic, and the term "average crystal grain size" refers to the average grain size of the crystal grains contained in a metal. Hereinafter, the embodiments of this application will be described using these terms.

[0020] (Embodiment of Retort Pouch Manufacturing Method) First, an example of a retort pouch manufacturing method of the present invention will be described. In the retort pouch manufacturing method of this embodiment, a cylindrical component (hereinafter referred to as a "cylindrical part") 10a that constitutes a retort pouch 10 is manufactured in the manner shown in Figures 1(a) to 1(c).

[0021] The cylindrical part 10a can be manufactured by bending a plate-shaped base material 11 into a cylindrical shape so that both end faces face each other, and then welding the joints of the two end faces. The bending of the base material 11 can be performed using existing equipment and a conventional method.

[0022] The base material 11 can be made of a nickel-based alloy (Ni-based alloy) containing 90.0% by weight or more of nickel (Ni) and 2.0% by weight or more of aluminum (Al).

[0023] Specifically, in addition to 90.0% by weight or more of Ni and 2.0% by weight or more of Al, one or more of silicon (Si), manganese (Mn), boron (B), zirconium (Zr), and chromium (Cr) can be used.

[0024] For example, the alloy may contain 90.0% by weight or more of Ni and 2.0 to 5.0% by weight of Al, as well as 0.1 to 2.5% by weight of Si, 0.1 to 1.5% by weight of Mn, 0.001 to 0.01% by weight of B, and 0.001 to 0.1% by weight of Zr.

[0025] In addition, for example, a material containing 90.0 wt% or more Ni and 2.0 to 5.0 wt% Al, as well as 0.1 to 2.5 wt% Si, 0.8 to 4.0 wt% Cr, 0.1 to 1.5 wt% Mn, 0.001 to 0.01 wt% B, and 0.001 to 0.1 wt% Zr can be used. The components and content ratios of the Ni-based alloy shown here are merely examples, and other components and content ratios may be used.

[0026] The welding of the joints can be performed, for example, by a method using plasma (plasma welding). In general plasma welding, a filler metal is used during welding, but in the retort manufacturing method of this embodiment, plasma welding is performed without using a filler metal.

[0027] When a filler is used, the filler needs to be melted, which increases the output and the spraying time. As the output increases and the spraying time increases, the crystal grains in the heat-affected zone 11a become larger, and the difference in average crystal grain size between the base material 11 and the heat-affected zone 11a increases. When the difference in average crystal grain size between the base material 11 and the heat-affected zone 11a increases, the mechanical strength decreases, and cracks may occur when the material is bent.

[0028] In this regard, when plasma welding is performed without using a filler as in this embodiment, the output can be reduced and the spraying time can be shortened, thereby suppressing the enlargement of the crystal grains in the heat-affected zone 11a and minimizing the difference in average crystal grain size between the base material 11 and the heat-affected zone 11a, and as a result, the occurrence of cracks when bending can be suppressed.

[0029] Furthermore, unlike electron beam welding, plasma welding does not require a chamber to place the workpiece in. This has the advantage that it can weld large workpieces (such as a retort 10 with a diameter of 1700 mm and a length of 2000 mm) that cannot be welded using electron beam welding.

[0030] After welding, the joint can be reinforced. The welding material (welding rod) for the reinforcement can be the same material as the base material 11, or a different material. An example of a material different from the base material 11 is TIG617 (corresponding to JIS SNi6617). It is preferable to use a welding rod that has excellent strength at high temperatures and high-temperature oxidation resistance. Reinforcement can be performed as needed, and can be omitted if not required.

[0031] After manufacturing a plurality of tubular parts 10a in the above manner, they are used to complete a retort 10 of a desired length. Specifically, as shown in Figures 2(a) to 2(d), two or more tubular parts 10a are arranged so that their internal spaces are in communication with each other and their end faces face each other, and the joints at the end faces of the butted tubular parts 10a are welded.

[0032] The tubular parts 10a can be welded together using the same welding method as used to manufacture the tubular parts 10a described above. As with manufacturing the tubular parts 10a, in this case too, excess filler can be applied to the molten parts as needed. Thereafter, multiple tubular parts 10a are joined in the same manner as described above to complete the retort shell 10 of the desired length.

[0033] The retort pouch manufacturing method of the present invention is merely an example, and the retort pouch manufacturing method of the present invention is not limited to this embodiment. The retort pouch manufacturing method of the present invention can be modified, such as by replacing, adding, or omitting steps, within the scope of achieving the intended object.

