DJM Technical Introduction

    Casting of high manganese steel casting with V method

    Casting of high manganese steel casting with V method
    1 the necessity of choosing V method for casting process:
    1) we look at the old craft of water glass sand, the production of the rough surface of the castings and the whole
    2) using V method to produce the casting blank, the surface and do not clear the whole cooling after the comparison.
    3) comparison of production of high manganese steel casting production technology and molding sand for several
    2 casting crystallization of the more fine strength, the higher the microstructure, the performance of the decision, which is a famous casting industry
    In this regard, technical personnel to produce wear-resistant high manganese steel casting should be engraved. Wear resistance of high manganese steel casting required the most basic mechanical properties, high strength, high hardness and impact toughness and hardness for proper matching material, both hard and tough; the impact of surface hardening, and the intrinsic performance, compact structure we must make the casting, fine grain size and uniform distribution. So, how to get the product wear structure with excellent casting process produced by V? V method casting and the most prominent is the dry sand filling mould under the condition of negative pressure casting cooling and cooling slowly disappear die, so far the crystal grains of castings than the sand casting casting coarse grain, tissue density is low especially high manganese steel alloy wear resistant casting life significantly reduced, to the domestic and foreign EPC production has brought great The problem won't advance innovation. I think these problems are determined by the law of metal crystallization, can only use artificial means to change the conditions of crystallization of solving these problems. To change the production characteristics of metal crystal. At least from the following three aspects: 1, with the reasonable design process of gating system respectively play their respective roles; 2, reducing pouring temperature; 3, to create good conditions for improving heat conduction cooling rate; 4, the clever use of flexible cold iron and pouring disturbance (vibration casting), the key is to make the liquidus temperature and stirring rapid cooling crystallization of the supercooled metal change of grain refinement, its purpose is to improve the mechanical performance and the physical properties. The scientific use of disturbance (vibration) influence on crystallization are favorable.
    3 good thermal conductivity
    The merits of casting solidification process is an exothermic process. In this process, mold heat performance good or bad determines the speed of casting solidification process, determines the density of the casting internal organization, so as to determine the casting performance. This is must pay attention to the first characteristic of V method casting.
    The dry sand is usually used in V process:
    1 (2.65g/cm) of quartz sand density refractoriness 1713 fand, c), particle size, size 40 ~ 100 mesh sieve; chemical reaction;
    2) using magnesium olivine sand has the advantages of high temperature resistance, alkali resistance, corrosion, chemical stability good advantages. (density of 3.2 ~ 3.6g/cm University and refractoriness > 1710 DEG C) size, sieve No. 40 - 100 mesh.
    (3) pearl sand packing density 1.95-2.05g/cm fand, refractoriness is higher than 1820 DEG C)
    The latter was slightly better than the former, casting no emissions of CO, CO2 and other harmful gases. Because of its greater density and heat storage capacity of slightly larger. However, the sand is not enough to enable anti-wear casting obtain compact organization. Because of poor thermal conductivity, the casting solidification time long caused the organizational structure of coarse and loose weight 5%, so wear resistance is poor.
    So, the V method casting process can produce high-quality wear-resistant castings to?? answer is certainly! First on how to select or would like to choose good thermal conductivity of special sand. Such as chromite sand (density of 0 ~ 4.8g/cm University and refractoriness > 1900 DEG C), its thermal conductivity or thermal storage is quartz sand of 3 ~ 4 times, after zircon sand (density 4.6g/cm University, refractory degrees 2430 DEG C) and metal type, use effect, of course, good. Price 3600 yuan per ton, pearl sand 2800 yuan.
    4 the correct design of casting process:
    When the other conditions are the same, process design of gating system is correct or not, mainly inherent in the improving the casting quality, thus affecting the use effect of wear-resistant casting. However, how to correct the design of pouring system? This is V method casting high manganese steel parts should pay attention to the two points.
    1) the runner should be located at the top of the casting.
    Liquid metal since the downward tilt pouring and arrived first at at the bottom of the liquid metal, in a relatively long process of sinking, temperature drop and take the lead in solidification. The whole casting according to the principle of solidification sequence. First solidification can be behind the upper part of the high temperature molten metal feeding; top after solidification can obtain gate or on the pressure side riser with high temperature molten metal full feeding, so in castings is not easy to generate shrinkage porosity, shrinkage hole and other casting defects.

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