CN114406195B - Method for producing elevator brake disc by vacuum sealing casting - Google Patents

Abstract

The invention belongs to the technical field of elevator brake disc casting, and provides a method for producing an elevator brake disc by vacuum sealing casting, which comprises the following steps: the method has the beneficial effects that the production practice of the vacuum seal casting ductile iron hub discovers that the production control difficulty is more on one hand, but stable ductile iron hub castings can be obtained through systematic research on the vacuum seal casting, such as mould, smelting, process and the like; on the other hand, the production of the ductile iron wheel hub by vacuum sealing casting has a plurality of advantages, and is mainly characterized by low production cost, high casting surface quality, high precision, small polishing amount, environmental protection and the like.

Description

Method for producing elevator brake disc by vacuum sealing casting

Technical Field

The invention belongs to the technical field of elevator brake disc casting, and particularly relates to a method for producing an elevator brake disc by vacuum sealing casting.

Background

With the continuous development of society, the demand for elevators is greatly increased, and the demand for castings related to elevators is also increasing. The elevator brake disc is used as the mounting pieces at the two ends of the elevator main shaft, and before use, the elevator brake disc must be tested by mounting, and the elevator brake disc can be put into use after being qualified in percentage.

Because of the defects of shrinkage cavity and shrinkage porosity, iron mold sand-coated casting technology is adopted for production to ensure the quality of products for a long time. However, the iron mold sand-lined casting process has the following defects that the process needs a certain draft angle for production, so that the subsequent processing amount of castings is increased and the cost is high; secondly, due to the chilling effect of the casting mould on the casting, the hardness of the casting is higher, about 160-210HB, and the processing difficulty of the casting is increased. Thirdly, because the mold of the process is a piece of one mold, the whole production line needs a large number of molds; fourth, because the technology mostly uses organic resin sand, a large amount of nitrogen-containing compounds, sulfides, sulfur dioxide and other gases are emitted in the casting process, so that the labor condition of casting production is deteriorated, and the environment is seriously polluted. In comparison, a smooth EVA film is used in the production process of the vacuum sealing casting process, so that the draft angle is almost zero, and the processing amount of castings is reduced; meanwhile, dry sand is used for vacuum molding in vacuum sealing casting, so that chilling effect on the casting is small, the surface is about 140-160HB, and the cutting performance of the casting is better. Moreover, the method adopting vacuum sealing casting only needs one set of wood die, and the cost is reduced by tens of times compared with the sand coating process of an iron die. The vacuum sealing casting is to manufacture the sand mold by vacuum, so that the vacuum sealing casting is green and environment-friendly and has good working environment. Therefore, attempts have been made to produce elevator ball iron hubs using vacuum seal casting and have been successful.

Disclosure of Invention

The invention is realized in the following way:

the invention provides a method for producing an elevator brake disc by vacuum sealing casting, which comprises the following steps:

s1, process design, namely process optimization design is carried out on a ball iron piece with a deep groove, such as an elevator brake disc, a riser-free design is adopted, a square riser arranged above the center of the elevator brake disc is mainly used for exhausting, and the post treatment of castings is also ensured to be greatly reduced; a sand core is adopted below the square riser, so that the safety of the elevator brake disc in non-drawing degree molding and demolding is ensured;

s2, manufacturing a die, designing a wood die for the vacuum sealing casting process of the elevator brake disc, optimizing the accuracy of the die to be +/-0.3 mm error value for ensuring the molding of the elevator brake disc, storing the original 3mm machining allowance at important machining parts, wherein the minimum machining allowance of non-important areas is 1mm, and improving the molding accuracy of castings while prolonging the service life of the wood die;

s3, manufacturing a sand box, namely, increasing the vacuum degree on the basis of the existing equipment by adjusting a vacuum pipeline, increasing the number and layout of vacuum pipes, mainly manufacturing the vacuum pipes by adopting stainless steel pipes with a plurality of holes, prolonging the service life, sealing the transverse end parts of the vacuum pipes by adopting pipe plugs, improving the vacuum degree of casting molds, completely wrapping the surfaces of the vacuum pipes by using stainless steel meshes, preventing sand from entering a vacuum system, and communicating the vacuum pipes by using pipe joints, thereby meeting the vacuum requirement of the production of a box of a plurality of spherical iron hubs with a plurality of varieties;

