A method of manufacturing a large-scale bucket lip as a whole

Abstract

The application relates to a manufacturing method of integrally manufacturing a large-scale bucket lip, which comprises the following steps: 1) vertical molding casting is adopted, a large plane of a bucket lip flange is taken as a parting surface, and a top box is a flat cover; 2) a pouring system adopts two layers of inner water inlets, and the number of each layer is more than 6; 3) the pouring temperature is less than or equal to 1460 DEG C, and the pouring time is not more than 150s; 4) chromite sand or a shaped outer cooling iron is placed at each round corner, and the outer cooling iron is uniformly distributed below 1 / 2 of the vertical plane height; 5) in the process of designing the chemical composition of the casting, the mass ratio of Mn to C is greater than or equal to 12.5; and 6) during the heat treatment of the casting, limiting fixing blocks are arranged at the top points of the bucket lip arcs, the middle parts of the arcs on both sides of the top points and the side walls of the bucket lip. The application realizes integrally casting a large-scale bucket lip, improves the production efficiency, guarantees and improves the service life of the bucket, reduces the influence of carbonides caused by welding on the strength of the bucket lip, changes the split casting into the integral casting through the vertical pouring, guarantees the integral size precision and mechanical strength of the bucket lip, and improves the production efficiency.

Description

Technical Field

[0001] This invention relates to the field of mechanical manufacturing technology, and in particular to a method for manufacturing a large bucket lip that is manufactured as a single piece. Background Technology

[0002] The bucket is one of the most important components of a loader. The bucket lip is the part of the bucket that directly contacts external materials and is subjected to the greatest stress from friction, impact, and bending. Its structural stability, overall manufacturing strength, and dimensional accuracy directly affect the welding quality between the bucket lip and the bucket body, the assembly quality, and the service life.

[0003] Generally, the bucket lip and forearm of small and medium-sized buckets are cast as a whole. However, large buckets with a capacity of more than 30 cubic meters usually have the bucket lip cast separately. Furthermore, due to the large size of the bucket lip, with a nominal size greater than 3.5m, and the need for dimensional accuracy and easy deformation of the structure, it is necessary to use the method of casting three parts and then assembling them into a complete bucket lip to ensure the strength of the bucket lip and the accuracy of the welding and installation.

[0004] According to the original process, the U-shaped lip casting needs to be cast in three parts: left, right, and bottom. Each part is cast separately, water-cooled, and cleaned before the joints are machined and welded together. This process is labor-intensive and inefficient. In particular, after water cooling, carbides precipitate at the weld joints of the high-manganese steel casting, making the weld brittle and prone to cracking, affecting its service life. It also increases the welding workload and reduces production efficiency.

[0005] However, when using integral casting for large bucket lips, the different shrinkage rates of various parts of the large bucket lip during the casting and water quenching process can easily cause deformation, making it difficult to guarantee the dimensional accuracy and mechanical performance requirements of the large bucket lip. Summary of the Invention

[0006] The purpose of this invention is to provide a method for manufacturing a large bucket lip that is integrally cast, thereby achieving the integral casting of large (55 cubic meters or single weight exceeding 8 tons) bucket lips, while improving production efficiency, ensuring and extending the service life of the bucket, reducing the impact of welding carbide precipitation on the strength of the bucket lip, and changing from split casting to integral casting by vertical casting, ensuring the overall dimensional accuracy and mechanical strength of the bucket lip, and reducing the workload of assembly welding to further improve production efficiency.

[0007] To achieve the above objectives, the present invention employs the following technical solution:

[0008] A method for manufacturing a large bucket lip as a single unit includes:

[0009] 1) Vertical molding and casting is adopted, with the large flat surface of the lip flange as the parting surface and the upper box as a flat cover; the upper box riser adopts a heating riser sleeve to improve the feeding efficiency.

[0010] Vertical molding and casting are adopted, and gravity feeding is used to make the shrinkage rate at the bottom of the lip 25% to 28% and the shrinkage rate at the top 15% to 20%.

[0011] The inner arc surface of the punch lip is formed from a single sand core from top to bottom. Horizontally, it is formed in multiple sections, preferably in six sections.

[0012] 2) The gating system adopts two layers of internal gating nozzles, with more than 6 nozzles on each layer.

