Rack casting process

Abstract

The invention relates to a machine frame casting process, in particular to a novel machine frame casting process for key components of mining machinery, which comprises the design of a riser, a patch, a chilling block, a pouring system and an anti-cracking measure. Sequential feeding is achieved through an exothermic open riser and a symmetrical patch, the cooling speed is optimized, and casting defects are reduced; the exhaust and scum effects are improved by adopting a vertical double-layer water inlet pouring gate scheme; and sand reducing holes and process tie bars are arranged to reduce cracks. The quality performance of the thick and large-section casting can be remarkably improved, and the requirements of the mining machinery field for high-quality and high-reliability rack products are met.

Description

Technical Field

[0001] The invention relates to the technical field of mining machinery parts manufacturing, in particular to a frame casting process. Background Art

[0002] As a key component and basic skeleton of mining machinery, the performance of the frame directly affects the mining efficiency, safety and economy. Due to the complex and harsh working environment, the frame needs to have good low-temperature toughness, wear resistance, and excellent internal quality and surface quality. In the existing technology, how to improve the internal quality of castings, reduce casting defects, optimize the cooling process, improve production efficiency and reduce costs remains the focus of research. For example, the patent with publication number CN115430810B proposes a jaw crusher frame casting tool and process method. The bottom plate-free integral core box design and hard point support structure reduce the amount of molding sand used and avoid crack defects caused by insufficient yield. However, this technical solution is mainly designed for the specific structural characteristics of the jaw crusher frame, with low versatility and difficulty in adapting to the diverse needs of other types of frame products. At the same time, the process does not fully consider the cooling rate control problem of thick and large-section castings, which may cause defects such as shrinkage holes and looseness inside the castings, affecting the overall mechanical properties. Another patent, CN114515817B, proposes a casting process based on the hot-slug method to determine riser compensation. This centralized feeding method achieves a favorable sequential solidification temperature gradient, significantly reducing thermal stress and thermal cracking, and improving microstructural uniformity through grain refinement. However, this technical solution relies on empirical formulas for calculating riser size and pour height, which has certain limitations and may not be fully applicable to all complex-shaped frame castings. Furthermore, while this process can meet the quality requirements of ultrasonic testing, its localized control of cooling rate is weak, which may result in suboptimal mechanical properties in certain key areas. These issues indicate that existing frame casting processes still have shortcomings in terms of versatility, precise cooling rate control, and quality assurance for thick and large-section castings. Therefore, developing a new frame casting process that aims to improve process versatility, optimize cooling rate control strategies, reduce casting defects, and improve the overall mechanical properties of castings is of great significance for meeting the demand for high-quality, high-reliability frame products in the mining machinery industry. Summary of the Invention

[0003] This invention addresses the challenges of existing frame casting processes, including limited versatility, imprecise cooling rate control, numerous casting defects, low production efficiency, and high costs. By optimizing riser and filler design, chiller placement, gating system design, and crack prevention measures, this process achieves high-quality casting of thick, large-section castings.

[0004] The present invention provides a frame casting process, which includes the design of risers, patches, chillers, pouring systems and anti-cracking measures, wherein:

[0005] The design of the risers and the padding is used to establish a sequential shrinkage feeding channel to ensure that the internal structure of the casting is dense and to reduce defects such as shrinkage cavities and looseness. Furthermore, the design of the risers and the padding specifically includes the following details: a heat-generating open riser is set at the sudden thickening position at the bottom of the straight section cylinder, and the heat-generating open riser is used to fully feed the shrinkage of this area; a symmetrical padding 1 is set at the connection between the inclined cylinder and the straight section cylinder to form a sequential shrinkage feeding channel from the straight section cylinder to the inclined cylinder; the shrinkage feeding channel is calculated upward according to the thermal pitch circle formed by the intersection of the inclined cylinder and the small flange, and a symmetrical padding 2 is set at the large flange to form a sequential shrinkage feeding channel from the inclined cylinder to the large flange; two round risers are set between the two large risers on the large flange to ensure the shrinkage feeding distance of the top large flange and the shrinkage feeding effect of the entire casting.

