CN112296260A - Shell mould and process for manufacturing gate valve body of carbon steel and stainless steel through precoated sand casting - Google Patents

Abstract

The invention discloses a shell mould of a gate valve body for casting carbon steel and stainless steel by precoated sand and a process thereof, wherein the shell mould comprises a shell mould whole synthesized by two sections of precoated sand shell moulds, a sand core and a chill component, the shell mould whole comprises a sprue cup, a dead head, a top sprue, a bottom sprue, a valve body, a flange and a drift diameter, the valve body is connected with the flange through the drift diameter, a sealing ring is arranged in the middle of the valve body, the flange and the drift diameter, and the sealing ring and the drift diameter are thick and thin joints, the chill component is placed in the precoated sand shell mould, the chill component is positioned at the thick and thin joint, a notch positioned between the chill components is formed in the lower part of the precoated sand shell mould, the chill component is increased to reduce the resistance of the precoated sand shell to contraction force, the sand shell can be easily broken up when a casting is cooled, the use efficiency of the chill is higher; the grooving treatment of the precoated sand shell is carried out between the two thick and thin joints of any casting, so that the pouring performance is ensured, the resistance to the shrinkage stress is reduced, and the casting cost of the complex casting is lower.

Description

Shell mould and process for manufacturing gate valve body of carbon steel and stainless steel through precoated sand casting

Technical Field

The invention relates to the technical field of precoated sand molds, in particular to a shell mold for casting a gate valve body of carbon steel or stainless steel by precoated sand and a process thereof.

Background

At present, no technology exists for producing complex products with various thickness combinations in a large scale and without defects, and the reason is that the shrinkage vector forces generated during cooling of castings are different because the heat dissipation capacity, the solidification time and the solidification shrinkage of casting parts with different thicknesses and lengths are different, and defects (including cracks, hidden cracks and deformation) are generated certainly when the shrinkage vector force is greater than the casting structure force and is less than the casting mold bearing force. And because the energy consumption and the material consumption of one-time casting of the metal casting are very large, the qualification rate and the cost of the product manufactured by the batch precoated sand casting are high, and the production is influenced.

Based on the above, the invention designs a shell mold of a gate valve body made of precoated sand casting carbon steel or stainless steel and a process thereof, so as to solve the above-mentioned problems.

Disclosure of Invention

The invention aims to provide a shell mold of a gate valve body of precoated sand casting carbon steel or stainless steel and a process thereof, which solve the problem of low yield when the product is cast by precoated sand in batches.

In order to achieve the purpose, the invention provides the following technical scheme: a shell mould of a gate valve body for casting carbon steel and stainless steel by precoated sand comprises a shell mould whole body, a sand core and a chill component, wherein the shell mould whole body is synthesized by two sections of precoated sand shell moulds and is fixed by binding steel wires, the sand core and the shell mould whole body are combined to form a complete valve body cavity, the shell mould whole body comprises a sprue cup, a dead head, a top sprue, a bottom sprue, a valve body, a flange and a through diameter, the valve body is connected with the flange through the through diameter, a sealing ring is arranged in the middle of the valve body, the flange, the through diameter and the sealing ring are in thick-thin connection parts, the chill component is placed in the precoated sand shell mould and is located in the thick-thin connection parts, a notch located between the chill components is formed in the lower part of the precoated sand shell mould, the sprue cup is connected with the top sprue through a cross gate at the top, and the sprue cup is connected with the bottom sprue through a straight gate and a, the top injection port and the bottom injection port are communicated with the valve body.

Preferably, the chiller assembly is a semicircular conformal chiller, and the chiller is designed to be thin at the top and thick at the bottom.

Preferably, at least one notch is formed at the joint of every two of the thick and thin parts, and the depth of each notch is the same as the average thickness of the precoated sand shell mold.

Preferably, the chiller assembly comprises a plurality of sections of chills, and the notches are formed between the plurality of sections of chills.

