A production process of elevator counterweight

Abstract

The application discloses a low-cost die-casting production process of elevator counterweight. It comprises the following steps in sequence: selecting long iron shavings, short iron shavings, particle steel, reduced iron powder and graphite powder as raw materials; adopting the short iron shavings and the particle steel to obtain a base material, adopting the short iron shavings and the long iron shavings and the particle steel to obtain an upper base material, and adopting the premixed powder; sequentially laying the base material and the upper base material into a mold, and performing three-stage feeding and cold pressing at normal temperature to obtain a blank; after the heat treatment of the blank, pressure is increased to perform hot pressing; and cooling and post-processing are performed. The method can significantly reduce internal composition segregation of the product, greatly optimize density uniformity and structural mechanical strength of the final product, reduce internal structural defects of the product, and significantly improve product performance.

Description

Technical Field

[0001] This invention relates to the field of elevator counterweight processing technology, and more particularly to a production process for elevator counterweights. Background Technology

[0002] The elevator counterweight is a core safety component of the elevator counterweight system, used to balance the car's own weight and rated load, directly determining the elevator's safety, stability, and energy consumption. Current mainstream counterweight manufacturing technologies have significant technical and cost shortcomings: Existing technologies often use cast iron counterweights, which, while having high density and strength, require high-temperature smelting above 1500℃, resulting in high energy consumption, large carbon emissions, and reliance on pig iron / scrap steel as raw materials, leading to high overall costs. Some existing technologies use high-density concrete to reduce costs, but concrete counterweights have low density (only 3.5–4.5 g / cm³), large volume, occupying shaft space, low compressive strength, poor impact resistance, and are prone to chipping and cracking, making them only suitable for low-end, low-speed elevators. Other existing technologies use iron filings pressed at room temperature, a simple process, but the interlocking strength between material particles is low, leading to easy breakage and chipping, with a density of only 4.0–5.2 g / cm³. 3 It cannot meet the requirements of mid-to-high-end elevators.

[0003] Furthermore, to reduce costs, there are currently publicly disclosed production processes for elevator counterweights using iron shavings, particle steel, and iron powder / scrap iron filings as raw materials. However, due to the significant differences in the shape, flowability, and other characteristics of the various raw material components, and the unreasonable design of the manufacturing process with key defects, the final product counterweights are prone to internal stratification, uneven density distribution, and structural defects such as numerous voids or cavities. For example, iron shavings are long, curled, and filamentous, easily forming arches, bridges, and clumps, resulting in large internal voids or cavities. Moreover, they have high resistance to plastic deformation and medium density. If they are simply mixed directly with other components such as particle steel and iron powder and processed using conventional die-casting processes, it is very easy to cause severe gravity segregation and structural stratification within the finished product, insufficient and uneven filling of particles of different sizes, or the presence of numerous voids or cavities, thus affecting the product's density, internal density uniformity, and structural mechanical strength. For example, CN 111283386A discloses a method for preparing elevator counterweights using iron shavings, particle steel, and iron powder / scrap iron filings as raw materials, and through main steps such as raw material processing, material mixing, room temperature cold pressing, and heating and hot pressing. This method can reduce porosity, improve product density, and ensure high density. However, the counterweights prepared by this method will have obvious compositional gravity segregation problems, which can easily cause uneven performance of the counterweight edge and core structure, as well as the upper, middle, and lower layers inside, and more serious preparation defects such as easy delamination and even cracking of the internal structure. Summary of the Invention

[0004] The purpose of this invention is to provide a low-cost die-casting production process for elevator counterweights. This method can significantly reduce internal component segregation, greatly optimize the density uniformity and structural mechanical strength of the final elevator counterweight, reduce internal structural defects, and significantly improve product performance.

[0005] The objective of this invention is achieved through the following technical solution: A low-cost manufacturing process for elevator counterweights, characterized by using the following raw materials in sequence and following these steps: (1) Raw material pretreatment: Iron shavings are pretreated to obtain long iron shavings and short iron shavings; (2) Raw material preparation: Long iron shavings and short iron shavings, particle steel, reduced iron powder and graphite powder are selected as raw materials; (3) Take a portion of the granulated steel and short iron shavings and mix them evenly to obtain the base material; take the long iron shavings and mix them evenly with the remaining granulated steel and short iron shavings to obtain the upper base material; take a portion of the reduced iron powder and mix it evenly with the graphite powder to obtain the premixed powder. (4) The base material and the upper substrate are sequentially laid into the mold and subjected to three-stage feeding and room temperature cold pressing. Specifically, the first stage is to add the premixed powder and press at room temperature and low pressure; the second stage is to add a large amount of reduced iron powder and continue to press at room temperature and medium pressure; the third stage is to add the remaining reduced iron powder and continue to press at room temperature and high pressure. After pressing, the pressure is released and the blank is demolded. (5) Heat treat the blank, then transfer it to the hot press mold, and quickly close the mold and press it to form a hot press. (6) Cooling and post-treatment.

[0006] Furthermore, the aforementioned low-cost elevator counterweight die-casting production process is characterized by using the following raw materials in sequence according to the following steps: (1) Raw material pretreatment: Iron shavings are degreased, impurities removed, crushed and screened to obtain long iron shavings and short iron shavings; Particle steel is subjected to impurity removal treatment; (2) Raw material preparation: Select long iron shavings and short iron shavings, particle steel, reduced iron powder and graphite powder with specific size requirements and weight ratios as raw materials; (3) Take 2 / 5 of the total particle steel and 1 / 2 of the total short iron shavings and mix them evenly to obtain the base material; take the long iron shavings and mix them evenly with the remaining particle steel and short iron shavings to obtain the upper base material; take 1 / 5 of the total reduced iron powder and mix them evenly with graphite powder to obtain the premixed powder. (4) The base material and the upper substrate are sequentially laid into the mold and subjected to three-stage feeding and room temperature cold pressing. Specifically, the first stage is to add the premixed powder and press at room temperature and low pressure; the second stage is to add reduced iron powder accounting for 3 / 5 of the total amount of reduced iron powder and continue to press at room temperature and medium pressure; the third stage is to add the remaining reduced iron powder and continue to press at room temperature and high pressure. After pressing, the pressure is released and the blank is demolded. (5) Heat treat the blank, then transfer it to the hot press mold, and quickly close the mold and press it to form a hot press. (6) Cooling and post-treatment.

[0007] To further clarify, the thickness of the iron shavings mentioned in step (1) above is 0.5 to 2.0 mm and the length is controlled between 10 and 50 mm. The source of the shavings can be various types of shavings obtained after processing materials such as Q235B, Q355B, and cast iron, or other conventional sources.

