Die-casting mold and production process of bimetallic composite hammer head for hammer crusher

Abstract

The present invention relates to a die-casting mold and production process of a bimetallic composite hammer head for a hammer crusher, belonging to the field of metal die-casting technology, wherein a replaceable core is installed inside the mold sleeve, a core is installed inside the mold core, and the core and the mold core are combined to form a casting mold cavity, firstly, a mold release agent is sprayed on the surface of the mold core and preheated, the mold core after preheating and expansion is loaded into the mold sleeve, 35# steel melt and high chromium cast iron melt are poured into the mold cavity, the filling speed is controlled until the excess high chromium cast iron melt flows out of the overflow tank, the casting is stopped, and then the hydraulic press is quickly operated to control the upper mold mechanism to press down, and the pressure is maintained for a period of time when the pressure reaches the lowest point, the hydraulic press is operated to lift the upper mold mechanism, the ejector rod ejects the core, and the hammer head after the liquid forging operation is completed is taken out, and the hammer head is placed in a resistance furnace for heat treatment. The internal grain structure of the bimetallic composite hammer head prepared by the present invention is more refined, the carbide distribution is more uniform, the bimetallic interface bonding strength is higher, and the service life is greatly increased.

Description

Technical Field

[0001] The invention relates to the technical field of metal die-casting, and in particular to a die-casting mold and a production process of a bimetallic composite hammer head for a hammer crusher. Background Art

[0002] Hammer crusher is a production equipment widely used in building materials, metallurgy, fertilizer and other industrial sectors. Since the materials to be crushed are generally hard objects such as rocks and metal ores, the working surface of the hammer head contacts the materials, resulting in high-stress wear, causing the hammer head to become a highly consumable and easily worn part.

[0003] In thermal power generation systems, circulating fluidized bed boilers with low pollution emissions are used on a large scale. In order to reduce economic costs, low-calorific value and low-quality coal are often used as fuel. Large pieces of low-quality coal are broken into small pieces by hammer crushers before use to enhance combustion performance and make it burn more fully.

[0004] Figure 1 This is a schematic diagram of the structure of the die-casting mold of the bimetallic composite hammer. The hammer head is the main force-bearing part. It needs to continuously strike and crush the coal blocks during the crushing process. Therefore, this part needs to have high hardness and high wear resistance. The tail part of the hammer is equipped with a lug for connecting to the hammer handle. Therefore, this part needs to have good impact toughness. If a high-hardness material is used, it is very easy for the lug to break and the hammer to fall into the crushing cavity and cause damage. The traditional bimetallic composite hammer adopts the sand casting production process. The hammer head and the tail of the hammer are cast with two metal solutions respectively, and the blank is formed after natural cooling. Due to the different casting temperatures and solidification ranges of the two metals, shrinkage, slag inclusions, pores and other defects are inevitable, which greatly affects the life of the bimetallic composite hammer.

[0005] The service life of the traditional sand casting bimetallic hammer can reach 9-12 months when crushing high-quality coal, but it is less than 3 months when crushing low-quality coal. Therefore, this application proposes to use liquid die forging technology to produce bimetallic composite hammers, aiming to improve the hardness of the hammer and significantly increase its service life when crushing low-quality coal. Summary of the invention

[0006] In view of the deficiencies in the prior art, the present invention provides a die-casting mold and production process for a bimetallic composite hammer head for a hammer crusher. The internal grain structure of the bimetallic composite hammer head is finer, the carbide distribution is more uniform, the bimetallic interface bonding strength is higher, and the service life is greatly increased. At the same time, a hydraulic die forging production process is adopted, the metal liquid utilization rate is high, and the remelting of the riser is eliminated, the efficiency is high and the energy consumption is low. Compared with sand core casting, the solid waste emission is significantly reduced, and green manufacturing is achieved.

[0007] The present invention is achieved through the following technical solutions:

[0008] A die-casting mold for a bimetallic composite hammer head for a hammer crusher comprises an upper mold mechanism, a mold sleeve and a lower mold mechanism. The upper mold mechanism comprises an upper mold plate and a punch, the punch is fixed to the upper mold plate by bolts, the lower mold mechanism comprises a lower mold plate and an ejector rod, the ejector rod is slidably mounted on the lower mold plate, the bottom of the mold sleeve is fixed to the lower mold plate by bolts, the upper mold plate is slidably assembled on the mold sleeve by a guide member, a replaceable mold core is installed inside the mold sleeve, a mold core is installed inside the mold core, the mold core and the mold core are combined to form a casting mold cavity, and an overflow groove is opened at an upper opening on one side of the mold core.

