A manufacturing method of a combined wear-resistant nozzle moving ring of a ZGM medium-speed coal mill

Abstract

This invention discloses a method for manufacturing a combined wear-resistant nozzle dynamic ring for a ZGM type medium-speed coal mill, belonging to the field of metal matrix composites. The method involves preparing ceramic particle-reinforced high-chromium cast iron-based wear-resistant blades, an outer wear-resistant ring, and an inner fixing ring. The components are assembled from the inside out in the following order: inner fixing ring, outer wear-resistant ring, and cermet wear-resistant blades. Each component is tightened from the outside in using bolts, with the bolt heads forming pre-drilled countersunk holes in the wear-resistant blades. The protruding structure in the wear-resistant blades is inserted into a pre-drilled irregular hole in the outer wear-resistant ring, and the opening is sealed with a steel plate after the fixing bolts are tightened to prevent it from affecting the airflow direction inside the coal mill. This method increases the overall wear resistance of the dynamic ring by using cermet composite materials. Simultaneously, this method offers the advantage of being repairable and replaceable, significantly reducing the maintenance and replacement costs of the dynamic ring.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of metal matrix composites, and more particularly relates to a manufacturing method of a combined wear-resistant nozzle dynamic ring of a ZGM medium-speed coal mill. BACKGROUND

[0002] With the continuous increase of environmental pressure, the voice and measures of environmental protection are increasing, and the high energy consumption and high emission industries such as electric power, metallurgy, building materials, coal, and chemical industry have become the key fields of compulsory energy saving and emission reduction. Eliminating backward production capacity, optimizing product structure, pursuing energy saving and environmental protection, and safety and efficiency have become the trend of industry development.

[0003] The coal mill is one of the necessary production equipment of the above-mentioned industries. The coal mill is the main equipment of the pulverizing system, which grinds coal into powder by crushing, crushing and grinding principles. The coal mill can be divided into low-speed, medium-speed and high-speed coal mills according to the speed. Generally, when the coal conditions permit, the medium-speed coal mill should be preferred; for the medium-speed coal mill, one of the commonly used types is the medium-speed roller type coal mill manufactured by Beijing Electric Power Equipment Factory (the product code is ZGM).

[0004] The coal mill is a device for crushing and grinding coal into powder. There are many types of coal mills for power plants, which can be divided into low-speed, medium-speed and high-speed coal mills according to the speed of the grinding part. At present, the three most commonly used medium-speed coal mills in domestic large-scale power plant boilers are RP mill (improved type HP), MPS (ZGM) mill and E-type mill. Their grinding parts are different, but they have the same working principle and basically similar structure. The working process is: driven by the motor, the grinding disc or grinding ring is rotated through the speed reducer and the vertical main shaft.

[0005] The nozzle dynamic ring of the medium-speed coal mill used in the coal-fired power plant is a key component of the coal mill. It combines with the static ring to form a primary air flow field, which plays a role in drying the coal powder with primary air and sending the coal powder to the boiler for combustion. The ZGM type nozzle dynamic ring is usually made of ZG50Mn by integral casting and then machined into shape. It has low hardness and is easy to wear and tear, with short service life. The wear of the dynamic ring directly affects the air-powder ratio, the output of the coal mill, the fineness of the coal powder and other operating parameters of the coal mill. In order to ensure the stable operation of the coal mill, the power plant needs to frequently replace the dynamic ring assembly. SUMMARY

[0006] The purpose of the present application is to solve the problems in the prior art and provide a manufacturing method of a combined wear-resistant nozzle dynamic ring of a ZGM medium-speed coal mill. The method uses metal ceramic composite material in the nozzle dynamic ring, which increases the overall wear resistance of the dynamic ring. At the same time, the method has the effect of repair and replacement, greatly reducing the maintenance and replacement cost of the dynamic ring.

[0007] Technical solution: The manufacturing method of the combined wear-resistant nozzle moving ring of the ZGM medium-speed coal mill comprises the following steps:

[0008] (1) Prepare ceramic particle reinforced high chromium cast iron base wear-resistant blade: first, uniformly mix ceramic particles, boron carbide powder, titanium carbide powder, zirconia powder, and high chromium cast iron powder to prepare a porous ceramic preform and solidify, the preform is fixed in an EPS lost mold, the mold is provided with a countersunk hole as a subsequent assembly, a high chromium cast iron melt is cast by using a negative pressure casting infiltration process, the mold is opened after 24 hours of heat preservation, and the preform is taken out and heat treated;