[0008] To further clarify, in step (2) above, the length of the long iron shavings is 12-20 mm, and the weight percentage is 14-16.9 parts; the length of the short iron shavings is 5-10 mm, and the weight percentage is 50.2-67.8 parts; the particle steel is selected from spherical particle steel with rounded particles and no sharp corners, and is composed of two types with particle sizes of 0.5-1.5 mm and 2.0-3.5 mm mixed in a weight ratio of 1:1, with an iron content ≥94%, and the weight percentage is 20-23.3 parts; the reduced iron powder is composed of 55%-65% by weight of 200-mesh coarse reduced iron powder and 35%-45% by weight of 400-mesh fine reduced iron powder, and the weight percentage is 10-11.7 parts; the weight percentage of the graphite powder is 0.5-0.8 parts.

[0009] To further clarify, in step (4) above, during the first stage of low-pressure pressing at room temperature, a pressure of 300 to 450 tons is applied, the pressing speed is 5 to 8 mm / s, and the pressure is held for 5 to 6 seconds; during the second stage of medium-pressure pressing at room temperature, the pressure is increased to 1200 to 1500 tons, the pressing speed is 3 to 5 mm / s, and the pressure is held for 5 to 6 seconds; during the third stage of high-pressure pressing at room temperature, the pressure is increased to 3000 tons, the pressing speed is 2 to 3 mm / s, and the pressure is held for 12 to 15 seconds. After pressing, the pressure is released and the blank is demolded.

[0010] To further clarify, step (5) above specifically involves placing the blank at 900±20℃ for 8 to 12 minutes, then transferring it to a hot press mold, ensuring that the mold entry temperature is ≥850℃, quickly closing the mold and increasing the pressure to 5000 tons, holding the pressure for 15 to 20 seconds for bidirectional hot pressing, and then demolding to obtain the counterweight block.

[0011] To further clarify, step (6) above specifically involves cooling the counterweight to a surface temperature ≤60°C using air cooling, removing burrs and surface oxide scale until the surface roughness reaches Ra12.5 or less, and finally spraying anti-rust paint.

[0012] Although existing technologies use iron shavings, granulated steel, and iron powder / scrap iron filings as raw materials, and process them sequentially through main steps such as raw material treatment, material mixing, room temperature cold pressing, and hot pressing, the density of elevator counterweights can be increased to over 99% and reach 7.4-7.6. However, due to the significant differences in the shape, bulk density, and flowability of each raw material, and the lack of any means to control segregation by combining only a single mixing process, the final product will inevitably have large density differences in different regions under the combined effects of gravity and pressure. This will result in poor uniformity of iron powder distribution and significant component segregation.

[0013] This invention mainly employs a multi-scale raw material gradation + different raw material premixing + a specific three-stage gradient room temperature cold pressing + high temperature hot pressing process. By matching the differences in raw material morphology, particle size, density, and the movement patterns of each material during compaction, specific amounts of different components are filled at different stages. This not only significantly cuts off and fills interconnected pores, reducing porosity and increasing product density, but also ensures that the uniformity of the distribution of components such as iron powder inside the product is improved, reducing the impact of component segregation on the overall performance of the product. Specifically, iron shavings serve as a connecting and supporting framework. By layering iron shavings of different lengths, particle steel is embedded into the millimeter-level cavities formed by overlapping and bending of the shavings, creating a three-dimensional support network with a gradient of pore size from top to bottom. The gradient distribution of pore size in the macro framework facilitates the uniform filling and distribution of materials added in subsequent pressing processes, effectively reducing gravitational segregation of components. Secondly, the process combines segmented feeding with three-stage pressing during room temperature cold pressing. In the first stage of low-pressure cold pressing, graphite powder is mixed with a small amount of iron powder and added as a primary micro-filler phase. Under the axial action of low pressure, the powder seeps downward. During this process, the internal channels gradually shrink, increasing the resistance to powder seepage and weakening the squeezing effect of gravity and axial pressure on the powder. This allows the powder added in the first stage to be evenly distributed at the bottom of the system, rather than directly settling to the bottom and forming aggregates.Furthermore, the slight addition of gravity settling effect is significantly weakened, reducing the density difference between the upper and lower parts of the structure from the source. The lowest possible pressing force is used, and continuous gas escape channels are maintained inside the billet, allowing a large amount of free air carried by the mixture to escape through the mold gaps. During the second stage of room temperature cold pressing, the large amount of reduced iron powder added seeps downwards under the influence of gravity and axial pressing force. The increased pressing pressure in the second stage causes slight plastic bending of the iron shavings and mutual compression and interlocking of the steel particles. The previously interconnected capillaries running through the billet are broken down into smaller, isolated cavities by particle compression. Additionally, the initial pore size at the bottom is small. Given that the powder effectively filled the lower layers during the first stage of pressing, the resistance to powder seepage in the second stage increases significantly. As the pressing force contracts the pores, the resistance to powder seepage gradually increases, counteracting the downward axial force and inhibiting the tendency of powder to accumulate at the bottom. The slowly seeping powder is mainly distributed in the upper and middle layers, forming a uniform density transition and mitigating abrupt density changes in the vertical direction. The third stage... During room temperature cold pressing and high pressure pressing, a very small amount of remaining reduced iron powder is added. At this point, the middle and lower layers are basically densified. Under higher pressure, the powder undergoes plastic rheology and continues to distribute to areas with weaker pressure within the structure. It continuously transports the remaining iron powder in the upper layer downwards and laterally to the micropores. The highest pressure in the third stage causes the overall blank to be significantly compressed. The interlayer interfaces caused by layered feeding are squeezed together by high pressure, weakening the layer boundary and avoiding weak interlayer bonding defects. At the same time, as the pores shrink in the vertical direction, the iron powder on the surface gradually sinks and distributes less. Finally, the iron powder content in the upper and lower areas of the mold becomes nearly equal. Ultimately, the specific setting of the reduced iron powder content distribution in the upper and lower parts offsets and compensates for the sinking trend of the iron powder due to its own weight and axial force, achieving a uniform distribution of reduced iron powder in the vertical direction and solving the problem of severe enrichment at the bottom when adding reduced iron powder in one go. Due to its relatively low density, graphite powder is initially distributed at the bottom during the pressing process. Under the action of gradually increasing pressing force, it slowly floats up from the bottom and is eventually evenly distributed in the system. Finally, hot pressing is performed under high temperature and high pressure, which forces the softened iron matrix to undergo plastic rheology, further squeezing and closing the closed microporous structure left by cold pressing. At high temperature, the coefficient of friction of graphite is extremely low, which greatly reduces the friction between materials. The ultra-high pressure can be evenly transmitted to the edges, corners, side walls and inner center of the billet, and the density of the whole area tends to be uniform, avoiding porosity caused by local pressure attenuation. Moreover, based on the specific three-stage gradient room temperature cold pressing stage, this invention also greatly shortens the pressing time of the hot pressing process, and also greatly eliminates the structural defects caused by segregation of different components inside the structure due to long-term hot pressing.

