Foundry Processes and Electric Arc Furnaces

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Questions and Answers

What is the maximum allowable warpage reading for wheels to pass the warpage measurement?

1.0 mm (correct)

2.0 mm

1.5 mm

2.5 mm

During the shot peening process, what is the main purpose of impacting the wheel with steel shots?

To increase the wheel's weight

To generate heat and soften the metal

To remove the surface finish

To produce a compressive residual stress layer (correct)

What type of insert is used for the hub bore machining process?

Diamond insert

Carbide insert (correct)

HSS insert

Ceramic insert

What is the range of receiving temperature for blowing compressed air during the cleaning stage of cope and drag preparation?

245-325°C Signup and view all the answers

What occurs during the warpage process if defects relating to the shape of the wheels exceed the limiting value?

Wheels are rejected Signup and view all the answers

Which component is responsible for protecting the furnace roof from excessive heat during the melting process?

Slag Signup and view all the answers

What is the primary function of the oxygen lancing pipe during the melting process?

To cut scrap through the slag door Signup and view all the answers

What is the typical temperature maintained during the melting of scrap in an electric arc furnace?

1650 to 1700 °C Signup and view all the answers

How long does the melting process generally take in the electric arc furnace?

45 to 55 minutes Signup and view all the answers

Which part of the three-electrode electric arc furnace contains the sidewalls and lower steel 'bowl'?

Shell Signup and view all the answers

What is the role of the electric arc in the melting process?

To melt the charged materials Signup and view all the answers

What type of materials are added to the electric arc furnace along with the scrap to aid the melting process?

Calcined lime and coke/graphite Signup and view all the answers

What is the primary purpose of the John Mohr Pit (JMP) after the melt is poured into the ladle?

To measure temperature and finalize the melt composition. Signup and view all the answers

How much Ferro-silicon can be added without draining metal?

140 kgs Signup and view all the answers

What temperature range is critical for immersing the Aluminum stars during the JMP process?

1560 to 1610 °C Signup and view all the answers

What is the role of ladle insulation material in the JMP?

To maintain the temperature of the melt. Signup and view all the answers

What is the significance of the ceramic pouring tube preparation in the casting process?

It takes about 1 day to withstand high temperatures. Signup and view all the answers

What element requires typically 3 kgs for a 0.01% increase in the furnace?

Manganese Signup and view all the answers

Which system is used during the casting process to fill the cavity?

Cope and drag system. Signup and view all the answers

What is the maximum temperature at which the ladle operations should ideally begin?

1610 °C Signup and view all the answers

What is the lowest temperature at which the melt can be sampled for final analysis?

Around 1560 °C Signup and view all the answers

What is the purpose of rim quenching in the wheel manufacturing process?

To increase the hardness of the rim only Signup and view all the answers

What temperature range of water is used during the rim quenching process?

18 to 35 °C Signup and view all the answers

Why is tempering necessary for wheels produced through casting?

To remove internal stresses within the wheel Signup and view all the answers

During hub cooling, how long is each region of the hub cooled?

45 seconds Signup and view all the answers

What pressure is used during the hub cooling process?

2.5 kg/cm2 Signup and view all the answers

What happens to the wheels after they are hub quenched?

They remain with a rough surface and are stacked for cooling Signup and view all the answers

How long do the wheels stay in the draw furnace during tempering?

2.5 hours Signup and view all the answers

What is the main purpose of the Wheel Final Process Shop (WFPS)?

To clean and finish rough surfaces of the wheels Signup and view all the answers

What issue does the hub cooling process specifically address?

Crack formation in the hub portion Signup and view all the answers

What unique challenge is presented by the casting process in wheel manufacturing?

Introducing internal stresses Signup and view all the answers

What is the primary purpose of apex grinding?

To eliminate extra material from the wheel Signup and view all the answers

What cleaning method uses high-velocity starch particles?

Roto blasting Signup and view all the answers

In Magnaglo testing, what role does the black light play?