[0013] 3) Low-temperature rapid casting should be adopted, with a casting temperature ≤1460℃ and a casting time not exceeding 150s.

[0014] 4) Place quenching measures at the rounded corners of each part, such as chromite sand or shaped external chills; evenly distribute external chills below 1 / 2 of the facade height; the external chills are cylindrical external chills with dimensions ≥φ60mm×60mm, and the placement spacing is within 200mm.

[0015] 5) In the design of the chemical composition of castings, the mass ratio of Mn to C is ≥12.5.

[0016] 6) During the heat treatment of the casting, limiting and fixing blocks are set at the top of the arc of the lip, the middle of the arc on both sides of the top, and the side wall of the lip. The limiting and fixing blocks at the top of the arc of the lip and the middle of the arc on both sides of the top are set on both sides of the lip wall, and the limiting and fixing blocks on the side wall of the lip are set on the inner wall of the lip.

[0017] The castings are cooled in the sand mold to below 300℃ and then cleaned by removing the sand. After that, heat treatment is carried out: the temperature is increased to 650-700℃ at a rate of 60-70℃ per hour and held at that temperature for 2-3 hours. Then, the temperature is increased to 1050-1080℃ at a rate of 80-100℃ per hour and held at that temperature for more than 3 hours before being taken out of the furnace and water-quenched.

[0018] The chemical composition of the lip casting, by mass percentage, is: C 0.75%–1.05%, Si 0.3%–0.5%, Mn 12.5%–14%, P ≤0.035%, S ≤0.035%, Mo 1%–1.2%, with the remainder being Fe and unavoidable impurities.

[0019] The properties of the castings after water toughening treatment according to this invention are: R m ≥755MPa, A%≥30%, Aku / J≥147, HBW≤300.

[0020] This invention employs self-hardening sand molding to ensure both surface quality and dimensional accuracy. The optimal sand particle size is 40-70 mesh dolomite or quartz sand. To reduce the difficulty of cleaning up fallen sand, resin-bonded self-hardening sand is the preferred choice. To further improve surface quality, chromite is preferred for the face sand at the corners of the mold and core; alcohol-based quick-drying coatings, pyroxene powder, and other refractory aggregates are used, but magnesia powder is the preferred coating aggregate. Small-hole sand cores for the castings are made using resin sand.

[0021] The bucket lip is 55 cubic meters or weighs more than 8 tons.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] 1) This invention is designed for the integral casting of large bucket lips. The large flat surface of the bucket lip flange is used as the parting surface, the upper box is a flat cover, and a vertical casting method is adopted. The static pressure head is used to ensure shrinkage compensation and effectively control the shrinkage rate of the bottom and top of the bucket lip, thereby preventing deformation in the easily deformable areas of the large bucket lip casting.

[0024] 2) This invention utilizes a static pressure head and controls the pouring temperature and pouring time to control the shrinkage rate at the bottom of the casting lip to be 25% to 28% and the shrinkage rate at the top to be 15% to 20%. The differentiated shrinkage rate design for different parts of the casting can effectively ensure the dimensional accuracy of the final casting.

[0025] 3) The sand core of this invention uses resin sand to ensure surface quality and cleaning efficiency.

[0026] 4) This invention utilizes numerical control of the chemical composition Mn / C to ensure the mechanical properties and performance of the castings.

[0027] 5) The present invention sets up a uniform external chill to ensure that the microstructure of the end zone and the chilled zone is dense.

[0028] 6) The present invention uses low-temperature casting and shortens the casting time to reduce shrinkage and avoid deformation in local areas.

[0029] 7) This invention utilizes heat treatment to modify molten steel, ensuring finer grains in the casting.

[0030] 8) During the heat treatment process, the easily deformable areas are positioned using limiting and fixing blocks to prevent deformation caused by changes in thermal stress during the heat treatment process. Attached Figure Description

[0031] Figure 1 This is the main view of the large punch lip part drawing.

[0032] Figure 2 This is a side view of the drawing of a large punch lip component.

[0033] Figure 3This is a process plan view of the casting of the present invention (part view is...) Figure 1 (Top view).

[0034] Figure 4 This is a schematic diagram of the limiting component during the heat treatment of the casting of the present invention.