[0009] (2) Prepare an outer wear-resistant ring: cut the bimetallic wear-resistant plate into a specified size by numerical control machining, uniformly cut a special-shaped hole in the inside, and roll the bimetallic wear-resistant plate into a ring shape by using a plate rolling machine;

[0010] (3) Prepare an inner fixing ring: cut the steel plate into a specified shape by numerical control machining, including a ring shape and a sector shape; roll the steel plate into a ring shape, then weld the sector shape at one end of the ring-shaped steel plate, process a threaded hole in the side surface of the ring-shaped plate to facilitate subsequent installation of other components, and process a counterbore in the sector-shaped plate as a subsequent mounting hole on the coal mill;

[0011] (4) Assemble the components from inside to outside in the following order: the inner fixing ring, the outer wear-resistant ring, and the wear-resistant blade, and lock the components from outside to inside by using bolts, the hole in the head of the bolt is the reserved countersunk hole of the wear-resistant blade, and the hole is sealed by using a steel plate after the fixing bolt is locked to prevent affecting the flow direction of the wind field inside the coal mill.

[0012] In some embodiments, the ceramic particles in step (1) are made of ZTA, wherein the content of zirconia is 30%-80%, and the particle size is 80-120 mesh.

[0013] In some embodiments, the ceramic particles, boron carbide powder, titanium carbide powder, zirconia powder, and high chromium cast iron powder are mixed in a mass ratio of 6:1:0.5:0.5:2, and then the mixed powder is mixed with high-temperature glue in a mass ratio of 9:1, wherein the high-temperature glue is one or a mixture of several of water glass, silica sol, and aluminum sol.

[0014] In some embodiments, the solidification method of the porous ceramic preform in step (1) is to pass carbon dioxide into the porous ceramic preform, the flow rate of the carbon dioxide is 800-1500 L / h, then the preform is placed in a heat preservation furnace for solidification, the temperature of the heat preservation furnace is 65-85℃, and the heat preservation time is 1-2 h.

[0015] In some embodiments, the density of the EPS mold in step (1) is 25-32 Kg / m 3The EPS mold is immersed in the iron ore powder coating slurry, so that a layer of coating is uniformly adhered to the surface of the mold, the coating is 56-70 Bh in Baume degree, 3 times of immersion coating are required on the surface of the mold, after the first and second times of immersion coating, the mold is placed in an oven at 50 DEG C for drying for 12 hours, after the third time of immersion coating, the mold is placed in an oven at 50 DEG C for drying for 24 hours, and then the mold is placed in a special sand box.

[0016] In some embodiments, the negative pressure casting process in step (1) is as follows: high chromium cast iron is smelted, the high chromium cast iron includes the following chemical components in percentage by mass: Cr: 20-24%, C: 3.0-3.5%, Mn: 1.5-2.0%, Si: 1.2-1.7%, Mo: 1.8-2.5%, Ni: 1.0-2.0%, V: 0.4-0.6%, Ti: 0.5-1.0%; the high chromium cast iron melt is poured into a sand mold, at this time, a negative pressure system is started, the pressure of the negative pressure system is 0.06-0.08 MPa, and the pressure maintaining time before and after pouring is 10 min.; the castings are taken out after being kept at temperature for 24 h.

[0017] In some embodiments, the heat treatment process in step (1) is as follows: the temperature is raised from 150 DEG C to 250 DEG C at a rate of 50 DEG C / h, and kept at temperature for 1 h; the temperature is raised to 550 DEG C at a rate of 50 DEG C / h, and kept at temperature for 1 h; the temperature is raised to 850 DEG C at a rate of 85 DEG C / h, and kept at temperature for 1 h; the temperature is raised to 1150 DEG C at a rate of 50 DEG C / h, and kept at temperature for 4 h; then air cooling is performed to room temperature; the castings after the foregoing normalizing process are placed into a holding furnace for tempering, the tempering process is as follows: the temperature is raised to 280 DEG C at a rate of 90 DEG C / h, and kept at temperature for 5 h, and then air cooling is performed to room temperature.

[0018] In some embodiments, the material of the outer wear-resistant ring in step (2) is high chromium cast iron / carbon steel bimetallic wear-resistant plate; the shape of the special-shaped hole is a sample curve with the outer contour of the wear-resistant blade being inwardly offset by 1-3 cm, and the blanked bimetallic wear-resistant plate is rolled into a ring shape using a plate rolling machine; the high chromium cast iron layer of the prepared ring-shaped bimetallic wear-resistant plate is outward.

