A method of ultra-fine grain rolling with reverse-cone helical rolls for large-size 45 steel bars

Abstract

The invention discloses a reverse conical spiral roller ultra-fine grain rolling method of a large-size 45 steel bar, and relates to the field of machining. The method comprises the following steps that a rolling tool is designed, wherein design specifically comprises roller design and guide plate design, and rollers are designed to be dual-curve-face round-table-shaped spiral rollers; a deformingarea is constructed, wherein curve faces of two guide plates are oppositely placed, the two rollers are placed between the guide plates, and the area defined by the guide plates and the rollers is the deforming area; an equal ovality deforming area is constructed, wherein ovality in the deforming area is kept unchangeable; and the inverted feeding manner is selected, wherein the pouring-in type rolling manner is adopted. According to the reverse conical spiral roller ultra-fine grain rolling method of the large-size 45 steel bar, through design of the dual-curve-face round-table-shaped spiralrollers and the curve guide plates, the equal ovality deforming area is constructed, and the violent plastic deforming is generated on the premise of obviously restraining the heart Mannesmann effect.

Description

technical field [0001] The invention relates to the field of mechanical processing, in particular to an ultra-fine-grained rolling method of a large-size 45 steel bar with reverse-cone helical rollers. Background technique [0002] Ultrafine crystal / nanocrystalline materials and their preparation technology are one of the research hotspots in the field of material science. Research in this direction embodies people's efforts to continuously improve the strength and toughness of polycrystalline materials through continuous refinement of grains. Among them, the research results of severe plastic deformation (Severe Plastic Deformation, referred to as SPD) technology are eye-catching. [0003] At present, the mainstream SPD process includes five methods: high pressure torsion (HPT), equal channel angular extrusion (ECAP), cumulative stack rolling (ARB), multidirectional forging (MF) and torsional extrusion (TE), among which: [0004] (1) High-pressure torsional deformation: W...

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Problems solved by technology

[0015] (1) During the ECAP deformation process, the blank is in full contact with the mold, and the friction force is large, so the forming load is large, the finished product size is small, and the material utilization rate is low, the production efficiency is low, and it is difficult to realize the preparation of large-scale ultra-fine-grained materials required by industrialization

[0016] (2) The forming load of HPT is huge. The existing forming equipment generally does not have the loading capacity of more than tens of GPa for industrialized large-scale products, and is only suitable for the forming of ultra-thin products such as films. Usually, the blank before deformation is Φ10~15×1~ 10mm cylinder

[0017] (3) The ARB process is limited by the volume of the deformation zone and the uniformity of deformation, and the thickness of the deformation zone is only mm level

At the same time, since the prepared ultrafine grains are elongated grains in the shape of cakes, their mechanical properties are worse than those of three-dimensional equiaxed grains.

Therefore, limited by the loading capacity and uneven deformation, ARB can only prepare ultra-thin sheets

[0018] (4) Due to the serious deformation inhomogeneity of MF and TE, the grain size is uneven, the stability of the grain structure is poor, and the performance is reduced, and it is also impossible to prepare large-size forgings

[0019] (5) The helical conical roll equidistant rolling method of large-size 45 steel ultra-fine grain bar (application number 201810172808.6) has the following problems: 1) The shape of the roll in the original technology is conical, and after the billet enters the roll, due to The diameter of the roll increases gradually, and the speed of the contact area between the roll and the billet increases gradually, which will lead to an increase in the deformation speed difference between the core and the edge of the billet, thereby aggravating the deformation unevenness

2) The distance between the rolls is equal, the diameter reduction rate gradually decreases, and the deformation is small, so the effect of grain refinement will gradually weaken

[0020] A comprehensive analysis shows that the 45 steel ultra-fine-grained process mentioned in the existing patents or papers can only produce small-sized ultra-fine-grained materials due to the volume limit of the deformation zone, and it is difficult to produce large-sized industrial-grade overall ultra-fine-grained (Φ60~ Φ500mm) material

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