Preferably, the precoated sand shell type is designed to be thick at the top and thin at the bottom.

Preferably, the inner wall of the lower part of the shell type whole body is provided with point-shaped and strip-shaped bulges, and the chilling block assembly is fixed through the point-shaped and strip-shaped bulges.

A technology for casting a carbon steel and stainless steel gate valve body by using precoated sand specifically comprises the following steps:

s1: manufacturing a cold iron assembly according to design requirements through a cold iron mold;

s2: manufacturing a mould, designing a structure of a chill position and a notch position of a reserved precoated sand shell mould in the mould, and reserving punctiform and strip-shaped protruding positions at corresponding positions of the chill position of the reserved precoated sand shell mould;

s3: installing a mould on sand shooting equipment, placing a chill at a designed mould chill position, heating the chill through an electric heating pipe on the mould, shooting the precoated sand into a mould cavity for curing after reaching a set temperature, determining the curing time according to the size of a sand shell, and taking out the sand shell for later use after curing is finished;

s4: casting: when the precoated sand shell mold is used for casting, a half of sand core is firstly filled into a half of corresponding precoated sand shell mold, then two sections of the filled precoated sand shell molds are combined together to form a finished cavity, then binding and fixing are carried out, then molten steel is poured from a bottom pouring port reserved at the bottom of the precoated sand shell mold through a pouring port, when the molten steel reaches the top pouring port, the molten steel starts to be poured continuously from the top pouring port until the molten steel reaches the top of the cavity, and pouring is finished.

Compared with the prior art, the invention has the beneficial effects that:

the shell mould of the valve body of the precoated sand casting carbon steel and stainless steel gate valve greatly improves the qualification rate of the precoated sand casting, increases the chill component, can reduce the resistance to the contraction force of the precoated sand shell, and can easily collapse when a casting is cooled. Compared with other cold iron processes, the cold iron forming process is more accurate, the cold iron using efficiency is higher, the sand consumption is reduced, and the cost is reduced. By carrying out slotting treatment on the precoated sand shell between two thick-thin joints of any casting, the resistance to shrinkage stress is reduced while the pouring performance of the precoated sand shell is ensured, and the casting cost of the complex casting is lower (low rejection rate and high qualification rate).

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a schematic axial view of the present invention;

FIG. 2 is a schematic top view of the structure of FIG. 1 according to the present invention;

FIG. 3 is a schematic view of the overall connection structure of the sand core and the shell mold according to the present invention;

FIG. 4 is a schematic view of the sand core structure of the present invention;

FIG. 5 is a side view of the FIG. 1 structure of the present invention;

FIG. 6 is a schematic view of the notch structure of the present invention;

FIG. 7 is a schematic view of the dot and stripe protrusion structure of the present invention.

In the drawings, the components represented by the respective reference numerals are listed below:

1. a shell-type monolith; 2. a sand core; 3. a chill assembly; 4. a pouring cup; 5. a riser; 6. a top pouring port; 7. a bottom injection port; 8. a valve body; 9. a flange; 10. passing through; 11. a seal ring; 12. a thick-thin junction; 13. a notch; 14. point-like and strip-like bulges; 15. a cross gate; 16. a sprue; 17. and (5) performing cold iron.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

Referring to fig. 1-7, the present invention provides a technical solution: the utility model provides a shell mould of tectorial membrane sand casting carbon steel, stainless steel gate valve body, includes the whole 1, psammitolite 2 and chill subassembly 3 of the synthetic shell mould of two sections tectorial membrane sand shell moulds, two sections tectorial membrane sand shell moulds are fixed through binding the steel wire, and inside tectorial membrane sand shell support piece for make up with covering the tectorial membrane sand shell and form 8 cavitys of a complete valve body, be used for preparing the sand shooting mould inner chamber of tectorial membrane sand shell in batches.