[0019] In some embodiments, the material of the steel plate of the inner fixed ring in step (3) is Q355, the outer diameter of the inner fixed ring is the same as the inner diameter of the bimetallic wear-resistant plate, threaded holes are processed on the side surface of the ring-shaped steel plate, the threaded holes are M16-M30, and the threaded holes are through holes.

[0020] In some embodiments, the bolt in step (4) is provided with an elastic gasket, the head of the bolt is spot-welded with the high chromium cast iron, so as to prevent the movable ring nozzle from falling off during use, and the material of the sealing steel plate is one of Q235, 304 and Q355.

[0021] Beneficial effects: the beneficial effects of the present application are as follows:

[0022] (1) the present application uses metal ceramic composite material in nozzle moving ring, increases the overall wear resistance of moving ring;

[0023] (2) the present application has the effect of repairable replacement, greatly reduces the maintenance and replacement cost of moving ring;

[0024] (3) the present application uses bolts between components from outside to inside locking, the hole of bolt head is reserved countersunk hole of wear-resistant blade, after locking of fixing bolt, steel plate is used to seal, prevent affecting the flow direction of wind field in coal mill;

[0025] (4) the outer wear-resistant ring increases the service life of the moving ring as a whole, prevents the body from failure due to wear;

[0026] (5) by setting the blade, prevent the accumulation of coal powder from blocking, affect the flow of wind field;

[0027] (6) reduce the number of maintenance, save maintenance cost; the preparation process is simple, easy to operate. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 it is the normalizing process temperature curve diagram of an embodiment of the present application;

[0029] Figure 2 it is the tempering process temperature curve diagram of an embodiment of the present application;

[0030] Figure 3 it is the inside fixed ring structure schematic diagram of an embodiment of the present application;

[0031] Figure 4 it is the outer wear-resistant ring structure schematic diagram of an embodiment of the present application;

[0032] Figure 5 it is the blade structure schematic diagram of an embodiment of the present application;

[0033] Figure 6 it is the nozzle moving ring overall assembly schematic diagram of an embodiment of the present application;

[0034] Figure 7 it is the nozzle moving ring structure front view of an embodiment of the present application;

[0035] Figure 8 it is Figure 7 A-A structure sectional view. EMBODIMENT

[0036] The technical solutions of the present application will be described clearly and completely in the following description of the drawings. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0037] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "inner", "outer" and the like indicate the orientation or positional relationship shown, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as limiting the devices or elements indicated or implied to have a specific orientation, to be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present application.

[0038] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connection" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0039] The present application will be further described in detail below through specific embodiments and in conjunction with the drawings. Embodiment

[0040] A manufacturing method of a combined wear-resistant nozzle moving ring of a ZGM medium-speed coal mill, comprising the following steps:

[0041] (1) Prepare ceramic particle reinforced high chromium cast iron base wear-resistant blade: first, uniformly mix ZTA ceramic particles, boron carbide powder, titanium carbide powder, zirconia powder, and high chromium cast iron powder to prepare a porous ceramic preform and solidify, the preform is fixed in an EPS lost mold, the mold is provided with a countersunk hole for subsequent assembly, a high chromium cast iron melt is cast by using a negative pressure casting infiltration process, the mold is opened after 24 hours of heat preservation, and the blade structure is taken out and heat treated, as shown in Figure 5 ;

[0042] In this embodiment, the content of zirconia in the ZTA (zirconia toughened alumina) ceramic particles accounts for 30% of the total mass percentage of the particles, and the particle size of the ceramic particles is 80-120 mesh.

[0043] In this embodiment, the ZTA ceramic particles, boron carbide powder, titanium carbide powder, zirconia powder, and high chromium cast iron powder are mixed according to the mass ratio of 6:1:0.5:0.5:2, and then the mixed powder is mixed with high temperature glue according to the mass ratio of 9:1, and the high temperature glue is sodium silicate.

[0044] In this embodiment, the solidification method of the porous ceramic preform is: carbon dioxide is introduced into the porous ceramic preform, the carbon dioxide gas flow is 800 L / h, and then it is placed in a holding furnace for solidification, the holding furnace temperature is 65℃, and the holding time is 1 h.

[0045] In this embodiment, the density of the EPS mold is 25 Kg / m 3 ; The EPS mold is immersed in the iron ore powder coating slurry to make the mold surface uniformly adhere to a layer of coating, the coating is 56Bh in the Beiersden scale, and 3 times of immersion coating are required on the mold surface, the first and second times of immersion coating are placed in a drying oven at 50℃ for 12 hours after drying, the third time of immersion coating is dried in a drying oven at 50℃ for 24 hours, and then the mold is placed in a special sand box.

