A composite slag discharge cone for magnesium reduction tank and its production process

Abstract

A composite slag cone for a magnesium reduction tank and its production process belong to the technical field of production of slag cones for reduction tanks used in magnesium metal refining. First, a hot-rolled large-diameter thick-walled seamless steel pipe with a diameter of 300mm to 1500mm, a thickness of 50mm to 120mm, a length of 0.5m to 1m and a material of P91 is manufactured. The seamless steel pipe is used as the base of the slag cone for the magnesium reduction tank, and the base is die-forged to obtain a cone blank, and then the cone blank is machined; finally, a 1-3mm thick nickel-based, molybdenum-based high-temperature resistant and corrosion-resistant alloy strengthening layer is laser-clad on the inner and outer surfaces of the cone; a composite magnesium reduction tank slag cone with inner and outer surfaces clad and strengthened is obtained. The product has good slag removal performance, high temperature oxidation resistance, thermal stability and high temperature creep resistance and other comprehensive properties.

Description

Technical Field

[0001] The invention belongs to the technical field of production of slag discharge cones for reduction tanks used in metal magnesium refining, and specifically relates to a composite slag discharge cone for a magnesium reduction tank and a production process thereof. Background Art

[0002] At present, the slag cone of the reduction tank for magnesium refining is mainly made of centrifugal castings made of ZG35Cr24Ni7SiN. It has high manufacturing cost, easy to stick slag, resulting in furnace shutdown and increasing the heating cost of magnesium reduction; poor high-temperature strength, short service life, increased maintenance and operating costs; and hindered the development direction of efficient energy saving in the magnesium refining industry. Summary of the invention

[0003] The object of the present invention is to provide a composite slag discharge cone for a magnesium reduction tank, which can achieve high high-temperature strength, strong high-temperature oxidation resistance, less slagging on the inner wall, long service life and low-cost manufacturing.

[0004] The technical solution to achieve the above purpose is: a composite slag discharge cone for a magnesium reduction tank, characterized in that it includes a magnesium reduction tank slag discharge cone blank prepared by a seamless steel pipe matrix, and the inner and outer surfaces of the magnesium reduction tank slag discharge cone blank are laser-clad with nickel-based and molybdenum-based alloy layers to obtain a composite slag discharge cone.

[0005] Furthermore, the material of the seamless steel pipe substrate is P91.

[0006] Since the present invention adopts P91 hot-rolled large-diameter thick-walled seamless steel pipe, on the one hand, as the matrix of the alloy layer, it has sufficient high-temperature strength, and on the other hand, it ensures the sealing of the gas inside it when refining magnesium; laser cladding nickel-based and molybdenum-based layers are used as the inner and outer layer structures of the product, which ensures its high-temperature resistance, high-temperature oxidation resistance and slag removal performance to meet the harsh environmental conditions of slag removal in the magnesium reduction furnace.

[0007] Furthermore, the composition and content of the nickel-based and molybdenum-based alloy layers are: 0%-0.1%, Mn: 1.0%-2.0%, Si: 0.5%-1.0%, P: 0%-0.015%, S: 0%-0.015%, Cr: 23.0%-25.0%, Ni: 54.0%-56.0%, Mo: 8%-10.0%, Ti: 0%-0.4%, Al: 0%-0.4%, Fe: 8.0%-10.0%, and the remainder is impurities.

[0008] In the nickel-based and molybdenum-based alloy layers, the Ni+Mo content reaches 62%~66%, which has good resistance to high-temperature oxidation corrosion and good thermal conductivity; and 23.0%-25.0% Cr not only improves the high-temperature creep resistance of the alloy layer, but also greatly improves the wear resistance of the alloy layer.

[0009] Compared with the cast magnesium reduction tank slag discharge cone, the present invention has the following beneficial effects:

[0010] 1) The composite magnesium reduction tank slag cone is formed by hot rolling process, with dense internal structure, improved material crystal structure, eliminated gaps, and greatly improved material strength and toughness. The high temperature strength and sealing performance of the composite slag cone are better than those of the centrifugal casting slag cone.