[0034] (Embodiments of Retort and Rotary Kiln) Next, an example of a retort 10 and a rotary kiln 100 of the present invention will be described. As an example, the rotary kiln 100 shown in Fig. 3 is a so-called externally heated rotary kiln 100, and includes, as its main components, a retort 10, an outer cylinder 20 provided on the outer periphery of the retort 10, a supply section 30 provided on one end side of the retort 10 in the longitudinal direction, and a discharge section 40 provided on the other end side.

[0035] The outer cylinder 20 is a part that heats the retort 10, the supply unit 30 is a part that supplies the object to be heat-treated into the retort 10, and the discharge unit 40 is a part that discharges the object to be heat-treated and gas generated during the heat treatment to the outside. Existing parts can be used for the outer cylinder 20, the supply unit 30, and the discharge unit 40.

[0036] The retort 10 is a furnace (heating furnace) for heating an object to be heat-treated. The retort 10 is rotatably supported by a support device 50. The retort 10 includes a plurality of tubular parts 10a that are aligned in the longitudinal direction and welded together. The tubular parts 10a can be manufactured, for example, by the method described in the embodiment of the retort manufacturing method described above (a method of plasma welding without using a filler).

[0037] The retort 10 of this embodiment uses the above-mentioned Ni-based alloy as the base material 11. The Ni-based alloy has already been described in the embodiment of the method for manufacturing a retort, and therefore, description thereof will be omitted here.

[0038] 4 is a conceptual diagram of the joining points of the retort shell 10. The joining points here include the opposing end faces of the tubular part 10a that are bent into a cylindrical shape during production, as well as the butted end faces of two adjacent tubular parts 10a.

[0039] 4, the joining location of the tubular part 10a of this embodiment includes a base material 11 and a weld metal portion 12, and a heat-affected zone 11a is present in the region of the base material 11 adjacent to the weld metal portion 12. In addition, an extra reinforcement portion 13 is formed on the upper surface side of the weld metal portion 12.

[0040] One of the features of the retort shell 10 of this embodiment is that the value obtained by the following formula 1 is 100 to 300%: (average grain size of heat-affected zone / average grain size of base material)×100 (formula 1)

[0041] According to a comparative test described below, the value obtained by the above formula 1 was 335% when plasma welding was performed using a filler, while it was 237% when plasma welding was performed without using a filler.

[0042] In the former, the value obtained by the formula 1 was 335%, and many cracks were confirmed in the bending test, whereas in the latter, the value obtained by the formula 1 was 237%, and no cracks were confirmed in the bending test.

[0043] For this reason, when the value obtained by Equation 1 is in the range of 100 to 300%, as in the case of the retort shell 10 of this embodiment, there is significance at least in bending strength compared to retort shells outside this range.

[0044] In the present application, the average grain size of the base material 11 and the heat-affected zone 11a was measured by the following method. This measurement method is based on JIS G 0551, Appendix A (Evaluation of grain size), except that the number of grains captured in the circular area observed in the micrograph was set to 10. The specific measurement method is as follows.

[0045] (1) An electron microscope is used to photograph an area including the joint and the base material 11, and a micrograph is obtained that includes the heat-affected zone 11a and the base material portion 11b of the base material 11. (2) An observation circle is set on the micrograph obtained in (1) at a magnification of 100 times, and the number of particles within the observation circle is defined as n1, and the number of particles intersecting the circumference of the circle is defined as n2, to determine the number of equivalent crystal grains n 100 The number of equivalent crystal grains n is calculated using the following formula (2). 100 The calculation is performed for each of the heat-affected zone 11a and the base material zone 11b. 100 = n1 + n2 / 2 (Equation 2) (3) Next, a 1 mm2 particle on the surface of the test piece at a magnification of 100 times in the micrograph was 2 The number of crystal grains per unit area, m, is calculated using the following formula (3): m = 2 × n 100(4) Using the values ​​obtained in (2) and (3), the average crystal grain size d is calculated using the following formula (4): d = 1 / √m (Formula 4)

[0046] The method for measuring the average crystal grain size described here is merely an example, and the average crystal grain size can also be measured by other methods.

[0047] In addition to the above-mentioned features, another feature of the retort shell 10 of this embodiment is that the average crystal grain size of the heat-affected zone 11a is less than 250 μm, preferably less than 200 μm.