[0006] In particular, the chiller arrangement is used to optimize the cooling rate of the casting and avoid quality defects caused by local overheating. Specifically, the chiller arrangement includes: arranging a first chiller on the outer wall of the two hot risers to prevent the heat-affected zone between the hot risers from causing quality defects in the casting; arranging a second chiller between the straight section of the cylinder and the two hot risers to further reduce the heat-affected zone; and arranging a third chiller between the inner cavity of the inclined cylinder and the second patch to ensure uniform cooling of key parts of the casting and avoid defects caused by local overheating.

[0007] Furthermore, the pouring system adopts a vertical double-layer water-inlet pouring scheme, including a lower pouring system and an upper pouring system. A bottom pouring ladle is used, the pouring temperature is controlled at 1540±20℃, the cross-sectional area ratio of the lower pouring channel to the upper pouring channel is 1:1.2, and the pouring time is 2000kJ / m2. (W is the casting weight, ρ is the molten steel density, and A is the total cross-sectional area of the runner) The liquid first flows into the lower gating system, then into the exothermic riser and straight barrel section, and then rises to the upper gating system, ultimately filling the entire inclined barrel and large riser. The upper gating system effectively removes air and slag while maintaining the temperature of the molten steel in the riser, thereby improving the riser's shrinkage feeding effect.

[0008] Specifically, the crack prevention measures are used to reduce stress concentration and cracks in castings during solidification. These measures include: installing sand-reducing holes in the straight section of the core to reduce stress concentration caused by core shrinkage; installing a first process tie bar within the inclined section of the core, and a second process tie bar at the large flange to eliminate or reduce cracks in the casting.

[0009] Furthermore, the sequential feeding mechanism achieves sequential feeding of the mold during the pouring and solidification process through the rational arrangement of risers, sluices, and chills. Specifically, the exothermic riser first feeds the sudden thickening at the bottom of the straight section. Sluices 1 and 2 then guide the molten steel toward the inclined section and the large flange, respectively. Finally, the large riser completes the top feeding. This sequential feeding mechanism ensures a dense internal structure in the casting, reducing defects such as shrinkage cavities and porosity.

[0010] Compared with the prior art, the beneficial effects of the present invention are as follows: through the modular design of risers, subsidies and chillers, the process can adapt to the casting needs of various types of frame products, especially thick and large-section castings. Furthermore, through the reasonable arrangement of the chillers and the sequential shrinkage compensation mechanism, the cooling rate of the castings is optimized, defects such as shrinkage cavities and porosity are reduced, and the mechanical properties of the castings are improved. In particular, through the design of sand reduction holes and process tie bars, problems such as deformation, cracks, sand inclusions, air holes and cold shuts in the casting process are significantly reduced, and the intrinsic quality and surface quality of the castings are improved. In addition, the vertical double-layer water inlet runner solution not only improves the exhaust and slag effects, but also shortens the pouring time and improves production efficiency. By reducing casting defects and optimizing material utilization, production costs are reduced.

[0011] In summary, the present invention solves the problems existing in the prior art through scientific and reasonable process design, significantly improves the quality and performance of the frame casting, and meets the demand for high-quality and high-reliability frame products in the mining machinery field. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is the product structure diagram of the rack;

[0013] Figure 2 This is a schematic diagram of the frame pouring system and riser design;

[0014] Figure 3 This is a schematic diagram of the frame casting process;

[0015] Figure 4 This is a detailed view of the rack.

[0016] In the figure: 1. Large riser; 2. Round riser; 3. Exposed riser; 4. Upper pouring system; 5. Lower pouring system; 6. Subsidy 1; 7. Subsidy 2; 8. Process tie rod 1; 9. Process tie rod 2; 10. Sand reduction hole; 11. Chill 1; 12. Chill 2; 13. Chill 3; 14. Large flange; 15. Small flange; 16. Straight section cylinder; 17. Inclined cylinder. DETAILED DESCRIPTION

[0017] The present invention provides a frame casting process, which achieves high-quality casting of thick and large-section castings by optimizing risers, patches, chiller layout, pouring system design and crack prevention measures. Figures 1 to 4 Detailed description of the implementation process and operation details of the present invention.

