3D printing sand core structure of cast steel regulating valve

Abstract

The invention discloses a cast steel adjusting valve 3D printing sand core structure. A conceding groove is formed in the position, corresponding to the transition position of a thick wall and a thin wall of a casting, of a sand core. The yielding grooves are additionally formed in the corresponding positions, so that the sand mold has good yielding performance, the cooling shrinkage stress of a casting is reduced, and cracks at the junction of the thick wall and the thin wall of the casting are reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sand casting, in particular to a 3D printing sand core structure of a cast steel regulating valve. BACKGROUND

[0002] As a key fluid control component in the fields of petrochemical industry, electric power energy, metallurgical equipment, etc., the valve body and valve cover of the cast steel regulating valve need to bear alternating loads of high temperature, high pressure and corrosive medium for a long time, so that the structural integrity, density and crack resistance of the castings are required. According to the GB / T12234-2019 "Steel Stop Valve and Lift Check Valve for Petroleum, Petrochemical and Related Industries" standard, the valve body casting needs to pass the RT3 level radiographic inspection, and no crack defects with a length of >2mm are allowed, otherwise it is directly judged as scrap.

[0003] At present, traditional sand casting mainly adopts resin sand core or cold box core process, which has the following inherent defects when adapting to the complex structure of the cast steel regulating valve: thermal cracks caused by solidification stress concentration; mechanical cracks caused by insufficient sand core retreatability; and gas hole induced cracks caused by poor sand core exhaust. According to statistics, the scrap rate of the regulating valve castings produced by the traditional sand casting process due to cracks is as high as 10%-15%, which not only causes waste of raw materials, but also prolongs the production cycle by more than 30% due to rework and repair, and more seriously, if the castings containing micro-cracks are put into use, crack propagation may occur under the action of long-term alternating load, causing medium leakage or even valve body explosion, which has a major safety hazard.

[0004] Therefore, it is an urgent problem for those skilled in the art to provide a 3D printing sand core structure of a cast steel regulating valve which can reduce cracks. SUMMARY

[0005] Therefore, the present application provides a 3D printing sand core structure of a cast steel regulating valve to at least solve one of the problems mentioned in the background.

[0006] In order to achieve the above-mentioned purpose, the present application adopts the following technical scheme:

[0007] A 3D printing sand core structure of a cast steel regulating valve, the sand core is provided with a retreat groove at the position corresponding to the transition of thick wall and thin wall of the casting.

[0008] By adopting the above technical scheme, the present application has the following beneficial effects:

[0009] The sand mold has good retreatability, thereby reducing the cooling shrinkage stress of the casting and reducing the cracks at the junction of the thick wall and the thin wall of the casting.

[0010] Further, a plurality of exhaust holes are provided on the sand core.

[0011] The beneficial effect of adopting the above-mentioned further technical solution is that the reaction gas in the sand core cavity is eliminated, so as to avoid intrusion into the casting cavity and the generation of porosity and gas-induced crack defects.

[0012] Furthermore, the wall thickness of the sand core is homogenized.

[0013] The beneficial effects of adopting the above-mentioned further technical solutions are that the sand core has more consistent collapsibility, less stress is generated in the casting during shrinkage, thereby reducing the probability of casting cracks.

[0014] Furthermore, the recessed groove is in the shape of an inverted triangle.

[0015] Furthermore, the vent holes are located at the ends of the sand core, and each vent hole is semi-circular.

