Research On ERW Weld Performance Of The Dewatering Screen Made By The Work Hardening Material Of304Austenitic Stainless Steel

In coal industries the vibrating screen is often used to sieve, dewater, separatecoal, etc. Screening is one of the important process for washing coal，and sievingplate plays a very important role in it. The screen is one of the main components ofthe vibration screen, and it plays a very important role in the screening performanceand operating reliability of the vibration sieve. In coal washing operations, thevibrating screen is generally made of the non-magnetic304stainless steel toguarantee the life of screen and to prevent the magnetic adsorption washing mediuminfluence the washing effect. Under normal circumstances, the304stainless steelworks well because of its excellent plasticity, toughness and certain strength.However, in the working conditions of large impact, the screen is generally weldedwith the304stainless steel, which is by means of cold drawing process. The partialfracture problem of the screen shows in the working process because of theunreasonable weld microstructure and internal stress, leads to failure before anexpected life and affecting the normal operation of the coal washing seriously at thesame time. For this purpose, it’s of great practical significance to research themicrostructure and properties of the weld of dewatering screen formed by the colddrawing material of the304stainless steel,so as to improve the welding process andto increase the using life of the screen plate.In this paper, the mainly aspects of work are as the follows:(1) Research andanalyze the microstructure and properties of the original and cold drawn state of the304stainless steel wire;(2) Research and analyze the microstructure and properties ofwelding of the dewatering screen production retrieving from the working place;(3)According to the research results, improve the welding process parameters of colddrawing304stainless steel resistance welding;(4) Research the microstructure andproperties of the dewatering screen weld that has improved the welding parameters,and compare it with the one retrieved from the working place;(5) Make the heattreatment for the weld of the dewatering screen formed by the improving welding parameters, and test the performance of the weld with the heat treatment measure;(6)After the heat treatment, the vibrating screen product welded by improving process istested the performance in the working place.Having improved the welding process parameters, the micro-crack is observed inthe weld caused by the internal welding stress by researching the microstructure ofthe weld. Adopting the weld stress treatment is used in this experiment to reduce theinternal welding stress. Considering the production cost of the enterprise, the heattreatment of the screen is mainly under the low temperature. The heat treatmentmeasures are as follows: keeping the welded screen under the condition of260℃for2h,2.5h and3h; keeping the screen under the condition of330℃for2h,2.5h and3h;keeping the screen under the condition of385℃for2h,2.5h and3h. And thenmainly by means of XRD testing, microstructure observation, micro-hardness testing,corrosion resistance and fatigue performance testing for the screen and the heattreatment screen respectively.The test results show that the appropriate heat treatment for the dewateringscreen made by the work hardening material of the304stainless steel is kept at thetemperature of260℃for2.5h. Being used in the working place, the original life ofthe screen is from about1month up to about2months compared with the original.This measure has solved the problem of short time on working caused by the weldingstress. In the end, the dewatering screen is of heat treatment measure bring theeconomic benefits for the enterprise.