CN103105477A - Method for predicting forge crack initiation of forged steel - Google Patents

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 of method for predicting the germinating of forged steel forge crack

Technical field

The invention belongs to forging technology technical field, and in particular to a kind of method of prediction forged steel forge crack germinating.

Background technology

Solving the method for forge crack both at home and abroad at present has two kinds：During one kind is production, after forging process is cracked, the reason for just looking for cracking is stopped for concrete reason tool and solved, rather than is just predicted before forge crack formation, and this brings very big economic loss to factory and enterprise；Another is in theoretical research, to be all to set up fracture criterion, the fracture damage factor is obtained based on fracture criterion, predicts the generation of crackle with damage factor, but this method poor operability in actual production, can not be applied in actual forging process.

The content of the invention

The forged steel method that forge crack germinates under the conditions of different temperatures and strain rate is predicted there is provided a kind of the present invention seeks to the shortcoming existed for prior art, foundation is provided to formulate rational forging technology.

What the object of the invention was realized in, it is characterised in that implementation steps are：

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

（2）Do tensile test at high temperature：The forging range and strain rate scope of steel are taken, tensile test at high temperature is done on thermal simulation machine, sample fracture is stretched to, the true stress-true strain curve under the conditions of different temperatures and strain rate is obtained, peak strain is read, the strain is exactly crack initiation strain.

（3）The determination of crack initiation strain correspondence specimen finish：The tensile test at high temperature under same deformation condition is done on thermal simulation machine again, crack initiation strain stopping is stretched to, sample constriction smallest cross-sectional diameter is then measured, the diameter value is exactly that crack initiation strains corresponding diameter value.

（4）Finite element modelling：Flow stress plots are inputted in finite element software, the drawing by high temperature process under the conditions of different temperatures and strain rate is simulated by finite element software, it is identical that simulation is stretched to specimen finish diameter corresponding with crack initiation strain, now, the corresponding impairment value of sample central point is read 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, actual forging basic working procedure jumping-up and pulling are simulated on flat anvil, taper anvil and spherical anvil etc. respectively, the forging critical strain amount under the conditions of different anvil shapes, different distortion is obtained.

（6）Forge the checking of critical strain amount：Critical strain amount is verified by the forging small scale test under the conditions of different anvil shapes, different distortion, to ensure the correct reliability of critical strain amount.

（7）The drafting of critical strain amount curved surface：Using mapping software, critical strain amount curved surface when drawing jumping-up with pulling under the conditions of different anvil shapes, different distortion, as shown in Figure 1.

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

Advantages of the present invention and good effect are：This method application is simple, conveniently, has good operability in factory and enterprise, as long as according to given deformation condition, the critical strain spirogram under correspondence corresponding conditionses, it is determined that corresponding deflection just can be with.This method can predict germinating of the steel in forging process crackle well, so as to avoid forging process from cracking, this provides reference to formulate rational forging technology, and very big economic benefit is brought to enterprise, is had great application prospect.

Brief description of the drawings

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

Fig. 2 is 316LN steel in 900 DEG C -1250 DEG C of temperature 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

By taking 316LN austenitic stainless steel smooth anvil upsettings as an example, deformation condition is：Temperature：900 DEG C -1250 DEG C, strain rate：0.005s^-1-1s^-1, its critical strain amount curved surface is obtained according to the inventive method implementation steps, as shown in Figure 2.

When formulating 316LN steel smooth anvil upsetting techniques, first according to the combination of temperature and strain rate, corresponding diagram 2 determines the critical strain amount under the conditions of this, and deflection during actual upset is less than critical strain amount.For example：Want 1200 DEG C of temperature, strain rate 0.005s^-1Under the conditions of jumping-up critical strain amount, corresponding diagram 2 as can be seen that this under the conditions of critical strain value be 0.58, so, Upsetting amount is less than 58% under this condition, and if greater than 58%, crack initiation is just had on forging surface.

Claims (1)

1. a kind of method for predicting the germinating of forged steel forge crack, it is characterised in that implementation steps are as follows：

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

（2）Do tensile test at high temperature：The forging range and strain rate scope of steel are taken, tensile test at high temperature is done on thermal simulation machine, sample fracture is stretched to, the true stress-true strain curve under the conditions of different temperatures and strain rate is obtained, peak strain is read, the strain is exactly crack initiation strain；

（3）The determination of crack initiation strain correspondence specimen finish：The tensile test at high temperature under same deformation condition is done on thermal simulation machine again, crack initiation strain stopping is stretched to, sample constriction smallest cross-sectional diameter is then measured, the diameter value is exactly that crack initiation strains corresponding diameter value；

（4）Finite element modelling：Flow stress plots are inputted in finite element software, the drawing by high temperature process under the conditions of different temperatures and strain rate is simulated by finite element software, it is identical that simulation is stretched to specimen finish diameter corresponding with crack initiation strain, now, the corresponding impairment value of sample central point is read 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, actual forging basic working procedure jumping-up and pulling are simulated on flat anvil, taper anvil and spherical anvil etc. respectively, the forging critical strain amount under the conditions of different anvil shapes, different distortion is obtained；

（6）Forge the checking of critical strain amount：Critical strain amount is verified by the forging small scale test under the conditions of different anvil shapes, different distortion, to ensure the correct reliability of critical strain amount；

（7）The drafting of critical strain amount curved surface：Using mapping software, critical strain amount curved surface when drawing jumping-up with pulling under the conditions of different anvil shapes, different distortion；

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

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