Anti-deformation method for large-diameter ring casting

Abstract

The invention relates to an anti-deformation method for a large-diameter ring casting. The anti-deformation method comprises the steps of casting process design, post-treatment control and heat treatment optimization. In the casting process design step, a tie bar assembly is designed in an inner cavity of the large-diameter ring casting, and a supporting assembly is designed on the outer side of the large-diameter ring casting; in the post-treatment control step, normal-temperature box dismantling is adopted; before residues of a pouring system are cut, a casting is preheated; in the heat treatment optimization step, an anti-deformation tray is welded to the bottom of the casting for heat treatment, and the heat treatment process comprises an intermittent quenching process. According to the anti-deformation method for the large-diameter ring casting, easy-to-deform joints in the production process of the casting are researched and analyzed, anti-deformation measures are provided according to the characteristics of the joints, the measures are matched with one another, deformation of the casting in the production process is effectively prevented, the size stability and mechanical performance of the casting are improved, and the rejection rate is reduced; the production efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of casting, in particular to a method for preventing deformation of large-diameter ring castings. Background Art

[0002] Control rings are widely used in various key equipment due to their high strength, wear resistance and excellent mechanical properties. In the actual casting process, due to the large thermal expansion coefficient and strong cooling shrinkage of the control ring casting material itself, especially when the size of the casting increases, its deformation problem is more prominent, which seriously affects the quality and performance of the casting, and also increases the difficulty and cost of subsequent processing.

[0003] The traditional casting method can be used for other castings to meet production needs, but it still has many shortcomings in terms of deformation of control ring castings, especially when casting large-diameter control rings. Due to the large size and complex structure of the casting, its internal stress distribution is more complex and the deformation problem is more prominent. In addition, since the casting material is ASTM A216 Grade WCC, the mechanical properties are required to be high, and the quality heat treatment must be quenched, but the deformation tendency of the quenching process is greater. Therefore, how to effectively prevent the deformation of such control ring castings during the casting process has become an urgent problem to be solved in the actual production process. Summary of the invention

[0004] Based on this, it is necessary to provide a method for preventing deformation of large-diameter ring castings in order to solve the technical problem that the castings are easily deformed during the casting and heat treatment of the control ring castings.

[0005] In order to solve the above problems, the present invention adopts the following technical solutions:

[0006] An embodiment of the present invention discloses a method for preventing deformation of large-diameter ring castings, including casting process design, post-processing control and heat treatment optimization; in the casting process design step, a tie rod assembly is designed for the inner cavity of the large-diameter ring casting, and a support assembly is designed for the outer side of the large-diameter ring casting; in the post-processing control step, boxing is adopted at room temperature; and before cutting the residue of the casting system, the casting is preheated; in the heat treatment optimization step, an anti-deformation tray is welded on the bottom of the casting, and the casting and the anti-deformation tray are put into the furnace for heat treatment together, and the heat treatment process includes an intermittent quenching process.

[0007] In one embodiment, the tie rod assembly includes a first tie rod and a second tie rod, and the first tie rod and the second tie rod are vertically cross-arranged.

[0008] In one embodiment, the support assembly includes a first support rib, and a plurality of first support ribs are spaced apart between an upper flange and a lower flange on the outer side of the large-diameter ring casting.

[0009] In one embodiment, the cross-sectional dimension of the first supporting rib is greater than the wall thickness of the large-diameter ring casting.

[0010] In one embodiment, the support assembly further includes a second support rib; a pair of ears are symmetrically arranged on the top of the upper flange, and a second support rib is arranged between the upper flange and the ears.

[0011] In one of the embodiments, in the boxing step, the boxing temperature is controlled below 200°C; after the surface of the casting is cleaned, the casting is controlled to cool slowly, and the process is continued after the surface temperature of the casting drops below 150°C.

[0012] In one embodiment, the intermittent quenching process includes a water cooling stage and an air cooling stage, the water cooling stage and the air cooling stage are arranged in an interval cycle, and the cycle duration of the water cooling stage and the air cooling stage are gradually increased.