The whole 1 of shell mould includes pouring basin 4, rising head 5, top notes mouth 6, end notes mouth 7, valve body 8, flange 9 and latus rectum 10, and valve body 8 is the foundry goods of setting for according to the demand, and flange 9 is the pipeline connection pad of valve body 8 foundry goods, and on large-scale pipeline valve, the thickness of flange 9 is the biggest, and sealing washer 11 is valve body 8 middle part thickening part, valve body 8 is through latus rectum 10 flange 9, valve body 8 middle part is equipped with sealing washer 11, flange 9 and latus rectum 10, sealing washer 11 are thickness junction 12 with latus rectum 10, are in thickest place, and latus rectum 10 is the thinnest structure of valve body 8 foundry goods, solidifies the shrink in advance easily. The cold iron assembly 3 is placed in the precoated sand shell mold, the cold iron assembly 3 is located at a thickness connection part 12, a notch 13 located between the cold iron assemblies 3 is formed in the lower part of the precoated sand shell mold, the pouring cup 4 is connected with the top pouring port 6 through a cross pouring channel 15 at the top, when molten steel reaches the top pouring port 6, the top pouring is automatically mainly performed (the weight of the molten steel with high temperature is light), the cooled molten steel is located below, and the high-temperature molten steel which is continuously poured is naturally located at the upper part. The upper half part of the whole cavity is guaranteed to be solidified finally, the sprue cup 4 is connected with the bottom sprue 7 through the sprue 16 and the cross runner 15 at the bottom, molten steel can firstly flow downwards from the sprue cup 4 and the sprue 16 to the shell type whole body 1 through the bottom sprue 7 under the action of gravity, the bottom sprue 7 is used for pouring firstly, the molten steel can not scour the inside of a sand shell, the molten steel can be cooled from the lower part, and the top sprue 6 and the bottom sprue 7 are communicated with the valve body 8.

Wherein, chiller subassembly 3 adopts semicircular shape chiller 17 along with, chiller 17 designs for going up thin thick down, and chiller subassembly 3 includes multistage chiller 17, notch 13 is seted up between multistage chiller 17, can make things convenient for the fluting, does benefit to the whole shrink of foundry goods and sand shell simultaneously.

The chilled iron 17 is adopted to rapidly cool the molten steel of the casting, and the sectional type semicircular chilled iron 17 is used, so that the resistance of the precoated sand shell to the shrinkage force can be reduced, and the sand shell can be easily dispersed when the casting is cooled. Compared with other cold iron 17 processes, the cold iron 17 conformal process is more accurate, and the cold iron 17 has higher use efficiency.

At least one notch 13 is formed at each two thickness connecting parts 12, and the depth of each notch 13 is the same as the average thickness of the precoated sand shell mold.

By slotting the connecting parts 12 of the thickness of each casting of the precoated sand, the stress dispersion degree of the precoated sand shell can be smaller, and the connecting parts 12 of the thickness of the two castings can be subjected to large resistance when being contracted, so that flaws are generated.

During the use, through carrying out earlier stage review to the precoated sand casting product, through the review to the foundry goods drawing, obtain the shrink of foundry goods and the stress relation of tectorial membrane sand shell, will shrink when the foundry goods cools off, this is general physics phenomenon, but well just do not have the technique in sand casting production and go to do the prestressing force and handle, make some sand shells into the form that has the fluting, can be so in order to guarantee the overall structure dynamics of sand shell, also can break apart from the weakest place when the foundry goods cools off the shrink to shrink power to the foundry goods releases.

The precoated sand shell is designed to be thick at the top and thin at the bottom, so that the molten steel can be conveniently solidified from bottom to top (the thinner the part is, the faster the heat dissipation is, the faster the molten steel is solidified).

Wherein, the lower part inner wall of shell mould whole 1 is equipped with punctiform and strip arch 14, chill subassembly 3 is fixed through punctiform and strip arch 14 for chill 17 makes it when the high-speed shooting, can not remove.