[0014] Specifically, this invention provides a low-cost die-casting production process for elevator counterweights, characterized by using the following raw materials in sequence and following these steps: (1) Raw material pretreatment: Iron shavings with a thickness of 0.5-2.0 mm and a length of 10-50 mm obtained by processing materials such as Q235B, Q355B, and cast iron are subjected to heat treatment at 320℃ for 2 hours to remove oil, magnetic separation to remove impurities, crushing, and sieving to obtain long iron shavings with a length of 12-20 mm and short iron shavings with a length of 5-10 mm; the particle steel is subjected to magnetic separation to remove impurities such as aluminum, copper, and sand. (2) Raw material preparation: The weight of the long iron shavings is 14-16.9 parts; the weight of the short iron shavings is 50.2-67.8 parts; the particle steel is spherical particle steel with rounded particles and no sharp corners, composed of two specifications with particle sizes of 0.5-1.5mm and 2.0-3.5mm mixed in a weight ratio of 1:1, with an iron content ≥94%, and the weight is 20-23.3 parts; the reduced iron powder is composed of 55%-65% by weight of 200-mesh coarse reduced iron powder and 35%-45% by weight of 400-mesh fine reduced iron powder, and the weight is 10-11.7 parts; the weight of the graphite powder is 0.5-0.8 parts. (3) Take 2 / 5 of the total particle steel and 1 / 2 of the total short iron shavings and mix them evenly to obtain the base material; take the long iron shavings and mix them evenly with the remaining particle steel and short iron shavings to obtain the upper base material; take 1 / 5 of the total reduced iron powder and mix them evenly with graphite powder to obtain the premixed powder; the mixing speed is 30-40 rpm each time and the mixing time is 5-8 min. (4) The base material and the upper substrate are laid into the mold in sequence, and the mold is vibrated for 30 seconds to eliminate local accumulation. Three-stage feeding and room temperature cold pressing are carried out. The feeding process is carried out by vibrating the material, with a vibration frequency of 30-40Hz and an amplitude of 3-5mm: The first stage is to add the premixed powder, apply a pressure of 300-450 tons, press at a speed of 5-8mm / s, and hold the pressure for 5-6 seconds for room temperature low-pressure pressing; The second stage is to add 3 / 5 of the total amount of reduced iron powder, continue to increase the pressure to 1200-1500 tons, press at a speed of 3-5mm / s, and hold the pressure for 5-6 seconds for room temperature medium-pressure pressing; The third stage is to add all the remaining reduced iron powder, continue to increase the pressure to 3000 tons, press at a speed of 2-3mm / s, and hold the pressure for 12-15 seconds for room temperature high-pressure pressing. After pressing, the pressure is released and the mold is demolded to obtain the blank. (5) Place the blank at 900±20℃ for 8 to 12 minutes, then transfer it to the hot press mold, ensure that the mold temperature is ≥850℃, quickly close the mold and press up to 5000 tons, hold the pressure for 15 to 20 seconds for bidirectional hot pressing, and then demold to obtain the counterweight block. (6) The counterweight block is cooled to a surface temperature of ≤60°C by air cooling, and then the flash and surface oxide scale are removed by automatic shot blasting equipment until the surface roughness reaches Ra12.5 or less. Finally, epoxy anti-rust paint is sprayed on.

[0015] The present invention has the following beneficial effects: This invention provides a low-cost die-casting process for elevator counterweights. While reducing product porosity, improving density, and ensuring high density, it further solves the problems of poor density distribution uniformity and gravity segregation often found in conventional die-casting processes. This ensures highly uniform and consistent performance across the counterweight's edges, core, and all internal layers, eliminating potential defects such as internal delamination and cracking. The elevator counterweight prepared by this invention has an average bulk density of 7.722 g / cm³. 3 Furthermore, the density distribution within the structure is relatively uniform. When divided into five layers, the difference between the minimum and maximum density at the same sampling point (i.e., the center or corner) is only 0.004. The average porosity of the entire block is 0.57%. The compressive strength of each part within the structure is more uniformly distributed. It has excellent impact resistance, and the internal metallurgical bonding is sufficient. Minor impacts do not cause structural damage, which can meet the requirements for use in transportation and installation conditions. Attached Figure Description

[0016] Figure 1 This is a photograph showing the product morphology of the elevator counterweight block obtained in Embodiment 1 of the present invention.

[0017] Figure 2 This is a photograph showing the cross-sectional structure of the elevator counterweight product obtained in Embodiment 1 of the present invention after destruction. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments and experimental data. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Any non-substantial changes and adjustments made by those skilled in the art based on an understanding of the core ideas of this invention should be covered within the scope of protection of this invention.

[0019] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; the materials and reagents used are commercially available unless otherwise specified. Where specific techniques or conditions are not specified in the examples, they can be performed according to the techniques or conditions described in the literature in this field or according to the product instructions.

[0020] A low-cost die-casting production process for elevator counterweights is carried out in the following steps: (1) Raw material pretreatment: Select Q235B, Q355B, cast iron obtained by cutting and machining, with a thickness of 0.8-1.5mm and a length controlled at 10-45mm, and heat-treat at 320℃ for 2h to completely remove cutting oil and rust-preventive oil; use strong magnetic roller to remove impurities and separate sand, aluminum shavings and copper shavings; crush and screen to obtain long iron shavings with a length of 12-15mm and short iron shavings with a length of 5-8mm; perform two magnetic separations on the particle steel to remove impurities such as aluminum, copper and sand. (2) Raw material preparation: The weight of the long iron shavings is 15.2 parts; the weight of the short iron shavings is 60 parts; the particle steel is spherical particle steel with rounded particles and no sharp corners, which is composed of two specifications with particle sizes of 0.5-1.5mm and 2.0-3.5mm mixed in a weight ratio of 1:1, with an iron content of ≥96%, and the weight is 21.8 parts; the reduced iron powder is composed of 60wt% of 200-mesh coarse reduced iron powder and 40wt% of 400-mesh fine reduced iron powder, and the weight is 10.7 parts; the graphite powder is high-purity natural flake graphite, and the weight is 0.6 parts. (3) Take 2 / 5 of the total particle steel and 1 / 2 of the total short iron shavings and mix them evenly to obtain the base material; take the long iron shavings and mix them evenly with the remaining particle steel and short iron shavings to obtain the upper base material; take 1 / 5 of the total reduced iron powder and mix them evenly with graphite powder to obtain the premixed powder; the mixing speed is 35 rpm and the mixing time is 5 min each time. (4) The base material and the upper substrate are laid into the mold in sequence, and the mold is vibrated for 30 seconds to eliminate local accumulation. The three-stage feeding and room temperature cold pressing is adopted. The feeding process is carried out by vibrating the material, the vibration frequency is 35Hz and the amplitude is 4mm: the first stage is to add premixed powder, apply 380 tons of pressure, press at a speed of 6mm / s, and hold the pressure for 6 seconds for room temperature low pressure pressing; the second stage is to add 3 / 5 of the total amount of reduced iron powder, continue to increase the pressure to 1350 tons, press at a speed of 4mm / s, and hold the pressure for 6 seconds for room temperature medium pressure pressing; the third stage is to add all the remaining reduced iron powder, continue to increase the pressure to 3000 tons, press at a speed of 2.5mm / s, and hold the pressure for 14 seconds for room temperature high pressure pressing. After pressing, the pressure is slowly released and the mold is demolded to obtain a complete blank without cracks. (5) Place the blank at 900℃ for 10 minutes, then transfer it to the hot press mold, ensure that the mold temperature is ≥860℃, quickly close the mold and press up to 5000 tons, hold the pressure for 18 seconds to perform bidirectional hot pressing, and then demold to obtain the counterweight block. (6) The counterweight block is cooled to a surface temperature of 55°C by air cooling, and then the flash and surface oxide scale are removed by a fully automatic crawler shot blasting machine until the surface roughness of the workpiece stabilizes below Ra6.3. Finally, epoxy anti-rust paint is sprayed and dried and cured.

