JB/T 7946.2-1999 JB/T 7946.2-1999 Cast aluminum silicon alloy overburning JB/T7946.2-1999 Standard download decompression password: www.bzxz.net

ICS77.120.10
Machinery Industry Standard of the People's Republic of China
JB/T7946.2—1999
Metallography of cast aluminium alloys
Cast aluminium-silicon alloys-Burning
Metallogr aphof cast aluminium alloysCastaluminium-silicon alloys-Burning1999-06-24Promulgated
National Bureau of Machinery Industry
Implementation on 2000-01-01
JB/T7946.2-1999
This standard is a revision of JB/T7946.2—95 "Cast aluminium-silicon alloys-Burning". During the revision, editorial changes were made to the original standard, and the main technical content remained unchanged.
This standard replaces JB/T
7946.2—95
This standard is 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. 1
1 Scope
Mechanical Industry Standard of the People's Republic of China
Metallography of cast aluminium alloysCastaluminium-silion alloysBuming This standard specifies the classification principles and rating methods for the heat-treated burnt microstructure of cast aluminium-silion alloys. This standard is applicable to the evaluation of the heat-treated burnt microstructure of cast aluminium-silion alloys. 2 Definitions
This standard adopts the following definitions.
2.1 Overburning
JB/T 7946.2—1999
Replaces JB/T7946.2—95
Any alloy with overburning triangle or grain boundary melting, remelting ball, and remelting eutectic metallurgical structure is called overburning. 2.2 Overburning triangle
When casting aluminum silicon alloy crystallizes, the intersection of grains is often the last to solidify, so a large number of low-melting eutectics are concentrated. During heat treatment, these eutectics are easy to overburn and remelt, and form sharp triangles under the action of surface tension, which is the so-called overburning triangle. 2.3 Remelting ball
When casting aluminum silicon alloy is heat treated, the low-melting eutectic in the dendrite melts, and under the action of surface tension, the liquid phase spheroidizes, forming remelting eutectic spheroids.
2.4 Remelting eutectic
During the process of heat treatment and heat preservation, the temperature of cast aluminum-silicon alloy is relatively high. In the overburned triangle, grain boundary area and low-melting materials in the grain melt and cool to form ternary, binary and other remelting eutectics. 3. Sample cutting and preparation
3.1 Metallographic samples are usually cut from tensile test bars that are heat treated with castings. If there are special requirements, they can be cut according to the provisions of the technical documents. 3.2 The metallographic samples are mechanically polished after rough grinding and fine grinding with metallographic sandpaper. If necessary, manual fine polishing can be performed. 3.3 The metallographic samples for evaluating overburned structures do not need to be etched. 3.4 In the process of cutting and preparing metallographic samples, it should be ensured that the structure does not change. Microscopic inspection
The overburned structure of cast aluminum-silicon alloy is evaluated by optical microscope, and the magnification is 400 times. 4.2 During microscopic inspection, the entire inspected surface should be viewed first, and then the most serious field of view corresponding to the level diagram should be selected for evaluation. 4.3 The burnt structure of cast aluminum-silicon alloy is divided into five levels: normal structure, overheated structure, slightly burnt structure, burnt structure and severely burnt structure.
Approved by the State Bureau of Machinery Industry on June 24, 1999 and implemented on January 1, 2000
JB/T7946.2—1999
4.4 The classification of burnt structure of cast aluminum-silicon alloy is shown in Table 1. Table 1
Grade name
Normal structure
Overheated structure
Slightly overburned structure
Overburned structure
Severely overburned structure
Microstructure characteristics
Eutectoid silicon corners are rounded, but not aggregated and grownEutectoid silicon corners are rounded, aggregated and grown, but no overburned structure characteristicsEutectoid silicon grows further, and the corners have begun to become polygonal (the eutectic silicon edges are straight), but most of the eutectic silicon corners are still smooth, and overburned triangles or grain boundary meltingEutectoid silicon aggregates and grows, most of the corners are straight, and typical remelting balls and multi-component remelting eutectic structures appearThe silicon phase is almost completely polygonal, and the remelting eutectic structure is coarseFigure 1
Normal structure
Figure 3Slightly overburned structure
Overheated structure||tt| |Figure 4 Overburned structure
7946.2—1999
Severe overburned structure
Mechanical industry standard
Metallography of cast aluminum alloy
Overburned cast aluminum silicon alloy
JB/T7946.2-1999
Published by the Machinery Standardization Research Institute of the Ministry of Machinery Industry and printed by the Machinery Standardization Research Institute of the Ministry of Machinery Industry (No. 2 Shouti South Road, Beijing
Postal code 100044)bzxZ.net
Format 880×1230
Edition X, XX, 19XX
Printing number 1-XXX
Printing sheet XIX Number of words XXX,XXX
Xth printing, XX, 19XX
Price XXXXX Yuan
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