Experience and application of the latest water gla

2022-07-23
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Experience and lessons from the application of new water glass self hardening sand process in production lines

[Abstract]: through the application of our new water glass self hardening sand process in the production lines of more than a dozen domestic casting enterprises, we have gained some valuable experience and lessons. In order to make this process more and more perfect in the application process, better provide service guidance for the majority of users, and provide reference and help for the foundry enterprises that will undergo technological transformation, we elaborate on the selection of casting raw and auxiliary materials, the control of production inspection means, the responsibilities of the personnel in charge of molding materials and technology, the selection of casting equipment and matters needing attention with the majority of foundry workers

[Key words]: new water glass self hardening sand, raw and auxiliary materials, casting equipment, regeneration system

new water glass self hardening sand is developed by our company on the basis of raw ester cured water glass sand and is the third generation product of water glass sand. Since the first new sodium silicate sand self hardening sand production line of Dalian Hitachi Baoyuan mechanical equipment Co., Ltd. was put into use in July, 1998, there have been more than a dozen casting enterprises applying ester cured sodium silicate production lines in China. In the process of assisting users to debug the production line, guiding users to apply the new sodium silicate self hardening sand technology and solving the quality problems of castings, we have gained valuable experience and lessons, and continuously improved and innovated, making this technology more and more perfect. In 1999, it passed the appraisal of scientific and technological achievements presided over by Liaoning Provincial Science and Technology Commission, and in 2001, it won the national torch plan project. Our company has also been able to grow and gain a good reputation in the foundry industry. In order to better serve the majority of foundry enterprises and provide reference and help to foundry enterprises that will undergo technological transformation, we have written some accumulated experience and lessons and exchanged and discussed with foundry peers

reducing cost and improving quality is the eternal theme of enterprise development and the goal of technological transformation of foundry enterprises. From the application practice of new water glass self hardening sand, the bottleneck of reducing casting cost and improving casting quality is sand treatment quality. To ensure the quality of sand treatment, it is necessary to use good raw and auxiliary materials, perfect inspection and control means, and reliable operation of sand treatment equipment

I. select good raw and auxiliary materials

determine qualified suppliers from the aspects of quality, supply, price and service, which is one of the basic conditions for stable production. The supplier shall have more stable users. The production practice has proved that the product quality is stable and can meet the requirements of casting quality. The water glass and curing agent have good compatibility. They are special products, not chemical by-products. They can adapt to different production types and climatic conditions in different regions. They can easily adjust the hardening speed of the core sand to meet the operating requirements. The water glass has slow aging, few impurities and low viscosity, which is convenient to achieve stable flow of the water glass pump

the original sand has good grinding resistance and low pulverization rate. Only in this way can a higher reuse rate of old sand be achieved. Here is an example to illustrate the influence of raw sand condition on regeneration quality. Qinhuangdao Metallurgical Machinery Co., Ltd. originally used Liaoning Haicheng shaping sand. The angle coefficient of this sand is about 1.35, and small cracks can be seen on the surface of some sand particles. After the operation of the new sodium silicate self hardening sand production line for some time, it is found that the sand pulverization rate is very high after several sand treatments. There are many fine powders (micro powder plus mud) discharged from the dust collector. Thick fine powders are often hung in the dust collector bag to build a high-level graphene manufacturing innovation center. It is no longer helpful to rely on the self-cleaning of the dust collector. It is often necessary to manually remove the fine powders in the dust collector bag, and the fine powders in the regenerated sand often exceed the control standard. Such problems become more serious in high temperature weather. Old sand and reclaimed sand are easy to absorb moisture in the air. The old sand and regenerated sand hanging bucket block the lower sand opening, hang the cooling water pipe and rib of the sand temperature cooler, and even block the lower sand channel of the sand temperature cooler. The sand output of the sand mixer decreases, the permeability of the core sand decreases, the hard permeability of the core becomes poor, and the amount of water glass is nearly 4%. Old sand recycling rate%. Reclaimed sand residual Na2O 0 0%, even nearly 1.5%, fine powder nearly 2%, and the moisture content of reclaimed sand exceeds the standard

In October, 2003, the company replaced Haicheng shaping sand with Fujian Pingtan sand, and the quality of recycled sand improved immediately. The content of micro powder in recycled sand II. Improvement of inspection and control means

improve the inspection and control means, so that the molding materials are always in a good control state

1. inspection instrument

set up necessary inspection instruments in combination with the characteristics of the new water glass self hardening sand. Hydraulic strength testing machine, tensile sample core box, sand washing machine, test sand mixer (3~5kg), sand screening machine, sand dryer (or furnace), 1/1000 analytical balance

2. staffing

one engineer in charge shall be set up, and two sanders (one full-time and one part-time) shall be set up for each shift of each sand mixer. Molding workers with flexible mind, strong heart and careful handling shall be selected as Sanders. Select the molding worker as the sanding worker, so that the sanding worker can timely adjust the hardening speed of the core sand according to the operation time of the shape core, cooperate with the molding and core making operation, and flexibly adopt the set proportion

3. determination of standards

formulate technical standards for raw and auxiliary materials, control standards for core sand and recycled sand, and inspection standards

3.1. technical requirements for raw and auxiliary materials for steel castings production (Reference)