[0021] The elevator counterweight product obtained in Example 1 has the following morphology. Figure 1 As shown, photographs were taken of the cross-sectional structure after it was intentionally damaged, and the morphological photos of the cross-sectional structure are attached. Figure 2 As shown, from Figure 2 It can be seen that the product has no visible pores, excellent cross-sectional uniformity, and no obvious stratification within the structure.

[0022] Meanwhile, according to the test results of the verification experiment described in this embodiment of the invention (see Tables 1 and 2 below), the average bulk density of the counterweight pre-body prepared by the method in Embodiment 1 is 7.722 g / cm³. 3 Furthermore, the density distribution within the structure is relatively uniform (when divided into five layers, the difference between the minimum and maximum density at the same sampling point (i.e., the center or corner) is only 0.004, indicating a more uniform density distribution; the overall average porosity is 0.57%, and the porosity of all five layers within the structure is below 0.62%, with an overall density far below 1%; and the distribution of pores, which are present in very small quantities within the structure, is also more uniform, specifically manifested in the difference between the minimum and maximum porosity at the same sampling point (i.e., the center or corner) being only 0.05% (center) or 0.06% (corner). Comparative Example 1

[0023] The remaining steps are exactly the same as in Example 1, except that steps (3) and (4) in Example 1 are replaced with: (3) Take long and short iron shavings and put them into a horizontal mixer. Mix and stir for 2 minutes, then add all the particle steel and mix for 6 minutes at a stirring speed of 35 rpm. Finally, add graphite powder and all the reduced iron powder and mix for 4 minutes at a stirring speed of 35 rpm to obtain the base material. (4) Lay the base material into the mold, spread it flat and vibrate it for 30 seconds to eliminate local accumulation; send the base material into the cold press mold, use the press to set the pressure to 1000 tons and the holding time to 10 minutes, press at room temperature, and slowly release the pressure and demold to obtain a complete blank without cracks after cold pressing.

[0024] The counterweight prepared in this comparative example exhibited poor color uniformity in its cross-section; the color deepened towards the bottom, and the cross-sectional structure clearly showed problems with the uniformity of pore distribution. According to the test results of the verification experiment described in this embodiment (see Tables 1 and 2), the initial counterweight prepared using the method in Comparative Example 1 has an average bulk density of 7.669 g / cm³. 3 The density within its structure clearly shows a trend of gradually increasing from top to bottom in the vertical direction, and the density distribution within the structure varies considerably (when evenly divided into five layers, the difference between the center points of the upper and lower layers is 0.24 g / cm³). 3 The difference between the corner points is 0.253 g / cm. 3 The overall average porosity is 0.94%. Although the porosity within the structure clearly shows a gradual decrease from top to bottom in the vertical direction, the porosity distribution within the structure varies considerably (when divided into five layers, the difference between the center points of the upper and lower layers is 0.97%, and the difference between the corner points is 1.00%). Therefore, although the initial counterweight block obtained in this example has low porosity and high density, the density differences between the layers within the structure are significant, and the pore structure is not uniformly distributed within the overall structure. Comparative Example 2

[0025] The remaining steps are exactly the same as in Comparative Example 1, except that step (4) in Comparative Example 1 is replaced with: (4) Lay the base material into the mold, spread it flat and vibrate it for 30s to eliminate local accumulation; press it at room temperature in three stages: first, apply 380 tons of pressure, press speed of 6mm / s, hold pressure for 6s, and vibrate the material at 35Hz and 4mm amplitude throughout the process; second, continue to increase the pressure to 1350 tons, press speed of 4mm / s, hold pressure for 6s, and vibrate the material simultaneously; third, continue to increase the pressure to 3000 tons, press speed of 2mm / s, hold pressure for 14s, and after cold pressing, slowly release the pressure and demold to obtain a complete blank without cracks.

[0026] According to the test results of the confirmatory experiment described in the embodiments of the present invention (see Tables 1 and 2), the original counterweight prepared by the method in Comparative Example 2 has an average bulk density of 7.688 g / cm³. 3 The density within its structure clearly shows a trend of gradually increasing from top to bottom in the vertical direction, and the density distribution within the structure varies relatively greatly (when it is divided into five layers, the difference between the center points of the upper and lower layers is 0.222 g / cm³). 3 The difference between the corner points is 0.226 g / cm. 3The overall average porosity is 0.93%. Although the porosity within the structure clearly shows a gradual decreasing trend from top to bottom in the vertical direction, the porosity distribution within the structure varies considerably (when divided into five layers, the difference between the center points of the upper and lower layers is 0.92%, and the difference between the corner points is 0.99%). Similar to Comparative Example 1, although the initial counterweight obtained in this example has a lower porosity and higher density, the density variation range within the structure is large, and the pore structure is not uniformly distributed within the overall structure. Comparative Example 3

[0027] The remaining steps are exactly the same as in Example 1, except that steps (3) and (4) in Example 1 are replaced with: (3) Take long and short iron shavings, mix and break them apart, then add them to the particle steel and mix evenly to obtain the base material; take reduced iron powder and graphite powder and mix evenly to obtain the premixed powder; the mixing speed is 35 rpm and the mixing time is 5 min each time; (4) Lay the base material into the mold, spread it flat and vibrate for 30s to eliminate local accumulation; add material into the mold in three batches, and use vibrating cloth with a vibration frequency of 35Hz and an amplitude of 4mm during the material addition process: the first batch of 1 / 5 of the total premixed powder is added, 380 tons of pressure is applied, the pressing speed is 6mm / s, and the pressure is held for 6s for room temperature pressing, with vibrating cloth at 35Hz and an amplitude of 4mm throughout the process; the second batch of 3 / 5 of the total premixed powder is added, and the pressure is increased to 1350 tons, the pressing speed is 4mm / s, and the pressure is held for 6s for room temperature pressing, with vibrating cloth being turned on simultaneously; the third batch of all the remaining premixed powder is added, and the pressure is increased to 3000 tons, the pressing speed is 2.5mm / s, and the pressure is held for 14s for room temperature pressing. After cold pressing, slowly release the pressure and demold to obtain a complete blank without cracks.

