QC/T 273-2025Technical specifications of aluminum-alloy die casting for automobiles (English PDF)

3.1 High stress zone

The area in the CAE stress analysis cloud map of the casting where the value is greater than or equal to 60% of the minimum yield strength of the material.

3.2 Functional zone

The area that castings require sealing and assembly.

NOTE. Such as threaded holes and bearing mounting surfaces.

3.3 Non-critical zone

Areas on the casting other than high stress zones and functional zones.

3.4 Separately cast test sample

Standard casting samples that are obtained by using the same furnace of molten aluminum as the production castings, and by employing the same casting method and heat treatment process as the production castings.

3.5 Test sample from casting

A sample cut directly from the casting body and machined.

3.6 Porosity

The percentage of the total area of pores within the reference envelope shape to the area of the selected reference surface.

3.7 Maximum pore size

The maximum circumscribed circle diameter of a single hole.

6.1 Die casting method and heat treatment state

6.1.1 The die casting method (high pressure casting, vacuum high pressure casting) and heat treatment condition of the casting shall be agreed upon by the supplier and the purchaser.

6.1.2 Die castings are typically supplied in the as-cast state. For die castings that require

heat treatment to meet special application requirements, the heat treatment process shall be agreed upon by the supplier and the purchaser.

6.1.3 Mark the heat treatment state code on the drawings or technical agreement as per Chapter 4.

6.2 Chemical composition

The chemical composition of die-cast aluminum alloys shall conform to GB/T 15114 or the relevant material standards and technical agreements agreed upon by both the supplier and the purchaser. Annex A lists the composition requirements for commonly used die-cast aluminum alloys in the automotive industry.

6.3 Mechanical properties

6.3.1 When using separately cast test samples for testing, the mechanical properties

shall conform to GB/T 15114 or other standards and technical agreements agreed upon by the supplier and the purchaser. Annex B contains the mechanical property values of commonly used die-cast aluminum alloys in the automotive industry.

6.3.2 When testing with test samples from casting, their mechanical properties shall

meet the requirements of the drawings or technical agreements agreed upon by both the supplier and the purchaser.

6.3.3 Perform hardness testing on designated areas of the die casting. The hardness

value shall conform to the standards, drawings, or technical agreements adopted by both the supplier and the purchaser.

6.3.4 For Class III die castings, mechanical properties may not be used as an acceptance criterion. Whether mechanical properties are used as an acceptance criterion for other types of die castings shall be agreed upon by the supplier and the purchaser based on the usage requirements of the die castings.

6.4 Microstructure

6.4.1 Whether the microstructure of the die-cast parts shall be used as an acceptance

criterion shall be agreed upon by the supplier and the purchaser.

6.8.1 The airtightness requirements of die castings shall comply with the provisions of the drawings or technical agreements agreed upon by both the supplier and the purchaser.

6.8.2 Subject to the consent of the purchaser, the supplier may perform one

impregnation or leakage repair treatment on the die casting without affecting its use.

6.9 Repair and correction of die-cast parts

6.9.1 Surface defects in die-cast parts may be removed by grinding. However, the dimensions after grinding must meet the dimensional tolerances of the die-cast parts.

Furthermore, the roughness of the ground area must conform to the specifications agreed upon by both the supplier and the purchaser in the drawings or technical agreement.

6.9.2 With the purchaser's consent, mechanical shaping and straightening of die-cast parts are permitted. After straightening, the supplier shall conduct a comprehensive penetrating inspection of the die-cast parts surface to confirm the absence of cracks.

6.9.3 With the consent of the purchaser, die-cast parts may be repaired by welding. The welding wire, welding location, area, depth, and number of welds shall be agreed upon by both the supplier and the purchaser. Die-cast parts requiring heat treatment shall undergo heat treatment after the welding repair is completed.

7.1 Chemical composition

The chemical composition testing methods for die castings shall be in accordance with GB/T 20975 (all parts) or GB/T 7999.Other testing methods are permitted provided that the accuracy of the analysis is guaranteed. In case of disputes over the analytical results, arbitration shall be conducted in accordance with GB/T 20975 (all parts).

7.2 Mechanical properties

7.2.1 Mechanical property testing shall be conducted in accordance with GB/T 228.1.

The test samples shall be separately cast test samples or test samples from casting cut from die-cast parts.

7.2.2 Hardness testing shall be performed in accordance with GB/T 231.1.

7.3 Microstructure

7.3.1 Microstructure testing shall be conducted in accordance with GB/T 13298.

7.3.2 The overheating condition of the heat-treated die castings shall be tested according to JB/T 7946.2.

7.4 Dimensions

Dimensional inspection of die-cast parts can typically be performed using conventional inspection tools and methods such as 3D scanning and coordinate measuring machines.

Dimensions of deep cavities and internal structural features that are difficult to measure can be inspected using CT scanning or sectioning methods.

7.5 Surface quality

7.5.1 The roughness rating of the unmachined surfaces of die castings shall be in accordance with GB/T 15056.

7.5.2 The surface roughness of die castings that require shot peening, shot blasting, or sandblasting shall conform to the requirements of GB/T 6060.3.

7.5.3 When surface cracks of die castings need to be tested by penetrant testing, the requirements of HB/Z 61 shall apply.

7.6 Internal quality

7.6.1 When using X-rays to inspect the internal defects of die castings, the rating of defects such as internal porosity, looseness, and inclusions shall be in accordance with ASTM E505.Appropriate and reliable X-ray flaw detection methods shall be developed for different die castings to ensure the accuracy of the inspection results.

7.6.2 When metallographic sectioning is used to inspect internal defects (porosity, pore

size) in die castings, the sectioning location shall be agreed upon by both the supplier and the purchaser. The section to be inspected shall be pre-ground and metallographically polished, and shall comply with the provisions of Annex C.

7.6.3 When using CT to detect internal defects in die castings, the procedure shall be in accordance with GB/T 36589.

7.6.4 When there is a dispute over the X-ray testing results, the CT testing method shall

be used as the arbitration method.

7.7 Airtightness

The airtightness of die-cast parts can be tested using dry methods (such as leakage testing) and wet methods (such as water immersion method). The testing method shall be agreed upon by the supplier and the purchaser.

8.1 Batching rules

Die castings produced in the same smelting furnace, casting shift, and heat treatment ......