[0009] Preferably, the mold core adopts a vertical mold splitting method, and the mold core is divided into two parts, the left and right parts, and the parting surface runs through the entire mold cavity.

[0010] The present invention also relates to a production process of a bimetallic composite hammer head, comprising the following steps:

[0011] S1: Spray the mold release agent on the surface of the mold core and preheat it at a temperature of 200-300°C. Put the preheated and expanded mold core into the mold sleeve so that the gap between the mold core and the mold sleeve meets the exhaust requirements.

[0012] S2: Pour 35# steel melt into the mold cavity at a casting temperature of 1520-1550°C. Stop pouring after the 35# steel melt completely covers the core and wait for cooling to 1000-1100°C.

[0013] S3: Continue pouring high chromium cast iron melt into the mold cavity at a casting temperature of 1420-1450°C and a filling speed of 300-400 mm / s until excess high chromium cast iron melt flows out of the overflow trough, and then stop pouring;

[0014] S4: After stopping casting, quickly operate the hydraulic press to control the upper die mechanism to press down, and keep the pressing speed at 10-15mm / s. When pressing to the lowest point, keep the pressure for a while, and the holding pressure is 80-120MPa;

[0015] S5: Operate the hydraulic press to lift the upper die mechanism, and the ejector rod will eject the die core, and take out the hammer head after the liquid forging operation is completed.

[0016] Place in resistance furnace for heat treatment.

[0017] Preferably, the heat treatment in S5 specifically includes the following steps: after the hammer head is placed in the resistance furnace, the temperature is raised to 700°C within 2 hours, kept warm for 1 hour, then continued to be raised to 960°C within 2 hours, kept warm for 4 hours, and then quickly taken out of the furnace and cooled.

[0018] Preferably, after the heat treatment and quenching are completed, in order to eliminate the residual stress of the hammer head, it is tempered, the cold material is charged into the furnace, the temperature is raised to 350° C. with the furnace within 2 hours, kept at this temperature for 4 hours, and then taken out of the furnace and air-cooled.

[0019] Preferably, the holding time in step S4 is t, and the holding time t is calculated according to the formula σ K , where σ is the equivalent solidification thickness of the casting, which is 6-8 cm; K is the solidification constant, which is 20-30 .

[0020] In summary, the beneficial technical effects of the present invention are as follows: the bimetallic composite hammer prepared by the liquid die forging process can make the casting and the mold fully contact due to the pressure, increase the heat dissipation area, greatly accelerate the cooling rate of the molten metal, shorten the solidification time, so that the atoms such as C, Cr, and Mn in the molten metal have no time to diffuse and transfer, make the metallographic structure grains finer, and make the carbide distribution more uniform, which is conducive to the mutual penetration between the contact interfaces of the two molten metals, and the interface bonding strength is higher. The hardness and wear resistance of the hammer are significantly improved. At the same time, the utilization rate of the molten metal is high, and the remelting of the riser is eliminated. The efficiency is high and the energy consumption is low. Compared with sand core casting, the solid waste emission is significantly reduced, and green manufacturing is achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a structural schematic diagram of the die casting mold;

[0022] Figure 2 This is the metallographic diagram of the bimetallic composite hammer head cast by traditional sand core;

[0023] Figure 3 It is a metallographic diagram of the bimetallic composite hammer head forged by hydraulic die forging of the present invention.

[0024] In the figure, 1, upper template; 2, guide part; 3, punch; 4, die sleeve; 5, die core; 6, core; 7, ejector rod; 8, lower template. DETAILED DESCRIPTION

[0025] The present invention is further described in detail below in conjunction with the accompanying drawings.

[0026] Reference Figure 1 A die-casting mold for a bimetallic composite hammer head for a hammer crusher comprises an upper mold mechanism, a mold sleeve 4 and a lower mold mechanism, the upper mold mechanism comprises an upper mold plate 1 and a punch 3, the punch 3 is fixed to the upper mold plate 1 by bolts, the lower mold mechanism comprises a lower mold plate 8 and an ejector rod 7, the ejector rod 7 is slidably mounted on the lower mold plate 8, the bottom of the mold sleeve 4 is fixed to the lower mold plate 8 by bolts, the upper mold plate 1 is slidably assembled on the mold sleeve 4 through a guide member 2, a replaceable mold core 5 is installed inside the mold sleeve 4, a core 6 is installed inside the mold core 5, the core 6 and the mold core 5 are combined to form a casting mold cavity, an overflow groove is opened at the upper mouth of one side of the mold core 5, the mold core 5 adopts a vertical surface parting method, the mold core 5 is divided into left and right parts, and its parting surface runs through the entire mold cavity.