[0028] According to the test results of the confirmatory experiment described in the embodiments of the present invention (see Tables 1 and 2), the initial counterweight prepared by the method in Comparative Example 3 has an average bulk density of 7.651 g / cm³. 3 The density within its structure clearly shows a trend of first decreasing and then increasing vertically from top to bottom, with the middle layer having the lowest density and the bottom layer having the highest density (the difference between the two at the center point is 0.131 g / cm³). 3 The difference between the two values ​​at the corner points is 0.123 g / cm². 3The average porosity of the entire block is 1.23%. The porosity inside the structure shows a clear trend of decreasing first and then increasing from top to bottom in the vertical direction. The middle layer has the largest porosity and the bottom layer has the smallest porosity (the difference between the two at the center point is 1.10% and the difference between the two at the corner points is 0.99%). It is evident that the initial bulk material obtained in this example exhibits a relatively high porosity and the lowest density in its middle layer. This may be due to the fact that the entire base material is laid at the bottom of the mold, with the graphite premixed powder being layered and stacked in stages. During vibration distribution, the lightweight graphite continuously floats upwards. Initially, the base material forms a uniform pore structure, but due to the pressing action, the area directly in contact with the pressure head experiences the greatest pressure, the most complete plastic deformation, the most pore closure, and the greatest reduction in pore size. This results in a decrease in pore shrinkage from top to bottom, causing a severe difference in pore size between the upper and lower layers. During the first feeding process, the powder penetrates significantly to the bottom. After layer-by-layer pressing, the surface pores become denser. During the final feeding, the powder mainly accumulates on the surface and cannot penetrate further, resulting in premixed material accumulation at both the bottom and the surface. Ultimately, this leads to high porosity in the middle layer, graphite enrichment on the surface, and severe overall component segregation. In this invention, a pore size difference with larger upper and smaller lower diameters is preferentially formed when laying the base material. This pore size difference is gradually reduced during the pressing process, which further improves the uniformity of powder penetration. In addition, all the premixed material containing graphite powder is added in the first step. During the subsequent pressing process, it floats from the bottom to the top under the pressing action to form a relatively uniform distribution, thereby reducing the problem of component segregation.

[0029] The present invention also conducted the following verification experiments: I. Density and Porosity Verification: Archimedes Method (Vacuum Impregnation Method)

[0030] (a) Instruments and Consumables 0.001g precision analytical balance, vacuum impregnation tank, constant temperature drying oven, anhydrous kerosene, filter paper, suspension thread, vernier caliper; (II) Sample Preparation One standard counterweight prepared according to the preparation methods in Example 1 and Comparative Examples 1 to 4 was taken as a test sample. Five different test samples were combined into a test group for testing. When sampling a single test sample, the test sample was first divided into five layers along the height direction: upper surface layer, upper layer, middle layer, lower layer, and bottom layer. Then, one center and two random corners were sampled from each layer to cut and take samples as test samples. The size of the test samples was uniformly 50mm×50mm×60mm. The average value of the measured data from the two random corners was taken. (III) Operating methods and procedures 1. Grind away the 2-3mm loose oxide layer on the surface of the test sample; 2. Dry in an oven at 105℃ for 2 hours, cool to room temperature, weigh, and record the dry mass m1.

[0031] 3. Vacuum oil impregnation: After drying, the test sample is placed in a vacuum tank and the sample is completely immersed in kerosene; the vacuum is drawn to ≤5kPa, the pressure is maintained for 30min, the pressure is slowly released and then the sample is soaked for another 10min to ensure that all open pores are filled with kerosene.

[0032] 4. Saturated wet weight measurement m2: Take out the sample block to be tested, gently wipe the surface of the free kerosene with filter paper (do not squeeze out the kerosene inside the pores), and weigh and record immediately.

[0033] 5. Suspension mass measurement (m3): The sample to be tested is suspended by a thin thread and completely immersed in kerosene. The sample does not touch the container wall or bottom. The suspension mass is then read.

[0034] (iv) Calculation formula The total external volume V of the test sample 总 =(m2-m3) / ρ l Bulk density ρ=m1 / V 总 Total porosity Pt = (1 - m1・ρ) l / (ρ Fe •(m2-m3)))×100% Where, ρ l ρ is the density of kerosene at room temperature. Fe This is the density of pure iron.

[0035] Following the above method, an experiment was conducted on a test group, and the measurement data are shown in Tables 1 and 2 below.

[0036] Table 1. Density comparison of a test group

[0037] Table 2. Comparison of porosity of a test group

[0038] As shown in Tables 1 and 2 above, except for Comparative Example 3, Example 1 and Comparative Examples 1 and 2 can all ensure that the overall porosity of the product's counterweight is less than 1%. However, in Example 1, the porosity of the five layers evenly distributed inside the structure is all below 0.62%, and the overall density is far superior to that of Comparative Examples 1 and 2. Moreover, the pores with extremely small content inside the structure are also more evenly distributed. Specifically, the difference between the minimum and maximum porosity at the same sampling point (i.e., the center or the corner) inside the structure is only 0.05% (center) or 0.06% (corner), which is only about one-tenth of that in Comparative Examples 1 or 2 (the difference between the minimum and maximum porosity at the same sampling point inside the structure). Meanwhile, in terms of the uniformity of density distribution inside the structure, compared with comparative documents 1 and 2, Example 1 is better able to ensure a more uniform distribution of density inside the structure. The difference between the minimum and maximum density inside the structure (the same sampling points, i.e., the center or corners) is only 0.004, which is only about one-tenth of that in comparative documents 1 or 2, and its density distribution is more uniform.

