Maintenance, Meccanica, Pelleting
Nov 7, 2015
La Meccanica
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Study on Different treatment and its effects on roller shells

Study on Different treatment and its effects on roller shells

  1. Sample

This test use two roller shells with outside diameters around 300mm. Material in C50.

Treated in two different ways.

  1. Heat up method.

1-1 Heated up the shell in oven with gas protected environment. Then drop down to quenching liquid. We call it complete heated up.

1-2 Heat up the shell by using induction ring. Middle frequency. Spry the quenching liquid on to the shell.

  1. Microstructure checking After hardening cut both test shells. And check the microstructures.

Complete heated up

Figure 1 Micro-structure of Complete heated up

Induction heated

 

Figure 2 Micro-structure of induction heated

 

From the micro-structure difference, we can see, the “Complete heated up” method, leads to more martensitic transformed structure. While, the induction heated leads more fine structure.

 

  1. Hardness Test

On both shells, we made test from shell surface till 16mm deep on a cross cutted surface.

The result shows in the following:

Test Result from „Complete heated up“ shell

Test points

01   02    03    04     05    06    07    08    09    10

Distance to the surface (mm)

0    1.3    2.9    4.5    6.4    8.5    10    12    14    16

Hardness (HRc)

63    63    63    63     61     46     41    32    31    31

 

Test Result from Induction heated up shell

Test points

01    02    03    04    05    06    07    08

Distance to the surface (mm)

0     1.3    2.9    5.0  6.4   8.5    10    12

Hardness (HRc)

63    60   58     57    56    54     52     46

 

  1. Discussion

The hardness test result and micro-structure are matching.

5-1 Completed heated up treatment, with more time in keeping high temperature. The quenching is more deep, and leads more martensitic transformed structures, the surface hardness until 6.4mm still with HRc=61. But then the hardness dropped down sharply. To 10mm deep, which is only HRc=41. and further to 12mm, which dropped down to HRc=32. as basic hardness of the material.

5-2 Induction heated up with short time in heating, which leads more fine structure. The quenching through is not as deep as the complete heated up method. Because we can see the hardness obviously dropped down start with deep. To the application deep 6.4mm, which with HRc=56. However, the hardness effected deep is more then the complete heated up shell. As down to 10mm deep the hardness still have HRc=52.

5-3 Both treatment method can have same surface hardness HRc=62-64. But the wear resistance are different. If the shells are used for only 7mm deep, (as the eccentric shaft with only 7mm for adjustment). The complete heated up treated shells with better working result.

5-4 Now in the treatment factory use both way of heated up. By the limit of power of the equipment, and depend on different diameters, they can do induction heating only do with outside diameter upto 300mm. But for complete heating up in oven, have no limit.

5-5 Advantages and disadvantages

Complete heating up treatment with more unique surface hardness. From the result, we can see which from top surface until 6,4mm will have more than HRc=60. After normal application for 7mm, the hardness dropped down sharply. While the induction heating treated shells will have more deep hardness treatment effects. Which can reach even 8,5mm deep still have hardness HRc=54. It will be good for clients which use the shells until 8 to 9mm. The complete heating up treatment with more martensitic transformed structure, on deep about 7mm, and soft core. But as complete heated up, will have more treatment stress left in the shells which might cause surface cracks, if the after quenching stress release is not enough.

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