[0048] According to a comparative test described later, the average crystal grain size of the heat-affected zone 11a when plasma welding was performed using a filler was 277 μm, while the average crystal grain size of the heat-affected zone 11a when plasma welding was performed without using a filler was 158 μm.

[0049] In the former, in which the average crystal grain size of the heat-affected zone 11a was 277 μm, numerous cracks were observed in the bending test, whereas in the latter, in which the average crystal grain size of the heat-affected zone 11a was 158 μm, no cracks were observed in the bending test.

[0050] For this reason, when the average crystal grain size of the heat-affected zone 11a is less than 250 μm, preferably less than 200 μm, as in the retort 10 of this embodiment, there is significance at least in bending strength compared to those that do not meet this numerical value.

[0051] The retort 10 and rotary kiln 100 of the present embodiment are merely examples, and the retort 10 and rotary kiln 100 of the present invention are not limited to this embodiment. The retort 10 and rotary kiln 100 of the present invention can be modified, such as by appropriately replacing, adding, or omitting components, as long as the intended purpose can be achieved.

[0052] (Experimental Example) The applicant of the present invention conducted a comparative test using a plurality of test pieces to verify the effects of the retort pouch 10 manufactured by the retort pouch manufacturing method of the present invention. The outline and results of the comparative test are as follows.

[0053] - Overview of Comparative Test - Three test pieces shown in Table 1 were prepared, and a tensile test, a bending test, and a micro test were performed on each test piece.

[0054] As shown in Table 1, the examples are test pieces welded in the same manner as the retort manufacturing method, in which a Ni-based alloy (Ni-2Cr-4Al-1.5Si-0.5Mn) was plasma welded without using a filler, and an overfill was applied to the fusion zone. A TIG617 (JIS SNi6617 equivalent) welding rod was used for the overfill.

[0055] In Comparative Example 1, the same Ni-based alloy (Ni-2Cr-4Al-1.5Si-0.5Mn) as in the Example was plasma welded using a filler, and an overfill was applied to the fusion zone. The filler was the same Ni-based alloy (Ni-2Cr-4Al-1.5Si-0.5Mn) as the base material, and the welding rod for the overfill was the same Ni-based alloy (Ni-2Cr-4Al-1.5Si-0.5Mn) as the base material.

[0056] In Comparative Example 2, the same Ni-based alloy (Ni-2Cr-4Al-1.5Si-0.5Mn) as in the Example was electron beam welded without using a filler, and an overfill was applied to the fusion zone. The same Ni-based alloy (Ni-2Cr-4Al-1.5Si-0.5Mn) as the base material was used as the welding rod for the overfill.

[0057] In the tensile test, the tensile strength (N / mm 2 The tensile test was carried out in accordance with JIS Z3121 using a JIS Z3121 No. 1A test piece.

[0058] In the bending test, cracks during front bending and reverse bending were measured, and photographs were taken during front bending and reverse bending. The bending test was performed in accordance with JIS Z3122 using a JIS Z3122 No. 1A test piece.

[0059] In the micro test, the average grain size (μm) of the heat-affected zone and the average grain size (μm) of the base material were measured, and the values ​​were calculated by applying these values ​​to the above-mentioned formula 1. The micro test was carried out in accordance with JIS Z3122 using a JIS Z3122 No. 1A test piece.

[0060] - Results of the comparative test - Table 2 shows the results of the comparative test.

[0061] [Tensile test] As shown in Table 2, the tensile strength of the example was 643 N / mm 2 The tensile strength of Comparative Example 1 is 811 N / mm 2 The tensile strength of Comparative Example 2 is 670 N / mm 2 The joint efficiency of the example was 95.3%, the joint efficiency of the comparative example 1 was 120.1%, and the joint efficiency of the comparative example 2 was 99.3%.

[0062] [Regarding the bending test] As shown in Table 2, no cracks occurred in either the front bending or the back bending in Example and Comparative Example 2. On the other hand, in Comparative Example 1, many cracks were observed during the front bending.

[0063] [Regarding Micro Tests] As shown in Table 2, in the example, the average grain size of the heat-affected zone was 158 μm and the average grain size of the base material was 67 μm. Furthermore, the value obtained by applying these values ​​to the above-mentioned formula 1 was 237%, which was within the range of 100 to 300%.

