Cooling in grind-hardening operations

Original Article

Abstract

The grind hardening process utilizes the heat dissipation in the grinding area for inducing metallurgical transformation on the surface of the ground workpiece. The workpiece surface is selectively heated above the austenitisation temperature and subsequently is self-quenched so as to achieve the anticipated surface hardening. In order for self-quenching to occur sufficient material mass must be present to conduct the heat away from the surface. However, in the case of grind-hardening of thin workpieces or cylindrical workpieces of small diameter, the quenching has to be assisted with the application of coolant fluid. In this paper, the utilization of the coolant fluid for the grind-hardening of small diameter cylindrical parts is investigated. The rapid heating of the workpiece and the short austenitising time are taken into consideration both for the estimation of the hardness profile and the hardness penetration depth (HPD). A finite element analysis (FEA) model is developed for this specific case and its predictions are verified experimentally.

Keywords

Grinding Grind-hardening Heat treatment process Process modeling Surface hardening 

Abbreviations

HPD

Hardness penetration depth

FEA

Finite element analysis

CCT

Continuous cooling temperature

Nomenclature

Ac

Austenitising temperature (°C)

ae

Depth of cut (m)

b

Grinding wheel width (m)

C

Specific heat (J/kgK)

d

Diameter (m)

f

Martensite transformation fraction (-)

h

Heat transfer coefficient (W/m2K)

HPD

Hardness penetration depth (mm)

HV

Hardness in Vickers

k

thermal conductivity (W/mK)

lg

Geometric contact length (m)

Ms

Temperature at which transformation from martensite to austenite begins (°C)

q

Heat flux (W/mm2)

Qw

Heat rate entering the workpiece (W)

r

Cylindrical coordinates (m)

rw

Workpiece radius (m)

T

Temperature (°C)

t

Time (s)

u

Speed (m/s)

Greek letters and symbols

θ

Cylindrical coordinate (rad)

ρ

Density (kg/m3)

ω

Rotational speed (rad/s)

Subscripts

a

Air

f

Fluid

w

Workpiece

o

Ambient and initial

c

Coolant

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Copyright information

© Springer-Verlag London Limited 2006

Authors and Affiliations

  1. 1.Laboratory for Manufacturing Systems and Automation, Department of Mechanical Engineering and AeronauticsUniversity of PatrasPatrasGreece

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