Souvik Das

Failure Analysis of Motor Tire Bead Wires During Torsion Test

Torsion testing is used to determine the quality of steel wire used for motor tire beads in pneumatic tires. These steel wires must have good-tensile strength so that the tire bead can support the finished tire safely, and yet retain adequate ductility to deform easily around the forming wheel. The present paper highlights premature failure of bead wire which failed during torsion test. Torsion property is one of the important parameters of tire bead as it monitors both the metallurgical soundness and surface quality of a drawn wire. From the analysis, it has been concluded that probable reason for premature failure is due to strain aging (dynamic and static) caused by interstitial atoms which bounds the mobile dislocations resulting in increases yield strength and decreases bead formability. Moreover, the microstructural study indicates that failed specimen has misaligned and broken lamella of pearlite with globular cementite which creates the array of voids. These voids hinder the rotation of pearlite during torsion test thus leading to brittle fracture.

Metallurgical investigation of wire breakage of tyre bead grade.

Highlights • Tyre bead grade wire is used for tyre making application.• During tyre making operation at tyre manufacturer company, wire failed frequently in brittle mode.• Crow feet like defects including button like surface abnormalities were also observed.• The analysis revealed that, surface martensite was formed and it caused the final breakage.

Pinch Roller Failure Analysis and Resulting Enhancement of Rebar Mechanical Properties

Reinforcing bars, popularly termed “rebars,” are used to impart tensile strength to concrete structures. Concrete has high resistance to weathering and fire and high compressive strength but almost no tensile strength, hence rebars are used to provide the latter to concrete. Property consistency along the length of rebars is an important prerequisite. When the finished product is subjected to thermomechanical treatment (TMT), proper control of rolling and water box parameters and efficient pinch rolling are needed to achieve acceptable properties. Variation of yield strength (YS) along TMT bars from the front to back end has been observed within the same heat treatment. In the presented investigation, it was observed that pinch rolling ineffectiveness is the main reason for the poor mechanical properties at the back end. The pinch roller was unable to support the back end of the TMT bars properly to maintain the speed and tension of the bars, resulting in nonuniform cooling of the back end through the water box and subsequent mechanical property failure. Due to the substandard material of the pinch roller, it was unable to hold the back end of the bar properly. Based on analysis of the roller it was concluded that it failed due to improper microstructure, resulting in inadequate hardness and toughness for the stringent operating conditions. AISI H13 is a better material to use in such high-service-temperature conditions. Moreover, proper heat treatment is needed to achieve adequate hardness and microstructure properties. After proper heat treatment of pinch rollers, their service life was increased twofold, minimizing the YS variation along the rebars.

Prevention of In-Service Failure of Seal Valve Axles of Blast Furnace Through Non-destructive Condition Monitoring

The upper and lower seal valves together form a key part in the top charging system of blast furnaces. The valves serve to create a gas-tight chamber during the charging of furnaces preventing the escape of blast furnace gas into the atmosphere during the operation. The axles in these valves are an integral part in the sealing mechanism of the valve flaps. Several accounts of failure of these axles in service at a Blast Furnace prompted the need for a predictive maintenance practice. This paper accounts for the failure analysis done on these axles to arrive at the root cause of failure and further the implementation of suitable NDT techniques for condition monitoring of the axles. This ultimately led to prevention of further in-service failures.