CASTASIL® 37
AlSi9MnMoZr HPDC ALLOY
Castasil 37 is an AlSi9MnMoZr aluminium high pressure die casting alloy developed for large, complex and structural castings. It combines excellent castability with high ductility in the as-cast condition, dimensional stability and strong joining performance.
In particular, the low magnesium content supports long-term stability of the mechanical properties. Furthermore, Castasil® 37 can be used for many structural applications without conventional T6 or T7 solution heat treatment. As a result, distortion and quench-related processing risks can be reduced.
STRUCTURAL HPDC
WITHOUT COMPLEX HEAT TREATMENT
Castasil 37 was designed to provide useful strength and high elongation directly after high pressure die casting. Therefore, complex structural components can often remain in the F, or as-cast, condition.
In addition, silicon, manganese, molybdenum, zirconium and strontium define the alloy concept. Meanwhile, magnesium is deliberately kept at a very low level. Consequently, the alloy offers excellent long-term dimensional and mechanical stability.
CASTASIL 37
CHEMICAL COMPOSITION
The Castasil 37 chemical composition is based on the AlSi9MnMoZr alloy concept. Silicon represents the main alloying range, while manganese, molybdenum, zirconium and strontium are controlled within defined limits.
In contrast, magnesium is deliberately restricted to a very low maximum value. Therefore, the chemistry supports high ductility and long-term stability in the as-cast condition.
AlSi9MnMoZr
| Range | Si | Fe | Cu | Mn | Mg | Zn | Mo | Zr | Ti | Sr | Others |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Minimum | 8.50 | – | – | 0.35 | – | – | 0.10 | 0.10 | – | 0.006 | – |
| Maximum | 10.50 | 0.15 | 0.05 | 0.60 | 0.06 | 0.07 | 0.30 | 0.30 | 0.15 | 0.025 | 0.10 |
Reference manufacturer values for Castasil® 37 ingot composition. Values are expressed as mass percent. Current manufacturer specifications should always be verified for production and engineering release.
CASTASIL 37
MECHANICAL PROPERTIES
The Castasil 37 mechanical properties depend strongly on casting wall thickness and the resulting solidification conditions. Nevertheless, the manufacturer specifies high elongation of 10–14 % across the documented 2–7 mm wall-thickness range.
In particular, thinner sections achieve the highest strength levels. Therefore, component geometry and wall thickness should be evaluated together when defining mechanical requirements for structural HPDC.
MECHANICAL PROPERTY RANGE · F CONDITION
| Wall Thickness | Yield Strength Rp0.2 | Tensile Strength Rm | Elongation A |
|---|---|---|---|
| 2–3 mm | 120–150 MPa | 260–300 MPa | 10–14 % |
| 3–5 mm | 100–130 MPa | 230–280 MPa | 10–14 % |
| 5–7 mm | 80–110 MPa | 200–250 MPa | 10–14 % |
WALL THICKNESS
MATTERS
Increasing wall thickness slows local solidification. Consequently, the documented yield and tensile strength ranges decrease as the wall thickness increases.
However, the specified elongation remains between 10 and 14 % throughout all three thickness ranges. As a result, Castasil 37 retains a strong ductility profile even in comparatively thick structural sections.
CASTASIL 37 FATIGUE,
CORROSION & STABILITY
Castasil 37 fatigue performance, corrosion behavior and long-term stability are particularly relevant for automotive structural applications. Therefore, the material must be evaluated beyond static tensile properties alone.
DYNAMIC
STRENGTH
RHEINFELDEN publishes fatigue data for Castasil® 37 in the as-cast condition. At 50 million cycles and 5 % fracture probability, the documented calculation range is:
However, fatigue performance depends strongly on casting structure, defects, surface condition, geometry and local stress concentration.
VERY GOOD
CORROSION RESISTANCE
RHEINFELDEN characterizes Castasil® 37 as having very good corrosion resistance. Furthermore, comparative salt-spray testing has shown strong resistance under defined laboratory conditions.
In that manufacturer comparison, the high-purity Castasil 37 alloy showed a greater tendency toward localized pitting rather than the more general corrosion pattern observed with the comparison alloy.
NO THERMAL
LONG-TERM AGING
A defining Castasil 37 characteristic is the very low magnesium content. According to RHEINFELDEN, this is important for long-term stability of the mechanical properties.
Consequently, structural parts can avoid the dimensional changes, residual stresses and process complexity associated with extensive solution heat-treatment routes.
CASTASIL 37 HPDC
& HEAT-TREATMENT STRATEGY
Castasil 37 HPDC processing is designed around strong as-cast performance. Therefore, many structural applications can avoid conventional solution heat treatment and the associated quenching process.
Furthermore, the manufacturer describes Castasil 37 as suitable for minimum wall thicknesses and complex geometries. An optional single-stage treatment can also increase ductility when required.
EXCELLENT
CASTABILITY
The alloy was specifically developed for high pressure die casting. Therefore, large and complex structural geometries can be produced while maintaining useful mechanical properties.