[0018] In this embodiment, the frame structure includes a large flange 14, a small flange 15, a straight section cylinder 16 and a bevel cylinder 17. The connection area of these components forms multiple heat nodes, and casting defects need to be eliminated through reasonable shrinkage compensation design. First, a heat-generating open riser 3 is set at the sudden thickening position at the bottom of the straight section cylinder 16 to ensure that this area has sufficient molten steel supply during the solidification process. The design of the heat-generating open riser 3 adopts a high-heat-generating material, which contains, by mass percentage, 30-35% Al powder, 40-45% Fe2O3, 35-8% NaNO, and a binder balance. It can continuously release heat during the solidification stage and prolong the liquid time of the molten steel in the riser, thereby achieving sufficient shrinkage compensation for the bottom of the straight section cylinder 16. The height of the heating open riser is H = 1.5δ + 50mm (δ is the wall thickness of the straight section cylinder), the diameter is D = 2δ, and the error range is ± 5% (Example: when δ = 80mm, H = 170mm, D = 160mm), so as to ensure the shrinkage feeding effect while avoiding waste of molten steel.

[0019] Symmetrically distributed sub-additions 6 are provided at the connection between the inclined cylinder 17 and the straight cylinder 16, forming a sequential shrinkage feeding channel from the straight cylinder 16 to the inclined cylinder 17. The design purpose of sub-additions 6 is to guide the molten steel from the hot riser 3 to the inclined cylinder 17, reducing shrinkage holes and porosity problems caused by hot nodes. The size of sub-additions 6 is determined by calculating the hot node circle, and its shrinkage feeding capacity is verified by combining with actual casting simulation. At the same time, the shrinkage feeding channel is calculated upward according to the hot node circle formed by the intersection of the inclined cylinder 17 and the small flange 15, and symmetrically distributed sub-additions 7 are provided at the large flange 14. The function of sub-additions 7 is to provide a shrinkage feeding channel for the area between the inclined cylinder 17 and the large flange 14, ensuring sequential solidification of the entire casting. The shape and position of sub-additions 7 have been adjusted through multiple tests, and it was finally determined that it can meet the shrinkage feeding requirements and maintain the dense internal structure of the casting.

[0020] To further enhance the feeding efficiency of the large flange 14, two round risers 2 are installed between the two large risers 1. The design of the round risers 2 takes into account the size and wall thickness of the large flange 14. Their diameter and height are precisely calculated to ensure they cover the entire feeding distance of the top large flange 14. The use of the round risers 2 not only reduces the molten steel consumption of a single riser but also improves feeding efficiency. Furthermore, the combination of the round risers 2 and the large risers 1 ensures more uniform feeding of the top, avoiding localized overheating or insufficient feeding.

[0021] Based on the design of risers and fillets, the chiller arrangement is used to optimize the cooling rate of the casting and avoid quality defects caused by local overheating. Figure 4 As shown, chill 11 is installed on the outer wall of the two heating risers 3 to prevent casting quality defects caused by the heat-affected zone between the heating risers 3. A second chill 12 is installed between the straight section barrel 16 and the two heating risers 3. The position of chill 12 has been precisely adjusted to effectively reduce the scope of the heat-affected zone and promote uniform cooling of the straight section barrel 16. A third chill 13 is installed between the inner cavity of the inclined barrel 17 and the second patch 7. The design of chill 13 focuses on ensuring uniform cooling of key parts of the casting and avoiding defects caused by local overheating. The layout and dimensions of chills 11, 12, and 13 were verified through simulation analysis and testing to ultimately meet cooling requirements. Chills 1 through 3 are made of HT250 gray cast iron with a thermal conductivity of 52 W / (m·K) and dimensional tolerances in accordance with GB / T9439-2010 Class 2.