[0039] Furthermore, it can be seen that although Comparative Examples 1 and 2 have different cold pressing steps, the overall density and porosity distribution of their products are not significantly different. The difference between the two in terms of the uniformity of internal structural density and porosity distribution is not significant. This also indirectly shows that in the method system of the present invention, simply optimizing the pressing process has little practical effect or significance. It is necessary to combine it with specific feeding methods and other aspects to improve the uniformity of density and porosity distribution of the counterweight. II. Mechanical Property Testing

[0040] (a) Compressive strength test (Universal testing machine for whole materials, GB / T 1041-2008) Method and steps: 1. Sample preparation: Take one standard counterweight prepared according to the preparation method in Example 1 and Comparative Examples 1 to 4 as the test sample. Five different test samples are combined into a test group for testing. When sampling from a single test sample, first divide the test sample into five layers along the height direction: upper surface layer, upper layer, middle layer, lower layer, and bottom layer. Then, take one center and two random corner samples from each layer to cut and take samples as test samples. The size of the test samples is uniformly 50mm × 10mm × 10mm, and the surface is flat and without defects. Among them, two 1. Take the average value of the measured data at random corner points as the compressive strength value of the edge of the layer; 2. Measure the dimensions: record the cross-sectional area and height of the test sample; 3. Clamp the sample: place the sample in the center of the compression plate; 4. Set the parameters: select the compression mode, set the loading speed and range; 5. Loading test: continuously apply a pressure of 0.5 MPa / s at a uniform speed, and record the force-displacement curve; 6. Stop and unload: stop after the test sample fails, and record the critical load of failure; 7. Calculate the compressive strength: compressive strength = maximum pressure / initial cross-sectional area of ​​the test sample. The compressive strength data for each layer are shown in Table 3.

[0041] Table 3 Comparison of compressive strength tests of each layer in a test group

[0042] As can be seen from Table 3 above, except for Comparative Example 3, the compressive strength at the same point inside the structure in Embodiment 1 of the present invention increases slightly from top to bottom in the vertical direction, while the compressive strength inside the structures in Comparative Examples 1 and 2 clearly shows a gradual increasing trend from top to bottom in the vertical direction. Regarding the uniformity of the compressive strength distribution among the layers inside the structure, compared with comparative documents 1 and 2, Embodiment 1 is better able to ensure a more uniform distribution of compressive strength among the layers inside the structure. The minimum and maximum compressive strength values ​​of each layer inside the structure (comparing the same sampling point, i.e., the center or corner) are... The difference in maximum values ​​(0.4 MPa at the center and 0.5 MPa at the corners) is only about one-tenth of that in Comparative Example 1 (correspondingly, 4.9 MPa at the center and 5 MPa at the corners) or Comparative Example 2 (correspondingly, 4.7 MPa at the center and 5 MPa at the corners). This confirms that the compressive strength of each layer within the structure of the test sample in Example 1 is more uniform, similar to its porosity and density distribution. This also indirectly indicates that the material distribution within each layer of its structure is more uniform compared to Comparative Examples 1 and 2, with less compositional segregation. Similarly, it can be seen that although Comparative Examples 1 and 2 have different cold pressing steps, the compressive strength distribution of each layer within the structure of their resulting products is not significantly different. This indirectly confirms that simply optimizing the pressing process in the system of this invention has little practical effect or significance; it requires specific feeding methods and other aspects to improve the density uniformity of the counterweight and reduce the problem of component segregation in the system.

[0043] (ii) Drop hammer impact test (simulating elevator installation and transportation collision conditions) The specimen is the same as the specimen used in (I) compressive strength test; Method: A 10kg steel hammer was used to drop freely from a height of 0.8m to impact the side of the test block; result: Example 1: (1) Impact appearance phenomenon: After a single drop hammer impact, the test block only had slight local metal particles peeling off at the impact point, without penetrating cracks or interlayer separation; the surface only had small pits and slight chipping at the edges. (2) Result judgment: Excellent impact resistance, sufficient metallurgical bonding, no structural damage from minor impacts, and can meet the requirements for use in transportation and installation conditions.

[0044] Comparative Example 1: (1) Impact appearance phenomenon: After the first impact, the upper surface and upper layer showed obvious flaking, with a peeling size of 10-15mm. The upper surface layer was particularly brittle and had severe flaking (graphite-rich area); the middle layer showed transverse fine through cracks, without complete fracture; the bottom and lower layers remained intact without large pieces falling off. (2) Result judgment: There was obvious difference in impact resistance between the layers. The upper and middle parts had insufficient impact resistance. During long-distance transportation and multiple loading and unloading, the surface layer was prone to large pieces peeling off, posing a risk of appearance damage.

[0045] Comparative Example 2: The experimental phenomena, performance, and result determination were similar to those of Comparative Example 1.

[0046] Comparative Example 3: (1) Impact appearance phenomenon: After a single drop hammer impact, the upper layer and upper surface layer are broken and fragmented in large areas, and the matrix is ​​brittle; the middle layer is directly fractured after impact; the bottom layer and lower layer only have local pits after impact, without cracks. (2) Result judgment: Poor impact resistance, severe segregation causes the bonding force to fail easily, and large-scale fracture and delamination are likely to occur under simulated transportation and installation collision conditions, resulting in insufficient product reliability. Example 2

[0047] A low-cost die-casting production process for elevator counterweights is carried out in the following steps: (1) Raw material pretreatment: Select Q235B, Q355B, cast iron obtained by cutting and machining, with a thickness of 0.5-0.8mm and a length controlled at 20-50mm, and heat-treat at 320℃ for 2h to completely remove cutting oil and rust-preventive oil; use strong magnetic roller to remove impurities and separate sand, aluminum shavings and copper shavings; crush and screen to obtain long iron shavings with a length of 15-20mm and short iron shavings with a length of 5-8mm; perform two magnetic separations on the particle steel to remove impurities such as aluminum, copper and sand. (2) Raw material preparation: The weight of long iron shavings is 16.9 parts; the weight of short iron shavings is 67.8 parts; the particle steel is spherical particle steel with rounded particles and no sharp corners, which is composed of two specifications with particle sizes of 0.5-1.0 mm and 2.0-2.5 mm mixed in a weight ratio of 1:1, with an iron content of ≥95%, and the weight is 23.3 parts; the reduced iron powder is composed of 65 wt% of 200 mesh coarse reduced iron powder and 35 wt% of 400 mesh fine reduced iron powder, and the weight is 10 parts; the graphite powder is high-purity natural flake graphite, and the weight is 0.5 parts. (3) Take 2 / 5 of the total particle steel and 1 / 2 of the total short iron shavings and mix them evenly to obtain the base material; take the long iron shavings and mix them evenly with the remaining particle steel and short iron shavings to obtain the upper base material; take 1 / 5 of the total reduced iron powder and mix them evenly with graphite powder to obtain the premixed powder; the mixing speed is 40 rpm and the mixing time is 5 min each time. (4) The base material and the upper substrate are laid into the mold in sequence, and the mold is vibrated for 30 seconds to eliminate local accumulation. The three-stage feeding and room temperature cold pressing is adopted. The feeding process is carried out by vibrating the material, the vibration frequency is 40Hz, and the amplitude is 3mm: The first stage is to add premixed powder, apply 450 tons of pressure, press at a speed of 5mm / s, and hold the pressure for 6 seconds for room temperature low pressure pressing; The second stage is to add 3 / 5 of the total amount of reduced iron powder, continue to increase the pressure to 1500 tons, press at a speed of 5mm / s, and hold the pressure for 6 seconds for room temperature medium pressure pressing; The third stage is to add all the remaining reduced iron powder, continue to increase the pressure to 3000 tons, press at a speed of 3mm / s, and hold the pressure for 12 seconds for room temperature high pressure pressing. After pressing, the pressure is slowly released and the mold is demolded to obtain a complete blank without cracks. (5) Place the blank at 920°C for 8 minutes, then transfer it to a hot press mold, ensuring that the mold entry temperature is ≥870°C, quickly close the mold and press up to 5000 tons, hold the pressure for 20 seconds for bidirectional hot pressing, and then demold to obtain the counterweight block. (6) The counterweight block is cooled to a surface temperature of 50°C by air cooling, and then the flash and surface oxide scale are removed by a fully automatic crawler shot blasting machine until the surface roughness of the workpiece reaches Ra6.3 or below. Finally, epoxy anti-rust paint is sprayed and dried and cured.

