2nd International Conference ICRF 2014

PROCESS CHAINING APPROACH WITH SIMULATION:

FROM CAST INGOT TO FINAL PROPERTIES OF FORGED COMPONENT

Valente Lorenzo(1)

Viscardi Cristian(2)

ABSTRACT:

The aim of this study is to evaluate, through FEM software simulation, the quality and properties that can be achieved on a forged component, taking into account results of casting process used to produce ingot . In this article it will be presented how to chain ingot casting simulation to cogging and heat treatment simulation.

The FEM simulation software ProCAST allows to perform complete analysis of ingot casting process. On cast ingot it will be possible to perform thermo-fluid dynamics simulation coupled with thermo-mechanical stresses and deformations studies, including Microstructure (phase, grain size/shape/orientation) and Defects (Porosity, Segregation, Hot tearing).

The FEM simulation software DEFORM performs cogging analysis using as input data ProCAST ingot casting simulation results. DEFORM allows to evaluate final properties and soundness of forged components according to forming and heating operations, provides informations on thermo-mechanical and microstructural properties and gives details for plant dimensioning.

Actual simulation standards doesn’t link casting result to forging process inputs; in this way there are important missing information that reduce simulation reliability. The scope of this paper is to present this innovative and more robust chaining simulation approach which can be used to help the Ingot Casting and Forging industry to increase the quality and the productivity of their plants, processes and products. Keywords: Ingot Casting Simulation, Forging Simulation, Software, DEFORM, ProCAST

INTRODUCTION In this paper ProCAST, FEM simulation software of ESI-Group dedicated to Casting Processes, is used for simulation of filling, solidification and cooling of a round steel ingot in ASTM A350 LF2 (S355) Chemical composition used is reported in table 1; ingot dimensions are: diameter 1000 mm and height 1920 mm. Element C Si Mn V Cr Ni Mo Cu S P

% 0.18 0.3 1.15 0.05 0.3 0.3 0.08 0.25 0.005 0.01

Table 1. Steel ASTM A350 LF2 (S355) chemical composit ion

Casting simulation provides results for thermo-mechanical state, defects and microstructure of ingot. These results are exported from ProCAST as input data for following operations:

1. Cooling to Room Temperature and Heating in Furnace at 1200 °C 2. Cogging and Re-heating operations

DEFORM, FEM simulation software of SFTC dedicated to Forming Simulation, is used for calculation of Cooling, Heating and Cogging. ProCAST Casting Simulation has been done both with Tetrahedral Elements as well as Cooling/Heating and Cogging Simulation with DEFORM. These two softwares share the same mesh and results at nodes and elements without any conversion or mapping . Cogging Simulation has been performed on a slug of 650 mm height, forged with an Hydraulic Press of 3500 tons with flat dies. Cogging simulation has been performed with two different methodologies:

1. Standard Simulation: ingot with initial homogeneous field for temperature, stress, deformation and microstructure, without any defect coming from casting phase.

2. Process Chaining Approach: initial conditions for ingot at cogging stage are results of all previous operations of casting, cooling and heating and take into consideration also defects coming from these operation.

Results of simulations obtained with these two methodologies are finally compared with experimental data on real component. Through this novel approach it will be possible to make processes more robust both in terms of process parameters and in terms of geometries, in order to reach in the fastest way the requested quality.

INGOT CASTING SIMULATION ProCAST is dedicated to all Ingot and Continuous Casting Processes. ProCAST allows to perform complete analysis of ingot casting process. On the final component it will be possible to analyze: thermo-mechanical stresses and deformations, Microstructure (phase, grain size/shape/orientation) and Defects (Porosity, Segregation, Hot tearing). In this paper an ingot casting process has been simulated for a round shape, with cross section of 1000 mm and an height of 1920 mm with chemical composition of a steel grade ASTM A350 LF2 (S355).

Figure 1. Ingot casting Fi l ling.

For this simulation Tetrahedral mesh has been used. The goal of this simulation is to model the entire production cycle of ingot, from full pouring system including ceramic to final strip when ingot is sent to forging shop. In order to obtain this result complete casting layout is introduced. Pouring temperature is 1570 °C and pouring time is 25 minutes. As for forging production requested stock feed is 1000 mm diameter for an height of 650 mm, three different casting layout have been investigated. Different layouts provide ingots with different quality levels; it means that forging is receiving same size stock feed having anyway different quality level, as shown by shrinkage porosities plot of Figure 2.