s4, vacuum molding, wherein an outer cavity of a thin-wall uniform part and an outer cavity of a shaft end cover are arranged in an upper sand box, a sprue and a pouring gate are arranged in the upper sand box, an inner cavity of the thin-wall uniform part and an inner cavity of the shaft end cover are arranged in a lower sand box, a cross runner is arranged on a parting surface of the lower sand box, the upper sand box and the lower sand box are a box with a plurality of sand boxes, a plurality of cavities are formed, a chill is arranged at a part which is easy to generate defects after box closing, and designated talcum powder and paint are selected to obtain castings with good surface quality and small machining allowance;

s5, pouring, namely reasonably controlling the feeding sequence and the pouring time by using 80% of scrap steel and 20% of return furnace material as smelting raw materials, and finishing the process through three steps of ladle ironing, cover Bao Fa spheroidizing and cooling;

s51, pouring molten iron into a ladle for ladle ironing treatment when the molten iron smelting temperature is 1480-1520 ℃, pouring the preheated molten iron into an electric furnace, carrying out primary slag removal operation on the molten iron in the furnace before discharging the molten iron, and carrying out secondary slag removal operation on the molten iron in the ladle ironing process after discharging the molten iron;

step S52, cover Bao Fa spheroidizing, transferring molten iron into a spheroidizing ladle at 1480-1500 ℃ for spheroidizing, putting a spheroidizing agent, ferrosilicon and a covering agent into the spheroidizing ladle according to a certain proportion, tamping, and performing first inoculation in the process of transferring the spheroidizing ladle into a pouring ladle;

and step S53, cooling and pouring, namely reducing the temperature of the molten iron, performing slag skimming operation, pouring when the molten iron reaches a specific temperature, and performing secondary inoculation to obtain a better inoculation effect.

Further, in the step S53, the specific temperature is set to a value ranging from 1360 to 1380 ℃.

Further, in the step S4, the designated talcum powder and the designated paint are selected for convenient mold separation, in order to ensure the adjustment of the casting rhythm and the feeding and forming of the elevator brake disc, the sprue adopts a ceramic tube with a certain diameter, and is matched with the runner and the inner runner with a certain flow to ensure the molten iron filling speed and flow, and the runner pit adopts a ceramic runner pit, and an indirect external chill is arranged in the hot joint part and the sand layer of the thick and large part of the brake disc, so that the defects of the brake disc at the important parts are effectively controlled.

Further, the height of the inner pouring channel is 8-10 mm, and the outer cooling iron is of a circular structure and is arranged at the positions of the hot joint part and the thick part of the brake disc and the sand layer 5-10mm apart from the casting.

In the step S4, dry sand with 70-140 meshes is adopted, and upper and lower sand molds are manufactured under the negative pressure condition of 0.04-0.06 MPa.

Further, in the step S5, the production casting time range is controlled to be 40-60 seconds.

Further, in the step S5, the feeding sequence is sequentially as follows: scrap steel, carburant, furnace returns and ferroalloys.

The beneficial effects of the invention are as follows:

the invention has the beneficial effects that the production practice of the ductile iron hub by vacuum seal casting discovers that the production control difficulty of the ductile iron hub by vacuum seal casting is more on one hand, but stable ductile iron hub castings can be obtained by systematic research on the vacuum seal casting, such as a mould, smelting, a process and the like; on the other hand, the production of the ductile iron wheel hub by vacuum sealing casting has a plurality of advantages, and is mainly characterized by low production cost, high casting surface quality, high precision, small polishing amount, environmental protection and the like.

The foregoing description is only an overview of the present invention, and is intended to be implemented in accordance with the teachings of the present invention in order that the same may be more clearly understood and to make the same and other objects, features and advantages of the present invention more readily apparent.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some examples of the present invention and therefore should not be considered as limiting the scope, and other related drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a flow chart of the method of the present disclosure;

fig. 2 is a schematic cross-sectional view of an elevator brake disc disclosed in the present invention;

FIG. 3 is a schematic view of a sand mold structure according to the present disclosure;

FIG. 4 is a schematic plan view of a vacuum tube for a flask according to the present invention;

FIG. 5 is a schematic diagram of the distribution structure of the indirect external chill disclosed in the present invention;

FIG. 6 is a schematic perspective view of a flask according to the present disclosure;

FIG. 7 is a photograph of a flask of the present invention.

