CN103105477B

CN103105477B - Method for predicting forge crack initiation of forged steel

Info

Publication number: CN103105477B
Application number: CN201310024108.XA
Authority: CN
Inventors: 段兴旺; 刘建生; 郑晓华; 田继红; 赵晓东; 张秀芝
Original assignee: Taiyuan University of Science and Technology
Current assignee: Taiyuan University of Science and Technology
Priority date: 2013-01-23
Filing date: 2013-01-23
Publication date: 2015-02-04
Anticipated expiration: 2033-01-23
Also published as: CN103105477A

Abstract

The invention discloses a method for predicting forge crack initiation of forged steel and belongs to the technical field of forging processes. The method is characterized by comprising the steps of: carrying out a high-temperature tension test at different temperatures and strain rates to obtain a material flow stress curve line, crack initiation strain and corresponding diameter value; simulating a high-temperature tension process at different temperatures and strain rates by utilizing finite element software to obtain a critical damage value of crack initiation; based on the critical damage value, simulating a basic forging process by utilizing finite elements to obtain critical forging deformation amount; and drawing a critical deformation curve for critical deformation data subjected to verification of a forging shrink ratio experiment. All points below the curve are non crack initiation points, all points above the curve are crack initiation points, and all points on the curve are critical points. The method has the advantages that the deformation amount of forge pieces without cracks in the forging process can be determined by the simple and convenient method.

Description

A kind ofly predict the method that forged steel forge crack germinates

Technical field

The invention belongs to Forging Technology technical field, be specifically related to a kind of method that forged steel forge crack germinates of predicting.

Background technology

The method solving forge crack at present both at home and abroad has two kinds: one is in producing, after forging process cracks, just go to find the reason cracked, stop for concrete reason tool and solve, instead of just predicted before forge crack is formed, this brings very large economic loss to factory and enterprise; Another kind is in theoretical research, is all setting up fracture criterion, obtains the fracture damage factor based on fracture criterion, predicts the generation of crackle with damage factor, but this method poor operability in actual production, cannot apply at actual forging process.

Summary of the invention

The present invention seeks to the shortcoming existed for prior art, a kind of method predicting forged steel forge crack germinating under different temperatures and strain rate condition being provided, providing foundation for formulating rational Forging Technology.

The present invention seeks to realize like this, it is characterized in that implementation step is:

(1) material property experiment is done: do material property experiment according to practical distortion condition, obtain material flowing deformation stress curve.

(2) tensile test at high temperature is done: forging range and the strain rate scope of getting steel, thermal simulation machine does tensile test at high temperature, be stretched to sample fracture, obtain the true stress-true strain curve under different temperatures and strain rate condition, read peak strain, this strain is exactly crack initiation strain.

(3) crack initiation strains the determination of corresponding specimen finish: on thermal simulation machine, do the tensile test at high temperature under same deformation condition again, be stretched to crack initiation strain to stop, then measure sample constriction smallest cross-sectional diameter, this diameter value is exactly diameter value corresponding to crack initiation strain.

(4) finite element analogy: flow stress plots is inputted in finite element software, by the drawing by high temperature process under finite element software simulation different temperatures and strain rate condition, simulation is stretched to specimen finish and crack initiation, and to strain corresponding diameter identical, now, read impairment value corresponding to sample central point from simulation softward, this impairment value is exactly the critical damage value of crack initiation.

(5) forge the determination of critical strain amount: according to crack initiation critical damage value, simulation actual forging basic working procedure jumping-up and pulling on flat anvil, taper anvil and spherical anvil respectively, obtains the forging critical strain amount under different anvil shape, different distortion condition.

(6) checking of critical strain amount is forged: verify critical strain amount by the forging small scale test under different anvil shape, different distortion condition, to guarantee the correct reliable of critical strain amount.

(7) drafting of critical strain amount curved surface: application mapping software, draws jumping-up and the critical strain amount curved surface under different anvil shape, different distortion condition during pulling, as shown in Figure 1.

(8) prediction of forge crack germinating: according to critical strain amount surface chart, all points be in below critical strain amount curved surface are all safe points, and this puts not crack initiation; All points be in above critical strain amount curved surface are all the points of crack initiation; All points be on curved surface are critical points.

Advantage of the present invention and good effect are: the method application is simple, convenient, has good operability at factory and enterprise, as long as according to given deformation condition, the critical strain spirogram under corresponding corresponding conditions, determines that corresponding deflection is just passable.The method can predict the germinating of steel at forging process crackle well, thus avoids forging process to crack, and this provides reference for formulating rational Forging Technology, brings very large economic benefit, have great application prospect to enterprise.

Accompanying drawing explanation

Fig. 1 is critical strain amount surface chart of the present invention.

Fig. 2 is that 316LN steel is at temperature 900 DEG C-1250 DEG C and strain rate 0.005s ^-1-1s ^-1critical strain amount surface chart during smooth anvil upsetting.

A in Fig. 1 and Fig. 2 represents critical strain amount; B represents strain rate; T represents temperature.

Embodiment

For 316LN austenitic stainless steel smooth anvil upsetting, deformation condition is: temperature: 900 DEG C-1250 DEG C, strain rate: 0.005s ^-1-1s ^-1, obtain its critical strain amount curved surface according to the inventive method implementation step, as shown in Figure 2.

When formulating 316LN steel smooth anvil upsetting technique, first according to the combination of temperature and strain rate, corresponding diagram 2, determine the critical strain amount under this condition, deflection during actual upset is less than critical strain amount.Such as: temperature 1200 DEG C be determined, strain rate 0.005s ^-1the critical strain amount of jumping-up under condition, corresponding diagram 2 can be found out, the critical strain value under this condition is 0.58, so Upsetting amount is less than 58% under this condition, if be greater than 58%, just has crack initiation on forging surface.

Claims

1. predict the method that forged steel forge crack germinates, it is characterized in that implementation step is as follows:

(1) material property experiment is done: do material property experiment according to practical distortion condition, obtain material flowing deformation stress curve;

(2) tensile test at high temperature is done: forging range and the strain rate scope of getting steel, thermal simulation machine does tensile test at high temperature, be stretched to sample fracture, obtain the true stress-true strain curve under different temperatures and strain rate condition, read peak strain, this strain is exactly crack initiation strain;

(3) crack initiation strains the determination of corresponding specimen finish: on thermal simulation machine, do the tensile test at high temperature under same deformation condition again, be stretched to crack initiation strain to stop, then measure sample constriction smallest cross-sectional diameter, this diameter value is exactly diameter value corresponding to crack initiation strain;

(4) finite element analogy: flow stress plots is inputted in finite element software, by the drawing by high temperature process under finite element software simulation different temperatures and strain rate condition, simulation is stretched to specimen finish and crack initiation, and to strain corresponding diameter identical, now, read impairment value corresponding to sample central point from simulation softward, this impairment value is exactly the critical damage value of crack initiation;

(5) forge the determination of critical strain amount: according to crack initiation critical damage value, simulation actual forging basic working procedure jumping-up and pulling on flat anvil, taper anvil and spherical anvil respectively, obtains the forging critical strain amount under different anvil shape, different distortion condition;

(6) checking of critical strain amount is forged: verify critical strain amount by the forging small scale test under different anvil shape, different distortion condition, to guarantee the correct reliable of critical strain amount;

(7) drafting of critical strain amount curved surface: application mapping software, draws jumping-up and the critical strain amount curved surface under different anvil shape, different distortion condition during pulling;