Establishment and Application of the Void Closure Prediction Model of 316LN

Min Qin,Jingdan Li,Jiansheng Liu

doi:10.1155/2020/5717860

Min Qin, Jingdan Li + Show 1 more

Open Access

https://doi.org/10.1155/2020/5717860

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Abstract

The presence of voids in the ingot affects the mechanical properties of the final products of the forging process. It is essential to establish a void closure model to predict cavity closure in the forging process to optimize the forging process and improve forging quality. The main purpose of this study is to obtain an accurate prediction model of void closure for 316LN stainless steel. Using the FEM simulation method to study the closure of spherical voids during forging compression of 316LN materials, we can accurately characterize the state of void closure. The void closure ratio K under different deformations at 1,200°C was counted, and the relationship between K and the effective strain was established to obtain the void closure prediction model of 316LN stainless steel. The void closure prediction model is implanted into DEFORM software through the secondary development method to generate the void closure ratio K. In the postprocessing module of DEFORM software, the void closure status of each part during the forming process can be directly observed. Comparing the results of large-scale upsetting experiments and simulation results, the closure error of each part was only 3%, which indicates that the void closure model established in this paper has higher accuracy, which is helpful for the optimization of the forging process and the control of forging quality.

Highlights

As the key parts for heavy machinery and equipment, large forgings are widely used in the fields of nuclear power plants, metallurgy, shipbuilding, aerospace, and the national defense industry
Park [11] found that the void closure is dependent on the aspect ratio of the cross section of a void but not on the size of the void. e relationship between the effective strain and the aspect ratio was established by which the closure of such a void with any aspect ratio can be predicted in terms of the effective strain in uniaxial forging
In order to describe the void closure and analyze the relationship between the void closure and effective strain, hydrostatic stress, stress triaxiality, and other factors, this paper introduces the void closure ratio K as a parameter for description and analysis: K D − Hz × 100%, (3)

Summary

Introduction

As the key parts for heavy machinery and equipment, large forgings are widely used in the fields of nuclear power plants, metallurgy, shipbuilding, aerospace, and the national defense industry. Park [9] found that a closure criterion of the spherical void is a function of the effective strain and stress triaxiality. Rahul et al [10] brought out at every stage the load and torque distribution, effective strain, stress triaxiality factor, void volume fraction, and void healing hydrostatic integration parameter in a model which enabled void closure. E void closure is the first stage At this stage, the forging is deformed at high temperatures, and the void gradually diminishes until the upper and lower surfaces of the void contact. Through the comparison of simulations and large-scale upsetting experiment results, the accuracy and practical significance of the void closure prediction model were verified

FEM Simulation Analysis

Establishment of the Prediction Model of Void Closure

Secondary Development and Application of the Void Closure Prediction Model

Findings

Conclusion