A method for ultra-fine grain rolling of large-size titanium alloy rods with reverse-cone helical rolls

Abstract

The invention relates to the field of machining, in particular to a reversed cone spiral roller ultra-fine grain rolling method of a large-sized titanium alloy bar. The reversed cone spiral roller ultra-fine grain rolling method of the large-sized titanium alloy bar comprises the following steps that of designing a rolling tool, wherein roller design and guide plate design are involved specifically, and each roller is arranged to be a hyperboloid circular-truncated-cone-like spiral roller; forming a deformation area, wherein the curved faces of the two guide plates are oppositely arranged, thetwo rollers are placed between the two guide plates, and the area defined by the two guide plates and the two rollers is the deformation area; forming a constant-ovality deformation area, wherein theovality in the deformation area is kept constant; and selecting a rolling feeding manner, wherein inverted feeding type rolling manner is adopted. By the adoption of the reversed cone spiral roller ultra-fine grain rolling method of the large-sized titanium alloy bar, by designing the hyperboloid circular-truncated-cone-like spiral rollers and the curved-face guide plates and forming the constant-ovality deformation area, severe plastic deformation can be generated on the premise of remarkably restraining the Mannesmann effect of the core portion.

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 titanium alloy rod 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 deformat...

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Problems solved by technology

[0014] (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

[0015] (2) The HPT forming load 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

[0016] (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

[0017] (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

[0018] (5) A helical conical roll equidistant rolling method for large-scale titanium alloy ultra-fine-grained rods (application number 201810172814.1) has the following problems: 1) The shape of the original roll is conical, and the billet enters After rolling, due to the gradual increase of the diameter of the roll, the speed of the contact area between the roll and the billet will gradually increase, 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

[0019] A comprehensive analysis shows that the titanium alloy ultra-fine-grained processes mentioned in the existing patents or papers all adopt the traditional multi-pass rolling method, limited by the volume of the deformation zone, only small-sized ultra-fine-grained materials can be prepared, and it is difficult to prepare industrial-grade Large size (Φ60-Φ500mm) material with overall ultra-fine grain

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