[0064] In Comparative Example 1, the average grain size of the heat-affected zone was 277 μm and the average grain size of the base material was 83 μm. Furthermore, the value obtained by applying these values ​​to the above-mentioned formula 1 was 335%, which was not within the range of 100 to 300%.

[0065] In Comparative Example 2, the average grain size of the heat-affected zone was 69 μm, and the average grain size of the base material was 68 μm. The value obtained by applying these values ​​to the formula 1 was 102%, which was within the range of 100 to 300%.

[0066] From the results of this comparative test, it was confirmed that in the test piece (Comparative Example 1) that was plasma welded using a filler, the crystal grains in the heat-affected zone 11a became enlarged, the difference in average crystal grain size between the heat-affected zone 11a and the base material portion 11b became larger, and cracks occurred in the bending test due to the increase in the difference in average crystal grain size between the heat-affected zone 11a and the base material portion 11b.

[0067] On the other hand, in the test pieces (embodiments) that were plasma welded without using a filler, it was confirmed that the enlargement of the crystal grains in the heat-affected zone 11a was suppressed, the difference in average crystal grain size between the heat-affected zone 11a and the base material portion 11b did not become large, and the difference in average crystal grain size between the heat-affected zone 11a and the base material portion 11b did not become large, so that cracks did not occur in the bending test.

[0068] Note that the same results as in the example were obtained with a test piece (Comparative Example 2) that was electron beam welded without using a filler. However, electron beam welding requires a chamber to contain the workpiece, and it is not practical to prepare a chamber that can contain a large retort. Therefore, for the manufacture of large retorts, a method of plasma welding without using a filler is preferable.

[0069] The retort 10 and its manufacturing method of the present invention can be used for various purposes, but are particularly suitable for use as a retort 10 and its manufacturing method for sintering positive electrode materials for lithium ion batteries. In particular, a retort 10 using a Ni-based alloy that does not contain Cr can be particularly suitable for use as a retort 10 for sintering positive electrode materials for lithium ion batteries.

[0070] In the case of an alloy containing a large amount of Cr (for example, an alloy containing 20% ​​by weight or more of Cr), the Cr in the alloy may react with lithium (Li), causing the Cr to be incorporated into the positive electrode material and causing malfunctions. However, in the case of a retort 10 using a Ni-based alloy with a low Cr content, such a risk can be reduced.

[0071] REFERENCE SIGNS LIST 10 retort 10a tubular part 11 base material 11a heat-affected zone 11b base material portion (portion of base material other than the heat-affected zone) 12 weld metal portion 13 excess filler portion 20 outer cylinder 30 supply portion 40 discharge portion 50 support device 100 rotary kiln

Claims

1. A method for manufacturing retorts for rotary kilns, characterized in that the joints of base materials made of a Ni-based alloy containing 90.0% by weight or more of Ni and 2.0% by weight or more of Al are plasma welded without using a filler.

2. A retort for a rotary kiln, comprising: a base material made of a Ni-based alloy containing 90.0% by weight or more of Ni and 2.0% by weight or more of Al; and a weld metal zone formed at a joint of the base material; the base material comprising a heat-affected zone formed around the weld metal zone and a base material portion that is the portion of the base material other than the heat-affected zone; and the value obtained by (Equation 1) (average crystal grain size in the heat-affected zone / average crystal grain size in the base material portion) x 100 is 100-300%, or / and the average crystal grain size in the heat-affected zone is less than 250 μm.

3. The retort according to claim 2, wherein the Al content is 2.0 to 5.0 wt %.

4. The retort according to claim 2, wherein the Ni-based alloy contains at least 90.0% by weight of Ni and at least 2.0% by weight of Al, as well as 0.1 to 2.5% by weight of Si, 0.1 to 1.5% by weight of Mn, 0.001 to 0.01% by weight of B, and 0.001 to 0.1% by weight of Zr.

5. A retort according to claim 2, wherein the Ni-based alloy contains at least 90.0% by weight of Ni and at least 2.0% by weight of Al, as well as 0.1 to 2.5% by weight of Si, 0.8 to 4.0% by weight of Cr, 0.1 to 1.5% by weight of Mn, 0.001 to 0.01% by weight of B, and 0.001 to 0.1% by weight of Zr.

6. A rotary kiln, characterized in that it is equipped with a retort as defined in any one of claims 2 to 5.

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