It enhances the visibility of the magnaglo powder Signup and view all the answers

What is the function of using radium chalks during the Magnaglo inspection?

To mark areas needing further grinding Signup and view all the answers

During ultrasound testing, what does the third indication signify?

A defect within the wheel material Signup and view all the answers

Which frequency range is utilized during ultrasound testing?

0.1 to 15 MHz Signup and view all the answers

What happens to the back wall indication amplitude when a defect is detected during ultrasound testing?

It reduces in amplitude Signup and view all the answers

What type of testing is Magnaglo classified as?

Non-destructive testing Signup and view all the answers

What is the purpose of the Brinell hardness test in the described procedures?

To display the hardness values digitally Signup and view all the answers

Which substance is used as a suspension medium in Magnaglo testing?

Water Signup and view all the answers

Study Notes

Wheel Shop Processes

The wheel shop is the first unit of RWF, producing eight different types of wheels.
Wheels average 500 kg.
The shop recycles scrap metal to obtain the correct composition for wheels.
Wheel production involves melting, moulding, machining, finishing, and inspection to meet customer requirements.
The shop is divided into three main divisions: Melting, Moulding, and Finishing (WFPS).

Melting Process

Scraps (rejected wheels, axles, worn-out wheels, machining chips) are the basic materials for producing wheels.
Scraps are sorted into three categories (heavy metals, light metals, and machine chips) to ensure consistent heat distribution during melting in the electric arc furnace.
Charging of scrap involves adding scrap, lime, calcined lime, and coke/graphite to the furnace.
Electrodes are raised, and an electromagnet lifts metal chips into the furnace.
Buckets charge scraps in the correct order (heavy metals, then light and machine).
The charge usually includes 9000-1200 kg calcined lime and 200-250kgs of coke/graphite.
The electric arc furnace has three sections: the shell, the hearth, and the roof.
The electrodes are lowered, and an arc is struck between the electrodes and the charge for 45-55 minutes.
Oxygen lancing is used to cut scrap and slag.
Temperatures during this process are 1650-1700°C.
Slag floats on the surface, preventing oxidation and protecting the roof.
Slag removal involves spreading dolomite over the cleaned slag door and removing all slag when the temperature is 1630°C.
If slag is sluggish, 55-65kgs of Fluorspar or 150kgs of slag reducing mixture and Ferro-manganese is used.
Spectro-analysis is used to determine the metal composition.

Carburisation/Decarburization

Samples of melt are tested for carbon, silica, and manganese composition.
Carburisation is used when the carbon content is low, adding graphite to the melt at 1640°C.
Decarburization is used when the carbon content is high, using slag-coated oxygen lancing to reduce the carbon.
Materials used in decarburization control include ferro-manganese, silica-manganese, and ferro-silicon.
Samples are taken after 3-4 minutes of arcing.

Tapping

The molten metal from the furnace is poured into ladles using furnaces A, B, and C with capacities ranging from 20-23 metric tons.
Required amounts of ferro-silicon, ferro-manganese, or silicon manganese are added to the ladle after preparation.
The tapping temperature should be 1660°C to 1720°C.
The furnace base is tilted, and the metal starts pouring.
Tapping is completed within 3-4 minutes to avoid heat loss.
The ladle is carried to the JMP (John Mohr Pit).

Moulding Room

The controlled pressure pouring of wheels process is used to pour metal into the mould.
Materials such as graphite mould, cope, drag, cast wheel, air-tight cover, ceramic tube, molten steel, and pressurized air, are used in this process.
Specific ingredients and quantities are required for different wheel types (e.g., 2 kg of carbon for 0.01% increase).

John Mohr Pit (JMP)

The wheel is poured, and the temperature is monitored/maintained to be below 1610°C.
The aluminum stars and appropriate ladle insulation materials are used.
A sample is tested to confirm the composition.
The ceramic pouring tube is installed and the wheel is prepared for casting.