3.1.1. quartz sand

sio2 ≥ 97%, particle size 40-100 mesh, angle coefficient about 1.30, micro powder content ≤ 1.0%, mud content ≤ 0.30%, water content ≤ 0.50%. The specific particle size distribution for reference is shown in brackets (>40 mesh, ≤ 3%; 40 mesh,%; 50 mesh,%; 70 mesh,%; 100 mesh,%; 0.5mpa

simple or small and medium-sized, simple core 0.4-0.5mpa

backing sand or manufacturing simple castings (such as sand box, flat plate, etc.) 0.2-0.3 mpa

storage time. For the storage time of cores made, please refer to the following time

when the relative humidity of the air is ≥ 80%, The heat-resistant temperature of polymer material refers to that when the relative air temperature is ≤ 12h under a constant load,

when the relative air temperature is% or less, it can be used after the natural gas flame is dried if the core is obviously hygroscopic within one week

inspection frequency: core sand strength shall be inspected twice per shift. The residual Na2O content and moisture of reclaimed sand shall be checked once per shift. The micro powder content of reclaimed sand shall be checked once a day

control index of reclaimed sand: residual Na2O ≤ 0.5%. If residual Na2O ≥ 0.8%, it indicates that reclaimed sand has been very deteriorated. Moisture ≤ 0.5%, in any case, moisture ≥ 1% is not allowed, micro powder ≤ 0.5%, mud content ≤ 0.3% (pay attention to the influence of residual Na2O during detection)

4. formulate the operation guidance documents for each post of sand treatment

here, copy two documents of a user: the responsibilities of the Engineer in charge of modeling materials and the operation guidance for sand preparation

responsibilities of the Engineer in charge of molding materials

fully responsible for the technology and management of molding materials in the Foundry Branch

1. determine the technical standards of raw and auxiliary materials used by the branch. Control standard for core sand and reclaimed sand

under the leadership of the company's technology department, assist the company's quality inspection department to complete the inspection means of molding materials, determine the inspection methods of molding materials, and establish the inspection system. Establish close working contact with the technical department, quality inspection department, production management personnel and suppliers of the branch on matters related to molding materials. According to the production arrangement and inventory of the branch, provide the deputy production director and supplier of the branch with the recent purchase list of raw and auxiliary materials, indicating the specifications, quantities and technical indicators of the materials

2. guide the operation of sand treatment personnel

responsible for the business training of operators

prepare operation instruction documents for sand treatment personnel

formulate assessment methods for sand treatment personnel. Supervise, inspect and assess the work of sand treatment personnel

1 the system is controlled by microcomputer. 3. master the working principle, structure, working condition and operation method of sand treatment equipment. Understand the causes and troubleshooting of common faults, and provide reference suggestions for the maintenance, repair and improvement of sand treatment equipment

4. according to the quality inspection results of raw and auxiliary materials and mixtures, the proportion of new sand and recycled sand, and the addition amount of sodium silicate and curing agent shall be determined in combination with the operation requirements of molding, box closing, pouring, sand dropping, sand cleaning and regeneration and the quality status of castings

5. master the inspection method of molding materials adopted by the branch, understand the principle and be able to operate

guidance on sand mixing work

under the guidance of the Engineer in charge, be specifically responsible for sand mixing, adding liquid materials, adding sand, operating the sand mixer, and doing a good job in the daily maintenance and cleaning of the sand mixer

1. check the cleaning of sand mixing tank, sand mixing blade, liquid material nozzle and sand outlet. Check shift change records and temperature and humidity table

2. daily minimum temperature III. reliable guarantee of equipment

the production line equipment of new sodium silicate self hardening sand is developed on the basis of furan resin sand equipment in combination with the characteristics of new sodium silicate self hardening sand. It is similar to furan resin sand equipment. With the development in recent years, domestic equipment can basically meet the needs of users of different production types

the new sodium silicate self hardening sand equipment mainly includes sand mixing equipment and old sand regeneration equipment. The new sodium silicate self hardening sand mold (core) line with automatic control can be formed mainly by sand mixing equipment and equipped with vibrating table, overturning mold lifter, conveying roller table and electrical control device. Most of the used sand regeneration systems have the functions of sand block crushing, screening, magnetic separation, used sand regeneration, micro powder separation, sand temperature adjustment, etc. the connection between equipment and the transportation of materials mostly adopt bucket elevator, belt conveyor or pneumatic conveying and other conventional conveying equipment. In order to meet the requirements of environmental protection, labor protection and micro powder separation, the production line must also be equipped with good dust removal equipment

1. selection of sand mixer

the selection of sand mixer includes two aspects, one is the type of sand mixer to be selected, and the other is the type of sand mixer with large production capacity

1.1 selection of the type of sand mixer

the selection of the type of sand mixer should consider the characteristics of production. For the production of small sand cores or for mixing a small amount of special sand, it is better to select the intermittent sand mixer. The intermittent sand mixer mixes sand evenly without head and tail sand, and can also be used for the production verification of the process

for manufacturing large sand mold (core), continuous sand mixer shall be selected. If the sand box is large, it is inconvenient to move. Mobile sand mixer can be used, and factors such as workshop transportation, area and production organization mode shall be considered when selecting

1.2 selection of the capacity of the sand mixer

the production capacity of the sand mixer is usually selected by considering the output of the castings, the representative products of the castings produced, the size and type of the sand box. If it is produced by the molding line, both the size of the sand box and the production beat should be considered. Like any equipment, the selection of sand mixer shall consider the reliability of its use, that is, the reliability of hydraulic, pneumatic, electrical and other components used in the product, the design and manufacturing quality, the source of maintenance accessories, maintainability, product price and other factors

1.3 selection of pendulum pre lift angle: the 150 ° sand mixer should be clear about the difference between the new sodium silicate self hardening sand and furan resin self hardening sand, and fully consider the characteristics of the new sodium silicate self hardening sand

1.3.1 binder pump and binder reversing valve

viscosity of new water glass> viscosity of furan resin

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