The use state is as follows:

design of

Firstly, process evaluation is carried out according to a drawing, the thickness joint 12 of the casting is examined, and the final structure of the product is determined according to the evaluation result.

Secondly, designing a conformal chiller 17 according to a drawing structure, designing a weak link (a place where cracks easily occur) of a product structure, and accelerating rapid solidification of the part by using the chiller component 3.

Taking the valve body 8 as an example

Generally, the casting product of the precoated sand valve body 8 has different cooling time at each part of the casting due to the thick flange 9 and the thin drift diameter 10, so that the shrinkage time generated by cooling solidification is different, and the root of the flange 9 is cracked due to the shrinkage speed difference. The drift diameter 10 is thin in wall, cooling speed is high, solidification forming time is high, solidification speed of the flange 9 is low, the drift diameter 10 and the solidification speed of the flange can contract towards the flange after solidification, and cracks can be generated at the connecting part of the drift diameter 10 and the flange under the tensile force, namely the root of the flange 9. Meanwhile, the general sand shell has high hardness, low shrinkage and high metal shrinkage, so that the shrinkage stress of the casting product cannot be released, and finally the stress of the casting product acts on the thickness joint 12 of the casting product to cause cracks. The conformal cold iron 17 is designed according to the position where the valve body 8 is easy to have crack defects.

According to structural evaluation of the valve body 8, the thickness joint 12 (the position easy to crack) of the valve body is provided with a conformal semi-circular cold iron 17 at the R corner of the root part of the flange 9 and the R corner of the joint of the sealing ring 11 and the drift diameter 10, and the design standard of the cold iron 17 is that the cold iron is thin at the top and thick at the bottom so that products are sequentially solidified from bottom to top. The semicircular conformal cold iron 17 can achieve the optimal state of the molten steel utilization rate. The over-small conformal chill 17 can cause the riser 5 to be over-large, thereby wasting molten steel materials, and the over-large conformal chill 17 can cause the casting product to generate cold cracks due to too high cooling speed, thereby causing product defects and even scrapping.

The outside chill 17 of flange 9 can let the cooling with higher speed of flange 9 lower part, and flange 9 forms a process that upwards solidifies in proper order from the bottom, reduces the erosion rate of high temperature molten steel knot sand shell, prolongs the heat-resisting time of shell mould, slows down the speed of collapsing of sand shell, has reduced the volume of using sand of sand shell. The chilling block 17 belongs to a recycling product and can be reused.

If the built-in chills 17 are not designed, the shell thickness must be increased to ensure the shell heat-resistant time, but the increased shell thickness also slows the cooling of the flange 9, increases resistance against the shrinkage stresses of the cast product, and causes cracks.

With the shell mold of the present invention, the sand usage is reduced compared to conventional processes because of the design of the internal chills 17. The original process is as follows: 1 designing a sand shell. This is where the mass ratio of the molding sand to the cast product is the same. After designing the chill 17, the sand-to-iron (i.e., sand to cast product) ratio was (0.6-0.8): 1, the sand consumption is greatly reduced, and the cost is reduced. Meanwhile, the original sand shell has no quenching effect of the chilling block 17, and the sand shell can be made thick to meet the requirement of sand mold matching pouring.

The precoated sand shell is required to be arranged at the lower half part, because the casting shrinks when cooled, when the casting is not grooved, the sand shell can prevent the casting from shrinking to cause the tensile crack at the joint 12 of the thickness of the casting, after the grooving process is used, the shrinkage resistance of the sand shell to the casting when the casting shrinks is solved, and the generation of cracks is avoided. During shrinkage, the sand shell slotting position firstly collapses to form a shrinkage joint to provide a space for the shrinkage of the casting, the middle position of each lower half part of the casting is provided with a slot, the pulling crack generated during the shrinkage of the casting can be avoided to a certain extent, but cracks are possible, and the most preferable scheme is that at least one slot is arranged at each two thick-thin connecting positions 12 of the casting.