[0022] The pouring system adopts a vertical double-layer water-inlet pouring scheme, including the lower pouring system 5 and the upper pouring system 4. The bottom pouring ladle is used, the pouring temperature is controlled at 1540±20℃, the cross-sectional area ratio of the lower pouring channel to the upper pouring channel is 1:1.2, and the pouring time is 2000kJ / m2. (W is the weight of the casting, ρ is the density of the molten steel, and A is the total cross-sectional area of the runner), it first flows into the lower pouring system 5, and then enters the hot riser 3 and the straight section cylinder 16. As the molten steel level rises to the upper pouring system 4, the molten metal mainly enters the mold from the upper layer, and eventually fills the entire inclined cylinder 17 and the large riser 1. The design of the vertical double-layer water inlet runner can significantly improve the exhaust and slag effects, while maintaining the temperature of the molten steel in the riser to ensure the shrinkage compensation effect of the riser. Specifically, the lower pouring system 5 is responsible for evenly distributing the molten steel to the hot riser 3 and the straight section cylinder 16, while the upper pouring system 4 ensures that the molten steel can quickly fill the complex structure of the inclined cylinder 17 and the large flange 14 through a higher pouring pressure and flow rate. The design of the upper pouring system 4 also takes into account the position and number of exhaust holes to further improve the exhaust effect.

[0023] To reduce stress concentration and cracks in castings during solidification, crack prevention measures include the design of sand-reducing holes 10, process ties 1 and 8, and process ties 2 and 9. Sand-reducing holes 10 are set in the mud core of the straight section cylinder 16. The diameter of the sand-reducing holes 10 is d = 0.3D (D is the mud core diameter), the depth is h = 0.7L (L is the mud core length), and the spacing between adjacent holes is ≤ 2d. Process ties 1 and 8 are set in the inner cavity of the inclined cylinder 17. The shape and position of process ties 1 and 8 were adjusted through multiple tests and ultimately determined to be able to effectively share the stress of the inclined cylinder 17 and reduce the occurrence of cracks. Process ties 2 and 9 are set at the large flange 14. The design focus of process ties 2 and 9 is to eliminate stress concentration between the large flange 14 and the straight section cylinder 16, avoiding cracks caused by excessive temperature differences. The combined use of the sand reduction holes 10, process tie bars 1 8 and process tie bars 2 9 significantly reduces deformation, cracks, sand inclusions, air holes and cold shut problems during the casting process, and improves the intrinsic quality and surface quality of the casting. The cross-sectional width of the process tie bars is 0.6-0.8 times the wall thickness of the connecting part, and the extension distance in the length direction is ≥3 times the cross-sectional width.

[0024] In the actual pouring process, a bottom pouring ladle is used, the pouring temperature is controlled at 1540±20℃, the cross-sectional area ratio of the lower runner to the upper runner is 1:1.2, and the pouring time is (W is the weight of the casting, ρ is the density of molten steel, and A is the total cross-sectional area of the runner) Figure 3 The path shown flows through the lower runner 5, the heated riser 3, the straight section cylinder 16, the upper runner 4 in sequence, and finally fills the entire inclined cylinder 17 and the large riser 1. After confirming that the mold is full, the entire casting process is completed. The entire mold follows a sequential shrinkage compensation mechanism during the pouring and solidification process. The heated riser 3 first compensates the sudden thickening position at the bottom of the straight section cylinder 16, and then the compensation 1 6 and the compensation 2 7 guide the molten steel to flow toward the inclined cylinder 17 and the large flange 14 respectively, and finally the top compensation is completed by the large riser 1. The design of the sequential shrinkage compensation mechanism ensures that the internal structure of the casting is dense and reduces defects such as shrinkage cavities and looseness.

