Rolling bearing rings comprise a large reserve for expanding powder metallurgy production. This reserve is being incompletely implemented. The hot forging of porous preforms makes it possible to produce high-density materials for the fabrication heavy loaded wares, in particular, rolling bearing rings. The problem of fabricating hot-forged bearing rings is associated with the presence of a large amount of impurities in the initial powders, as well as with residual one-side open pores and microcracks in the surface layer of parts caused by cooling a heated porous preform when performing operations of a hot repressing process. The possibility of improving the mechanical properties and rolling contact endurance of hot-forged steels of a eutectoid composition fabricated based on the chromium–molybdenum iron powder, as well as unalloyed iron powders with different impurity contents due to sodium microalloying, is considered. Sodium is introduced in the form of bicarbonate. To decrease the oxidation probability of a heated porous preform during hot forging (HF), the previously proposed method of fabricating the high-density iron-based chromium-containing powder material is used. This method foresees the formation of cold-pressed preforms with porosity of 10–12%, their sintering in a vacuum furnace, and subsequent HF. To determine the mechanical properties and perform the structural analysis, prismatic samples 10 × 10 × 55 mm in size are fabricated. The rolling contact endurance is investigated using cylindrical samples ∅26 × 6 mm. The tests are performed by rolling flat surfaces of cylindrical samples by balls. The introduction of Na microadditives makes it possible to substantially increase the rolling contact endurance of powder steels when compared with unalloyed samples, as well as with respect to test samples made of thermally treated steel ShKh15, which is caused by a decrease in the austenite grain size, increase in quality of interparticle intergrowth, and decrease in surface porosity. Carbon powder steels containing the optimal amount of sodium microadditive (0.2 wt %) can be used when fabricating structural products operating under contact loads.

中文翻译：

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钠微合金化对热变形粉末钢滚动接触寿命和力学性能的影响

滚动轴承圈具有很大的储备量，可用于扩展粉末冶金生产。此储备金未完全实施。多孔预成型件的热锻造可以生产高密度材料，用于制造重载商品，特别是滚动轴承套圈。制造热锻轴承圈的问题与初始粉末中存在大量杂质有关，并且与零件的表面层中残留的一侧开孔和微裂纹有关，这是由于冷却加热的多孔预成型件而造成的。在执行热压制过程的操作时。改善基于铬钼铁粉制造的共析成分的热锻钢的机械性能和滚动接触耐久性的可能性，以及由于钠微合金化而具有不同杂质含量的非合金铁粉。钠以碳酸氢盐的形式引入。为了降低热锻造（HF）期间加热的多孔预成型件的氧化可能性，使用了先前提出的制造高密度铁基含铬粉末材料的方法。这种方法可以预见孔隙率为10-12％的冷压预成型坯的形成，在真空炉中的烧结以及随后的HF。为了确定机械性能并进行结构分析，制造了尺寸为10×10×55 mm的棱柱形样品。使用cylindrical26×6 mm的圆柱样品研究了滚动接触耐久性。通过用球滚动圆柱形样品的平坦表面来进行测试。与非合金样品以及由奥氏体晶粒尺寸减小引起的由热处理钢ShKh15制成的测试样品相比，钠微添加剂的引入可以显着提高粉末钢的滚动接触耐久性。 ，提高了颗粒间共生的质量，并降低了表面孔隙率。当制造在接触载荷下工作的结构产品时，可以使用含有最佳量的钠微添加剂（0.2重量％）的碳粉钢。颗粒间共生质量的提高，表面孔隙率的降低。当制造在接触载荷下工作的结构产品时，可以使用含有最佳量的钠微添加剂（0.2重量％）的碳粉钢。增加颗粒间共生的质量，并降低表面孔隙率。当制造在接触载荷下工作的结构产品时，可以使用含有最佳量的钠微添加剂（0.2重量％）的碳粉钢。