D D2.1 Database on Defects - Stacast project

1 Stacast - New Quality and Design Standards for Aluminium Alloys Cast Products FP7-NMP-2012-CSA-6 - project N. 319188 Stacast : New Quality and Design Standards for Aluminium Alloys Cast Products deliverable : Database on Defetcs Authors: F. Bonollo, G. Timelli, E. Fiorese, E. Gariboldi, P. Parona, L. Arnberg 1 COORDINATION AND SUPPORT ACTION (SUPPORTING) Call: FP7-NMP-2012-CSA-6 Support for standardisation needs project full title: New Quality and Design Sta ndards for Aluminium Alloys Cast Products project acronym: Stacast Co-ordinator name Franco BONOLLO Co-ordinator organisation name University of Padova DTG Co-ordinator email and fax +39 0444 998889 Co-ordinator phone + 39 0444 998743 deliverable Database on Defects AUTHORS: F.

2 BONOLLO, G. TIMELLI, E. FIORESE (UNIVERSITY OF PADOVA DTG) E. GARIBOLDI, P. PARONA (ITALIAN ASSOCIATION OF METALLURGY AIM) L. ARNBERG (UNIVERSITY OF TRONDHEIM NTNU) Date: March 29th, 2013 Stacast - New Quality and Design Standards for Aluminium Alloys Cast Products FP7-NMP-2012-CSA-6 - project N. 319188 Stacast : New Quality and Design Standards for Aluminium Alloys Cast Products deliverable : Database on Defetcs Authors: F. Bonollo, G. Timelli, E. Fiorese, E. Gariboldi, P. Parona, L. Arnberg 2 Database on Defects 1. Introduction Defects are intrinsically generated by casting processes, due to several reasons. The final properties and in-service behaviour of castings are always related to microstructural features and to Defects : both microstructure and Defects are the results of process stages, alloys properties and dies & tools design.

3 As an example, it should be considered that in HPDC filling stage extreme conditions are established: complexity of components leads to complex dies, and the high production rates required (up to 120 shots/h) lead to very high filling velocities for the molten alloy (up to 40 m/s) with strong generation of turbulence in the flow. Solidification takes place in few seconds, and the die is first in contact with a molten alloy at more than 700 C and, after 30-40 seconds, with a sprayed lubricant at room temperature. For these reasons HPDC (as well as other Aluminium alloys casting processes, such as permanent mold casting process) can be considered a defect generating process.

4 Not only an average 5-10% scrap is typically produced, but the type, size and severity of Defects are varying. From these considerations, it seems that the potential of high-pressure die-casting and permanent mold casting processes will be completely exploited only when the quality level will be perfectly optimised. In this regard, the analysis of Defects allows the foundry to monitor the products quality respect to a quality standard. Further, the analysis of Defects provide to the foundry useful correlations between Defects type/distribution and their origin, so that it could be possible to define process modification for improving the quality.

5 One of the current targets of the Stacast project is the compilation and dissemination of common tools to allow foundries to define a proper, comparable, quality standard. The first tool to be proposed is a common basis of language, a terminology and classification of Defects in order to help die-casting foundries to face with increased confidence and ability the defect-related issues, to assure quality and reliability of their products. 2. The path towards a new Standard on Defect Classification Previous classifications of Defects There are three main approaches for Defects classification of cast components proposed in literature or currently adopted by foundries: - Cocks approach based on Defects geometry/location - Campbell approach based on Defects metallurgical origin/causes - NADCA approach based on Defects morphology.

6 The first approach was proposed by Cocks and discerns between surface and internal Defects (Table 1). The surface Defects are visible by naked eye and impact both on the product aesthetics and functionality. On the other hand, the internal Defects influence only the in-service properties of the component. As shown in Table 2, the second approach, proposed by Campbell, classifies Defects on the basis of their metallurgical origin/causes (casting geometry, cast alloy, die characteristics, die lubrication, process parameters, etc.). The main advantage offered by this classification is the opportunity to design and adopt strategies to improve products quality.

7 The main disadvantage of this approach is that the origin/causes of the defect must be defined concurrently to defect identification and that a single defect can be due to several concurring factors. Further, this approach is less suitable for Stacast - New Quality and Design Standards for Aluminium Alloys Cast Products FP7-NMP-2012-CSA-6 - project N. 319188 Stacast : New Quality and Design Standards for Aluminium Alloys Cast Products deliverable : Database on Defetcs Authors: F. Bonollo, G. Timelli, E. Fiorese, E. Gariboldi, P. Parona, L. Arnberg 3 direct application in foundries with respect to geometry/position-based approaches, where specific inspections can be proposed to reveal different defect groups.

8 The third approach was proposed by NADCA (North America Die Casting Association) and is based on Defects morphology. NADCA suggested seven Defects categories, that are indicated by a letter (Table 3). Each category is divided into groups, that are divided into subgroups. Category Class Type 1-General 2-Splash and shotting 3-Vortex 1-Cold shut 4-Lamination 1-Blisters 2-Sinks 2-Smooth irregularities 3-Lakes 1-Drag marks 1-Surface Defects 3-Rough surface 2-Solder 1-Hydrogen 1-Gas porosity 2-Oxidizing gases 1-Gross 2-Intergranular Cocks classification 2-Internal Defects 2-Shrink porosity 3-Cracks - hot tears Table 1. Classification of casting Defects according to Cocks.

9 Gas in solution (hydrogen) Gas entrapment during filling (air) Gas porosity Binder breakdown (core gases) Macro-porosity Shrinkage porosity Micro-porosity (interdendritic) Campbell classification Hot tearing, cracks Table 2. Classification of casting Defects according to Campbell. Category A-Metallic projection B-Cavities C-Discontinuities D-Defective surface E-Incomplete casting F-Incorrect dimension or shape NADCA classification G-Inclusion or structural anomalies Table 3. Classification of casting Defects according to NADCA. Stacast - New Quality and Design Standards for Aluminium Alloys Cast Products FP7-NMP-2012-CSA-6 - project N. 319188 Stacast : New Quality and Design Standards for Aluminium Alloys Cast Products deliverable : Database on Defetcs Authors: F.

10 Bonollo, G. Timelli, E. Fiorese, E. Gariboldi, P. Parona, L. Arnberg 4 Proposal of new classification of Defects Recently, the AIM (Italian Association of Metallurgy), after a 2-years survey carried out involving about 50 Al-alloys foundries, suggested a new classification approach, based on a 3-levels Defects individuation: I) morphology/location of Defects (internal, external, geometrical); II) metallurgical origin of Defects ( gaseous porosity, solidification shrinkage, etc.); III) specific type of Defects (the same metallurgical phenomenon may generate various Defects ). The level I is based on morphology/location of Defects , with reference to the investigation techniques suitable for their detection (visual inspections and controls involving the bulk material): there are internal and external (or surface) Defects .