JB/T 7946.3-1999 This standard is a revision of JB/T 7946.3-95 "Pinholes in Cast Aluminum Alloys". During the revision, only editorial changes were made according to relevant regulations, and the main technical content remained unchanged. This standard specifies the classification principles and rating methods for the low-magnification pinhole degree of cast aluminum alloys. This standard is applicable to the assessment of the pinhole degree of cast aluminum alloys. JB/T 7946.3-1999 Pinholes in Cast Aluminum Alloys JB/T7946.3-1999 Standard download decompression password: www.bzxz.net

ICS 77. 120. 10
Mechanical Industry Standard of the People's Republic of China
JB/T7946.1~7946.4--1999
Metallograph of cast aluminium alloys1999-06-24 Issued
National Machinery Industry Week
2000-01-01 Implementation
JB 7946.3-1999bzxz.net
This standard is a revision of JB/T7946.3..-95 "Pinholes in cast aluminium alloys". During the revision, the original standard was edited and the main technical content remained unchanged.
This standard replaces JB 7946.3-95 from the date of implementation. This standard was proposed and managed by the National Technical Committee for Casting Standardization. The drafting units of this standard are: Shenyang Foundry and Shenyang Foundry Research Institute. 10
1 Scope
Mechanical Industry Standard of the People's Republic of China
Metallograph or cast aluminium alloysCast aluminium alloys --Pinhole This standard specifies the classification principle and rating method of low-power pinhole of cast aluminium alloys. This standard is applicable to the evaluation of pinhole of cast aluminium alloys. 2 Cutting and preparation of samples
JB/T7946.3-1999
Replaces JB/T7946.3-95
2.1 Metallographic samples are usually taken from the thick and large parts of the castings where solidification is slow, and can also be cut from the designated parts of the castings according to the provisions of the technical documents. 2.2 The metallographic samples should be machined to a surface roughness R value of not more than 1.6 μm, and can be polished with sandpaper if necessary. 2.3 The prepared metallographic samples should be cleaned with gasoline, alcohol or acetone before corrosion. The cleaned metallographic specimen is etched with 10%~15% sodium hydroxide aqueous solution. The etching temperature and etching time are determined according to the low-power etching temperature-time curve in Figure 2.4. The recommended etching temperature is controlled at 25℃+5℃, which is more suitable: 18 Figure 1 Low-power etching temperature-time curve National Machinery Industry Bureau [999-06-24 approved 2000-01-01 implementation JB/T7946.3-1999 2.5 The ratio of the amount of etching agent to the volume of the sample diffused part should not be less than 10. For the corrosive agent used for a long time, the etching time should be appropriately extended, and the new etching agent should be replaced or supplemented regularly. 2.6 After etching, the sample is rinsed with water, and then the corrosion film on the surface of the sample is removed with a 20%~25% nitric acid aqueous solution. After removing the film, the sample is washed with water and dried.
2.7 It is allowed to use the abrasion method to corrode the metallographic sample, but in case of dispute, the etching method shall prevail. 3 Macro inspection
3.1 Compare the sample after corrosion, cleaning and drying with the grading standard picture for daylight viewing. Determine the pinhole grade of the sample. 3.2 The pinhole degree of cast aluminum alloy is divided into five levels. The standard pictures are Figure 2 (level 1), Figure 3 (level 2), Figure 4 (level 3), Figure 5 (level 4) and Figure 6 (level 5
Figure 2 Level 1
Figure 4 Level 3
Figure 3 Level 2
Figure 5 Level 4
JB/T7946.3—1999
Figure 6 Level 5
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