Sprue Washing

Removing the sprue (channel for molten material flow) and the runner/riser that is not removed during splitting.
Process occurs after controlled air-cooling, when the wheel temperature is 400-500°C.
Wheel stamping is done to apply markings and numbers to the wheel
Stamping is done after sprue washing.

Hub Cutting

Cutting of the center hub portion to attain the required diameter (188 mm for BOX-N).
This involves using a cutting machine to cut the hub according to the required diameter.
Pneumatic air is used along with a gas flame for cutting the hub portion.
The leftover part of the stopper pipe in the hub is called the pilot hole.

Normalizing

A heat treatment process involving heating the metal to and holding for a period before controlled cooling .
Aim is to reach a specific internal condition or state.
This helps to maintain uniformity in the grain structure of the metal.
The rotary hearth furnace is used for the process with seven zones for heating and temperature distribution.
This process takes around 90 minutes and accommodates 45 wheels in two rows.

Quenching

A stage where the metal undergoes rapid cooling from a high temp.
Purpose is to increase the hardness of the rim of the wheels (outer part of wheel contacting rails).
This is done by using water jets with pressure from 2.5 kg/cm² to 3.5 kg/cm².
Water temp range for this process is 18-35°C.

Tempering

The process of removing internal stresses in the wheels that could lead to cracks during service.
This occurs after wheel casting.
The wheels are placed in a draw furnace that maintains a high temp for 2.5 hrs.
The furnace's capacity is 80 wheels.

Hub Cooling

Process to cool and harden the hub portion of the wheel after quenching.
The wheel is cooled in three separate zones (upper, middle, inner) taking 45 seconds for each zone.
The cooling uses high-pressure water jets (2.5 kg/cm²) to maintain uniformity in the cooling process.
The wheel is air-cooled for additional cooling after the water cooling stage.

Wheel Final Process Shop (WFPS)

Cleaning and finishing operations in the WFPS ensure wheels have a smooth surface for usage.
This process involves cleaning the wheels and removing dirt or any imperfections on the surface.
Apex grinding is used to trim excess material on the wheel parting line.
Cleaning is done by using a variety of cleaning techniques.

Magnaglo Testing

A non-destructive test conducted in a dark room.
Magnaglo powder using water as a suspension medium is applied to the wheel’s surface
A black light illuminates these particles making any flaws visible as bright points.
Cracks are highlighted and marked via radium chalk powder

Ultrasound Testing

Is a non-destructive testing method that detects interior flaws or imperfections within the wheel’s structure.
The process sends ultrasonic waves into the wheel and observes the reflection patterns. Any abnormalities will be indicated during this process
Detected defects or flaws are identified in the form of codes.

Warpage Testing

Measures and checks for warpage or bending of wheels to ensure that the wheels conform to the required specifications.
This is done following the casting and heat treatment processes and is done on cooled wheels.

Shot Peening

A cold working process that causes compressive stresses and improves surface hardness.

Hub Bore Machining

Enlarging the hub bore hole to fit the axle using a square-shaped carbide insert.

Cope and Drag Preparation

Cope and drag parts are sent for preparation after being split.
Cope and drag parts are cleaned through the use of high pressured air.
Cope parts are coated with resin and baked before additional sand blasting.
Fused silica powder is mixed with additives to create a mould spray, used as binder.
Different regions of the cope and drag assembly have different quantities of spray mixture based on their size (Example: Plate - 185ml, Hub - 125ml, Rim - 170ml).
Spraying process takes place when temperature is above 245°C.
The cope is sprayed, then the drag parts that conform to the desired standards are sent for further processing while those lacking standards are rejected.

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Description

Test your knowledge on foundry processes, including wheel warpage measurements, shot peening techniques, and the operation of electric arc furnaces. This quiz covers essential topics such as temperature controls and component functions critical to efficient melting and manufacturing in metal casting. Perfect for students and professionals in metallurgy and engineering.