[0013] In one embodiment, the initial duration of the water cooling stage is 1 minute, and the subsequent cycle increment is 1 minute / time; the initial duration of the air cooling stage is 30 seconds, and the subsequent cycle increment is 30 seconds / time.

[0014] In one embodiment, the heat treatment process also includes tempering treatment, and the casting is intermittently quenched and cooled to below 200° C. and then put into the furnace for tempering treatment.

[0015] The technical solution adopted by the present invention can achieve the following beneficial effects:

[0016] The anti-deformation method of large-diameter ring castings disclosed in the present invention studies and analyzes various production nodes that are prone to deformation during the casting, heat treatment and other processes of the castings, and then proposes anti-deformation measures according to the production characteristics of each node. Anti-deformation component tooling is added in the casting process design stage, the operating temperature is controlled in the boxing and post-processing stages, and an anti-deformation tray and intermittent quenching process are used in the heat treatment stage. Each stage cooperates with each other to effectively prevent large-diameter ring castings from being deformed during the production process, improve the dimensional stability and mechanical properties of large-diameter ring castings, reduce the scrap rate, and improve production efficiency.

[0017] The anti-deformation method for large-diameter ring castings disclosed in the present invention adds anti-deformation component tooling in the casting process design stage to improve the rigidity of the overall structure of the casting; controls the operating temperature in the boxing and post-processing stages to effectively prevent deformation of the casting caused by high-temperature boxing and local thermal cutting; welds an anti-deformation tray to the bottom of the casting before loading the furnace for heat treatment to effectively prevent deformation of large-diameter ring castings during heat treatment; and adopts an intermittent quenching process to effectively reduce the quenching stress of the material. The anti-deformation method for large-diameter ring castings disclosed in the present invention strictly controls each node in the production process, which not only effectively prevents deformation of the casting, but also further improves the quality of the casting, shortens the production cycle, and saves costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the structure of the control ring casting disclosed in an embodiment of the present invention;

[0019] Figure 2 This is a schematic diagram of the structure of the control ring casting after welding the anti-deformation tray;

[0020] Description of reference numerals:

[0021] 100-control ring casting, 110-upper flange, 120-lower flange, 130-ear;

[0022] 200-tensioning assembly;

[0023] 310-first supporting rib, 320-second supporting rib;

[0024] 400-Anti-deformation tray. DETAILED DESCRIPTION

[0025] In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present invention are given in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thoroughly understood.

[0026] It should be noted that when an element is referred to as being "disposed on" another element, it may be directly on the other element or there may be a centered element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a centered element at the same time. The terms "vertical", "horizontal", "left", "right", "top", "bottom", "bottom end", "top end" and similar expressions used herein are for illustrative purposes only and are not intended to be the only implementation method.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0028] The embodiment of the present invention discloses a method for preventing deformation of a large-diameter ring casting. Research and analysis show that the large-diameter ring casting is prone to deformation during the casting process, the box cleaning process, and the heat treatment process. Therefore, the embodiment of the present invention proposes anti-deformation measures according to the production characteristics of each node, which may specifically include the following contents:

[0029] The casting process is designed to add anti-deformation component tooling to improve the rigidity of the overall structure of the casting.

[0030] Post-processing control uses boxing at room temperature and preheats the casting before cutting residues such as the gating system.

[0031] Heat treatment is optimized. An anti-deformation tray is welded to the bottom of the casting before loading the furnace for heat treatment, which effectively prevents deformation of large-diameter ring castings during heat treatment. Intermittent quenching process is used for quenching to further reduce the tendency of quenching deformation.

