Industrial valve body forming method

Abstract

According to the industrial valve body forming method, through optimal design of a parting surface, optimal design of a pouring system, optimal design of a dead head, optimal design of chiller arrangement and optimal design of reduced scale and smelting process parameters in sequence, the size precision of a casting can be guaranteed, and meanwhile the quality of a flange face and the internal quality can be guaranteed; oxidation slag inclusion defects caused by turbulent flow are effectively reduced, the solidification speed of thick and large parts is increased, the shrinkage cavity and shrinkage porosity defects of key positions of castings are eliminated, the size precision and the internal quality of the valve body castings both meet the requirements of design drawings, and the product percent of pass is increased.

Description

Technical Field

[0001] The invention belongs to the technical field of valve body casting, and in particular relates to an industrial valve body forming method. Background Art

[0002] Large-size industrial valve bodies are one of the core components of modern industrial production equipment and are widely used in industries such as tap water, oil, natural gas, and chemicals. The valve body structural unit is special and complex, and the valve body outline size is mainly below Ф1480×1500, and generally uses lost foam or coated sand casting technology.

[0003] With the development of industry and the improvement of valve body technical standards, the valve body contour size is getting larger and larger, the wall thickness is getting thicker and thicker, and the internal structure is getting more and more complicated. Lost foam or coated sand casting processes are prone to shrinkage, pores, cracks and other defects during the production process. The product qualification rate is only about 50%-60%, and the production cost has increased significantly. It can no longer meet the needs of high-quality valve body production and the development needs of modern enterprises to reduce costs and increase efficiency. Therefore, it is necessary to make improvements. Summary of the invention

[0004] The technical problem solved by the present invention is as follows: to provide an industrial valve body forming method, which can ensure both the dimensional accuracy of the casting and the flange surface and internal quality by optimizing the design of the parting surface, the pouring system, the riser, the chiller arrangement, the reduction and the smelting process parameters in sequence, effectively reduce the oxidation slag inclusion defects caused by turbulence, eliminate the shrinkage holes and shrinkage defects at the key positions of the casting, so that the dimensional accuracy and internal quality of the valve body casting meet the requirements of the design drawings, and improve the product qualification rate.

[0005] The technical solution adopted by the present invention: an industrial valve body forming method, comprising the following steps:

[0006] 1) Selection of parting surface: The connection surface of the important flange is facing downward and the connection surface of the connecting flange is facing upward, and a three-opening mold including parting surface 1 and parting surface 2 is used, so that the valve body casting is completely located in the lower box of the mold;

[0007] 2) Design of pouring system: adopt an open bottom pouring pouring system with a filter, wherein the open bottom pouring pouring system includes a horizontal runner, a vertically arranged straight runner connected to the middle of the horizontal runner, and multiple ingates connecting the cavity with the horizontal runner through the filter. The cross-sectional ratio of the straight runner, horizontal runner and ingate of the open bottom pouring pouring system is 1.5:1:2.5. When pouring, high temperature slow pouring is adopted to introduce from the lowest point of the cavity;

[0008] 3) Riser design: Four equal diameter sections of φ160mm to φ200mm are evenly distributed on the plane of the connecting flange, and the riser neck at the lower end is a φ90mm insulation riser, which provides liquid shrinkage compensation for the entire valve body casting;

[0009] 4) Chill design: Chills are arranged on important processing surfaces of the valve body casting with a wall thickness greater than 100 mm in the cavity of the mold base. The thickness of the chill is designed to be 2 / 3 of the wall thickness of the cooled part of the valve body casting, and the gap between adjacent chills is 20 to 30 mm;

[0010] 5) Feeding the shrinkage of the pouring cup: Based on the principle of communicating vessels, the outlet pipes of all insulation risers are raised to more than 150mm above the bottom plane of the pouring cup, and more than 150mm of molten iron can be left in the pouring cup. The molten iron in the pouring cup provides a continuous pressure head to the valve body casting, thereby feeding the bottom of the valve body casting;

[0011] 6) Smelting process and parameter design: The silicon content of the original molten iron is controlled between 2.2 and 2.4%, the carbon content is controlled between 3.4 and 3.6%, the manganese content is controlled below 0.3%, the phosphorus content is controlled below 0.05%, and the sulfur content is controlled below 0.02%; the amount of spheroidizer is 1.3%, and the amount of inoculant is 1.0%, so that the final silicon content of the valve body casting reaches 3.4-3.6%.

[0012] In the above step 2), the sprue and the inner runner are both made of porcelain tubes with different diameters.

[0013] In the above step 2), the cross section of the runner is a trapezoidal structure.

[0014] In the above step 2), the high temperature slow pouring method is a pouring method in which the pouring temperature is 1360-1370° C. and the total pouring time is controlled within 60±5 s.

[0015] In the above step 2), filters are provided at both ends of the cross runner, and the filters are connected to the corresponding ends of the three inner runners on the same side, and the upper port of the straight runner is connected to the bottom of the pouring cup.

[0016] In the above step 5), the shrinkage rate of the ductile iron valve body casting is 0.9%.

