20
2019
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09
Key Points of Attention in Heat Treatment of Alloy Steel
The alloying of high manganese steel is mainly by adding Cr, Mo, V, Ti, rare earth and other elements to the traditional composition of high manganese steel to improve its performance, of which Cr is particularly widely used. Related text
The alloying of high manganese steel is mainly by adding Cr, Mo, V, Ti, rare earth and other elements to the traditional composition of high manganese steel to improve its performance, of which Cr is particularly widely used. The relevant literature holds that: in the process of high manganese steel processing and hardening, dynamic strain aging will be produced, that is, the formation of C- Mn atomic pairs, the altar escapes the line of the scale and talks about the plant of the harsh industry to raise the в of the r element has the effect of expanding the cluster of C- Mn ordered atomic pairs in high manganese steel. In this paper, the changes in the organization, structure, resistance and wear resistance of alloy high manganese steel and ordinary high manganese steel with different tempering temperatures are studied, and the results show that the alloy high manganese steel has better wear resistance than ordinary high manganese steel under the condition of relatively low carbon content. And alloy high manganese steel in different tempering temperature of different organizational structure showed different wear resistance.
After the water toughening treatment of alloy high manganese steel, the wear loss of alloy high manganese steel decreases and the wear resistance increases with the tempering temperature gradually increasing to 250 ℃, and the maximum value is at 250 ℃. When the temperature rises from 250 ℃ to 350 ℃, the wear loss increases slightly and the wear resistance decreases, but it is still better than the wear resistance of alloy high manganese steel after conventional water toughening treatment. When the temperature continues to rise to 500 ℃, the amount of wear continues to increase, and the wear resistance decreases, which is lower than that in the water-tough state, which further proves the existence of ordered micro-regions in the alloy high manganese steel.
For ordinary high manganese steel, with the increase of temperature, the carbon atoms in the austenite matrix also migrate and form C- Mn atomic pairs with Mn. However, due to the relatively weak combination between manganese and carbon atoms, the size of the short-range ordered micro-region is relatively small, and the lattice distortion is restored to a certain extent after tempering at 250 ℃, therefore, the wear resistance exhibited after tempering at 250 ° C. is hardly improved compared with the wear resistance of the water-tough state. Due to the weakening of solid solution strengthening, its wear resistance decreased slightly. When the tempering temperature continues to rise from 250 ℃ to 350 ℃, the activity of carbon atoms in alloy high manganese steel continues to increase with the increase of temperature. After tempering at this temperature, there is still no carbide precipitation, but the lattice distortion degree of austenite is further reduced and the solid solution strengthening effect is weakened. However, since carbide has not yet precipitated, there are still a large number of micro-regions, and its wear resistance is reduced compared with that of tempering at 250 ℃, but still higher than the water toughness wear resistance. For ordinary high manganese steel, when the temperature rises to 400 ℃, it can be seen from the diffraction spectrum that some carbides in the carbon-rich micro-region begin to precipitate. At this time, the newly precipitated carbides have not yet grown up, and the dispersion strengthening effect is ideal. In addition, some micro-regions are still in the sub-structural state before carbide precipitation, because the micro-regions of these sub-structural states are carbon-rich regions, so the C- Mn ordered atomic pairs are more abundant. These dispersed evenly distributed micro-regions and the pinning effect of dispersed carbides on dislocations make up for the weakening of solid solution strengthening to a certain extent, so the macro-mechanical properties show that the wear resistance is not obvious. When the temperature continues to rise to 500 ℃, it can be seen from fig. 4 that carbides begin to precipitate in alloy high manganese steel, and the basic lattice constant of austenite has basically tended to be normal at this time. moreover, due to the precipitation of alloy carbides, the carbon content in the matrix obviously decreases, which greatly affects the formation of ordered micro-regions, thus affecting the effect of work hardening, so the macro wear resistance shows a downward trend.
It can be seen that the micro-domain clusters of C- Mn ordered atoms have an important influence on the wear resistance of high manganese steel. The alloy high manganese steel treated by water toughening and tempering at 250 ℃, due to the "hinge effect" of Cr on the C- Mn atom pair, its wear resistance is higher than that of ordinary high manganese steel with high carbon content. After the tempering temperature of alloy high manganese steel is increased to 500 ℃, the strengthening effect of ordered clusters is weakened due to the precipitation of carbides, and the wear resistance of alloy high manganese steel is obviously reduced due to the weakening of solid solution strengthening.
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