Appication
of Medium Frequency Hardening in Slewing Bearing
As the component parts of
construction machinery,slewing bearing is mainly used in tower
crane,crane,excavator and port machinery. Because of the specificity in
composition,the quality impact the usage efficiency of host directly.
Slewing bearing ‘s ife time depends on the quality of
medium frequency hardening,and the inner quality depends on the depth of
hardening zone, shape distribution,hardness,crack condition, hardening
organization and other aspects,so we control the hardening quality by sensor,
sprinkler,heat temperature and hardening liquid.
1.
processing and technical
requirements
Slewing bearing processing:
Rough lathing - Finish lathing
-Hardening-Drilling-Grinding- Assembly
Technical requirements:
Depth of hardening zone:3-5mm, hardness:55-62HRC,no crack.
The chemical composition of the material
|
No
|
The chemical
composition %
|
|
C
|
Si
|
Mn
|
Mo
|
Cr
|
Ni
|
S
|
P
|
Cu
|
|
42CrMo
|
0.38~0.45
|
0.17~0.37
|
0.50~0.80
|
0.15~0.25
|
0.90~1.2
|
≤0.30
|
≤0.035
|
≤0.035
|
≤0.30
|
|
50Mn
|
0.48~0.56
|
0.17~0.37
|
0.70~1.00
|
---
|
≤0.25
|
≤0.25
|
≤0.035
|
≤0.035
|
≤0.25
|
|
Note: The chemical
composition of the other material must obey the standard set by the country,
the allowed dispersion of the chemical composition must accord to the
provision of GB222
|
2. Establish of induction hardening
1) Characteristic of induction heating
The induction heating uses the
principle of electromagnetic induction, create the induced current in the
working surface,means forming the turbulent flow.
2) Confirmation of induction hardening
technical data
Medium Frequency Hardening process include:
confirming hardening temperature,pre-cold time, density of
hardening liquid and so on.
l
Hardening heat time
Induction heat means quick heat, the temperature is more
higher than normal hardening heat.
l
Heating temperature is closely
related to the steel's original organization . The more thin , the more easier
phase transition occurs in heating. . Therefore, the heating temperature can be
appropriately reduced .
l
the majority of rough materials
used in factory is in pre-modulated modulation and normalizing state ,quenching
temperature can be lower .As to the 50Mn and 42CrMo material , quenching
temperature should be 900-950 degrees .
l Pre-cooling time
the purpose of pre-cooling is to
reduce quenching deformation, stop quenching cracks .
l
Cooling
The way of
cooling shoud be linked to the workpiece material, heating method and depth of
hardened layer.
l
Tempering
Slewing bearing hardening will do rapid heating and cooling
to partial surface of the workpiece, leading to large thermal stress and
organizational stress . After the completion of organizational changes, form
into higher residual stress. So, must be done low temperature tempering in
order to eliminate part of the stress.
2.
Technology application
Technology application above is also used in different size rolling or
different material but basically same carbon content, hardenability slewing
bearing . Detection after quenching , the test results can basically meet the
technical requirements.
JIANGSU TEYO SLEWING BEARING CO., LTD.