MINIMUM
WALL THICKNESS
RHEINFELDEN highlights Castasil® 37 for thin-wall structural applications. Consequently, it supports lightweight design and large integrated cast structures.
AS-CAST
PERFORMANCE
High elongation is already available in the F condition. As a result, extensive solution heat treatment is not automatically required for every structural application.
SINGLE-STAGE
TREATMENT
Manufacturer documentation states that ductility can be increased further through a single-stage heat treatment. However, the correct treatment must be validated for the actual component and process.
DIMENSIONAL
STABILITY
Avoiding solution treatment can remove an important source of distortion, blistering and quench-induced residual stress. Therefore, the as-cast concept can simplify downstream production for suitable structural parts.
Nevertheless, casting quality remains decisive. Melt cleanliness, venting, vacuum strategy, mold filling, wall thickness and local solidification conditions still determine the structural quality of the finished HPDC component.
CASTASIL 37 JOINING
& MANUFACTURING
Castasil 37 joining performance is important because structural castings normally become part of larger vehicle assemblies. Therefore, weldability, mechanical joining and adhesive bonding are central parts of the material concept.
EXCELLENT
WELDABILITY
The manufacturer highlights excellent weldability as a defining property. Consequently, cast components can be integrated into suitable welded aluminium structural concepts.
SELF-PIERCING
RIVETING
Riveting trials in the as-cast state produced good manufacturer results. High elongation is especially beneficial because the material must deform locally during the joining operation.
ADHESIVE
BONDING
Castasil® 37 is also identified as suitable for adhesive connections in automotive structures. Therefore, hybrid mechanical and adhesive joining strategies are possible.
MACHINING
& CLINCHING
Manufacturer literature describes the alloy as highly machinable and suitable for clinching. As a result, functional interfaces and additional joining operations can be integrated after casting.
WHY AS-CAST DUCTILITY MATTERS FOR JOINING
Mechanical joining processes introduce significant local deformation. Therefore, maintaining useful elongation directly in the as-cast state offers an important manufacturing advantage. Furthermore, avoiding extensive heat treatment can help preserve component geometry before the joining operation.
CASTASIL 37
AUTOMOTIVE APPLICATIONS
Castasil 37 automotive applications demonstrate the advantage of combining large HPDC geometry with high as-cast ductility and dimensional stability.
In addition, manufacturer documentation and historical technical project material show Castasil® 37 in body structure, roof, door and space-frame applications. Consequently, the alloy is closely associated with structural automotive die casting.
SHOCK
TOWER
RHEINFELDEN currently presents a Castasil® 37 high pressure die cast shock tower as a structural application example. Such components combine complex geometry with body-load transfer.
REAR LONGITUDINAL
MEMBER
Current RHEINFELDEN material also shows a large rear longitudinal vehicle structure produced in Castasil® 37. Therefore, the alloy is relevant to large integrated body structures.
AUDI A8
SPACE-FRAME NODES
The RHEINFELDEN roadshow material hosted by ALUMAG® documents Castasil 37 space-frame nodes for the Audi A8. Importantly, these parts were used in the as-cast condition.
JAGUAR XK
DOOR STRUCTURE
Historical technical documentation also describes Castasil ® 37 door components for the Jaguar XK. The components were used in the as-cast state and mechanically joined.
CASTASIL 37 APPLICATION LANDSCAPE
CASTASIL 37
TECHNICAL FAQ
The following answers summarize key engineering questions regarding Castasil 37 composition, mechanical properties, HPDC processing, fatigue behavior, joining and automotive applications.
What is Castasil 37?
Castasil® 37 is an AlSi9MnMoZr aluminium high pressure die casting alloy developed for large and complex structural castings with high ductility in the as-cast state.
What is the Castasil 37 alloy designation?
The chemical designation published by RHEINFELDEN ALLOYS is AlSi9MnMoZr.
Does Castasil 37 require heat treatment?
Not necessarily. One of the alloy’s defining advantages is high ductility in the as-cast condition. However, a single-stage treatment can further increase ductility when required.
What elongation does Castasil 37 achieve?
RHEINFELDEN specifies an elongation range of 10–14 % in the as-cast condition for wall thicknesses from 2 to 7 mm.
Is Castasil 37 suitable for structural HPDC?
Yes. Documented applications include shock towers, longitudinal members, space-frame nodes and other large structural automotive castings.
Is Castasil 37 weldable?
Yes. Manufacturer documentation describes excellent weldability. Furthermore, the alloy is suitable for mechanical and adhesive joining concepts.
What fatigue strength is reported for Castasil 37?
RHEINFELDEN publishes a range of 80–95 MPa at 50 million cycles for the documented 5 % fracture-probability fatigue evaluation. Component design requires separate validation.
Why is magnesium kept low in Castasil 37?
According to RHEINFELDEN, the very low magnesium content is essential for the long-term stability of the mechanical properties.
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