DEPARTMENT OF AUTOMOBILE ENGINEERING

18AU206 – MANUFATUIRNG PROCESSES I

Lecture : 05

Unit I : CASTING

Topic : Cleaning of castings, Inspection methods

Prepared By
Dhayaneethi S
CLEANING & INSPECTION
 CLEANING & INSPECTION

Prerequisite Knowledge:

 Sand Mould

General Objective (GO):

To analyze the cleaning process and inspection methods of casting.

Specific Objectives (SO):

SO1 To infer the working principle of various inspection methods in casting. (U) (C) (S)

SO2 To select the suitable cleaning process based on the requirement. (Ap) (C) (T)

SO3 To compare the different types of inspection method based on their working principle. (An) (C) (T)
 CLEANING OF CASTINGS
Casting Cleaning :
The final stage of casting process is cleaning. The process refers to different activities that are performed to
remove the sand, scale and excess metal from the casting.

Some of the activities performed in cleaning are:

The casting is separated from the mold and transported to the cleaning department.
Burned-on sand and scale are removed.
Excess metal is removed (Fins, wires, parting line fins, and gates).
Subsequently the casting can be upgraded using welding or other such as procedures.
Final testing and inspection to check for any defects.

Advantages:
Improves the surface appearance and finish of casting
Improves overall quality and functionality by removing impurities, such as sand, scale and excess metal
Finally the sand from the mold is separated and processed through a reclamation system for further use.
 INSPECTION METHODS OF CASTING

Two basic objectives of inspection are

(i) To reject castings that fail to meet the customer's requirements

(ii) To serve as a means of maintaining the quality of workmanship and materials used in the foundry.

1. Visual inspection

2. Mechanical testing

3. Non-destructive methods

4. Metallurgical inspection
 VISUAL INSPECTION

 Common defects such as surface roughness, obvious shifts, the omission of cores and surface cracks can

be detected by a visual inspection of the casting. Cracks may also be detected by hitting the casting with a

mallet and listening to the quality of the tone produced.

 MECHANICAL TESTING

HARDNESS TEST TENSILE TEST IMPACT TEST

 DPT

 Dye penetrant testing is used to detect the presence of surface cracks in components.

 The ideology to detect these cracks is by means of a dye usually highly colorful and less viscous that enables

it to penetrate into cracks in the surfaces. This happens mainly due to the capillary action.

 The dye tends to remain inside the crack, which is made to surface out by the use of appropriate chemicals

thus indicating the size and structure of the crack.

 DPT

Steps:
Required Materials:
Pre Cleaning

Cleaner Penetrant Application

Penetrant Removal
Penetrant
Developing

Developer
Inspection
 DPT

Applications:

 The dye penetrant testing is applicable in all areas where the surface finish tends to be quite good.

 For checking of cracks in roll formed sections

 Surface crack detection in railway rails

 Crack detection in gear teeth

 Detection of cracks in welding’s particularly in boiler weldings for detection of surface cracks.

 Detection of surface cracks caused by high speed grinding

 DPT

Advantages:

 Very low cost method for determination of surface cracks.

 Portable kit enables easy carrying of the kit

 Instant results can be obtained by the user and no highly trained personal required to interpret results

Disadvantages:

 Only surface cracks can be detected. Any cracks below the surface or sub surface cracks cannot be detected

 Method works well only for surfaces that are machined or polished. Irregular or very rough surfaces tend to

provide false results.

 MPT

 Magnetic particle examination (MT) can be a useful nondestructive exam method during new constructution
or in-service inspections. For quick, low-cost inspections, MT is often the best NDE method for detecting
surface and slightly subsurface discontinuties.
 MPT

 The following visual illustrates steps of dry powder, nonfluroescent, yoke technique of Magnetic

Particle testing.

A. The surface to be examined is cleaned using ultrasonic cleaning methods

B. A magnetic field is introduced into the part

C. Ferromagnetic medium is applied while the part is still magnetized

D. Excess ferromagnetic medium is removed with a light air stream from a bulb, syringe, or other source of

low pressure dry air

E. Indications are interpreted and evaluated to the applicable accpetance standards

F. The yoke is turned 90 degrees from the original position and steps B - F are repeated.
 MPT

Advantages:

•It is quick and relatively uncomplicated

•It gives immediate indications of defects

•It shows surface and near surface defects, and these are the most serious ones as they concentrate stresses

•The method can be adapted for site or workshop use

•It is inexpensive compared to radiography

•Large or small objects can be examined

•Elaborate pre-cleaning is not necessary

 MPT

Disadvantages

• It is restricted to ferromagnetic materials - usually iron and steel, and cannot be used on austenitic stainless

steel

• Most methods need a supply of electricity

• It is sometimes unclear whether the magnetic field is sufficiently strong to give good indications

• The method cannot be used if a thick paint coating is present

• Spurious, or non-relevant indications, are probable, and thus interpretation is a skilled task
 RADIOGRAPHIC TESTING

 In radiographic testing, the part to be inspected is placed between the radiation source and a piece of
radiation sensitive film.