[0017] The advantages of the present invention compared with the prior art are:

[0018] 1. This technical solution can ensure the dimensional accuracy of castings and reduce the seams to improve production efficiency by optimizing the design of the parting surface and adopting the three-opening process design;

[0019] 2. The higher pouring temperature of this technical solution is combined with the bottom pouring rain pouring system with a filter, so that the pouring time is controlled to about 60 seconds, realizing the high-temperature slow pouring process, which can effectively reduce the occurrence of slag inclusion defects in castings;

[0020] 3. This technical solution provides a heat-insulating riser at the highest point of the casting position of the valve body casting for liquid shrinkage compensation, and provides a chiller at the thick and large part of the casting, which effectively eliminates shrinkage holes and shrinkage defects at key positions of the casting;

[0021] 4. This technical solution uses the principle of communicating vessels to allow a certain amount of molten iron to remain in the pouring cup, maintaining continuous pressure head and shrinkage compensation at the bottom of the casting, thereby reducing shrinkage holes and shrinkage defects at key positions at the bottom of the base, so that the dimensional accuracy and internal quality of the valve body casting meet the requirements of the design drawings and improve the product qualification rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The parting surface structure of the present invention is shown in the figure;

[0023] Figure 2 It is a schematic diagram of the pouring system structure of the present invention;

[0024] Figure 3 This is a front view of the riser position of the present invention;

[0025] Figure 4 It is a top view of the riser position structure of the present invention;

[0026] Figure 5 This is a schematic diagram of the cold iron arrangement structure of the present invention;

[0027] Figure 6 It is a schematic diagram of the valve body pouring cup shrinkage compensation design of the present invention. DETAILED DESCRIPTION

[0028] The following will be combined with the embodiments of the present invention Figure 1-6 , the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] It should be noted that, in this document, unless otherwise stated, it should be understood that the terms "center", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", etc., are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0030] In this document, the terms "comprises", "comprising" or any other variation thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further limitations. The elements defined by the sentence "comprising a ..." do not exclude the presence of other identical elements in the process, method, article or device comprising the elements.

[0031] The industrial valve body forming method takes a large industrial valve body with a base size of 1480×1500mm, a blank weight of 4300Kg, a pouring liquid weight of 4700Kg, a main wall thickness of 28mm, and a maximum wall thickness of 35mm as a reference object. The scheme of the present invention is designed from the aspects of parting surface, pouring system, riser, chill, scale reduction and smelting process parameters, and includes the following steps:

[0032] 1) Selection of parting surface: The connection surface of the important flange 1 is facing downward and the connection surface of the connecting flange 2 is facing upward, and a three-opening mold including a parting surface 1 3 and a parting surface 2 4 is used, so that the valve body casting 5 is completely located in the lower box 6 of the mold, which is conducive to ensuring the size and the flange surface and internal quality;

[0033] 2) Design of pouring system: an open bottom pouring pouring system with a filter 7 is adopted, wherein the open bottom pouring pouring system comprises a runner 8 with a trapezoidal cross section, a vertically arranged straight runner 9 connected to the middle of the runner 8, and a plurality of ingates 10 connecting the cavity with the runner 8 through the filter 7. Filters 7 are arranged at both ends of the runner 8, and the filter 7 is connected to the corresponding ends of the three ingates 10 on the same side. The upper end of the straight runner 9 is connected to the bottom of the pouring cup 13. The cross-sectional ratio of the straight runner 9, the runner 8 and the ingate 10 of the open bottom pouring pouring system is 1.5:1:2.5. During pouring, a high-temperature slow pouring method is adopted to introduce the pouring from the lowest point of the cavity. The straight runner 9 and the ingate 10 are both made of porcelain tubes with different diameters. The high-temperature slow pouring method is a pouring method in which the pouring temperature is 1360-1370°C and the total pouring time is controlled within 60±5s; the molten iron is introduced from the lowest point of the cavity, and the molten iron level rises steadily with the open ingates, which is conducive to reducing the oxidation slag defects caused by turbulence; the sprue 9 adopts a Φ90mm porcelain tube, the cross runner 8 is a trapezoidal surface with a cross section of 70mm at the upper end, 90mm at the lower end, and 60mm at the height, and the ingates 10 are 6 Φ50 porcelain tubes. In the open bottom pouring system, the sprue 9 serves as a flow-blocking section, and the molten iron is introduced from the sprue 9 to the cross runner 8, through the filter 7, and dispersedly introduced from the lowest surface of the cavity. The total pouring time is about 60 seconds, and the higher pouring temperature of 1360-1370°C is matched, which belongs to high-temperature slow pouring;

[0034] 3) Riser design: Four insulating risers 11 with equal diameter sections of φ180 mm and a riser neck of φ90 mm at the lower end are evenly distributed on the plane position of the connecting flange 2, and the insulating risers 11 provide liquid shrinkage compensation for the entire valve body casting 5 to ensure the internal quality of the connecting flange;