[0027] By vertically parting the mold, the parting surface can run through the entire mold cavity, which is beneficial to the discharge of gas in the mold cavity during die-casting, avoiding defects such as pores and shrinkage in the workpiece, and improving the quality of the finished product. By setting an overflow groove, the height of the molten metal in the mold cavity can be effectively controlled to ensure the dimensional accuracy in the height direction. At the same time, impurities such as oxides and coating slag floating on the top of the molten metal during pouring can be discharged from the mold cavity together to ensure the stability of the workpiece composition.

[0028] The present invention also relates to a production process of a bimetallic composite hammer head, comprising the following steps:

[0029] S1: Spray a mold release agent on the surface of the mold core 5 and preheat it at a temperature of 200-300°C. Place the preheated and expanded mold core 5 into the mold sleeve 4 so that the gap between the mold core 5 and the mold sleeve 4 meets the exhaust requirements.

[0030] S2: Pour 35# steel melt into the mold cavity at a casting temperature of 1520-1550°C. Stop pouring after the 35# steel melt completely covers the core 6 and wait for cooling to 1000-1100°C.

[0031] S3: Continue pouring high chromium cast iron melt into the mold cavity at a casting temperature of 1420-1450°C and a filling speed of 300-400 mm / s until excess high chromium cast iron melt flows out of the overflow trough, and then stop pouring;

[0032] S4: After stopping casting, quickly operate the hydraulic press to control the upper die mechanism to press down, and keep the pressing speed at 10-15mm / s. When pressing to the lowest point, keep the pressure for a while, and the holding pressure is 80-120MPa;

[0033] S5: Operate the hydraulic press to lift the upper die mechanism, and the ejector rod 7 ejects the die core 5, and take out the hammer head after the liquid forging operation is completed, and put the hammer head into the resistance furnace for heat treatment.

[0034] Specifically, the heat treatment in S5 specifically includes the following steps: after the hammer head is placed in the resistance furnace, the temperature is raised to 700°C with the furnace within 2 hours, kept at this temperature for 1 hour, and then continued to be raised to 960°C within 2 hours, kept at this temperature for 4 hours, and then quickly removed from the furnace for cooling. After the heat treatment quenching is completed, in order to eliminate the residual stress of the hammer head, it is tempered, the cold material is loaded into the furnace, and the temperature is raised to 350°C with the furnace within 2 hours, kept at this temperature for 4 hours, and then removed from the furnace for air cooling.

[0035] Specifically, the holding time in step S4 is t, and the holding time t is calculated according to the formula σ K , where σ is the equivalent solidification thickness of the casting, which is 6-8 cm; K is the solidification constant, which is 20-30 .

[0036] In this embodiment, the casting temperature of the 35# steel melt in S2 is 1520°C, and the temperature is cooled to 1300°C; the casting temperature of the high chromium cast iron melt in S3 is 1420°C, and the filling speed is 300mm / s; the pressing speed in S4 is 10mm / s, and the holding time t is calculated according to the formula σ K In this embodiment, σ is 8 cm and K is 25 , substituting into the formula, we can get t=10min, and the holding pressure is 80MPa.

[0037] Reference Figure 2 and Figure 3 , Figure 2 This is the metallographic diagram of the bimetallic composite hammer head cast by traditional sand core. Figure 3 This is a metallographic diagram of the bimetallic composite hammer head of the hydraulic die forging of the present invention. The present invention pressurizes the molten metal during the solidification process to increase the degree of supercooling, so that the austenite has no time to grow and is restricted by the eutectic structure. The austenite crystals are continuously refined. Figure 2 and Figure 3 It can be seen that the martensite structure in the bimetallic composite hammer head of the liquid die forging process is smaller, and while maintaining the basic shape, it can form a phase distribution trend with the carbide, so that there is more austenite in the same space and the structure is more uniform. The external manifestation is that the hardness and wear resistance of the hammer head are significantly improved.

[0038] The hardness of the bimetallic composite hammers of the two processes was tested under the same parameters. The test results are shown in the following table.

[0039] Molding process Sand Casting Liquid die forging Heat treatment process Sub-temperature quenching Sub-temperature quenching Average hardness 56.5 59.3

[0040] The wear resistance of the bimetallic composite hammer heads produced by the two processes was compared under the same parameters. The test results are shown in the following table.

[0041] Molding process Sand Casting Liquid Die Forging Weight before grinding / kg 10.3 11.3 Weight after grinding / kg 9.5 10.8 Grinding weight ratio / % 7.7 4.4 Grinding thickness / mm 10 6

[0042] It can be seen from the above two tables that compared with traditional sand casting, the average hardness and wear resistance of the bimetallic composite hammer head of liquid die forging are significantly improved, the crushing performance is better, and the service life is longer.