Figure 2. Ingot casting Shrinkage Porosit ies.

Casting simulation has covered entire production cycle, including filling as shown in figure 3.

Aim of this analysis was the identification of defects, like inclusions, typical of filling stage which can be generated by ceramic degradation as well as by trapping of slag or covering powders.

Figure 3. Ingot casting Shrinkage Porosit ies.

Round shape provides an ingot with internal shrinkage defects; these defects are located in general at center line of ingot, covering an area from 70 to 240 mm width as shown in figure 4.

Figure 4. Internal shrinkage defects. S lice at mid-section of ingot.

Casting simulation results have been analyzed to detect all defects that could be transferred to forging operation. Hot tearing, cold cracking, segregation, shrinkage porosities, dissolved gas content in the liquid, are some of problems investigated; these results have been transferred, together with mesh and thermo-mechanical field, to forging simulation.

Figure 5. Segregation of Mn. Slice at mid-section of ingot.

Figure 6. Von Mises stress at stripping (left) and after cooling before heating at 1200 °C (right). Slice at mid-section of ingot.

Figure 7. Gas [H] porosity formation during solidification. Slice at mid-section of ingot

FORGING AND HEAT TREATMENT SIMULATION DEFORM is dedicated to all Ingot forging and heat treatment Processes. On the final component it will be possible to analyze: thermo-mechanical stresses and deformations, Microstructure (phase, grain size/shape/orientation) and Defects localization (Porosity, Segregation, Hot tearing).

Figure 8. Ingot casted Forging

The goal of this simulation is to model the entire production cycle of forging, from furnace to forging and finally to heat treatment. Previous different ingot casted layouts have provide different shrinkage porosity maps that has been closed or deformed during forging operation. DEFORM is showing ProCAST porosity tracking during forging In case of shrinkage porosity inside a contour delimited by a diameter of 100mm defect is trimmed by last forging operation (Figure 9). If ingot has some shrinkage porosity extended out of this 100mm diameter, defects appear in final forged part (Figure 10).

Figure 9. Porosity tracking during forging

Porosity inside 50mm diameter of central ingot out of forged part

Figure 10. Porosity tracking during forging

Porosity inside 200mm diameter of central ingot inside forged part

After forging simulation it will be necessary to simulate heat treatment to avoid internal cracks and

to guarantee mechanical properties on forged components.

This is a simulation process chaining approach: casting-forging-heat treatment. (Figure 11-12).

Figure 11. Heat Treatment cycle with casting and forging simulation results

Figure 12. Heat Treatment simulation on casted and forged component with Martensite evolution

CONCLUSION This paper summarizes the evolution in Casted Forging Simulation from a Standard Approach that

consider Casted Forging as a stand-alone operation to a "Process Chaining Approach" that consider

also the production phase of profile to be forge, taking into account both Ingot Casting, Cooling /

Heating operations before Forging and Heat Treatment after Forging.

Even if the same geometry and process parameters have been used, differences between two

simulations are present, in particular on casting porosity tracking during forging.

Temperature, stress and strain are also different as well.

It’s been found that Plastic Strain coming from Ingot Casting, as well as Carbon distribution and

Plastic Stresses, play an important role in obtainment of a finished forging product that satisfy

drawing requests and working parameters.

In this paper it’s shown chaining between two different commercial FEM software: ProCAST of

ESI-Group and DEFORM of SFTC

These two softwares share the same mesh and results at nodes and elements without any conversion

or mapping.

Computation time is similar for both approaches and this justify the choose of Fully Integrated

Approach, to reduce approximation and achieve requested quality and productivity of the Forging

and Heat Treatment Processes in the fastest way.

ACKNOWLEDGMENTS Authors want to thank Marco Aloe and Jean-Christophe Makuch of ESI-Group for creation of

native link in ProCAST for export .key file to DEFORM.

Authors want to thank Chris Fischer and Mike Foster of SFTC for support provided in realization of

this work and information given to allow creation of direct data transfer between Ingot Casting and

Forging operation.

(1) Valente Lorenzo – ECOTRE Valente srl - l.valente@ecotre.it (2) Viscardi Cristian – ECOTRE Valente srl - c.viscardi@ecotre.it ECOTRE Valente srl - Via S. Orsola,145 – 25135 – BRESCIA – Italy Tel: +39.030.3365383 www.ecotre.it