Development of "Box" casting process

Contents

Contents

Introduction

1 General characteristic of cast part

2 Selection and substantiation of the selected casting method

3 Calculation of casting complexity group

4 Rod Design

5 Calculation of the number of castings in the mold

6 Calculation of mechanical machining allowances as per GOST 26645-85 and casting weight. Definition of K.I.M

7 Runner System and Runner System Mass Calculation

Mass of casting with runner system is determined by formula

8 Preparation of metal balance. Determination of yield factor of suitable castings

9 Moulding and rod mixtures

10 Calculation of shape weight before and after filling

11 Characteristics of the model set

12 Description of the technology of making a mold, rods, assembling a mold, pouring, knocking, cutting and cleaning a cast

13 Description of smelting technology

14 Charge calculation

15 Calculation of consumption rates of main and auxiliary materials for 1 t. of suitable castings

16 Advantages of developed technology, reduction of power consumption, reduction of materials consumption

17 Occupational and environmental protection

Conclusion

List of sources used

Introduction

Topic: Development of technological process of "Box" casting No. BM1802.00.11.001.

The growth rate of foundry production largely determines the successful development of mechanical engineering and other sectors of the national economy.

Foundry is one of the most important branches of mechanical engineering. In various designs of modern machines and devices, about 70% by weight of the parts are castings of steel, cast iron, copper, aluminum, magnesium and other alloys. Castings in the structures of metallurgical equipment, turbines, forge-press machines, metal cutting machines occupy a particularly large place. In the machine tool industry, cast parts account for up to 90% of the total weight of blanks. The foundry owes wide distribution to its advantages over other methods of producing blanks. By means of various casting methods, it is possible to obtain articles of complex configuration from any metals and their alloys, most of which cannot be obtained, for example, by stamping, forging or machining.

The configuration of the castings can be varied. It is determined by the ability to produce the tooling and mold, the minimum thickness of the cavity that the metal is able to fill, and economic calculations that allow comparing the cost of manufacturing and the operating conditions of the casting, on the one hand, and a similar article obtained by another method or made up of separate cast parts, on the other.

The perspective of casting technology is due to versatility, which allows you to obtain products from alloys of almost any composition, of various weights, with dimensions up to tens of meters.

The purpose of the course project: to consolidate, improve and expand practical and theoretical knowledge, learn to use the technical documentation, norms, standards necessary for the development of casting technology, acquire skills in the performance of design work on foundry technology. Develop the manufacturing process of the "Box" casting.

Selection and justification of the selected casting method

The choice of molding method (manual, machine, automatic) depends on the size of the casting, the configuration and the nature of the production. Manual moulding in soil is used in the manufacture of small and large castings. Machine molding is used mainly for small and medium castings, and sometimes large ones in conditions of serial and mass production.

Molding on automatic lines is used only in mass production conditions. Machine molding has a number of advantages over manual molding:

Improved performance

possibility of complex mechanization and automation of casting processes;

higher accuracy of castings and reduced allowance for mechanical treatment.

Casting in raw molds is the most common in mass production and mass production workshops in the production of castings weighing up to 200 kg. In recent years, the production of raw molds has been further developed due to the effective use of modern molding machines and automatic lines.

Machine molding according to metal models with mechanized removal of models from the semi-mold is an economical version of manufacturing the most complex thin-walled castings in serial and mass production and provides 8-13 for colored and 9-14 for black alloys classes of dimensional accuracy GOST 26645-85. At the same time, smaller values ​ ​ of accuracy classes relate to simple castings and conditions of mass automated production, large ones - to complex castings of single and serial production, medium ones - to castings of medium complexity and conditions of mechanized serial production.

The Box cast is made of 35L steel, has a mass of 220 kg, the production characteristic is serial. All of the above allows you to obtain a Box cast using manual molding.

Characteristics of the model kit

A model kit is a process accessory that is required to form casting loops. The main elements of the model kit are the model and rod boxes.

According to the model, a cavity is obtained in the mold, mainly reproducing the external contours of the future casting. Inner cavity of casting is shaped with rod produced in rod box. The working surface of the box corresponds to the inner contour of the future casting.

In addition to models, and rod boxes, the model kit includes the following elements:

- models of feeders, slag catchers, risers, evaporators, profits and other parts of the runner system;

- submodel plates for installation and attachment of casting models and runner system;

- devices for adjustment and control of shapes and rods;

Single molds are manufactured mainly by machine molding methods. Machine molding models must be simple in design and have a minimum of connectors.