[0046] In this embodiment, the negative pressure casting and infiltration process is: smelting high chromium cast iron, the high chromium cast iron includes the following chemical components by mass percentage: Cr: 20%, C: 3.0%, Mn: 1.5%, Si: 1.2%, Mo: 1.8%, Ni: 1.2%, V: 0.5%, Ti: 0.6%, and the balance is iron and impurities; the high chromium cast iron melt is poured into a sand mold, at this time the negative pressure system is started, the pressure of the negative pressure system is 0.06 MPa, and the pressure holding time before and after pouring is 10 min. The casting is taken out after 24 h of heat preservation.

[0047] In this embodiment, as shown in Figure 1 , the heat treatment process is: increasing from 150℃ to 250℃ at a rate of 50℃ / h, holding for 1 hour; increasing to 550℃ at a rate of 50℃ / h, holding for 1 hour; increasing to 850℃ at a rate of 85℃ / h, holding for 1 hour; increasing to 1150℃ at a rate of 50℃ / h, holding for 4 hours; then air cooling to room temperature; the casting after the above normalizing process is placed in a holding furnace for tempering, the tempering process is (as shown in Figure 2 ): increasing to 280℃ at a rate of 90℃ / h, holding for 5 hours, and then air cooling to room temperature.

[0048] (2) Prepare the outer wear-resistant ring: cut the bimetallic wear-resistant plate into a specified size by numerical control machining, uniformly cut a special-shaped hole in the inside, and roll the bimetallic wear-resistant plate into a ring shape using a plate rolling machine, and the final outer wear-resistant ring structure is as shown in Figure 4 ;

[0049] In this embodiment, the outer wear-resistant ring material is high chromium cast iron / carbon steel bimetallic wear-resistant plate, and the thickness of high chromium cast iron and carbon steel is 6mm and 8mm respectively; the shape of the special-shaped hole is a sample curve with the wear-resistant blade outer profile inwardly offset by 1-3cm, and the blanked bimetallic wear-resistant plate is rolled into a ring shape by using a plate rolling machine; the outer layer of the prepared ring-shaped bimetallic wear-resistant plate is high chromium cast iron. The material of the high chromium cast iron layer is: C: 3.8%, Cr: 20%, Mo: 5%, Nb: 3%, V: 1%, W: 4%, and the balance is iron and impurities.

[0050] (3) Preparation of the inner fixed ring: the steel plate is blanked into a specified shape by numerical control processing, including a ring shape and a sector shape; the steel plate is rolled into a ring shape, and then the sector shape is welded at one end of the ring-shaped steel plate; threaded holes are processed on the side surface of the ring-shaped plate to facilitate the installation of other components later; a counterbore is processed on the sector-shaped plate as a mounting hole on the mill later; and finally, the structure of the inner fixed ring is as shown in Figure 3

[0051] The steel plate material of the inner fixed ring is Q355, the outer diameter of the inner fixed ring is the same as the inner diameter of the bimetallic wear-resistant plate, threaded holes are processed on the side surface of the ring-shaped steel plate, the threaded holes are M16-M30, and the threaded holes are through holes.

[0052] (4) The assembly sequence from inside to outside is as shown in Figure 6 to Figure 8 , that is, the inner fixed ring 2, the outer wear-resistant ring 1, and the wear-resistant blade 3, and the bolts 4 are used to lock from outside to inside between each component; the holes in the head of the bolt are the reserved countersunk holes of the wear-resistant blade, and a steel plate is used to seal after the fixed bolt is locked to prevent affecting the flow direction of the wind field inside the mill.

[0053] The bolt is provided with an elastic gasket, the head of the bolt is spot-welded with the high chromium cast iron to prevent the nozzle from falling off during use, and the material of the sealing steel plate is Q235. Embodiment

[0054] A manufacturing method of a combined wear-resistant nozzle movable ring of a ZGM medium-speed coal mill, comprising the following steps:

[0055] (1) Preparation of ceramic particle reinforced high chromium cast iron base wear-resistant blade: first, uniformly mix ZTA ceramic particles, boron carbide powder, titanium carbide powder, zirconia powder, and high chromium cast iron powder to prepare a porous ceramic preform and solidify it in an EPS lost mold, which is provided with a countersunk hole as a subsequent assembly hole; high chromium cast iron melt is poured by using a negative pressure casting infiltration process; after 24 hours of heat preservation, the mold is opened and the preform is taken out and heat treated; and finally, the blade structure is as shown in Figure 5

[0056] In this embodiment, the content of zirconia in the ZTA (zirconia toughened alumina) ceramic particles accounts for 50% of the total mass percentage of the particles, and the particle size of the ceramic particles is 80-120 mesh.​​

[0057] In this embodiment, the ZTA ceramic particles are mixed with boron carbide powder, titanium carbide powder, zirconia powder, high chromium cast iron powder according to the mass ratio of 6:1:0.5:0.5:2, and then the mixed powder is mixed with high-temperature glue according to the mass ratio of 9:1, and the high-temperature glue is silica sol.