[0032] In order to better understand the concept of the present invention, the following takes the control ring casting as an example to further explain the anti-deformation method disclosed in the present invention. Figure 1 , Figure 2 As shown, the control ring casting 100 is a steel casting made of ASTM A216 Grade WCC, with an outline size of 4500mm×4000mm×1200mm, a maximum wall thickness of 130mm, and a weight of 9t. The control ring casting 100 belongs to a large-diameter ring casting. Due to the large size and complex structure of the casting, its internal stress is more complex. During the production process, its ring structure is prone to deformation. In addition, an upper flange 110 and a lower flange 120 are arranged on the outside of the control ring casting 100, and a pile of ears 130 are symmetrically arranged on the top of the upper flange 110. The upper flange 110, the lower flange 120 and the ears 130 are prone to deformation defects such as warping and sagging during the production process. In view of the structure, material and other characteristics of the control ring casting 100, the anti-deformation method of this embodiment may include three parts: casting process design, post-processing control, and heat treatment optimization.

[0033] Casting process design, such as Figure 1As shown, a tie rod assembly 200 can be designed in the inner cavity of the control ring casting 100 to pull the ring structure of the control ring casting 100 to prevent the ring structure from being deformed and causing insufficient roundness. A support assembly can be designed on the outside of the control ring casting 100 to, on the one hand, strengthen the ring wall of the control ring casting 100 to prevent the ring of the control ring casting 100 from being deformed; on the other hand, the support assembly can also pull the upper and lower flanges, ears 130, etc. to prevent the upper and lower flanges and ears 130 from warping and sagging.

[0034] The tie rod assembly 200 may include a first tie rod and a second tie rod, the first tie rod and the second tie rod are vertically cross-connected to form a "cross" tie rod, and the four ends of the "cross" tie rod are all fixed to the inner wall of the ring portion of the control ring casting 100 to ensure the overall structural rigidity of the casting. The support assembly may include 6 first support ribs 310 and 2 second support ribs 320. The 6 first support ribs 310 are evenly spaced and fixed between the upper flange 110 and the lower flange 120 to prevent the upper flange 110 and the lower flange 120 from sagging or tilting. When the control ring has a tendency to deform, the support ribs will provide a reverse force to curb the deformation. When designing, the cross-sectional diameter of the first support rib 310 can be larger than the wall thickness of the control ring casting 100, so as to prevent the first support rib 310 from breaking due to insufficient strength when curbing the deformation of the casting. Since the ear portion of the control ring casting 100 has the greatest deformation tendency and is a severely deformed portion, a second support rib 320 is fixedly connected to the inner side of each ear portion 130, and the other end of the second support rib 320 is fixedly connected to the top of the upper flange 110. Furthermore, an anti-deformation rib plate can be added between the upper and lower flanges directly below each ear portion 130, and the cross-sectional area of ​​the anti-deformation rib plate should be greater than the cross-sectional area of ​​the first support rib 310.

[0035] Of course, the number of "cross" tie bars in this embodiment is not limited to one group, and multiple groups can be added according to the casting structure and production requirements. The embodiment of the present invention does not impose specific restrictions on this.

[0036] Post-processing control: Due to the special structure of the control ring casting 100, it is easy to deform during the boxing process. Therefore, boxing is adopted at room temperature, and the casting temperature should be controlled below 200°C during the boxing process. After the boxing is completed, the casting sand box is removed in time, the molding sand on the surface of the control ring casting 100 is cleaned, and the control ring casting 100 is kept slowly cooled in the pit. The next sequence can be carried out only after the surface temperature of the casting drops below 150°C. The pouring system residues such as runners, risers, and casting subsidies left on the control ring casting 100 after boxing need to be cut. Before cutting, the control ring casting 100 needs to be preheated. After the control ring casting 100 is kept at the target preheating temperature for a set time, it is taken out of the furnace and transferred to the cutting operation area to cut the pouring system residues on the control ring casting 100.

[0037] Heat treatment optimization, such as Figure 2 As shown, before heat treatment, the control ring casting 100, together with the tie rod assembly 200 and the support assembly, is transported to the anti-deformation tray 400, and six welding points are evenly selected at the contact position between the lower flange 120 of the control ring casting 100 and the anti-deformation tray 400 for welding to connect the control ring casting 100 and the anti-deformation tray 400; the control ring casting 100, together with the tie rod assembly 200, the support assembly and the anti-deformation tray 400, is put into the furnace for heat treatment.