In addition, the design of the model kit shall provide castings with dimensional deviations within the limits specified in the specification.

Aluminium-based alloys and grey irons are the most common materials in the mold models. We will use models from gray cast iron to make castings. They have lower cost and higher strength. Metal models, rod boxes, submodel plates are recommended to be made as thin-walled as possible, reinforcing them with stiffening ribs and fastening tides.

On a model plate, models are bolted and centered with pins in multiple locations

Model-casting instructions are developed in accordance with GOST 242373, GOST 26645-80, GOST 321280, GOST 3606-80. These GOST determine the amount of allowance for mechanical processing, the amount of forming slopes, the dimensions of rod signs and gaps, etc. The selected values in accordance with GOST 3.112585 are applied to the part drawing, which also indicates the necessary additions and changes in the design provided by the technology.

Description of the technology of making a mold, rods, assembling a mold, pouring, knocking, cutting and cleaning a cast

The use of a single molding mixture allows you to make a mold and rods without the use of special molding equipment, using only mixing devices, as well as auxiliary lifting and vehicles.

Molds are made as follows: the model and the submodel plate are cleaned with rags from dust, sand, and the remains of an adhered mixture. On the model, a separation coating is applied with a rags uniform layer. Standpipe, gas vents, evaporators models are installed. On the submodel plate, a clean post is installed along the pins. The pre-prepared bulk mixture is fed by conveyors and periodically discharged by a dropping scraper into a mixer funnel, into which liquid components of the mixture are simultaneously supplied through a pipeline. After preparation of the kneading, the service unit opens the outlet of the mixer and the single moulding mixture by gravity fills the incoming supports. The process of making molds is reduced to pouring the liquid mixture into the supports, where it spontaneously solidifies for 30-40 minutes. A riser, evaporation, and gas vents are removed from the semi-mold. Ventilation inclines are made and half-mold is tilted. After that support is secured from submodel plate. The single form after extraction of the model is cured chemically by blowing with carbon dioxide.

For the manufacture of rods, a rod machine is used, the principle of operation of which is based on sandstorming the hot section with a rod mixture.

The rod machine is a single-position machine, which is started by pressing the button. The operation of pressing the rod box to the inflatable plate, clamping the rod box, blowing the rod mixture, exhaust air and loading the working tank of the machine with the mixture is automatically performed.

The rod machine performs the following operations: inflating the section with a rod mixture, curing the rod, ejecting the finished rod from the section.

The rods are placed manually. Blow the bottom half mold with compressed air. Prior to assembly, top and bottom half-molds and rods are inspected.

Assembly pins are inserted into bushings of upper half-mold and lower half-mold is covered. The mould is then loaded to prevent metal from escaping to the mould plane when the mould is poured.

Collected molds are transported by conveyor for pouring. Pouring is carried out on a semi-automatic pouring machine with a roller table for changing a bucket with a capacity of 10 tons. Cast mold is fed by conveyor into cooling tunnel .

After cooling the mold, by means of a bridge crane, it is transferred to a knock-out inertial impact grille. Periodically including the grid, the mixture is removed from the stack. Casting is removed from mold by means of bridge crane. And then it is sent to the chop, where the elements of the runner system, profits, bays along the mold connector are separated from the castings. Chopping is performed with pneumatic hammers using teeth, air-arc cutting is used to remove bays. Then the casting follows to the heat tube compartment, where the rod is removed in the hydraulic chamber as follows: the casting is installed on the trolley, the trolley is pushed inside the chamber, the body is closed and the water supplied from the special tube under high pressure removes the rod from the casting. Next, the casting should be cleaned in the blasting chamber. The casting is installed on the trolley, the trolley is pushed inside the chamber, where the fraction under the action of centrifugal force hits the casting, thereby cleaning it. This is followed by a casting cleaning operation on the pendulum pendulum .

Castings are delivered to the finished product warehouse.

Description of smelting technology

Steel smelting is performed in electric arc furnaces (DPS1.5).

Power supply power - 1800 kW, melt melt time 40 min.

Advantages over similar AC arc furnaces:

Decrease of graphite electrodes consumption to 1.5 kg/t of liquid metal;

Reduction of metal carbon monoxide to 24% (increase of HVG);

Reduction of ferroalloys consumption by an average of 1520%;

Noise reduction by 1520 decibels.