[0035] In the diagram: 1-Cylindrical external chill, 2-Limiting and fixing block, 3-Casting, 4-Slide plate. Detailed Implementation

[0036] The embodiments of the present invention will be further described below with reference to the accompanying drawings:

[0037] See Figures 1-4 The embodiment describes a 55 cubic meter bucket lip, and the manufacturing method for an integrally manufactured large bucket lip specifically includes:

[0038] 1) such as Figures 1-3 As shown, the large plane B of the lip flange is the parting surface (see...). Figure 1 All castings are molded in the lower box and cast using a vertical molding method (see...). Figure 3 The upper box has a flat cover; the upper box riser uses a heating riser sleeve to improve the feeding efficiency.

[0039] Vertical molding and casting are adopted, and gravity feeding is used to make the shrinkage rate at the bottom of the lip 25% to 28% and the shrinkage rate at the top 15% to 20%.

[0040] The inner arc surface (C-surface) of the punch lip is formed from a single sand core from top to bottom. Horizontally, it is formed in multiple sections, preferably six sections. See [link / reference]. Figure 3 For the sand cores of "1#, 2#, 3#, 4#, and 5#", resin sand is the best choice as it is beneficial for casting shrinkage.

[0041] 2) The gating system adopts two layers of internal gating nozzles, with more than 6 nozzles on each layer.

[0042] 3) Low-temperature rapid casting is adopted, with a casting temperature of 1460℃ and a casting time of 150s.

[0043] 4) See Figure 1 Cooling measures are placed at the rounded corners of each part, and chromite sand or shaped external chills are placed there; external chills are evenly distributed below 1 / 2 of the facade height; the external chills are cylindrical external chills 1 with a size of ≥φ60mm×60mm, and the placement spacing is within 200mm.

[0044] 5) See Figure 4 During the heat treatment of casting 3, limiting and fixing blocks 2 are set at the top of the arc of the lip, the middle of the arc on both sides of the top, and the side wall of the lip. The limiting and fixing blocks 2 at the top of the arc of the lip and the middle of the arc on both sides of the top are set on both sides of the lip wall, and the limiting and fixing blocks 2 on the side wall of the lip are set on the inner wall of the lip.

[0045] The positioning structure for heat treatment of casting 3 includes casting 3, slide 4, several limiting and fixing blocks 2, and the large flat surface of the flange of casting 3. Figure 1 The B side of the casting 3 is placed on the slide plate 4. Several limiting and fixing blocks 2 are respectively set at the arc apex, the middle of the arc on both sides of the apex, and the side wall of the lip. The limiting and fixing blocks 2 at the arc apex and the middle of the arc on both sides of the apex of the casting 3 are set on both sides of the arc wall of the casting 3. The limiting and fixing blocks 2 on the side wall of the lip are set on the inner wall of the lip. Several of the limiting and fixing blocks 2 are fixedly connected to the slide plate 4. Figure 4 The part view of casting 3 is as follows Figure 1 In the B-side view, the slide plate 4 is located at the top of the B-side view. During heat treatment, the slide plate 4 is used to support the integral casting 3 of the punch lip.

[0046] Limiting and fixing block 2 is a metal block.

[0047] The limiting and fixing block 2 has a square cross-section and a height of 30mm; the cross-sectional dimensions are 30mm × 20mm.

[0048] Casting 3 is cooled in the sand mold to below 300℃ and then cleaned by removing the sand. After that, it is heat treated: the temperature is increased to 650℃ at a rate of 70℃ per hour and held at that temperature for 3 hours. Then, the temperature is increased to 1050℃ at a rate of 80℃ per hour and held at that temperature for more than 3 hours before being taken out of the furnace and water-quenched.

[0049] The chemical composition of the bucket lip casting in the example, by mass percentage, is: C 0.80%, Si 0.4%, Mn 13%, P 0.02%, S 0.02%, Mo 1%, with the remainder being Fe and unavoidable impurities.

[0050] The properties of the castings after water toughening treatment according to this invention are: R m The pressure is 800 MPa, A is 31%, Aku / J is 150, and HBW is 300.