 The radiation source can either be an X ray machine or a radioactive source (Ir-192, Co-60).

 The part will stop some of the radiation where thicker and more dense areas will stop more of the radiation.

 The radiation that passes through the part will expose the film and forms a shadowgraph of the part.

 The film darkness (density) will vary with the amount of radiation reaching the film through the test object
where darker areas indicate more exposure (higher radiation intensity) and liter areas indicate less
exposure (higher radiation intensity).

 This variation in the image darkness can be used to determine thickness or composition of material and
would also reveal the presence of any flaws or discontinuities inside the material.
 RADIOGRAPHIC TESTING

Advantages:

 Both surface and internal discontinuities can be detected.

 Significant variations in composition can be detected.

 It has a very few material limitations.

 Can be used for inspecting hidden areas

 Very minimal or no part preparation is required.

 Permanent test record is obtained.

 Good portability especially for gamma-ray sources.

 RADIOGRAPHIC TESTING

Disadvantages:

 Hazardous to operators and other nearby personnel.

 High degree of skill and experience is required for exposure and interpretation.

 The equipment is relatively expensive (especially for x-ray sources).

 The process is generally slow.

 Highly directional (sensitive to flaw orientation).

 Depth of discontinuity is not indicated. It requires a two-sided access to the component

 ULTRASONIC TESTING
 Ultrasonic Testing (UT) uses high frequency sound waves (typically in the range between 0.5 and 15 MHz) to

conduct examinations and make measurements. Besides its wide use in engineering applications (such as

flaw detection/evaluation, dimensional measurements, material characterization, etc.), ultrasonics are also

used in the medical field (such as sonography, therapeutic ultrasound, etc.).

 In general, ultrasonic testing is based on the capture and quantification of either the reflected waves (pulse-

echo) or the transmitted waves (through-transmission).

 Each of the two types is used in certain applications, but generally, pulse echo systems are more useful since

they require one-sided access to the object being inspected. Basic Principles A typical pulse-echo UT

inspection system consists of several functional units, such as the pulser/receiver, transducer, and a display

device.
ULTRASONIC TESTING
 ULTRASONIC TESTING
 A pulser/receiver is an electronic device that can produce high voltage electrical pulses.

 Driven by the pulser, the transducer generates high frequency ultrasonic energy.

 The sound energy is introduced and propagates through the materials in the form of waves.

 When there is a discontinuity (such as a crack) in the wave path, part of the energy will be reflected back from

the flaw surface.

 The reflected wave signal is transformed into an electrical signal by the transducer and is displayed on a screen.

 Knowing the velocity of the waves, travel time can be directly related to the distance that the signal traveled.

From the signal, information about the reflector location, size, orientation and other features can sometimes be

gained.
 ULTRASONIC TESTING

Advantages:

It is sensitive to both surface and subsurface discontinuities.

The depth of penetration for flaw detection or measurement is superior to other NDT methods.

It is highly accurate in determining reflector position and estimating size and shape.

Minimal part preparation is required.

It provides instantaneous results.

Detailed images can be produced with automated systems.

It is nonhazardous to operators or nearby personnel and does not affect the material being tested.
 ULTRASONIC TESTING

Disadvantages:

 Surface must be accessible to transmit ultrasound.

 Skill and training is more extensive than with some other methods.

 It normally requires a coupling medium to promote the transfer of sound energy into the test specimen.

 Materials that are rough, irregular in shape, very small, exceptionally thin or not homogeneous are difficult
to inspect.

 Cast iron and other coarse grained materials are difficult to inspect due to low sound transmission and high
signal noise.

 Linear defects oriented parallel to the sound beam may go undetected.

 Reference standards are required for both equipment calibration and the characterization of flaws.
 MIND MAP

Cleaning Process

CASTING
MIND MAP