[0011] 2) The surface of the casting slag cone is prone to slagging, causing blockage, so the entire reduction tank needs to be pulled out of the reduction furnace to clean the slag on the inner wall of the slag cone once every 20 days on average, wasting a lot of manpower and energy, seriously affecting production efficiency. The same furnace test shows that the slagging situation of the composite slag cone surface is significantly better than that of the casting slag cone, and it can be cleaned up for up to 45 days.

[0012] 3) High temperature strength: At 1000℃, the tensile strength of cast steel slag cone is ≤10MPa; composite slag cone is ≥25MPa.

[0013] Comparison of experimental data of the present invention with the existing cast steel slag removal cone:

[0014] Wear rate: at 1000℃, cast steel slag cone ≥5mm / month; composite slag cone ≤0.5mm / month 25MPa.

[0015] Service life: cast steel slag cone has a service life of 1 month, and composite slag cone has a service life of 12 months.

[0016] Another object of the present invention is to provide a production process for a composite slag discharge cone of a magnesium reduction tank, which is characterized by comprising the following specific steps:

[0017] S1. Manufacturing of hot-rolled large-diameter thick-walled seamless steel pipes with a diameter of 559mm~1500mm, a thickness of 50mm~120mm, a length of 0.5m~1m, and a material of P91;

[0018] S2, heating the hot-rolled large-diameter thick-walled seamless steel pipe to 1150° C., and forging it using inner and outer dies to obtain a magnesium reduction tank slag discharge cone billet;

[0019] S3. Machining the slag cone blank of the magnesium reduction tank to remove the surface oxide layer.

[0020] S4. A nickel-based and molybdenum-based alloy layer with a thickness of 1 to 3 mm is respectively clad on the inner and outer surfaces of the magnesium reduction tank slag discharge cone blank after turning.

[0021] Furthermore, in step S1, the hot-rolled large-diameter thick-walled seamless steel pipe is obtained by using P91 continuous casting billet through the processes of cutting, center hole punching, heating, perforation, pipe rolling, sizing, heat treatment, sampling, testing, straightening, inner and outer wall grinding, non-destructive testing, sawing, surface polishing, and finished product inspection.

[0022] Furthermore, in step S4, the nickel-based and molybdenum-based alloy layers are clad on the inner and outer surfaces of the magnesium reduction tank slag discharge cone blank by using a laser cladding process.

[0023] The process of the invention is simple and reasonable, the manufactured product has good stability, high yield rate and low manufacturing cost and meets the design requirements.

[0024] Oblique rolling and punching is a method for producing seamless steel pipe rough tubes in a hot state. Oblique rolling and punching has a fast production rhythm and a high yield rate. The present invention uses P91 continuous casting billet to punch a center hole, heats it to 1240°C, and performs oblique rolling and punching and tube rolling to form the required seamless rough tube; then annealing, shot peening, straightening, sizing, and heat treatment are combined to change the wall thickness uniformity and geometric size accuracy, and enhance the density of the organization, thereby improving the comprehensive performance of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the forging state of the slag-discharging cone billet of the magnesium reduction tank;

[0026] Figure 2 It is a schematic diagram of the structure of the composite slag discharge cone of the magnesium reduction tank. DETAILED DESCRIPTION Example 1

[0027] The present invention discloses a composite slag removal cone for a magnesium reduction tank, comprising a magnesium reduction tank slag removal cone blank 3 prepared by a seamless steel tube substrate, wherein a layer of nickel-based and molybdenum-based alloy layer 4 is laser-clad on the inner and outer surfaces of the magnesium reduction tank slag removal cone blank 3 to obtain a composite slag removal cone, specifically, the nickel-based and molybdenum-based alloy layer 4 is laser-clad on the inner and outer surfaces of the substrate using a high-power solid laser using a synchronous powder feeding method, and the single-pass powder feeding cladding thickness is 1.5 mm.