[0048] The average bulk density of the elevator counterweight prepared in this embodiment is 7.684 g / cm³. 3 Furthermore, the internal density distribution is relatively uniform, with an average porosity of 0.62%. The compressive strength of each part of the structure is more uniformly distributed. It has excellent impact resistance, and the internal metallurgical bonding is sufficient. Minor impacts do not cause structural damage, which can meet the requirements for transportation and installation. Example 3

[0049] A low-cost die-casting production process for elevator counterweights is carried out in the following steps: (1) Raw material pretreatment: Iron shavings with a thickness of 0.5-2.0 mm and a length of 10-50 mm obtained by processing materials such as Q235B, Q355B, and cast iron are subjected to heat treatment at 320℃ for 2 hours to remove oil, magnetic separation to remove impurities, crushing, and sieving to obtain long iron shavings with a length of 12-20 mm and short iron shavings with a length of 5-10 mm; the particle steel is subjected to magnetic separation to remove impurities such as aluminum, copper, and sand. (2) Raw material preparation: The weight of the long iron shavings is 14 parts; the weight of the short iron shavings is 50.2 parts; the particle steel is spherical particle steel with rounded particles and no sharp corners, which is composed of two specifications with particle sizes of 0.5-1.5mm and 2.0-3.5mm mixed in a weight ratio of 1:1, with an iron content of ≥94%, and the weight is 20 parts; the reduced iron powder is composed of 55% by weight of 200-mesh coarse reduced iron powder and 45% by weight of 400-mesh fine reduced iron powder, and the weight is 11.7 parts; the weight of the graphite powder is 0.8 parts. (3) Take 2 / 5 of the total particle steel and 1 / 2 of the total short iron shavings and mix them evenly to obtain the base material; take the long iron shavings and mix them evenly with the remaining particle steel and short iron shavings to obtain the upper base material; take 1 / 5 of the total reduced iron powder and mix them evenly with graphite powder to obtain the premixed powder; the mixing speed is 30 rpm and the mixing time is 8 min each time. (4) The base material and the upper substrate are laid into the mold in sequence, and the mold is vibrated for 30 seconds to eliminate local accumulation. The three-stage feeding and room temperature cold pressing is adopted. The feeding process is carried out by vibrating the material, the vibration frequency is 30Hz, and the amplitude is 5mm: The first stage is to add premixed powder, apply 300 tons of pressure, press at 8mm / s, and hold the pressure for 5 seconds for room temperature low pressure pressing; the second stage is to add 3 / 5 of the total amount of reduced iron powder, continue to increase the pressure to 1200 tons, press at 3mm / s, and hold the pressure for 5 seconds for room temperature medium pressure pressing; the third stage is to add all the remaining reduced iron powder, continue to increase the pressure to 3000 tons, press at 2mm / s, and hold the pressure for 15 seconds for room temperature high pressure pressing. After pressing, the pressure is slowly released and the mold is demolded to obtain a complete blank without cracks. (5) The blank is placed at 880°C for 12 minutes and then transferred to a hot press mold. Ensure that the temperature of entering the mold is ≥850°C. Quickly close the mold and press up to 5000 tons. Hold the pressure for 15 seconds to perform bidirectional hot pressing. Then demold to obtain the counterweight block. (6) The counterweight is cooled to a surface temperature of 45°C by air cooling, and then the flash and surface oxide scale are removed by automatic shot blasting equipment until the surface roughness reaches Ra12.5 or less. Finally, epoxy anti-rust paint is sprayed and dried and cured.

[0050] The average bulk density of the elevator counterweight prepared in this embodiment is 7.693 g / cm³. 3 Furthermore, the density distribution within the structure is relatively uniform, with an average porosity of 0.60%. The compressive strength of each part within the structure is more evenly distributed. It has excellent impact resistance, and the internal metallurgical bonding is sufficient. Minor impacts do not cause structural damage, and it can meet the requirements for use in transportation and installation conditions.

Claims

1. A low-cost die-casting production process for elevator counterweights, characterized in that, Follow these steps in sequence: (1) Raw material pretreatment: Iron shavings are pretreated to obtain long iron shavings and short iron shavings; (2) Raw material preparation: Long iron shavings and short iron shavings, particle steel, reduced iron powder and graphite powder are selected as raw materials; (3) Take a portion of the granulated steel and short iron shavings and mix them evenly to obtain the base material; take the long iron shavings and mix them evenly with the remaining granulated steel and short iron shavings to obtain the upper base material; take a portion of the reduced iron powder and mix it evenly with the graphite powder to obtain the premixed powder. (4) The base material and the upper substrate are sequentially laid into the mold and subjected to three-stage feeding and room temperature cold pressing. Specifically, the first stage is to add the premixed powder and press at room temperature and low pressure; the second stage is to add a large amount of reduced iron powder and continue to press at room temperature and medium pressure; the third stage is to add the remaining reduced iron powder and continue to press at room temperature and high pressure. After pressing, the pressure is released and the blank is demolded. (5) Heat treat the blank, then transfer it to the hot press mold, and quickly close the mold and press it to form a hot press. (6) Cooling and post-treatment.

