Study On The Technology Of Wear Resistant Of Wheat Mill Rollers Based On Laser Quenching

Mill is important processing equipment in wheat milling industry,rollers are the key components of mill,and in the working process of the mill,severe friction occurs between roller and wheat powder,wear occurs on the surface of rollers,when the roller wear reach a certain degree,the productivity and milling rate of mill decrease significantly,and sandblasting or wire drawing processing need to be carried out for the roller surface.It can be seen that the wear of roller has a obvious influence on the working performance of the mill,and the wear reduction technology research of mill roller is important subject in wheat milling industry.Laser quenching technology is the process of rapidly heating the surface of the work-piece by using laser beam to make phase change and form the martensite,it is the surface heat treatment process which strengthened the hardness of the metal material.Since the wear failure of mill roller is mainly the result of abrasive wear and surface fatigue wear,the strengthening of hardness and wear of the roller surface material could be reduced by using the laser quenching technology.In this paper,the laser quenching test was carried out in the surface material of the mill roller,using the principle of Central Composite Design of response surface,the test of laser power,spot diameter,scanning speed and surface hardness of mill roller material was completed according to the three-factor five-level test method,laser power,scanning speed and the spot diameter optimal combination between the three factors were analyzed,the influence of the interaction between various factors and factors on the surface hardness of the mill roller was also explored,the samples with different heat treatment(such as the original samples without heated treatment,the samples with normal heat treatment and the samples with laser quenching)were compared,and the wear mechanism of the mill roller after laser quenching was analyzed.The main research results are as follows:1.The tests of laser power,spot diameter,scanning speed and response values of surface hardness were completed by using the Central Composite Design of response surface,the influence of laser power,scanning speed,spot diameter and the interaction between factors were analyzed by applying the variance analysis method.The order of three factors on the significance of the hardness is laser power,spot diameter and scanning speed;the interaction of laser power and scanning speed on thehardness is more significant while the interaction between other factors are not significant,and optimal combination of process parameters is laser power 190 w,spot diameter 0.70 mm and scanning speed 220mm/s,the hardness obtained under this parameter combination is 689 HV.2.The wear properties of the samples with the optimal combination of laser quenching process parameters were analyzed and compared with the normal heat treatment samples in the earlier stage of the research group,the following results were obtained: the quality loss of normal heat treatment sample by 960? with 1h air quenching and 250? with 2h tempering is about 42% of untreated sample,the quality loss of the laser-hardened sample is about 17% of normal heat-treated sample;and the wear rate of laser quenching sample is about 16% of normal heat treatment sample;the hardness of the laser quenching sample is 1.35 times to that of normal heat treatment sample;the laser quenching resulted in the refinement of the internal tissue grain of the sample,a large number of martensite were formed and a small amount of austenite remaining;the content of C and other non-metallic element of samples is increased with ordinary heat treatment and laser quenching while the content of metal element such as Fe is reduced;the contact angle of the original sample is 62.9 degrees,and the contact angle of the sample with laser quenching is 68.05 degrees,the increase of contact angle improves the wear performance of the material surface.3.Laser quenching treatment can effectively reduce the friction between wheat powder and samples,plastic deformation is reduced,fatigue damage occurs on the surface of the samples,the wear cycle of the material is improved,and the service life of the mill roller is extended;and the wear mechanism of the roller is the brittle fracture of surface material due to the plastic reinforcement and plastic exhaustion,which is separated from the surface of roller.