[0028] The chemical composition weight percentages of the nickel-based and molybdenum-based alloy layers are: C: 0.06%, Mn: 1.5%, Si: 0.5%, P: 0.010%, S: 0.010%, Cr: 24.0%, Ni: 55.0%, Mo: 9.0%, Ti: 0.2%, Al: 0.2%, Fe: 9.5%, and the remainder is impurities.

[0029] The following is a specific example of the production process of the composite slag cone of the magnesium reduction tank. In this embodiment, the design specifications of the slag cone blank of the magnesium reduction tank are: outer diameter φ300mm-φ1016mm, wall thickness 55mm-63.5mm, length 0.5m-1.2m.

[0030] S1. According to the design size specifications, select P91 round continuous casting billet with a size of φ219~φ760mm and a length of 4200±10mm, and punch a hole in the center.

[0031] S2. Place the P91 continuous casting billet with the holes punched in it into a ring furnace and heat it to 1240±10°C.

[0032] S3. After heating, the tube blank is pierced and hot rolled with an 800mm piercing machine and a 960mm tube rolling machine to obtain a rough tube. The cold size tolerance of the rough tube is controlled as follows: diameter tolerance: ±10mm; wall thickness tolerance: ±2mm; length tolerance: ±100mm.

[0033] S4. Use a trolley furnace to heat the rough tube to 810℃ for annealing and keep it warm for 180 minutes. The temperature deviation during the insulation period is ±10℃. After annealing, take it out of the furnace and air cool it.

[0034] S5. Use a shot peening machine to shot peen the outer wall of the rough pipe to clean the surface oxide scale.

[0035] S6. Use 2500T pressure straightener to straighten the rough pipe. After straightening, the curvature is ≤4mm / m and the curvature of the entire length is ≤15mm.

[0036] S7. Use an 1800mm sawing machine to cut the rough pipes flush. The recommended cutting length is ≤0.3 m.

[0037] S8. Use an internal grinder to polish the inner wall of the rough pipe.

[0038] S9. Use medium frequency heating sizing machine for internal sizing, dimensional tolerance: ±1mm.

[0039] S10. Normalize the rough pipe at 1050℃ for 65 minutes with a temperature deviation of ±10℃ during the holding period. After normalizing, take the pipe out of the furnace and cool it with air.

[0040] S11. Temper the rough pipe at 760℃ for 130 minutes. The temperature deviation during the temperature holding period is -10℃~+10℃. After tempering, take the pipe out of the furnace and air cool it.

[0041] S12. Take samples of the rough pipe after tempering for testing, composition analysis and physical properties testing.

[0042] S13. Use 2500T pressure straightener to straighten the rough pipe with temperature. After straightening, the curvature is ≤2mm / m and the curvature of the whole length is ≤5mm.

[0043] S14. Use internal and external grinders to grind the inner and outer walls. There should be no folds, cracks, scars, or concave and convex defects after grinding.

[0044] S15. Perform non-destructive testing on the base tube and manual blind area inspection 100% UT+ET.

[0045] S16. Use a 1800mm sawing machine to cut the base tube to a fixed length according to the specifications of the composite slag cone of the magnesium reduction tank.

[0046] S17, using a chamber furnace to heat the sawn substrate tube to 1150°C.

[0047] S18, such as Figure 1 As described above, a 6300T forging press is used to forge the heated base tube using an outer die 2 and an inner die 1 to obtain a slag removal cone blank 3.

[0048] S19, using a lathe to turn the inner and outer surfaces of the slag discharge cone blank 3 to a desired size.