Reference numerals illustrate: 1. riser; 2. a sand core; 3. a sprue; 4. a cross gate; 5. an inner runner; 6. a sprue bush; 7. a vacuum tube; 8. a pipe plug; 9. stainless steel mesh; 10. a pipe joint; 11. indirect external chill; 12. a cope flask; 13. and (3) a drag flask.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, based on the embodiments of the invention, which are apparent to those of ordinary skill in the art without inventive faculty, are intended to be within the scope of the invention.

Thus, the following detailed description of the embodiments of the invention, as presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, based on the embodiments of the invention, which are apparent to those of ordinary skill in the art without inventive faculty, are intended to be within the scope of the invention.

It should be noted that: like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further definition or explanation thereof is necessary in the following figures.

Examples

Referring to fig. 1-7, the invention provides a concrete implementation method for producing an elevator brake disc by vacuum sealing casting, which comprises the following steps:

step S1, design of vacuum sealing casting process of elevator brake disc

The elevator brake disc belongs to a uniform thin-wall structure, the feeding effect of the riser 1 is limited, so that a 'riser-free' design scheme is adopted, the existing riser 1 mainly aims at meeting the requirement of exhaust when molten iron enters a sand mould, a sand core 2 is adopted below the square riser 1, the forming of the elevator brake disc is guaranteed, the pouring speed in a sprue 3 and a runner 4 needs to be high for filling the runner to prevent a collapse box due to the utilization of a film and vacuum forming, but the unstable excessively fast entering of the molten iron into the casting mould can cause a plurality of problems, particularly strict nodular cast iron products are required, the casting mould is expected to be filled with molten iron which flows smoothly, the inverted cone type sprue 3 is adopted, the height of the ingate 5 is designed to be 8-10 mm, meanwhile, the ingate 5 is widened to accelerate the filling of the molten iron, the thinner ingate 5 is convenient for cleaning of later castings, and the parts of the elevator brake disc, which are prone to shrinkage cavity defects are provided.

As shown in fig. 5, an indirect external chill 11 is arranged at the hot joint position and the thick and large position of the brake disc and the position of the sand layer spaced 5-10mm away from the casting, and the chill adopts a circular chill, so that the defects of the brake disc at the important positions can be effectively controlled, the feeding capacity of the riser 1 is compensated, the solidification speed of the casting is accelerated, the structure is thinned, and the mechanical property of the casting is improved.

Step S2, designing and manufacturing vacuum sealing casting die of elevator brake disc

In order to cater to the market of high-end spheroidal graphite cast iron, the advantage of fully exerting vacuum seal casting is that the die-drawing gradient is not needed, and the machining allowance is reduced as much as possible, so that the precision of the vacuum seal casting die is improved to be within 0.3mm from 0.5mm for producing common gray iron products originally. The processing allowance of the original 3mm is saved in the important processing part, the processing allowance of the non-important area is reduced to 1mm at the minimum, most of the vacuum sealing casting technology adopts wood molds and resin molds, the vacuum sealing casting mold is almost not worn in the production process, and therefore the service life is long, but the three-dimensional diagrams of the upper sand box 12 and the lower sand box 13 of the vacuum sealing casting mold of the elevator brake disc in fig. 6 still need to be maintained and overhauled regularly in the storage process.

Step S3, designing and manufacturing a sand box

Through the optimization to sand box structure in practice, as shown in fig. 4 and 7, through adjusting vacuum tube 7, the vacuum degree has been increased on the basis of current equipment, the quantity and the overall arrangement of vacuum tube 7 have been increased, vacuum tube 7 mainly adopts the stainless steel pipe preparation that has many holes, increase of service life, and all adopt pipe end cap 8 to seal at each vacuum tube 7 lateral end, be used for improving casting vacuum degree, wrap up completely through stainless steel mesh 9 at the surface of vacuum tube 7, prevent sand entering vacuum system, each vacuum tube 7 all communicates through coupling 10, thereby satisfy the vacuum demand of many multiple variety ductile iron wheel hub production of a case, thereby the sand mould intensity that obtains is higher than traditional sand mould, the shrinkage cavity shrinkage defect that can be fine prevention graphitization expansion leads to the casting mould to give off.