[0035] 4) Chill design: Chill 12 is arranged on the important processing surface of the valve body casting 5 with a wall thickness greater than 100 mm in the cavity of the mold base. The thickness of the chill 12 is designed to be 2 / 3 of the wall thickness of the cooled part of the valve body casting 5, between 60 and 80 mm, and the gap between adjacent chills 12 is 20 to 30 mm, so as to accelerate the solidification speed of these thick parts;

[0036] 5) Shrinkage compensation of pouring cup: Based on the principle of communicating vessels, the outlet pipes 14 of all the insulating risers 11 are raised to more than 150mm above the bottom plane of the pouring cup 13, and more than 150mm of molten iron can be retained in the pouring cup 13. The molten iron in the pouring cup 13 provides a continuous pressure head to the valve body casting 5, thereby compensating the shrinkage of the bottom of the valve body casting 5 and reducing the shrinkage and shrinkage cavity defects of the tower connection surface; specifically, the shrinkage rate of the ductile iron valve body casting 5 is 0.9%.

[0037] 6) Smelting process and parameter design: The silicon content of the original molten iron is controlled between 2.2 and 2.4%, the carbon content is controlled between 3.4 and 3.6%, the manganese content is controlled below 0.3%, the phosphorus content is controlled below 0.05%, and the sulfur content is controlled below 0.02%; the amount of spheroidizer is 1.3%, and the amount of inoculant is 1.0%, so that the final silicon content of the valve body casting 5 reaches 3.4-3.6%.

[0038] By applying the above method, our company has continuously produced two bases of this type of QT500-14 material. After the marking size detection, ultrasonic and magnetic particle flaw detection, and body anatomy verification, the dimensional accuracy and internal quality meet the requirements of the design drawings, with an average tensile strength of 520MPa, a yield strength of 349MPa, an elongation of 18%, and a hardness of 173HB.

[0039] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0040] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. Industrial valve body forming method, characterized in that The following steps are involved: 1) Selection of parting surface: A three-opening mold is used in which the connection surface of the important flange (1) faces downward and the connection surface of the connecting flange (2) faces upward, and includes a first parting surface (3) and a second parting surface (4), so that the valve body casting (5) is completely located in the lower box (6) of the mold; 2) Design of pouring system: an open bottom pouring pouring system with a filter (7) is used, wherein the open bottom pouring pouring system comprises a horizontal runner (8), a vertically arranged straight runner (9) connected to the middle of the horizontal runner (8), and a plurality of ingates (10) connecting the mold cavity with the horizontal runner (8) through the filter (7), the cross-sectional ratio of the straight runner (9), the horizontal runner (8) and the ingates (10) of the open bottom pouring pouring system is 1.5:1:2.5, and a high-temperature slow pouring method is used to introduce the material from the lowest point of the mold cavity during pouring; 3) Riser design: Four heat-insulating risers (11) with equal diameter sections of φ160 mm to φ200 mm and a riser neck of φ90 mm at the lower end are evenly distributed on the plane position of the connecting flange (2), and the heat-insulating risers (11) provide liquid shrinkage compensation for the entire valve body casting (5); 4) Chill design: a chill (12) is arranged on an important processing surface of the valve body casting (5) with a wall thickness greater than 100 mm in the cavity of the mold base. The thickness of the chill (12) is designed to be 2 / 3 of the wall thickness of the cooled portion of the valve body casting (5), and the gap between adjacent chills (12) is 20 to 30 mm. 5) Shrinkage compensation of pouring cup: Based on the principle of communicating vessels, the outlet pipes (14) of all the heat-insulating risers (11) are raised to more than 150 mm above the bottom plane of the pouring cup (13), and more than 150 mm of molten iron can remain in the pouring cup (13). The molten iron in the pouring cup (13) provides a continuous pressure head to the valve body casting (5), thereby compensating the shrinkage of the bottom of the valve body casting (5); 6) Smelting process and parameter design: the silicon content of the raw iron water is controlled between 2.2% and 2.4%, the carbon content is controlled between 3.4% and 3.6%, the manganese content is controlled below 0.3%, the phosphorus content is controlled below 0.05%, and the sulfur content is controlled below 0.02%; the amount of spheroidizer is 1.3%, and the amount of inoculant is 1.0%, so that the final silicon content of the valve body casting (5) reaches 3.4-3.6%.

2. The industrial valve body forming method according to claim 1, characterized in that: In the above step 2), the sprue (9) and the ingrowth (10) are both made of porcelain tubes with different diameters.

3. The industrial valve body forming method according to claim 2, characterized in that: In the above step 2), the cross section of the runner (8) is a trapezoidal structure.

4. The industrial valve body forming method according to claim 1, characterized in that: In the above step 2), the high temperature slow pouring method is a pouring method in which the pouring temperature is 1360-1370° C. and the total pouring time is controlled within 60±5 s.

5. The industrial valve body forming method according to claim 1, characterized in that: In the above step 2), filters (7) are provided at both ends of the cross runner (8), and the filters (7) are connected to the corresponding ends of the three inner runners (10) on the same side, and the upper port of the sprue (9) is connected to the bottom of the pouring cup (13).

6. The industrial valve body forming method according to claim 1, characterized in that: In the above step 5), the shrinkage rate of the ductile iron valve body casting (5) is 0.9%.

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