[0043] Since the casting temperatures of 35# cast steel and high chromium cast iron are different, their shrinkage rates are also different. The hammer head cast by sand mold is very likely to have pores and flaky scars at the junction of the two metals, affecting the yield rate. The hydraulic die-forged bimetallic composite hammer head, due to its continuous pressure compensation shrinkage characteristics, greatly reduces the defects of the bonding surface, the interface of the two metals is more delicate, and the permeability between them is stronger.

[0044] The implementation principle of this embodiment is: the bimetallic composite hammer head prepared by liquid die forging process can make full contact between the casting and the mold due to pressure, increase the heat dissipation area, greatly accelerate the cooling rate of the molten metal, shorten the solidification time, so that the atoms such as C, Cr, Mn in the molten metal have no time to diffuse and transfer, make the metallographic grains more refined, and the carbide distribution more uniform, which is conducive to the mutual penetration between the contact interface of the two molten metals, and the interface bonding strength is higher. The hardness and wear resistance of the hammer head are significantly improved. At the same time, the utilization rate of the molten metal is high, and the remelting of the riser is omitted. It is efficient and energy-saving. Compared with sand core casting, solid waste emissions are significantly reduced, realizing green manufacturing.

[0045] The embodiments of this specific implementation method are all preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Therefore, all equivalent changes made based on the structure, shape, and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A production process for a bimetallic composite hammer head for a hammer crusher, wherein the die casting mold using the production process comprises an upper die mechanism, a die sleeve (4) and a lower die mechanism, wherein the upper die mechanism comprises an upper die plate (1) and a punch (3), wherein the punch (3) is fixed to the upper die plate (1) by bolts, wherein the lower die mechanism comprises a lower die plate (8) and an ejector rod (7), wherein the ejector rod (7) is slidably mounted on the lower die plate (8), wherein the bottom of the die sleeve (4) is fixed to the lower die plate (8) by bolts, wherein the upper die plate (1) is slidably mounted on the die sleeve (4) by a guide member (2), wherein a replaceable die core (5) is installed inside the die sleeve (4), wherein a mold core (6) is installed inside the mold core (5), wherein the mold core (6) and the mold core (5) are combined to form a casting mold cavity, wherein an overflow groove is provided at an upper opening on one side of the mold core (5), wherein the mold core (5) is split by a vertical surface, wherein the mold core (5) is divided into left and right parts, wherein the split surface thereof runs through the entire mold cavity, ... The production process includes the following steps: S1: Spray a mold release agent on the surface of the mold core (5) and preheat it at a temperature of 200-300° C. Place the preheated and expanded mold core (5) into the mold sleeve (4) so ​​that the gap between the mold core (5) and the mold sleeve (4) meets the exhaust requirements; S2: pouring 35# steel melt into the mold cavity at a casting temperature of 1520-1550°C, and stopping pouring after the 35# steel melt completely covers the core (6), and waiting for cooling to 1000-1100°C; S3: Continue pouring high chromium cast iron melt into the mold cavity at a casting temperature of 1420-1450°C and a filling speed of 300-400 mm / s until excess high chromium cast iron melt flows out of the overflow trough, and then stop pouring; S4: After stopping casting, quickly operate the hydraulic press to control the upper die mechanism to press down, and keep the pressing speed at 10-15mm / s. When pressing to the lowest point, keep the pressure for a while, and the holding pressure is 80-120MPa; S5: The hydraulic press is operated to lift the upper die mechanism, and the ejector rod (7) ejects the die core (5), and the hammer head after the liquid forging operation is taken out, and the hammer head is placed in a resistance furnace for heat treatment.

2. The production process of a bimetallic composite hammer head for a hammer crusher according to claim 1, characterized in that: The heat treatment in S5 specifically includes the following steps: after the hammer head is placed in the resistance furnace, the temperature is raised to 700°C within 2 hours, kept at this temperature for 1 hour, and then further raised to 960°C within 2 hours, kept at this temperature for 4 hours, and then quickly taken out of the furnace and cooled.

3. The production process of a bimetallic composite hammer for a hammer crusher according to claim 1, characterized in that: After the heat treatment and quenching are completed, in order to eliminate the residual stress of the hammer head, it is tempered. The cold material is loaded into the furnace, and the temperature is raised to 350℃ with the furnace within 2 hours, kept at this temperature for 4 hours, and then taken out of the furnace for air cooling.

4. The production process of a bimetallic composite hammer for a hammer crusher according to claim 1, characterized in that: The holding time in step S4 is t, and the holding time t is calculated according to the formula σ K , where σ is the equivalent solidification thickness of the casting, which is 6-8 cm; K is the solidification constant, which is 20-30 .

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