2. The die-casting production process for low-cost elevator counterweights as described in claim 1, characterized in that, The following steps are performed using the following raw materials in sequence: (1) Raw material pretreatment: Iron shavings are degreased, impurities removed, crushed and screened to obtain long iron shavings and short iron shavings; Particle steel is subjected to impurity removal treatment; (2) Raw material preparation: Select long iron shavings and short iron shavings, particle steel, reduced iron powder and graphite powder with specific size requirements and weight ratios as raw materials; (3) Take 2 / 5 of the total particle steel and 1 / 2 of the total short iron shavings and mix them evenly to obtain the base material; take the long iron shavings and mix them evenly with the remaining particle steel and short iron shavings to obtain the upper base material; take 1 / 5 of the total reduced iron powder and mix them evenly with graphite powder to obtain the premixed powder. (4) The base material and the upper substrate are sequentially laid into the mold and subjected to three-stage feeding and room temperature cold pressing. Specifically, the first stage is to add the premixed powder and press at room temperature and low pressure; the second stage is to add reduced iron powder accounting for 3 / 5 of the total amount of reduced iron powder and continue to press at room temperature and medium pressure; the third stage is to add the remaining reduced iron powder and continue to press at room temperature and high pressure. After pressing, the pressure is released and the blank is demolded. (5) Heat treat the blank, then transfer it to the hot press mold, and quickly close the mold and press it to form a hot press. (6) Cooling and post-treatment.

3. The die-casting production process for low-cost elevator counterweights as described in claim 1 or 2, characterized in that: The thickness of the iron shavings in step (1) is 0.5-2.0 mm and the length is controlled between 10-50 mm. The shavings are obtained from various types of shavings after processing Q235B, Q355B, and cast iron.

4. The die-casting production process for low-cost elevator counterweights as described in claim 1 or 2, characterized in that: In step (2), the length of the long iron shavings is 12-20 mm, and the weight percentage is 14-16.9 parts; the length of the short iron shavings is 5-10 mm, and the weight percentage is 50.2-67.8 parts; the particle steel is spherical particle steel with rounded particles and no sharp corners, composed of two types with particle sizes of 0.5-1.5 mm and 2.0-3.5 mm mixed in a weight ratio of 1:1, with an iron content ≥94%, and the weight percentage is 20-23.3 parts; the reduced iron powder is composed of 55%-65% by weight of 200-mesh coarse reduced iron powder and 35%-45% by weight of 400-mesh fine reduced iron powder, and the weight percentage is 10-11.7 parts; the weight percentage of the graphite powder is 0.5-0.8 parts.

5. The die-casting production process for low-cost elevator counterweights as described in any one of claims 1-3, characterized in that: In step (4), during the first stage of low-pressure pressing at room temperature, a pressure of 300-450 tons is applied, the pressing speed is 5-8 mm / s, and the pressure is held for 5-6 seconds; during the second stage of medium-pressure pressing at room temperature, the pressure is increased to 1200-1500 tons, the pressing speed is 3-5 mm / s, and the pressure is held for 5-6 seconds; during the third stage of high-pressure pressing at room temperature, the pressure is increased to 3000 tons, the pressing speed is 2-3 mm / s, and the pressure is held for 12-15 seconds. After pressing, the pressure is released and the blank is demolded.

6. The die-casting production process for low-cost elevator counterweights as described in any one of claims 1-4, characterized in that: The specific step (5) involves placing the blank at 900±20℃ for 8 to 12 minutes, then transferring it to a hot press mold, ensuring that the mold entry temperature is ≥850℃, quickly closing the mold and increasing the pressure to 5000 tons, holding the pressure for 15 to 20 seconds for bidirectional hot pressing, and then demolding to obtain the counterweight block.

7. The die-casting production process for low-cost elevator counterweights as described in any one of claims 1-5, characterized in that: The specific step (6) involves cooling the counterweight block to a surface temperature ≤60°C using air cooling, removing the flash and surface oxide scale until the surface roughness reaches Ra12.5 or less, and finally spraying anti-rust paint.

8. A low-cost die-casting production process for elevator counterweights, characterized in that, The following steps are performed using the following raw materials in sequence: (1) Raw material pretreatment: Select Q235B, Q355B, and cast iron obtained by processing, with a thickness of 0.5-2.0mm and a length controlled at 10-50mm, and successively heat-treat at 320℃ for 2h to remove oil, remove impurities by magnetic separation, crush and screen to obtain long iron shavings with a length of 12-20mm and short iron shavings with a length of 5-10mm; and remove impurities by magnetic separation of the particle steel. (2) Raw material preparation: The weight of the long iron shavings is 14-16.9 parts; the weight of the short iron shavings is 50.2-67.8 parts; the particle steel is spherical particle steel with rounded particles and no sharp corners, composed of two specifications with particle sizes of 0.5-1.5mm and 2.0-3.5mm mixed in a weight ratio of 1:1, with an iron content ≥94%, and the weight is 20-23.3 parts; the reduced iron powder is composed of 55%-65% by weight of 200-mesh coarse reduced iron powder and 35%-45% by weight of 400-mesh fine reduced iron powder, and the weight is 10-11.7 parts; the weight of the graphite powder is 0.5-0.8 parts. (3) Take 2 / 5 of the total particle steel and 1 / 2 of the total short iron shavings and mix them evenly to obtain the base material; take the long iron shavings and mix them evenly with the remaining particle steel and short iron shavings to obtain the upper base material; take 1 / 5 of the total reduced iron powder and mix them evenly with graphite powder to obtain the premixed powder; the mixing speed is 30-40 rpm each time and the mixing time is 5-8 min. (4) The base material and the upper substrate are laid into the mold in sequence, and the mold is vibrated for 30 seconds to eliminate local accumulation. Three-stage feeding and room temperature cold pressing are carried out. The feeding process is carried out by vibrating the material, with a vibration frequency of 30-40Hz and an amplitude of 3-5mm: The first stage is to add the premixed powder, apply a pressure of 300-450 tons, press at a speed of 5-8mm / s, and hold the pressure for 5-6 seconds for room temperature low-pressure pressing; The second stage is to add 3 / 5 of the total amount of reduced iron powder, continue to increase the pressure to 1200-1500 tons, press at a speed of 3-5mm / s, and hold the pressure for 5-6 seconds for room temperature medium-pressure pressing; The third stage is to add all the remaining reduced iron powder, continue to increase the pressure to 3000 tons, press at a speed of 2-3mm / s, and hold the pressure for 12-15 seconds for room temperature high-pressure pressing. After pressing, the pressure is released and the mold is demolded to obtain the blank. (5) Place the blank at 900±20℃ for 8 to 12 minutes, then transfer it to the hot press mold, ensure that the mold temperature is ≥850℃, quickly close the mold and press up to 5000 tons, hold the pressure for 15 to 20 seconds for bidirectional hot pressing, and then demold to obtain the counterweight block. (6) The counterweight block is cooled to a surface temperature of ≤60°C by air cooling, and then the flash and surface oxide scale are removed by automatic shot blasting equipment until the surface roughness reaches Ra12.5 or less. Finally, epoxy anti-rust paint is sprayed on.

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