[0038] The heat treatment process includes quenching + tempering process, in which the quenching adopts an intermittent quenching process, and the quenched casting is cooled to below 200°C before tempering. The intermittent quenching process specifically heats the casting to the target quenching temperature, keeps it warm for a set time, and then takes it out of the furnace for quenching and cooling. The intermittent quenching process can effectively alleviate the deformation caused by excessive stress in the casting during the quenching process. Quenching and cooling can include a water cooling stage and an air cooling stage, and the water cooling stage and the air cooling stage are set in interval cycles, and the cycle lengths of the water cooling stage and the air cooling stage are gradually increased. Among them, the initial duration of the water cooling stage can be 1min, and the subsequent cycle increase can be 1min / time; the initial duration of the air cooling stage can be 30s, and the subsequent cycle increase can be 30s / time, until the casting is cooled to below 200°C for tempering. That is, the quenching cooling method can be designed as 1 minute water cooling - 30 seconds air cooling - 2 minutes water cooling - 1 minute air cooling - 3 minutes water cooling - 1.5 minutes air cooling... until the casting is cooled to below 200°C and then put into the furnace for tempering treatment.

[0039] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for preventing deformation of large diameter ring castings, characterized in that: Including casting process design, post-processing control and heat treatment optimization; In the casting process design step, a tie rod assembly is designed in the inner cavity of the large-diameter ring casting, and a support assembly is designed on the outer side of the large-diameter ring casting; In the post-processing control step, boxing is performed at room temperature; and the casting is preheated before the residue of the gating system is cut; In the heat treatment optimization step, an anti-deformation tray is welded to the bottom of the casting, and the casting and the anti-deformation tray are put into the furnace for heat treatment together. The heat treatment process includes an intermittent quenching process.

2. The method for preventing deformation of large-diameter ring castings according to claim 1, characterized in that: The tie rod assembly includes a first tie rod and a second tie rod, and the first tie rod and the second tie rod are arranged vertically and crosswise.

3. The method for preventing deformation of large diameter ring castings according to claim 1, characterized in that: The support assembly includes a first support rib, and a plurality of first support ribs are spaced apart and arranged between the upper and lower flanges on the outer side of the large-diameter ring casting.

4. The method for preventing deformation of large diameter ring castings according to claim 3, characterized in that: The cross-sectional dimension of the first supporting rib is greater than the wall thickness of the large-diameter ring casting.

5. The method for preventing deformation of large diameter ring castings according to claim 3, characterized in that: The support assembly further includes a second support rib; a pair of ears are symmetrically provided on the top of the upper flange, and a second support rib is provided between the upper flange and the ears.

6. The method for preventing deformation of large diameter ring castings according to claim 1, characterized in that: In the post-processing control step, the boxing temperature is controlled to be below 200° C.; after the casting surface is cleaned, the casting is controlled to cool slowly, and the process is not continued until the casting surface temperature drops below 150° C.

7. The method for preventing deformation of large diameter ring castings according to claim 1, characterized in that: The intermittent quenching process includes a water cooling stage and an air cooling stage, the water cooling stage and the air cooling stage are arranged in an intermittent cycle, and the cycle lengths of the water cooling stage and the air cooling stage are gradually increased.

8. The method for preventing deformation of large diameter ring castings according to claim 7, characterized in that: The initial duration of the water cooling stage is 1 minute, and the subsequent cycle increment is 1 minute / time; the initial duration of the air cooling stage is 30 seconds, and the subsequent cycle increment is 30 seconds / time.

9. The method for preventing deformation of large-diameter ring castings according to any one of claims 1 to 8, characterized in that: The heat treatment process also includes tempering treatment, in which the casting is intermittently quenched and cooled to below 200° C. and then put into the furnace for tempering treatment.

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