[0025] Through the above-mentioned process design, the present invention solves the problems existing in the prior art, such as insufficient versatility, inaccurate cooling rate control, numerous casting defects, low production efficiency and high cost. The modular design of risers, subsidies and chillers enables the process to adapt to the casting needs of various types of frame products, especially thick and large-section castings. The reasonable arrangement of the chillers and the sequential shrinkage compensation mechanism optimize the cooling rate of the castings, reduce defects such as shrinkage cavities and porosity, and improve the mechanical properties of the castings (see Table 1). The design of the sand reduction holes 10, process tie bars 1 8 and process tie bars 2 9 significantly reduces deformation, cracks, sand inclusions, air holes and cold shuts during the casting process, and improves the intrinsic quality and surface quality of the castings. The vertical double-layer water inlet runner solution not only improves the exhaust and slag effects, but also shortens the pouring time and improves production efficiency. Production costs are reduced by reducing casting defects and optimizing material utilization.

[0026]

[0027]

[0028] Table 1

[0029] In summary, this invention significantly improves the quality and performance of the frame casting through scientific and rational process design, meeting the demand for high-quality, high-reliability frame products in the mining machinery field. Currently, the new frame has been mass-produced with stable quality, which can meet the diverse needs of customers.

[0030] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A frame casting process, characterized in that The invention includes the design of risers, pads, chillers, pouring systems and anti-cracking measures, wherein the risers and pads are used to establish sequential shrinkage feeding channels, the chillers are used to optimize the cooling rate of the castings, the pouring system adopts a vertical double-layer water inlet runner scheme, and the anti-cracking measures include sand reduction holes and process reinforcements.

2. The frame casting process according to claim 1, characterized in that The risers include a heat-generating open riser (3), a large riser (1) and a round riser (2), wherein the heat-generating open riser (3) is arranged at a sudden thickening position at the bottom of the straight section cylinder (16), the large riser (1) is arranged at the top of the large flange (14), and the round riser (2) is arranged between the two large risers (1).

3. The frame casting process according to claim 2, characterized in that The height and diameter of the exothermic riser (3) are further determined by calculation based on the wall thickness of the straight section cylinder (16), and a high exothermic material is used to prolong the liquid state time of the molten steel in the riser. The high exothermic material contains, by mass percentage, 30-35% of Al powder, 40-45% of Fe2O3, 5-8% of NaNO3, and the remainder of the binder.

4. The frame casting process according to claim 1, characterized in that The subsidy includes subsidy one (6) and subsidy two (7), wherein subsidy one (6) is symmetrically arranged at the connection between the inclined cylinder (17) and the straight cylinder (16), and subsidy two (7) is symmetrically arranged at the intersection of the large flange (14) and the inclined cylinder (17).

5. The frame casting process according to claim 4, characterized in that The sizes of the first and second subsidies (6) and (7) are further determined by thermal pitch circle calculation, and their shrinkage compensation capabilities are verified by actual casting simulation.

6. The frame casting process according to claim 1, characterized in that The cold iron comprises cold iron one (11), cold iron two (12) and cold iron three (13), wherein cold iron one (11) is arranged on the outer wall of the two heating risers (3), cold iron two (12) is arranged between the straight section cylinder (16) and the two heating risers (3), and cold iron three (13) is arranged between the inner cavity of the inclined cylinder (17) and the second supplementary iron (7).

7. The frame casting process according to claim 6, characterized in that It is further defined that the first cold iron (11), the second cold iron (12) and the third cold iron (13) are made of high thermal conductivity materials, and their arrangement positions and sizes are verified through simulation analysis and experiments.

8. The frame casting process according to claim 1, characterized in that The anti-cracking measures include setting a sand reduction hole (10) in the mud core of the straight section cylinder (16), setting a process tie rod (8) in the inner cavity of the inclined cylinder (17), and setting a process tie rod (9) at the large flange (14).

9. The frame casting process according to claim 8, characterized in that The diameter and depth of the sand reduction hole (10) are further limited and optimized according to the shrinkage characteristics of the mud core, and the shapes and positions of the process tie rod 1 (8) and the process tie rod 2 (9) are verified through experiments to share the stress.

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