[0049] S20, such as Figure 2 As shown, a high-power solid-state laser is used to laser clad the inner and outer surfaces of the turned cone blank with a nickel-based and molybdenum-based alloy layer 4 using a synchronous powder feeding method. The single-pass powder feeding cladding thickness is 1.5 mm, and two passes are clad to obtain a composite magnesium reduction tank slag discharge cone with layers arranged on the inner and outer surfaces of the substrate. Example 2

[0050] The difference between Example 2 and Example 1 is that the chemical composition weight percentages of the nickel-based and molybdenum-based alloy layers in this embodiment are: C: 0.1%, Mn: 1.00%, Si: 1.0%, P: 0.015%, S: 0.015%, Cr: 25.0%, Ni: 56.0%, Mo: 8%, Ti: 0.33%, Al: 0.4%, Fe: 8.0%, and the remainder is impurities. Example 3

[0051] The difference between Example 3 and Example 1 is that the chemical composition weight percentages of the nickel-based and molybdenum-based alloy layers in this embodiment are: C: 0.02%, Mn: 2.0%, Si: 0.5%, P: 0.008%, S: 0.004%, Cr: 23.0%, Ni: 54.0%, Mo: 10.0%, Ti: 0.40%, Al: 0%, Fe: 10.0%, and the remainder is impurities.

[0052] Comparative Example

[0053] The centrifugal casting reduction tank slag discharge cone is made of ZG35Cr24Ni7SiN.

[0054] Table 1

[0055] It can be seen from Table 1 that the composite magnesium reduction tank slag cone is formed by hot rolling process + forging + alloy layer laser cladding welding. Compared with the cast structure, its internal organization eliminates the cast gap and looseness, improves the material density, and the addition of strengthening elements in the alloy layer, Cr improves the wear resistance of the material, Ni improves the high temperature oxidation resistance and service life, and Mo effectively improves the high temperature strength and high temperature creep strength of the cone, thereby comprehensively and effectively improving the high temperature strength, high temperature oxidation corrosion resistance, wear resistance and service life of the material.

Claims

1. A composite slag discharge cone for a magnesium reduction tank, characterized in that : It includes a magnesium reduction tank deslagging cone blank prepared by a seamless steel tube matrix, wherein the inner and outer surfaces of the magnesium reduction tank deslagging cone blank are laser-clad with nickel-based and molybdenum-based alloy layers to obtain a composite deslagging cone; The chemical composition weight percentage of the nickel-based and molybdenum-based alloy layers is: C: 0%-0.1%, Mn: 1.0%-2.0%, Si: 0.5%-1.0%, P: 0%-0.015%, S: 0%-0.015%, Cr: 23.0%-25.0%, Ni: 54.0%-56.0%, Mo: 8%-10.0%, Ti: 0%-0.4%, Al: 0%-0.4%, Fe: 8.0%-10.0%, and the remainder is impurities.

2. A composite slag discharge cone for a magnesium reduction tank according to claim 1, characterized in that :The material of the seamless steel pipe matrix is ​​P91.

3. The production process of a composite slag discharge cone for a magnesium reduction tank according to claim 1, characterized in that , including the following specific steps: S1. Manufacturing of hot-rolled large-diameter thick-walled seamless steel pipes with a diameter of 559mm~1500mm, a thickness of 50mm~120mm, a length of 0.5m~1m, and a material of P91; S2, heating the hot-rolled large-diameter thick-walled seamless steel pipe to 1150° C., and forging it with inner and outer dies to obtain a magnesium reduction tank slag discharge cone billet; S3, machining the slag cone blank of the magnesium reduction tank, turning off the surface oxide layer and achieving the required size; S4. A nickel-based and molybdenum-based alloy layer with a thickness of 1 to 3 mm is respectively clad on the inner and outer surfaces of the magnesium reduction tank slag discharge cone blank after turning.

4. The production process of a composite slag discharge cone for a magnesium reduction tank according to claim 3, characterized in that: In step S1, the hot-rolled large-diameter thick-walled seamless steel pipe is made of P91 continuous casting billet and is sequentially subjected to cutting, center hole punching, heating, perforation, pipe rolling, sizing, heat treatment, sampling, testing, straightening, inner and outer wall grinding, non-destructive testing, sawing, surface polishing, and finished product inspection.

5. The production process of a composite slag discharge cone for a magnesium reduction tank according to claim 3, characterized in that In step S4, the nickel-based and molybdenum-based alloy layers are clad on the inner and outer surfaces of the slag discharge cone blank of the magnesium reduction tank by using a laser cladding process.

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