DJM Technical Introduction

    High manganese steel wear-resistant castings cast water toughening treatment process research

    High manganese steel wear-resistant castings cast water toughening treatment process research
    High manganese steel is a wear-resistant materials with good comprehensive performance, the high content of manganese, production methods are usually produce castings, re heating of water toughening treatment. As cast microstructure of austenite and carbide, 1000, 1100 Deg. C, heating, carbide all or most of the dissolved in austenite, water toughening treatment after get single-phase austenite or austenite plus a small amount of carbides, the tissue under the impact force, forming a large number of dislocations and deformation twins and mosaic defects, the bulk microstructure and deformation induced martensite, surface hardness 190HBS increased to around 50HRC, internal casting still has good toughness.
    High manganese steel casting is widely used in metallurgy, mining, cement, construction, electricity, chemical industry, such as impact wear consumables, annual consumption is very large, market competition is fierce. This paper through research and practice, the high manganese steel casting casting waste heat water toughening treatment craft, production to meet the performance requirements, less energy consumption, the cost is relatively low high manganese steel castings.
    1 chemical composition of high manganese steel and conventional heat treatment
    1.1 chemical composition of high manganese steel
    Using 250kg alkaline medium frequency induction furnace of high manganese steel, the main chemical components of W: 0.09% to 1.05% C; 11 ~ 12% ~ 0.8% Mn; 0.3% Si; 0.2% ~ 0.3% RE; S = 0.04%; P = 0.07%; Mn/C ratio should be controlled in 10. The content of casting hardening and impact in the case of impact toughness of impact wear. Practice shows that the shield, mining machinery tooth plate, lining board, partition plate castings, carbon content control in 0.90% ~ 1.05% range. The best appropriate increase of Mn content on Microstructure of single austenite stability (especially favorable under high temperature conditions), not only can inhibit carbide precipitation, growth in the cast, accelerate the process of cementite dissolving during heat treatment, and work hardening on the properties of materials have no obvious effect. The mass fraction of silicon in high manganese steel usually should not be less than 0.3%, and to prevent the high content of silicon The hazards of the material impact toughness, wear resistance decreased, usually the quality fraction of silicon control in 0.3% ~ 0.8% range. The phosphorus in high manganese steel is very harmful elements, the liquid steel with extremely low solubility, and often to phosphide films appear at the grain boundary, the casting prone to crack, especially the carbon content is high, exacerbated by phosphorus, so phosphorus should be strict control in less than 0.07%. Adding 0.2% ~ 0.3 of rare earth elements for modification, can refine the grain, improve the impact toughness.
    1.2 conventional water toughening process for high manganese steel
    About 1370 DEG C the liquidus temperature of high manganese steel ZGMn13-1, tapping temperature control in 1430 ~ 1480 DEG C, temperature control for casting in 1470 1420 ~ C. Liquid steel released to standing for a certain period of time, make the gas and inclusion floatation, improve the quality of the casting. Casting to carry loose box, about 400 DEG C play box, and the removal of the riser, flying edge. Finally, re heating of water toughening treatment. To lining board, for example, water toughening treatment process for: first phase insulation 700 ~ 750 DEG C, the second phase insulation 1050 ~ 1080 DEG C, heat preservation time 2 ~ 3H. Cooling medium for water (less than or equal to 40 DEG C).
    2 high manganese steel casting cast water toughening treatment
    High manganese steel castings in accordance with the normal process of casting solidification, 980 DEG C by residual heat of casting directly sand cleaning water toughening treatment, surface decarbonization of parts can be reduced, saving energy, shortening the production cycle, reduce the labor intensity, greatly reduce the production cost. Sand cleaning water toughening treatment of difficult problem of the control in casting time out of the box and into the water temperature.
    2.1 high manganese steel casting water toughening treatment process test
    The mining machinery of high manganese steel wear-resistant parts classification, after pouring time test, different holding out of the box inspection organization, performance.
    2.2 high manganese steel casting water toughening treatment analysis of microstructure and properties
    According to the experimental results, after pouring early out of the box (holding time too short) into the water, can guarantee to obtain homogeneous austenite, but easy to form crack, so that the parts become waste; out of the box for a long time (longer retention time), more carbides precipitated, the impact of the use of performance, especially the impact toughness decreases; moderate time out of the box, the microstructure is austenite. So under the premise of no crack formed early out of the box can ensure access to single austenite.
    Conventional water toughening treatment and casting waste heat water toughening treatment impact toughness compared, to production of high manganese steel ladder scaleboard, Xiaoping lining board sampling, for example, each state to take two sample impact toughness (JB-30A semi automatic impact test machine), finally take the average value.
    All kinds of lining board installed operation, high manganese steel lining board with small ladder, Xiaoping liner as an example, using life.
    2.3 high manganese steel casting water toughening treatment process optimization
    On the basis of the experiment, after continuous summary and improvement, the optimization of the process as shown in the table.
    3 economic benefits
    With conventional water toughening process for the production of high manganese steel wear-resistant castings cost about 7600 yuan /t. using waste heat of casting water toughening treatment, can reduce the cleaning process, save water qunch heating energy consumption and corresponding auxiliary processes, shorten the production cycle, reduce the heat treatment heating equipment put into production at the same time. Cost is greatly reduced. The preliminary estimate of water toughening treatment costs about 2.19 yuan /kg, saved 2190 yuan per T, the use of waste heat of casting water toughening production of high manganese steel casting is the cost of conventional water toughening treatment method 70%, reduce the production cost of about 30%. at the same time, this method reduces the number of parts of the oxidation, decarburization, improved casting the quality, simplifies the production process, reduces the labor intensity of workers, greatly improving the economic benefits of these products have obvious advantages in market competition.
    4 conclusions
    (1) the production practice shows that the mining machinery wear resistance of high manganese steel casting cast water toughening treatment process is feasible.
    (2) according to the category and size of the parts, high manganese steel castings cast state water toughening treatment process parameters are accurate and reliable, operation, so as to solve the inlet water temperature is not easy to control problem of influencing the quality of castings.
    (3) using casting waste heat for water treatment production cycle is short, save energy, greatly reduce the cost of production, there is a very clear market competitive advantage.

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