Step S4, vacuum modeling

The method comprises the steps of manufacturing an upper sand box 13 and a lower sand box 13 under the negative pressure condition of 0.04-0.06MPa by adopting dry sand with 70-140 meshes, wherein an outer cavity with a uniform thin wall part and an outer cavity with a shaft end cover are arranged in the upper sand box 12, the upper sand box 12 is provided with a sprue 3 and a sprue pit 6, the lower sand box 13 is provided with an inner cavity with a uniform thin wall part and an inner cavity with a shaft end cover, and a cross runner 4 is arranged on a parting surface of the lower sand box 13; as shown in fig. 6, the cope and drag flasks 13 are a box of 6 pieces, the cope and drag flasks 13 are each provided with 6 cavities, as shown in fig. 5, chill is arranged at a position which is easy to generate defects after box closing, and castings with good surface quality and small machining allowance can be obtained by selecting special talcum powder and paint.

S5, pouring

The production of the ductile iron hub generally adopts an electric furnace to smelt to obtain pure molten iron, meanwhile, the raw materials need to be cleaned before entering the furnace, such as shot blasting and the like, the chemical components are unknown and a closed container, the materials with serious dampness and rust and more sediment and greasy dirt are not accurately fed into the furnace, the smelting raw materials are 80% scrap steel and 20% return materials, the chemical components in the front of the furnace are controlled in a control range, the scrap steel, the carburant, the return materials and the ferroalloy are sequentially added according to the sequence, the charging sequence and the proportion are strictly controlled, on one hand, the stable smelting quality is ensured, and on the other hand, the service life of the electric furnace is prolonged, as shown in table 1.

TABLE 1 chemical composition of molten iron before spheroidization

The molten iron smelting temperature is 1480-1520 ℃, the molten iron is poured into a ladle for ladle ironing treatment, and the molten iron is poured into an electric furnace after the ladle is preheated. And (3) carrying out primary deslagging operation on the molten iron in the furnace before molten iron is discharged, and carrying out primary deslagging operation on the molten iron in the ladle ironing process after molten iron is discharged.

And (3) spheroidizing by adopting a ladle covering method, transferring molten iron into a spheroidizing ladle at 1480-1500 ℃ for spheroidizing in order to obtain proper pouring temperature, and putting a spheroidizing agent, ferrosilicon and a covering agent into the spheroidizing ladle according to a certain proportion and tamping. The first inoculation is carried out in the process of transferring the nodulizing ladle into the pouring ladle, and the temperature of the molten iron is reduced by about 100 degrees. After slag skimming, casting is carried out at 1360-1380 ℃ of molten iron, and a better inoculation effect is obtained along with secondary inoculation, and chemical compositions of the molten iron after the furnace are shown in table 2.

TABLE 2 chemical composition of molten iron after spheroidization

Through ductile iron product development practice, components and performance of castings cast at different temperatures are detected, the optimal casting temperature obtained for elevator brake disc products is optimal at 1360-1380 ℃, the structural grains are overlarge due to overhigh temperature, the mechanical performance is reduced, the temperature is too low, defects such as cold insulation and shrinkage cavity are frequently generated at the thin wall of the castings, the casting speed of vacuum seal casting is closely related to the size and the process of the castings, and the casting time of vacuum seal casting is generally faster than that of other processes.

Because vacuum seal casting is carried out at the moment of casting, the stability of the cavity is kept by the positive pressure of molten iron entering the cavity, compared with other casting processes, the control requirement of the casting speed of vacuum seal casting is more strict, a box of six ductile iron is adopted for producing ductile iron, the weight is about 500kg, and the casting time is generally about 40-60 s.

It should be understood that the specific order or hierarchy of steps in the processes disclosed are examples of exemplary approaches. Based on design preferences, it is understood that the specific order or hierarchy of steps in the processes may be rearranged without departing from the scope of the present disclosure. The accompanying method claims present elements of the various steps in a sample order, and are not meant to be limited to the specific order or hierarchy.

In the foregoing detailed description, various features are grouped together in a single embodiment for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed embodiments of the subject matter require more features than are expressly recited in each claim. Rather, as the following claims reflect, invention lies in less than all features of a single disclosed embodiment. Thus the following claims are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate preferred embodiment of this invention.