[0058] In this embodiment, the solidification method of the porous ceramic preform is to introduce carbon dioxide into the porous ceramic preform, the carbon dioxide gas flow is 1200 L / h, and then it is placed in a holding furnace for solidification, the holding furnace temperature is 70℃, and the holding time is 1.5 h.

[0059] In this embodiment, the density of the EPS mold is 28 Kg / m 3 ; the EPS mold is immersed in the iron ore powder coating slurry, so that a layer of coating is uniformly adhered to the surface of the mold, the coating is 65Bh, and the mold surface needs to be immersed for 3 times, after the first and second immersion, it is placed in a drying oven at 50℃ for 12 hours, after the third immersion, it is placed in a drying oven at 50℃ for 24 hours, and then the mold is placed in a special sand box.

[0060] In this embodiment, the negative pressure casting and infiltration process is: smelting high chromium cast iron, the high chromium cast iron includes mass percentage of chemical components: Cr: 22%, C: 3.2%, Mn: 1.6%, Si: 1.5%, Mo: 2.0%, Ni: 1.5%, V: 0.5%, Ti: 0.8%, and the balance is iron and impurities; pouring the high chromium cast iron melt into the sand mold, at this time, the negative pressure system is started, the pressure of the negative pressure system is 0.07 MPa, and the pressure holding time before and after casting is 10 min, and the casting is taken out after 24 h of heat preservation.

[0061] In this embodiment, as shown in Figure 1 , the heat treatment process is: increasing from 150℃ to 250℃ at a rate of 50℃ / h, holding for 1 hour; increasing to 550℃ at a rate of 50℃ / h, holding for 1 hour; increasing to 850℃ at a rate of 85℃ / h, holding for 1 hour; increasing to 1150℃ at a rate of 50℃ / h, holding for 4 hours; then air cooling to room temperature; the casting after the above normalizing process is put into a holding furnace for tempering, and the tempering process is (as shown in Figure 2 ): increasing to 280℃ at a rate of 90℃ / h, holding for 5 hours, and then air cooling to room temperature.

[0062] (2) Preparing the outer wear-resistant ring: cutting the bimetallic wear-resistant plate into a specified size by numerical control machining, cutting a special-shaped hole uniformly inside, and rolling the bimetallic wear-resistant plate into a ring shape using a plate rolling machine, and the final outer wear-resistant ring structure is as shown in Figure 4 ;

[0063] In this embodiment, the outer wear-resistant ring material is high chromium cast iron / carbon steel bimetallic wear-resistant plate, and the thickness of high chromium cast iron and carbon steel is 6mm and 8mm respectively; the shape of the special-shaped hole is a sample curve with the wear-resistant blade outer profile offset inward by 1-3cm, and the blanked bimetallic wear-resistant plate is rolled into a ring shape using a plate rolling machine; the outer layer of the prepared ring-shaped bimetallic wear-resistant plate is high chromium cast iron. The material of the high chromium cast iron layer is: C: 4.0%, Cr: 30%, Mo: 5%, Nb: 6%, V: 2%, W: 5%, and the balance is iron and impurities.

[0064] (3) Preparation of the inner fixed ring: the steel plate is blanked into a specified shape by numerical control processing, including a ring shape and a sector shape; the steel plate is rolled into a ring shape, and then the sector shape is welded at one end of the ring-shaped steel plate. Threaded holes are processed on the side surface of the ring-shaped plate to facilitate the installation of other components later, and counterbores are processed on the sector-shaped plate as mounting holes on the mill later. The final structure of the inner fixed ring is shown in Figure 3

[0065] The steel plate material of the inner fixed ring is Q355, and the outer diameter of the inner fixed ring is the same as the inner diameter of the bimetallic wear-resistant plate. Threaded holes are processed on the side surface of the ring-shaped plate, and the threaded holes are M16-M30 through holes.