Example 2

The method also comprises a process for casting the gate valve body 8 of the carbon steel and the stainless steel by the precoated sand, wherein the casting process specifically comprises the following steps:

s1: manufacturing a cold iron assembly 3 according to design requirements through a cold iron 17 mould;

s2: manufacturing a mould, designing structures of a chill 17 position and a notch 13 position of a reserved precoated sand shell mould in the mould, directly manufacturing an opening position, and reserving 14 point-shaped and strip-shaped bulges at corresponding positions of the chill 17 position of the reserved precoated sand shell mould; so that the chills 17 can be confined to a designed location (wholly enclosed within the shell) to remain immobile during the sand blast.

S3: installing a mould on sand shooting equipment, placing a chilling block 17 at the designed chilling block 17 position of the mould, heating the chilling block by an electric heating pipe on the mould, shooting the precoated sand into a mould cavity for curing after reaching a set temperature (230 ℃ below zero) of 190-; the manufacturing process of the sand core 2 is the same as the sand shell process.

S4: casting: when the precoated sand shell mold is used for casting, a half of sand core 2 is firstly filled into a half of corresponding precoated sand shell mold, then two sections of the filled precoated sand shell molds are combined together to form a finished cavity, then binding and fixing are carried out, then molten steel is poured through a pouring gate from a bottom pouring gate 7 reserved at the bottom of the precoated sand shell mold, when the molten steel reaches a top pouring gate 6, the molten steel starts to be poured continuously from the top pouring gate 6 until the molten steel reaches the top of the cavity, and the pouring is finished.

The process adopts a mode of bottom pouring and top pouring to ensure that molten steel is poured more stably and reduce the scouring of molten steel to a cavity, when the molten steel reaches a top pouring opening 6, the top pouring is automatically mainly carried out (the molten steel with high temperature is light in weight), the cooled molten steel is positioned below, and the high-temperature molten steel which is continuously poured is naturally positioned at the upper part. The final solidification of the upper half part of the whole cavity is ensured. When the casting begins to solidify, the bottom of the casting begins to solidify firstly under the action of the chilling block 17 and the bottom of the casting solidifies sequentially from bottom to top, and a contraction space generated when the casting is cooled and contracted is continuously filled with high-temperature molten steel above the casting, so that the intercrystalline structure in the casting is more compact. In the casting cooling solidification process, due to the action of the chilling block 17, the thickness joints 12 of the flange 9 and the drift diameter 10 and the seal ring 11 and the drift diameter 10 can be solidified firstly, and then when the shrinkage stress generated after the solidification of the drift diameter 10, the flange 9 and the seal ring 11 can not cause the tension crack influence on the joints (the shrinkage force is smaller than the mechanical damage force of a steel body at the joints) and is solidified, the sand wall at the groove position is thin and can be firstly dispersed to form a shrinkage space, so that the stress during shrinkage is buffered, and the generation of cracks is also avoided. After the casting is cooled, the sand shell naturally collapses, the casting can be subjected to post-treatment, primary sand casting is completed, and the chiller 17 can be recycled.

The yield of the precoated sand casting is greatly improved by using the precoated sand casting for casting the shell mould of the carbon steel and stainless steel gate valve body 8, the mould opening manufacturing cost of the precoated sand mould can be greatly reduced by the earlier-stage evaluation method of the casting, and a large amount of mould development cost can be saved. Due to the reasonable design idea, the die opening accuracy is greatly improved, and the die opening cost is greatly reduced. From the design to the real use of the die, the trimming is carried out for several times, the die which cannot be trimmed can only be scrapped, and the die sinking cost is directly doubled. The shape following efficiency of the chiller 17 is higher. By slotting the precoated sand shell between the two thick-thin joints 12 of any casting, the resistance to shrinkage stress can be reduced while the pouring performance of the precoated sand shell is ensured, and the casting cost of the complex casting is lower (low rejection rate and high qualification rate).