Steel smelting can be carried out by the main process or by an acidic process. In the main process, melting is carried out under the main slag for guidance of which burnt lime and melting spar are used. In this case, the main refractory materials (magnesite bricks, magnesite powders.)

Melting is carried out under acidic slag for guidance of which quartz sand is used. The SiO2 content in slag is up to 65%.

Steel scrap of A1 grade GOST 2787 and return of own production are used as charge. Steel scrap is supplied to the workshop with a certificate with a mandatory indication of the steel grade and chemical composition of carbon, chromium, manganese, nickel. It is allowed to have near grades up to 20%. Storage of steel scrap on the site by marks.

Scrap metal should not be rusty, corroded by acids. Also, hollow vessels, pipes are not allowed. Scrap metal shall be checked for explosion. The dimensions of the pieces shall not exceed 1/3 part of the furnace roof diameter. Metal thickness is not less than 6 mm.

The furnace is loaded through the vault. Melting of materials loaded into the furnace is carried out intensively, with full use of the transformer power. After the charge is melted, the metal necessary to free the steel bath from gases is oxidized to purify particles of silica or silicates of various compositions suspended in it.

The bath shall boil evenly over the entire surface. To maintain the normal boiling of the bath, deposit the scale in frequent, but not large, portions, at a sufficiently high metal temperature, in an amount of 0.5-1.0% of the melting weight. The required amount of slag is achieved in addition to scale additives with small additives of dry limestone or burnt molding land and chamotte fighting.

If the bath does not boil after starting the scale additive and reaching the desired metal temperature 16701690◦ C, this indicates an increased silicon content in the metal. With the imprudent addition of scale to the furnace to increase the boiling of the bath after burning out of silicon, a violent reaction can occur, part of the melting will be thrown out through the fill window. After adding the last portion of scale, the bath is allowed to boil for 10 minutes. The end of the pure boiling is characterized by a gradual slowdown in the boiling of the bath. To prevent possible silicon reduction, finely divided dry limestone should be added to the slag at the beginning of the clean boiling period.

At the end of the active process, oxidizing slag is partially removed through the filling window with a metal scraper and fresh slag-forming materials are added: chamotte battle, sand, burnt earth and limestone in a ratio of 6:2; 1:2. The total flow rate of such a mixture is 0.5-0.6% of the melting weight.

After loading slag-forming materials into the furnace for faster deoxidation of slag, 0.1-0.2% of ground ferrosilicon and 0.1-0.2 of ground coke should be added. After 810 minutes after such treatment, the slag should be spread by a 47mm layer when drained onto the slab. The fracture of normal acid slag is light green or light blue. Chemical composition of slag before release: SiO2=50.3%; FeO=9.2%; MnO=20.5%; Al2O3=4.7%; CaO=5.5%.

After obtaining the normal slag and correcting the carbon content, the steel bath is deoxidized with ferroalloys. Preliminary deoxidation is carried out with an additive 45% forrosilicon according to the calculation, deoxidation by ferromanganese is carried out 5-7 minutes before the melting outlet. At the end of melting slag is removed through the filling window with a metal scraper.

The temperature of metal discharge from the furnace is 16500C, and pouring occurs at 150015500C.

Advantages of developed technology, reduction of power consumption, reduction of materials consumption

The developed technology of "Box" casting is the most efficient and convenient, since it helps to obtain a high-quality mold, with a minimum percentage of the consumption of the moulding mixture

The technology I have developed has several advantages:

1 Two castings are made in the mold, while there is a small consumption of the moulding mixture, and therefore savings in molding materials.

2 There is no compaction process, so performance is quite high.

3 Cast rods are made of CFC, the mixture has the following advantages:

- good knockout;

good gas permeability;

- good strength;

is a good vent.

5 Machining allowances are reduced and therefore K.I.M. is increased.

6 Decrease of metal consumption per runner system, respectively increase of HSV.

7 Electric power is saved by using an arc furnace for smelting.

Conclusion

In this course project, the technology for manufacturing steel casting "Box" VM1802.00.11.001 was developed.

During the work, calculations were made:

casting complexity groups;

the number of castings in the mold;

casting accuracy;

mass of allowances, mass of blousings, testing and assessment material;

casting masses;

metal utilization factor;

runner system and runner system mass;

mold mass before and after filling;

coefficient of yield of suitable castings;

charge and consumption rates of main and auxiliary materials per 1 ton of suitable castings.

Two castings are made in the mold. Casting is produced manually.