[0066] (4) The assembly sequence from inside to outside is shown in Figure 6 to Figure 8 , which includes the inner fixed ring 2, the outer wear-resistant ring 1, and the wear-resistant blade 3. The components are locked from outside to inside using bolts 4, and the holes in the heads of the bolts are reserved counterbores in the wear-resistant blade. After the fixed bolts are locked, the steel plate is sealed to prevent affecting the flow direction of the wind field inside the mill.

[0067] The bolts are provided with elastic washers, and the heads of the bolts are spot-welded to the high chromium cast iron to prevent the nozzle from falling off during use. The material of the sealing steel plate is 304. Embodiment

[0068] A method for manufacturing a combined wear-resistant nozzle movable ring of a ZGM medium-speed coal mill, comprising the following steps:

[0069] (1) Preparation of ceramic particle reinforced high chromium cast iron base wear-resistant blade: first, uniformly mix ZTA ceramic particles, boron carbide powder, titanium carbide powder, zirconia powder, and high chromium cast iron powder to prepare a porous ceramic preform and solidify it in an EPS lost mold. The mold is provided with counterbores as subsequent assembly holes. High chromium cast iron melt is cast by negative pressure infiltration process. After 24 hours of heat preservation, the mold is opened and the preform is taken out and heat treated. The final blade structure is shown in Figure 5

[0070] In this embodiment, the content of zirconia in the ZTA (zirconia toughened alumina) ceramic particles accounts for 80% of the total mass percentage of the particles, and the particle size of the ceramic particles is 80-120 mesh.​​

[0071] In this embodiment, ZTA ceramic particles, boron carbide powder, titanium carbide powder, zirconium oxide powder, and high-chromium cast iron powder are mixed according to a mass ratio of 6:1:0.5:0.5:2, and then the mixed powder is mixed with high-temperature glue according to a mass ratio of 9:1, wherein the high-temperature glue is prepared by mixing water glass and aluminum sol.

[0072] In this embodiment, the solidification method of the porous ceramic preform is as follows: carbon dioxide is introduced into the porous ceramic preform at a flow rate of 1500 L / h, and then the porous ceramic preform is placed in a holding furnace for solidification, wherein the temperature of the holding furnace is 85℃, and the holding time is 2 h.

[0073] In this embodiment, the density of the EPS mold is 32 Kg / m 3 ; the EPS mold is immersed in the iron ore powder coating slurry so that a layer of coating is uniformly adhered to the surface of the mold, the coating has a Bomee degree of 70 Bh, and the mold surface needs to be immersed in the coating for 3 times, after the first and second immersions, the mold is placed in an oven at 50℃ for drying for 12 hours, after the third immersion, the mold is placed in an oven at 50℃ for drying for 24 hours, and then the mold is placed in a special sand box.

[0074] In this embodiment, the negative pressure casting and infiltration process is as follows: high-chromium cast iron is smelted, the high-chromium cast iron includes chemical components with mass percentages of Cr: 24%, C: 3.5%, Mn: 2.0%, Si: 1.7%, Mo: 2.5%, Ni: 2.0%, V: 0.6%, Ti: 1.0%, and the balance is iron and impurities; the high-chromium cast iron melt is poured into a sand mold, at this time, a negative pressure system is started, the pressure of the negative pressure system is 0.08 MPa, and the pressure holding time before and after pouring is 10 min., and the casting is taken out after being kept at temperature for 24 h.

[0075] In this embodiment, as shown in Figure 1 , the heat treatment process is as follows: increasing the temperature from 150℃ to 250℃ at a rate of 50℃ / h, keeping the temperature for 1 hour; increasing the temperature to 550℃ at a rate of 50℃ / h, keeping the temperature for 1 hour; increasing the temperature to 850℃ at a rate of 85℃ / h, keeping the temperature for 1 hour; increasing the temperature to 1150℃ at a rate of 50℃ / h, keeping the temperature for 4 hours; and then air cooling to room temperature; the casting after the above normalizing process is placed in a holding furnace for tempering, and the tempering process is as shown in Figure 2 : increasing the temperature to 280℃ at a rate of 90℃ / h, keeping the temperature for 5 hours, and then air cooling to room temperature.

[0076] (2) Preparing the outer wear-resistant ring: the bimetallic wear-resistant plate is cut into a specified size by numerical control machining, a special-shaped hole is uniformly cut in the inside, and the bimetallic wear-resistant plate is rolled into a ring shape by using a plate rolling machine, and the final structure of the outer wear-resistant ring is as shown in Figure 4 .

