A method for ultra-fine grain rolling of large size 45 steel bars

Abstract

The invention discloses an ultrafine grain rolling method of a large-size 45 steel bar, and relates to the field of machining, particularly to the ultrafine grain rolling method of the large-size 45 steel bar. The ultrafine grain rolling method comprises the following steps of design of rolling tools, specifically comprising design of rollers and design of guide plates: setting the rollers as double-curved surface circular table rollers, specifically, forming generatrices of the rollers through connecting two curves, and setting one surfaces of the guide plates as curved surfaces; constructionof a deformation zone: oppositely placing the curved surfaces of the two guide plates, placing the two rollers between the guide plates, and setting a region refined by the two guide plates and the two rollers as the deformation zone; and selection of rolling feeding manner: selecting reverse feeding rolling manner, and constructing an even-ovality deformation zone. According to the ultrafine grain rolling method of the large-size 45 steel bar provided by the invention, the double-curved surface circular table rollers and the curved surface guide plates are designed, the even-ovality deformation zone is constructed, and severe plastic deformation under the precondition of the Mannesmann effect of a central part can be remarkably inhibited.

Description

technical field [0001] The invention relates to the field of mechanical processing, in particular to an ultrafine-grain rolling method for large-size 45 steel bars. 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: While loading a pressure of several GP...

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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 over 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

[0022] A comprehensive analysis shows that the 45 steel ultra-fine-grained process 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 produced, and it is difficult to produce industrial-grade steel. Large size (Φ60~Φ500mm) material with overall ultra-fine grain

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