Damage in metal forming

A new manufacturing approach has been developed, which applies energy-saving processes for forging parts from ingots with convex dies without the need for upsetting the ingots. A new forging process provides a complete closing of an ingot’s axial defects. It has been established that an increase in convex die wedge angle and an increase in the degree of reduction result in the linear growth of (a) the level of compressive stress and (b) the intensity of the axial defect closure. The rounding of a “four-beam” workpiece with concave cross-section using flat dies leads to a decrease in deformation force by a factor of 1.5–3.0 times in comparison with rounding using cut dies. The effective geometric shapes of die tooling and efficient process parameters have been determined. The convex die angle has to be in the range of 160–170°. The depth of the concavity faces has to be on the order of 25 %. The tool for rounding has to be in the shape of flat dies. The method of workpiece positioning in the dies has to be “edgeways.” A new process for forging large shafts with a 2000-mm diameter using convex dies without an upsetting operation has been proposed, reported, verified, and industrially implemented. Industrial implementation of this new technology resulted in an increase in forging process productivity of 15–20 % and a decrease in heating number from 8 to 6 during the forging of large parts. Research results in the form of process and design recommendations have been successfully validated and implemented at a metal forming industrial workplace.

A new process for forging shafts with convex dies. Research into the stressed state

In the present work, solidification structure and centre segregation in continuously cast bearing steel GCr15 blooms with 220mm×260 mm were obtained by different casting conditions (M-EMS, ...

Improvement of centre segregation in continuous casting bloom and the resulting carbide homogeneity in bearing steel GCr15

Molecular dynamics study on void collapse in single crystal hcp-Ti under hydrostatic compression

Investigation of new method of large ingots forging based on upsetting of workpieces with ledges

Investigation on the void closure efficiency in cogging processes of the large ingot by using a 3-D void evolution model

An evolution model for elliptic-cylindrical void in viscous materials considering the evolvements of void shape and orientation

Comparative Study on the Microstructure Characteristics and Enhanced Mechanical Properties of Spray Formed GCr15 Bearing Steel

The head of nuclear pressure vessel is a key component to guarantee the safety of nuclear power plant, so it is necessary to improve its mechanical properties during manufacturing. In the practical production, due to the huge size of the ingots from which the head is manufactured, coarse grains and voids are common defects existing in the material. Furthermore, cracks may appear in the forming process. It is highly demanded that the forming process must be properly designed with suitable parameters to compact the voids, to refine and homogenize the grains and to avoid cracks. Therefore, the research on the evolution of internal voids, grain size and cracks is very important to determine the forming process of huge components. SA508-3 steel is the material to manufacture the head of pressure vessel in the nuclear island. In the previous studies, we have separately built models to evaluate the evolution of internal voids, grain size and cracks during the hot forming process for SA508-3 steel. This study integrates the models for multi-scale simulation of the forging process of the head of nuclear pressure vessel in order to control the quality of the forgings. Through the software development, the models are integrated with a commercial finite element code DEFORM. Then, the extended forging and final forging processes of the head are investigated, and some appropriate deformation parameters are recommended.

Xiaoqing Shang

Papers

Investigation on the void closure efficiency in cogging processes of the large ingot by using a 3-D void evolution model

An evolution model for elliptic-cylindrical void in viscous materials considering the evolvements of void shape and orientation

Comparative Study on the Microstructure Characteristics and Enhanced Mechanical Properties of Spray Formed GCr15 Bearing Steel

Multi-Scale Simulation for the Forming of a Heavy Vessel Head Considering the Evolution of Defects and Microstructure