23-08-2012, 02:43 PM
Application of thermovision method to welding thermal cycle analysis
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Abstract
Purpose: of this paper is to determine the possibility of of thermovision method application in the thermal cycle of Inconel 625 on 13CrMo4-5 steel pad welding thermal cycle analysis.
Design/methodology/approach: Single- and multibead pad welding of steel 13CrMo4-5 by superalloy Inconel 625 has been carried out by means of GMA method in inert gas backing shielding, in horizontal position and 620 J/mm and 2100 J/mm heat input level. Quantitative data concerning infrared radiation emission as a basis for evaluation of thermal history of the applied object in order to assist interpretation changes occurring in padding welds and heat-affected have been obtained on the grounds of infrared radiation measurement by means of Flir Systems ThermaCAM SC2000 PAL infrared camera.
Findings: As a result of the performed inspection, temperature distribution in the weld made by heat input energy E = 2100 J/mm; of cooling, both cooling curves of padding welds and HAZ during single- and multi sequence pad welding have been determined and also single bead self-cooling time and durability time during single bead pad welding.
Practical implications: The full suitability of thermovision analysis of thermal cycle of pad welding. Specified self-cooling times will become a base for inference about microstructural transforms in HAZ, whereas cooling rate settlement determines necessary conditions to maintaining required intersequence temperature for assumed heat level input of pad welding, padding weld temperature in self-cooling time function and particular.
Originality/value: The thermovision effect and thermal cycle of Inconel 625 on 13CrMo4 -5 steel pad welding thermal cycle analysis has been no yet determined.
Introduction
Indirect investigations of temperature by infrared method depend on measurement infrared radiation emitted by applied object. The detection circuit of system transforms this radiation into electric signal, which is the source of information about the temperature of the object. To determine the fields and temperature values a thermometric diagram stored in the memory of the measuring device is used. Apart from infrared radiation emitted by the applied object, the detective structure records also the radiation of the environment reflected on the surface of the applied object, self-radiation emitted between the lens and the applied object as well as radiation of the internal parts of the camera which also reaches the radiation detector. Distribution of spectral concentration of radiation power depends on measurement conditions, which consist of dustiness, humidity, pressure and emission of objects. Taking into consideration all the factors that have an influence upon measurement values, infrared camera requires calibration on true object.
Conclusion
The conducted investigation of Inconel 625 superalloy on
13CrMo4-5 steel pad welding thermal cycle has shown a full
suitability of thermovision engineering in thermal cycle of pad
welding analysis.
Specified self-cooling times will become a base for inference
about microstructural changes in HAZ, whereas cooling rate
settlement determines necessary conditions to maintaining
required intersequence temperature for assumed heat level input
of pad welding.
The applied method can be characterized by great versatility
and it enables estimation of linear, flat and spatial temperature
distribution in the following welding sequence; it also enables
intersequence temperature control of t8-5 time or other
characteristic times regarding temperature range of phase changes
and separation processes in non-ferrous alloys. Moreover, it
enables estimation of breaks from welding - necessary in
maintaining assumed intersequence temperature as well as
versatile analysis of padding weld thermal course (history) in a
very wide range of temperatures. Restrictions to application of
thermovision method to thermal cycle analysis can be a low
availability of thermovision systems due to high prices of this
plant.