The foregoing description includes examples of one or more embodiments. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the aforementioned embodiments, but one of ordinary skill in the art may recognize that many further combinations and permutations of various embodiments are possible. Accordingly, the embodiments described herein are intended to embrace all such alterations, modifications and variations that fall within the scope of the appended claims. Furthermore, as used in the specification or claims, the term "comprising" is intended to be inclusive in a manner similar to the term "comprising," as interpreted when employed as a transitional word in a claim. Furthermore, any use of the term "or" in the specification of the claims is intended to mean "non-exclusive or".

Claims (6)

1. A method for producing an elevator brake disc by vacuum sealing casting, which is characterized by comprising the following steps:

s1, designing a process, namely adopting a riser-free design, and arranging a square riser above the center of an elevator brake disc; a sand core is adopted below the square riser, so that the safety of the elevator brake disc in non-drawing degree molding and demolding is ensured;

s2, manufacturing a die, namely, aiming at vacuum sealing casting of an elevator brake disc, adopting a wood die, wherein the accuracy of the die is +/-0.3 mm error value, the original 3mm machining allowance is reserved at an important machining part, and the machining allowance of a non-important area is reduced to 1mm at the minimum;

s3, manufacturing a sand box, wherein the vacuum pipes are manufactured by adopting stainless steel pipes with a plurality of holes, the transverse end parts of the vacuum pipes are sealed by adopting pipe plugs, the surfaces of the vacuum pipes are completely wrapped by stainless steel meshes, sand is prevented from entering a vacuum system, and the vacuum pipes are communicated through pipe joints;

s4, vacuum molding, wherein an outer cavity of a thin-wall uniform part and an outer cavity of a shaft end cover are arranged in an upper sand box, a sprue and a pouring nest are arranged in the upper sand box, an inner cavity of the thin-wall uniform part and an inner cavity of the shaft end cover are arranged in a lower sand box, a cross runner is arranged on a parting surface of the lower sand box, the upper sand box and the lower sand box are a box with multiple sand boxes, a plurality of cavities are formed, and a chill is arranged at a part which is easy to generate defects after box closing;

s5, pouring, namely adding scrap steel, carburant, furnace return material and iron alloy into a smelting raw material which is 80% scrap steel and 20% furnace return material in sequence according to the control range of chemical components in front of the furnace, and finishing the process through three steps of hot metal ladle ironing, cover Bao Fa spheroidizing and cooling;

s51, pouring molten iron into a ladle for ladle ironing treatment when the molten iron smelting temperature is 1480-1520 ℃, pouring the preheated molten iron into an electric furnace, carrying out primary slag removal operation on the molten iron in the furnace before discharging the molten iron, and carrying out secondary slag removal operation on the molten iron in the ladle ironing process after discharging the molten iron;

step S52, cover Bao Fa spheroidizing, transferring molten iron into a spheroidizing ladle at 1480-1500 ℃ for spheroidizing, putting a spheroidizing agent, ferrosilicon and a covering agent into the spheroidizing ladle according to a certain proportion, tamping, and performing first inoculation in the process of transferring the spheroidizing ladle into a pouring ladle;

and step S53, cooling and pouring, namely reducing the temperature of the molten iron, performing slag skimming operation, pouring when the molten iron reaches a specific temperature, and performing secondary inoculation.

2. A method of producing an elevator brake disc by vacuum seal casting according to claim 1, characterized in that: in the step S53, the specific temperature is set to a value ranging from 1360 to 1380 ℃.

3. A method of producing an elevator brake disc by vacuum seal casting according to claim 1, characterized in that: in the step S4, a ceramic pipe with a certain diameter is adopted as the sprue, and a transverse runner and an internal runner with a certain flow are matched, so that the molten iron filling speed and flow are ensured, a ceramic sprue pit is adopted as the sprue pit, and an indirect external chill is arranged in a hot joint part and a sand layer of a thick and large part of the brake disc.

4. A method of producing an elevator brake disc by vacuum seal casting according to claim 3, wherein: the height of the inner pouring channel is 8-10 mm, and the outer cooling iron is of a circular structure and is arranged at the positions of the hot joint part and the thick part of the brake disc and the sand layer with 5-10mm spacing between the thick part and the casting.

5. The method for producing an elevator brake disc by vacuum sealing casting according to claim 1, wherein in the step S4, dry sand of 70-140 meshes is used, and upper and lower sand molds are manufactured under the negative pressure condition of 0.04-0.06 MPa.

6. A method for producing an elevator brake disc by vacuum sealing casting according to claim 1, wherein in the step S5, the casting time is controlled to be 40-60 seconds.