DJM Technical Introduction

    high vanadium high wear resistant alloy hammer

    Development and application of high vanadium high wear resistant alloy hammer
    Abstract: by using the newly developed high vanadium high wear-resistant alloy material manufacture of cement clinker crusher hammerhead, due to the vanadium carbide micro hardness high (about HV2600) morphology of the spherical and highly dispersed, in use process is difficult to be cement clinker scratch and smash, approximate spherical carbide to separate the matrix small, matrix anti fatigue ability strong, not easy to crack and high resistance to wear. Wear resistance is more than three times the original high chromium cast iron hammer.
    Keywords: high vanadium alloy; high chromium cast iron; wear resistance; hammer; cement clinker
    introduction
    Studies have shown that vanadium can form high wear-resistant carbide VC, the microhardness HV2600 around [1], is much higher than that of M7C3 carbides; with the addition of vanadium carbide can be changed in the pattern, increase the toughness of the wear resistant alloy. We after years of practice, developed a contains large amounts of VC Gao Fangao wear-resistant alloy (hereinafter referred to as the high vanadium alloy). Made of this alloy hammer used for cement clinker crusher, cement clinker from 60 ~ 80mm broken into small particles of 3 ~ 5mm, the service life is 3 times more than that of the original high chromium cast iron hammer.
    1 materials
    1.1 chemical composition
    High vanadium alloy material specific components of [2,3] and the original hammer components are shown in Table 1
    % Table 1 chemical composition of high vanadium alloys and high chromium cast iron hammer
    Material Cr Mn Si S P, V Mo Cu C
    High vanadium alloy 2 ~ 2.5 and 4 ~ 8 and 0.2 ~ 0.5 and 0.3 ~ 0.8 less than 0.07 11 ~ 15 ~ 3.2 - 2.8
    High chromium cast iron 19.3 0.81 0.56 0.04 0.01 1.96 0.98
    1.2 metallographic structure
    Hammer clinker is low stress impact wear.
    High chromium cast iron hammer of Metallurgical Group of trifoliate orange carbide (mainly Cr7C3) and metal matrix (mainly martensite) constitute.Cr7C3 type carbides were hexagonal rod and strip distribution (Figure 1), hardness hv1300 ~ 1800, the hardness of martensite as HV500 to 1000[4]. high chromium cast iron hammer broken cement clinker wear failure process are as follows: due to the hardness of the matrix is lower than that of the carbides, first wear, carbides emerged, salience of carbide is scratched break and fall off, losing protection to the substrate. Matrix further wear, so the cycle. Because of this, to further improve the hammer wear resistance is the main way is:
      
    Figure 1 high chromium cast iron metallographic 400 x
    1) increase the hardness of carbide, reduce the scratch;
    2) to improve the carbide shape, so that the block into a ball or similar to the ball, to reduce the possibility of being crushed;
    3) to improve the carbide distribution, so that by the intermittent mesh into the dispersion distribution, reduce the matrix of fragmentation and weakening effect;
    4) increase the hardness of the matrix, in order to enhance its ability to resist low stress impact wear.
    High vanadium carbide (VC) hardness is high (HV2600), which is similar to the ball, and highly dispersed distribution (Figure 2), which reduces the carbide was scratched, the possibility of breaking, and the protection of the matrix, improve the wear resistance of the material.
      
    Figure 2 high vanadium alloy 400 x
    1.3 wear resistance
    The 10mm method for sample producing cutting line in the hammer on the body * 10mm * 30MM the wear resistance comparison test.
    Test on MLD-10 dynamic impact load and wear testing machine of. Impact frequency 100 times / min, abrasive for 50 ~ 70 mesh refined quartz sand, flow 350ml/min and impact energy for 1.0J. first will sample run for 10 min, and then weighed as the original weight, then wearing 1H, the second weighing, 2 times the weight difference wear weight loss. The test results are shown in Table 2.
    Table 2 the wear resistance of high vanadium alloy and high chromium cast iron
    Material wear weightlessness /g average weight loss /g relative wear resistance
    Sample No. 2, No. 1, No. 3
    High chromium cast iron 0.2796 0.2766 0.27611
    High vanadium alloy 0.0853 0.0876 0.0878 3.152
    Experiment results showed that the wear resistance of high vanadium alloy is 3.152 times of high chromium cast iron hammer, it proved that the chosen material is appropriate.
    2 smelting and casting process
    2.1 smelting
    Smelting high vanadium alloy should pay attention to improve the valuable and easy burning of elements vanadium absorption rate. In the melting process should prevent excessive oxidation of molten iron, or and ferrovanadium pre deoxidation. Addition of vanadium in the late melting. In addition, provided the temperature and temperature should not be too long a time. Vanadium absorption rate generally in about 85%. Other process with high chromium cast iron.
    2.2 casting process
    The production process of high vanadium alloys and similar high chromium cast iron, wood scale by 1.6%.
    The hammer head adopts composite casting process, handle the low alloy steel, wear part of the hammer with high vanadium alloy, two at the same time the material pouring compound and into one. This ensures that the hammer of high wear resistance, and improve the toughness, reduce the cost. The handle chemical into points in Table 3.
    Table 3 chemical composition% a
    Cr Mn Si Mo Re S C, P
    0.5 ~ 0.6 1 to 1.4 1.4 to 1.8 1 to 1.4 0.3 to 0.5 0.2 to 0.3 less than 0.04
    3 heat treatment process
    The excellent wear resistance of high vanadium alloy is guaranteed by the correct heat treatment technology.
    The hammer by little, belong to low stress abrasive wear, high vanadium alloys in this condition main failure forms of carbide fall off, secondly was fatigue spalling. Because of the high hardness carbide, not easy to scratch, and due to the wear of the matrix, leading to the carbide matrix to lose support and fall off as the main failure mode. Therefore, we should ensure that there is a sufficient number of VC and hard substrate, so as to ensure the wear resistance. Also, the use of high vanadium alloy of secondary hardening ability to improve the wear resistance and the heat treatment technology [3] are shown in Figure 3. Mechanical properties, see Table 4.
      
    Fig. 3 quenching and tempering process of high vanadium alloy
    Table 4 mechanical properties of high vanadium high chrome hammer and hammer
    The hardness of the material impact toughness of HRC / (J/cm2) microstructure
    High chromium cast iron 62.56 M + M7C3 + A (a small amount)
    High vanadium alloy 64.512 M + VC + M7C3 + A (a small amount)
    The T1 and T2 in the diagram can be determined according to the specific requirements.
    4 industrial test
    4.1 test conditions
    Testing machine installed in Pinghu, Zhejiang Province, the first building materials machinery factory of crusher. Test in high vanadium alloy hammer and high chromium cast iron hammer mixed.
    The motor power is 132kW, the spindle speed 320r/min, feed particle size less than 80mm, the grain size of 3 ~ 5mm.
    4.2 The results of the experiment are shown in Table 5
    Table 5 hammer installed test results
    A hammer hammer type crushing cement / 000 t relative wear resistance
    High chromium cast iron hammer 6.011
    High vanadium alloy hammer 20.37 3.39
    Can be seen from table 5, the wear resistance of high vanadium alloy hammer high chromium cast iron hammer is more than 3 times.
    5 conclusions
    1) the microstructure of high vanadium high wear resistant alloy is carbide (mainly VC) and metal matrix (mainly martensite).VC high hardness (HV2600), which is similar to spherical shape, and the dispersion distribution, so that the material has a high wear resistance.
    2) in the crushing cement clinker, the wear resistance of high vanadium alloy hammer high chromium cast iron hammer is more than 3 times.
     

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