TATA Metaliks DI Pipes
Hot Zone Project (Summer Internship)
for
Maulana Abul Kalam Azad University of Technology
Future Institute of Engineering and Management
by
Shayan Nandy
Sayontan Chandra
MAKAUT Roll No:- 14800715049 MAKAUT Roll No:- 14800715048ACKNOWLEDGEMENT
We,
Shayan
Nandy
and
Sayontan
Chandra
underwent a
training at TATA
1.
Abstract-At TATA Metaliks DI Pipes Division, the process of making ductile iron (DI) pipes has been divided into two zones:
Hot Zone Cold Zone
The two zones have very different nature of work. While in the hot zone the raw molten metals are given the shape of a pipe, in the cold zone the newly casted pipes are given the finishing it requires for longevity, durability and better properties for greater range of applications. Foundry industries suffer from poor quality and productivity due to involvement of a number of process parameters. Even in completely controlled process, defect in casting are observed and hence casting process is also known as process of uncertainty which challenges explanation about the cause of casting defects. In order to identify the casting defect and problem related to casting, the study is aimed in the research work. This will be beneficial in enhancing the yield of casting. Beside this, standardization (optimization) of process parameter for entire cycle of manufacturing of the critical part is intended in the proposed work. This study aims to finding different defects in casting, analysis of defect and providing their remedies with their causes. In this paper an attempt has been made to list different types of casting defects and their root causes of occurrence. This paper also aims to provide correct guideline to quality control department to find casting defects and will help them to analyse defects which are not desired.
2. Introduction:
control the process parameter to achieve zero defect parts. For controlling process parameters one must have knowledge about effect of process parameter on casting and their influence on defects. To obtain this all knowledge about casting defect, their causes, and defect remedies one has to be analyse casting defects. Casting defect analysis is the process of finding root causes of occurrence of defects in the rejection of casting and taking necessary step to reduce the defects and to improve the casting yield. In this review project an attempt has been made to provide all casting related defect with their causes and remedies often seen in the DI pipes industry.
During the process of casting there is always a chance that defect will occur. Minor defects may be adjusted easily, but high rejected rates could lead to significant change at high cost. Therefore, it is essential for the die caster to have knowledge on the type of defect and be able to identify the exact root cause and their remedies.
3. Processes in the hot zone
The Pig Iron is received at the DI Pipes plant in the molten form. This pig iron now has to be chemically converted to ductile iron. Here the first step is the mini blast furnace(MBF).
3.1. MBF:
The molten pig iron received is first put in the mini blast furnace to boost up the temperature to 1500˚C, as the temperature of the molten metal reduces during the transfer. From here a small sample is taken to the Quality Control of a quality check. The compositions of a few samples are as:
Batch C Si Mn P S Mg Ti Cr
MBF-02(A-output as given in the table below is to be achieved.
treatment is necessary to promote the formation of nodule-like structures. This treatment is done according to GF process. Then samples are again tested for the desired quality, as given
Batch C Si Mn P S Mg Ti Cr transferred by the help of trolleys and cranes to fixed ladles just over the Centrifugal Casting Machines.
3.5. Centrifugal Casting Machine:
3.6. The newly casted pipes are taken to the gantry, and it waits in line to undergo the annealing process in the chamber.
3.7. Annealing:
The annealing process is a heat treatment process to improve the mechanical properties of the metal. The newly casted pipes are very brittle, so to increase the ductility and to reduce the brittleness this process is done. The metal is heated to a temperature above the crystallisation temperature and is then allowed to cool down. This changes the mechanical properties. Here at TATA Metaliks DI Pipes, there is a 60m Annealing Chamber, and is divided into 4 parts namely, Heating Zone, Holding Zone, Cooling Zone and Slow Cooling Zone. In slow cooling zone the quenching medium is water, and in slow cooling zone the quenching medium is air.
With this the Hot Zone Processes are concluded and the pipes get transferred over to the cold zone for further processing.
4.
Casting Rejections:
The several casting defects occurring during the process of centrifugal casting of the pipes ultimately leads to the rejections of the pipe, further decreasing productivity of the plant. If the defects are known and the causes identified, then these rejections can be brought to minimum, thus profiting the organization.
4.1. Defect- Rough Surface
Definition
- ‘Rough surface’ is basically a large cold shut.Causes
- Caused when two metal streams do not come close and fuse together. This may happen due to vibrations in runner during casting. Adjust proper pouring temperature Modifying design
Modifying gating system.
4.2. Defect- Bend
Definition
- In a pipe, when the deviation from a straight line in mm is more than 1.25 times of length in meters then the pipe is said to be ‘Bend’.Causes
-a. The hanging portions (socket side and spigot side) of red hot pipes lying on the casting gantry will undergo plastic deformation and bend.
b. If annealing furnace temperature is too high or pipe is held for too long inside the furnace the pipes of smaller diameter will deform and bend.
Remedies-
The causes must be kept in mind and then operation must be carried.Definition
- A swelling of thin loose layer of metal (loose skin) on the pipe’s external surface is termed as ‘Blister’.Cause
- Entrapment of excess Ferro silicon powder between two layers of metal results in the formation of blisters.Note*- Blister is generally observed in the socket portion of pipes.
4.4. Defect-
Burst
Definition
- A pipe ‘Burst’ happens if a portion of the pipe breaks open under pressure during hydro testing or site operation.Causes
-a. Thin wall of pipe.
b. Microstructure failure.
c. Excessive clamping pressure of HPTM. d. Presence of slag or runner metal.
4.5. Defect- Cold Shut
Definition
- ‘Cold Shut’ are shallow voids on the pipe’s surface caused when two fronts of liquid metal do not fuse properly in the mould leaving an empty space.-a. Low temperature of molten metal. b. Low temperature of mould.
4.6. Defect- Core Burst
Definition
- Defective formation or shape of socket caused due to cracking or breakage of core during casting is termed as ‘Core Burst’.Cause
-a. Low strength of core.
b. Force of falling metal from trough breaking the core when casting point is less.
c. Defective core seating area.
d. Improper loading of core on the mould due to misalignment of core loader.
4.7. Defect- Drawn Body
Definition
- Circumferential hot crack on the barrel of pipeis termed as ‘Drawn Body’.
Causes
-a. Low temperature of molten metal, so metal layers do not fuse properly.
c. Pipe extracted before proper cooling down. d. Less chute powder.
4.8. Defect- Drawn Spigot
Definition
- Circumferential hot crack on the spigot side ofthe pipe is termed as ‘Drawn Spigot’.
Causes
-a. Low temperature of molten metal, so metal layers do not fuse properly.
b. High temperature of molten metal, so the pipe formed is torn while extracting (not solidified adequately).
c. Pipe extracted before proper cooling down. d. Less chute powder.
4.9. Defect- High DE
Definition
- When the average outer diameter of a pipe’sspigot end is more than the specified value, it is termed as ‘High DE’.
Causes
-a. Use of old mould with high internal diameter. b. Use of less than needed ULI powder.
Note- DE is the acronym of External Diameter.