[0051] This invention employs self-hardening sand molding for core making, ensuring both surface quality and dimensional accuracy. 40-70 mesh dolomite sand or quartz sand is optimally selected as the raw sand. Resin-bonded sand is the preferred type of self-hardening sand, with chromite being the best choice for both the molding and core surfaces. Alcohol-based quick-drying coatings, chromite powder, and other materials are used as refractory aggregates, but magnesia powder is the preferred choice. Resin-bonded sand is used for small-pore cores.

[0052] During the overall casting process of a large lip casting, there are two easily deformable stages that require special control. The first stage is at the end of casting, where the different shrinkage rates of different parts cause severe deformation of the two side walls. This invention employs vertical molding casting, using gravity-fed shrinkage compensation, and controlling the casting temperature and time to keep the shrinkage rate at the bottom of the lip controlled at 25%–28% and at the top at 15%–20%. This differentiated design of the top and bottom shrinkage rates effectively controls the amount of deformation and ensures the dimensional accuracy of the casting. The second easily deformable stage is the heat treatment stage. During the heat treatment process, this invention sets limiting and fixing blocks 2 at the apex of the lip arc, the middle of the arcs on both sides of the apex, and the side walls of the lip. This effectively controls the deformation caused by changes in thermal stress during heat treatment, ultimately ensuring the dimensional accuracy of the casting.

Claims

1. A manufacturing method of integrally manufacturing a large-sized bucket lip, characterized by, Specifically comprising: 1) vertical molding casting, with the flange large plane of the bucket lip as the parting surface, and the upper box as the flat cover; 2) the pouring system adopts two layers of inner water gap, each with more than 6 channels; 3) the pouring temperature is less than or equal to 1460℃, and the pouring time is not more than 150s; 4) placing chromite sand or shaped external chill at each round corner, and distributing external chill below 1 / 2 of the vertical height; 5) in the chemical composition design of the casting, the mass ratio of Mn to C is greater than or equal to 12.5; 6) during the heat treatment of the casting, limiting fixing blocks are arranged at the top point of the bucket lip arc, the middle part of the arc on both sides of the top point, and the side wall of the bucket lip, the limiting fixing blocks at the top point of the bucket lip arc and the middle part of the arc on both sides of the top point are arranged on both sides of the bucket lip wall, and the limiting fixing block of the side wall of the bucket lip is arranged on the inner wall of the bucket lip. The bucket lip is greater than or equal to 55 cubic meters or more than 8 tons in single weight.

2. The method of claim 1, wherein The inner arc surface of the bucket lip is formed by taking a whole sand core from top to bottom and taking multiple blocks in the horizontal direction.

3. The method of claim 1, wherein The vertical molding casting is made by gravity feeding to make the shrinkage rate of the bottom of the bucket lip be 25% to 28% and the shrinkage rate of the top be 15% to 20%.

4. The method of claim 1 wherein the method further comprises: The chemical composition of the bucket lip casting is as follows in terms of mass percentage: C 0.75% to 1.05%, Si 0.3% to 0.5%, Mn 12.5% to 14%, P less than or equal to 0.035%, S less than or equal to 0.035%, Mo 1% to 1.2%, and the rest is Fe and inevitable impurities.

5. The method of claim 1 wherein the method further comprises: The casting is cooled to below 300℃ in the sand mold and then cleaned by sand removal; then heat treatment is carried out: heating to 650 to 700℃ at a heating rate of 60 to 70℃ per hour, keeping constant temperature for 2 to 3 hours, heating to 1050 to 1080℃ at a heating rate of 80 to 100℃ per hour, keeping constant temperature for more than 3 hours, and then taking out the water toughening treatment.

6. The method of claim 1 or 5, wherein The properties of the castings after heat treatment are: R m ≥ 755 MPa, A% ≥ 30%, Aku / J ≥ 147, HBW ≤ 300.

7. The method of claim 1 wherein the method further comprises: The riser of the upper box adopts a heating riser sleeve.

8. The method of claim 1 wherein the method further comprises: Self-hardening sand molding and core making; the grain size of the molding sand is selected to be 40 to 70 mesh white dolomite sand or quartz sand as the raw sand; the surface sand at the corner of the mold and core is selected to be chromite sand, and an alcohol-based quick-drying paint is used.

9. The method of claim 1 wherein the method further comprises: In the step 4), the external chill is a cylindrical external chill with a size greater than or equal to φ60mm*60mm, and the placement interval is within 200mm.

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