[0077] In the embodiment, the outer wear-resistant ring material is high-chromium cast iron / carbon steel bimetallic wear-resistant plate, the thickness of the high-chromium cast iron and the carbon steel is 6 mm and 8 mm respectively; the special-shaped hole is a sample curve with the wear-resistant blade outer profile being inwardly offset by 1-3 cm, the blanked bimetallic wear-resistant plate is rolled into a ring shape by using a plate rolling machine; and the high-chromium cast iron layer of the prepared ring-shaped bimetallic wear-resistant plate is outward. The high-chromium cast iron layer material is: C: 5.5%, Cr: 35%, Mo: 9%, Nb: 8%, V: 2%, W: 7%, and the balance is iron and impurities.

[0078] (3) Preparation of the inner fixed ring: the steel plate is blanked into a specified shape by numerical control processing, including a ring shape and a sector shape; the steel plate is rolled into a ring shape, and then the sector shape is welded at one end of the ring-shaped steel plate; a threaded hole is processed on the side surface of the ring-shaped plate to facilitate the installation of other components in the subsequent process; a counterbore is processed on the sector-shaped plate as a mounting hole on the mill in the subsequent process; and finally, the structure of the inner fixed ring is as shown in Figure 3

[0079] The steel plate material of the inner fixed ring is Q355, the outer diameter of the inner fixed ring is the same as the inner diameter of the bimetallic wear-resistant plate, a threaded hole is processed on the side surface of the ring-shaped plate, the threaded hole is M16-M30, and the threaded hole is a through hole.

[0080] (4) The assembly sequence from the inside to the outside is as shown in Figure 6 to Figure 8 , the inner fixed ring 2, the outer wear-resistant ring 1, and the wear-resistant blade 3, the bolts 4 are used to lock the components from the outside to the inside, the holes in the heads of the bolts are counterbore holes reserved in the wear-resistant blade, and a steel plate is used to seal after the fixed bolts are locked to prevent affecting the wind field flow in the mill.

[0081] The bolts are provided with elastic washers, the heads of the bolts are spot-welded with the high-chromium cast iron to prevent the movable ring nozzle from falling off during use, and the material of the sealing steel plate is Q355.

[0082] The above is only a preferred embodiment of the present application, and does not limit the present application in any form. Although the present application has been disclosed as above with a preferred embodiment, it is not intended to limit the present application. Any person skilled in the art can make some changes or modifications to the above disclosed technical content without departing from the scope of the technical solution of the present application to obtain equivalent embodiments with equivalent changes, but any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present application shall still fall within the scope of the technical solution of the present application.​

Claims

1. A method for manufacturing a combined wear-resistant nozzle dynamic ring for a ZGM type medium-speed coal mill, characterized in that: Includes the following steps: (1) Preparation of ceramic particle-reinforced high-chromium cast iron-based wear-resistant blades: First, ceramic particles are uniformly mixed with boron carbide powder, titanium carbide powder, zirconium oxide powder and high-chromium cast iron powder to prepare a porous ceramic preform and solidify it. The preform is fixed in an EPS lost matter mold with countersunk holes for subsequent assembly. High-chromium cast iron melt is cast using a negative pressure casting process. After heat preservation for 24 hours, it is taken out of the box and heat-treated. The mass ratio of ceramic particles to boron carbide powder, titanium carbide powder, zirconium oxide powder and high-chromium cast iron powder is 6:1:0.5:0.5:

2. (2) Preparation of outer wear-resistant ring: The bimetallic wear-resistant plate is cut into the specified size by CNC machining, and irregular holes are cut evenly inside. The bimetallic wear-resistant plate is rolled into a ring shape using a plate rolling machine. (3) Preparation of inner fixing ring: The steel plate is cut into the specified shape by CNC machining, including ring and sector; the steel plate is rolled into a ring, and then the sector is welded to one end of the ring steel plate. Threaded holes are machined on the side of the ring plate to facilitate the installation of other components. Countersunk holes are machined on the sector plate as installation holes on the coal mill. (4) The assembly sequence of the above components from the inside to the outside is: inner fixing ring, outer wear-resistant ring, wear-resistant blade. Each component is locked from the outside to the inside with bolts. The hole at the head of the bolt is the countersunk hole reserved for the wear-resistant blade. After the fixing bolts are locked, the opening is sealed with a steel plate to prevent affecting the airflow direction inside the coal mill.

2. The method for manufacturing a combined wear-resistant nozzle dynamic ring for a ZGM type medium-speed coal mill according to claim 1, characterized in that: The ceramic particles mentioned in step (1) are made of ZTA, with a zirconium oxide content of 30%-80% and a particle size of 80-120 mesh.