In the description herein, references to the description of "one embodiment," "an example," "a specific example" or the like are intended to mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

The preferred embodiments of the invention disclosed above are intended to be illustrative only. The preferred embodiments are not intended to be exhaustive or to limit the invention to the precise embodiments disclosed. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, to thereby enable others skilled in the art to best utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims (7)

1. The utility model provides a tectorial membrane sand casting carbon steel, shell mould of stainless steel gate valve body which characterized in that: comprises a shell mold whole body synthesized by two sections of precoated sand shell molds, a sand core and a chill component, wherein the two sections of precoated sand shell molds are fixed by binding steel wires, the sand core and the shell mold are integrally combined to form a complete valve body cavity, the shell mold integrally comprises a sprue cup, a riser, a top sprue, a bottom sprue, a valve body, a flange and a drift diameter, the valve body is connected with a flange through a drift diameter, a sealing ring is arranged in the middle of the valve body, the connecting positions of the flange and the drift diameter, and the sealing ring and the drift diameter are in thickness and thinness, a chiller assembly is arranged in the precoated sand shell mold, the chiller assembly is positioned at the thickness connection part, the lower part of the precoated sand shell mold is provided with a notch positioned between the chilling block components, the sprue cup is connected with the top sprue gate through a horizontal pouring gate at the top, the sprue cup is connected with the bottom sprue through a sprue and a bottom cross gate, and the top sprue is communicated with the bottom sprue through a valve body.

2. The shell mold of a precoated sand cast carbon steel, stainless steel gate valve body of claim 1, wherein: the chiller component adopts a semicircular conformal chiller, and the chiller is designed to be thin at the top and thick at the bottom.

3. The shell mold of a precoated sand cast carbon steel, stainless steel gate valve body of claim 1, wherein: and at least one notch is formed at the joint of every two thicknesses, and the depth of each notch is the same as the average thickness of the precoated sand shell mold.

4. The shell mold of a precoated sand cast carbon steel, stainless steel gate valve body of claim 1, wherein: the chilling block assembly comprises a plurality of sections of chilling blocks, and the notch is formed between the plurality of sections of chilling blocks.

5. The shell mold of a precoated sand cast carbon steel, stainless steel gate valve body of claim 1, wherein: the precoated sand shell is designed to be thick at the top and thin at the bottom.

6. The shell mold of a precoated sand cast carbon steel, stainless steel gate valve body of claim 1, wherein: the lower inner wall of the shell type whole body is provided with point-shaped bulges and strip-shaped bulges, and the chilling block assembly is fixed through the point-shaped bulges and the strip-shaped bulges.

7. The utility model provides a technology of precoated sand casting carbon steel, stainless steel gate valve body which characterized in that: the casting process specifically comprises the following steps:

s1: manufacturing a cold iron assembly according to design requirements through a cold iron mold;

s2: manufacturing a mould, designing a structure of a chill position and a notch position of a reserved precoated sand shell mould in the mould, and reserving punctiform and strip-shaped protruding positions at corresponding positions of the chill position of the reserved precoated sand shell mould;

s3: installing a mould on sand shooting equipment, placing a chill at a designed mould chill position, heating the chill through an electric heating pipe on the mould, shooting the precoated sand into a mould cavity for curing after reaching a set temperature, determining the curing time according to the size of a sand shell, and taking out the sand shell for later use after curing is finished;

s4: casting: when the precoated sand shell mold is used for casting, a half of sand core is firstly filled into a half of corresponding precoated sand shell mold, then two sections of the filled precoated sand shell molds are combined together to form a finished cavity, then binding and fixing are carried out, then molten steel is poured from a bottom pouring port reserved at the bottom of the precoated sand shell mold through a pouring port, when the molten steel reaches the top pouring port, the molten steel starts to be poured continuously from the top pouring port until the molten steel reaches the top of the cavity, and pouring is finished.

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