Comparison of corrosive impact abrasion behavior between low carbon alloy steel and high manganese steel
The working conditions of the liners of the wet mill in metallurgical mines are harsh, and it is not only corroded by the pulp with strong pH but also worn by the ore and grinding balls. In addition, the ore and grinding balls that fall to a certain height also have a certain impact on the lining plate. At present, the main mill liners material used in China is still ZGMn13, but under this working condition, due to insufficient work hardening and poor corrosion resistance of high manganese steel, the service life of the lining is very short, generally 4-6 months. Although materials such as modified high manganese steel and medium carbon alloy steel have been developed at home and abroad in recent years, the effect is still unsatisfactory. On the other hand, the research on the corrosion and wear mechanism under impact conditions is rare, and this has positive significance for the development of high-quality lining materials. The impact corrosion and wear properties of the newly developed low-carbon high-alloy steel (for example, ASTM A335 P91 pipe) lining material were tested under simulated working conditions and compared with the current mainstream material of high-manganese steel for linings. Impact corrosion wear mechanism of a steel and its variation with time.
Comparison of two materials’ chemical composition and mechanical properties
|Material||Chemical Composition %||Mechanical Properties|
|Low Carbon Alloy Steel||0.15-0.3||–||7.0-10.0||1.5-2.0||0.7-1.0||0.3-0.6||≤0.035||≤0.035||48-51||＞50|
The impact corrosion and wear test was carried out on modified MDL-10 impact corrosion and wear testing machine, and the impact frequency of the testing machine was 200 times/mins. The sample to be tested is processed into a 10mm*10mm*30mm block by wire cutting method; it is installed on the ram, and it reciprocates up and down with the ram during the test. The slurry continuously enters the impact surface through the stirring device. From the current research on abrasives, testing with ores with a certain range of abrasive properties can effectively evaluate the wear resistance of materials, and the abrasives in industrial systems are mainly ores. On the contrary, the use of abrasives with too harsh characteristics may cause false impressions. Therefore, in this experiment, an iron ore acid slurry similar to the actual working condition was selected as the slurry, which was prepared with PH=3 sulfuric acid aqueous solution and 6-10 mesh iron ore. Considering the crushing and particle size changes of the ore and the weakening of acidity in the test, the wear behavior of the material may change greatly, so the ore is updated every 0.5 hours, and the pH value is adjusted at the same time. According to the characteristics of small-energy impact in the ball mill, we chose the impact energy as 2.7J and corrected the impact energy in time depending on the shortening of the sample during the test.
Before each test, the samples were cleaned with acetone in an ultrasonic cleaner, then dried immediately, and then weighed with an analytical balance with an accuracy of 0.00001 to obtain the initial mass W0, and then the samples were installed in the machine for impact corrosion and wear tests. The sample was worn for a total of 16 hours, during which the sample was cleaned and weighed every 2 hours, recorded as Wi (i=2, 4, 6…16), and the cumulative weight loss at each time point was calculated △Wi=W0 -Wi, the average value of △Wi of three samples was taken to measure the impact corrosion wear resistance of the material. Finally, Hitachi-X-650 was used to observe the surface morphology of impact corrosion wear, and Olympus PME optical microscope was used to observe the surface perpendicular to the wear resistance. The state changes of the surface layer and sub-surface layer of the surface were analyzed, and the mechanism of impact corrosion wear was analyzed.
Test Results and Analysis
Comparing the cumulative weight loss curves of the two steels with impact corrosion wear, it can be seen that with the prolongation of the impact corrosion wear time, the weight loss of the two steels increases continuously.
At the same time, the weight loss of low carbon and high alloy steel is always lower than that of high manganese steel, and this advantage becomes more and more obvious with the extension of time, indicating that the impact corrosion wear resistance of low carbon high alloy steel is significantly better than that of high manganese steel. High manganese steel. This result shows that the impact corrosion wear performance is a comprehensive index of the impact, corrosion and wear resistance of materials and the interaction of the three, rather than a single index can be determined. Relevant studies have shown that the interaction between corrosion and wear is much higher than the sum of their individual effects, and the ploughing pressure and cracks caused by the impact will greatly promote corrosion and wear. The lath martensite structure of low carbon and high alloy steel makes it have a good combination of hardness and toughness, while the single-phase matrix and high chromium content ensure its corrosion resistance. Although high manganese steel has high toughness, it has poor corrosion resistance, and low initial hardness, and is not conducive to impact wear after strong deformation and hardening, which leads to the decline of its overall impact corrosion wear performance.