3. The method for manufacturing a combined wear-resistant nozzle dynamic ring for a ZGM type medium-speed coal mill according to claim 2, characterized in that: The ceramic particles are mixed with boron carbide powder, titanium carbide powder, zirconium oxide powder, and high-chromium cast iron powder. Then, the mixed powder is mixed with high-temperature adhesive at a mass ratio of 9:

1. The high-temperature adhesive is made by mixing one or more of water glass, silica sol, and alumina sol.

4. The method for manufacturing a combined wear-resistant nozzle dynamic ring for a ZGM type medium-speed coal mill according to claim 1, characterized in that: The curing method of the porous ceramic preform in step (1) is as follows: carbon dioxide is introduced into the porous ceramic preform at a flow rate of 800-1500 L / h, and then it is placed in a heat preservation furnace for curing at a temperature of 65-85℃ for 1-2 h.

5. The method for manufacturing a combined wear-resistant nozzle dynamic ring for a ZGM type medium-speed coal mill according to claim 1, characterized in that: The density of the EPS lost-wax die mentioned in step (1) is 25-32 kg / m³. 3 Immerse the EPS disappearing mold in iron ore powder coating slurry to make the mold surface evenly adhere to a layer of coating. The coating has a Baume degree of 56-70 Bh. The mold surface needs to be coated three times. After the first and second coatings, place it in a drying oven at 50℃ for 12 hours. After the third coating, dry it in a drying oven at 50℃ for 24 hours. Then place the mold in a special sand box.

6. The method for manufacturing a combined wear-resistant nozzle dynamic ring for a ZGM type medium-speed coal mill according to claim 1, characterized in that: The negative pressure casting process described in step (1) is as follows: smelting high-chromium cast iron, the high-chromium cast iron including the following chemical composition by mass percentage: Cr: 20-24%, C: 3.0-3.5%, Mn: 1.5-2.0%, Si: 1.2-1.7%, Mo: 1.8-2.5%, Ni: 1.0-2.0%, V: 0.4-0.6%, Ti: 0.5-1.0%; pouring the high-chromium cast iron melt into the sand mold, at which time the negative pressure system is turned on, the pressure of the negative pressure system is 0.06-0.08 MPa, the holding time before and after casting is 10 min, and the casting is taken out after holding at the temperature for 24 h.

7. The method for manufacturing a combined wear-resistant nozzle dynamic ring for a ZGM type medium-speed coal mill according to claim 1, characterized in that: The heat treatment process described in step (1) is as follows: the temperature is increased from 150°C to 250°C at 50°C / h and held for 1 hour; the temperature is increased to 550°C at 50°C / h and held for 1 hour; the temperature is increased to 850°C at 85°C / h and held for 1 hour; the temperature is increased to 1150°C at 50°C / h and held for 4 hours; then the temperature is cooled to room temperature by air; the casting that has completed the above normalizing process is placed in a holding furnace for tempering. The tempering process is as follows: the temperature is increased to 280°C at 90°C / h and held for 5 hours, then the temperature is cooled to room temperature by air.

8. The method for manufacturing a combined wear-resistant nozzle dynamic ring for a ZGM type medium-speed coal mill according to claim 1, characterized in that: The outer wear-resistant ring in step (2) is made of high-chromium cast iron / carbon steel bimetallic wear-resistant plate; the irregular hole shape is a spline curve with the outer contour of the wear-resistant blade offset inward by 1-3cm. The cut bimetallic wear-resistant plate is rolled into a ring shape using a plate rolling machine; the high-chromium cast iron layer in the annular bimetallic wear-resistant plate is outward.

9. The method for manufacturing a combined wear-resistant nozzle dynamic ring for a ZGM type medium-speed coal mill according to claim 1, characterized in that: The inner fixing ring in step (3) is made of Q355 steel plate. The outer diameter of the inner fixing ring is the same as the inner diameter of the bimetallic wear-resistant plate. Threaded holes are machined on the side of the annular steel plate. The threaded holes are M16-M30 and are through holes.

10. The method for manufacturing a combined wear-resistant nozzle dynamic ring for a ZGM type medium-speed coal mill according to claim 1, characterized in that: The bolts described in step (4) are equipped with elastic washers, and the bolt heads are spot-welded to high-chromium cast iron to prevent the moving ring nozzle from falling off during use. The sealing steel plate is made of one of Q235, 304, or Q355.

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