[0016] Therefore, this invention provides a 3D-printed sand core structure for a cast steel regulating valve, which, compared with the prior art, has the following advantages:

[0017] 1) Reduce the scrap rate and rework rate of cast steel control valves, saving costs;

[0018] 2) Reduce the weight of 3D printed sand cores and reduce the amount of raw sand, curing agent, and resin used;

[0019] 3) Increase the efficiency of 3D printing sand core placement and reduce safety risks caused by excessive weight;

[0020] 4) Facilitates sand removal from boxes, improving work efficiency. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0022] Figure 1 The attached figure is a structural schematic diagram of the casting (cast steel regulating valve casting) provided by the present invention;

[0023] Figure 2 The attached figure is a cross-sectional view of the casting (cast steel regulating valve casting) provided by the present invention;

[0024] Figure 3 The attached figure is a schematic diagram of the structure of the sand core provided by the present invention;

[0025] Figure 4 The attached figure is a cross-sectional view of the sand core provided by the present invention. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] like Figures 1-4 As shown in the figure, this invention discloses a 3D-printed sand core structure for a cast steel regulating valve. The sand core 2 has a relief groove 21 at the transition position between the thick and thin walls of the casting 1 (the position of the shrinkage radius of the casting 1). In this embodiment, the relief groove 21 is inverted triangular in shape. By adding the relief groove 21 at the corresponding position of the sand core 2, this invention enables the sand mold to have good relief properties, thereby reducing the cooling shrinkage stress of the casting 1 and reducing cracks at the junction of the thick and thin walls of the casting 1.

[0028] Understandably, relief grooves 21 of different sizes are designed based on the ratio of thick wall to thin wall of casting 1.

[0029] To further optimize the technical solution of the present invention, multiple vent holes 22 are provided on the sand core 2 to remove the reaction gas from the cavity of the sand core 2, so as to avoid intrusion into the cavity of the casting 1 and the generation of porosity and gas-induced crack defects.

[0030] In this embodiment, the vent holes 22 are located at the ends of the sand core 2, and each vent hole 22 is semi-circular. Of course, the size of the vent holes 22 can be designed according to the volume of the cavity of the sand core 2. The larger the vent holes 22 are, the better, without affecting the casting and cooling process of the casting 1.

[0031] To further optimize the technical solution of this invention, the wall thickness of the sand core 2 is uniformized. While meeting the collapsibility requirements, it is made as thin as possible, thereby achieving more consistent collapsibility of the sand core 2 and reducing stress generation in the casting 1 during shrinkage, thus reducing the probability of cracks in the casting 1. Of course, this invention can be applied to regulating valves of different diameters and pressures. Sand cores 2 with different wall thicknesses can be designed to meet production needs for different wall thicknesses of the casting 1.

[0032] In summary, the sand core 2 of this invention has the functions of directional heat dissipation, gradient retreat and efficient venting, which reduces the cracks in the casting 1 from the root.

[0033] The working principle of this invention is as follows:

[0034] Since the wall thickness of the valve seat of casting 1 is relatively large, a large shrinkage stress will be generated at the thin wall during cooling. Therefore, a relief groove 21 is designed at the corresponding position of sand core 2 to increase the relief of sand core 2 and reduce cracks at the junction of the thick wall and thin wall of casting 1.

[0035] As the high-temperature molten steel comes into contact with the sand core 2, the resin and curing agent in the sand core 2 will react and generate reactive gas. If the gas is not removed in time, it will invade the cavity and cause the casting 1 to produce porosity and gas-induced cracks. Therefore, the venting hole 22 is added so that the reactive gas in the cavity of the sand core 2 can be discharged in time.

[0036] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0037] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A 3D-printed sand core structure for a cast steel regulating valve, characterized in that, The sand core has a relief groove at the transition position between the thick and thin walls of the casting.

2. The 3D-printed sand core structure for a cast steel regulating valve according to claim 1, characterized in that, The sand core has multiple vent holes.

3. A 3D-printed sand core structure for a cast steel regulating valve according to claim 1 or 2, characterized in that, The wall thickness of the sand core is homogenized.

4. The 3D-printed sand core structure for a cast steel regulating valve according to claim 1, characterized in that, The recessed groove is in the shape of an inverted triangle.

5. The 3D-printed sand core structure for a cast steel regulating valve according to claim 2, characterized in that, The vent holes are located at the ends of the sand core, and each vent hole is semi-circular.

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