This standard specifies the evaluation method and evaluation level of martensite and grain size of commonly used hot working die steel. This standard is applicable to the microstructure rating of hammer forging, machine forging, hot extrusion, hot blanking and die casting dies made of 5CrNiMo, 5Cr4W5Mo2V, 3Cr2Mo3W2V, 3Cr3Mo3W2V, 4Cr5MoSiV and 4Cr3Mo2NiVNbB steels and similar steel grades. JB/T 8420-1996 Microstructure rating of hot working die steel JB/T8420-1996 Standard download decompression password: www.bzxz.net

Mechanical Industry Standard of the People's Republic of China
JB/T 8420—96
Grading of Microstructure of Hot Working Die Steel
Published on September 3, 1996
Ministry of Machinery Industry of the People's Republic of China
Implementation on July 0, 1997
JB/T 8420—96
This standard is compiled on the basis of the scientific research work of "Selection and Application of Hot Working Die Steel". Six representative alloy steels are selected from the hot working die steels with large and wide applications in the mold industry at home and abroad. Through heat treatment at different temperatures, different microstructures are obtained. Then, a grade map is compiled according to the microstructure characteristics, the maximum length of martensite and its grain size. It is convenient for the comparison and evaluation of the determination method of the grain size of the product during production (B 6394-86. This standard is the first to be formulated and will be implemented from July 1, 1997. Appendix A and Appendix B of this standard are informative appendices. This standard was proposed and managed by the National Technical Committee for Heat Treatment Standardization. The drafting units of this standard are: Beijing Electromechanical Research Institute of the Ministry of Machinery Industry, Beijing Measuring Tool and Cutting Tool Factory, and Changchun First Automobile Factory. The main drafters of this standard are Lin Benghua, Ben Yalan, Zhang Yunian, Han Yuhui, and Yang Jing. 1 Scope
Machinery Industry Standard of the People's Republic of China
Microstructure Rating of Hot Working Die Steel
This standard specifies the evaluation method and rating level of the steel body and grain size of commonly used hot working die steels. JB/T842096
This standard is applicable to the microstructure rating of hammer forging, machine forging, hot extrusion, hot stamping and die casting dies made of 5CNiMo, 5Cr4W5Me2V, 3C-2W8V, 3C3M3W2V, 4Cr5MoSiV4Cr3Mo2NiVNbB steel and similar steel grades. 2 Reference standards
The provisions contained in the following standards constitute the provisions of this standard through reference in this standard. When this standard was published, the versions shown were valid. All standards will be revised. The parties using this standard should discuss the possibility of using the latest versions of the following standards. CB1299- 85
G1 6394- 86
GE1188-89
GB/T13298—91
3 Requirements
Technical conditions for alloy tool steel
Metal average grain size determination force method
Technical conditions for die forging hammers and forging presses Metal microstructure inspection method
3.1 The grade and chemical composition of hot working die castings shall comply with the provisions of GB1299 and Appendix A (suggestive appendix). 3. 2 The rough and plated parts of the mold should have sufficient pressure ratio and good post-forging heat treatment. The quality of forgings should comply with the provisions of GB1I880. + Test Specimen
4.1 The test specimen should be cut from the working part of the mold. The test specimen with the same melting furnace number, effective size, forging conditions and heat treatment specifications as the mold can also be used.
4.2 During the grinding and polishing process, the inspection surface of the test specimen is not allowed to be overheated to cause structural changes. The preparation of the test specimen should comply with GB/T13298 Regulations.
4.3 The sample slow agent is recommended to be H4% nitric acid ethanol solution or ethanol (80mL)-nitric acid (10mL)-hydrochloric acid (10mL) + picric acid () solution.
5 Microstructure grade characteristics and evaluation method
The microstructure is evaluated under a microscope with an effect of 500 times. 5.1
5.2 Each hot-working die steel is divided into 6 grades according to its microstructure characteristics and the maximum length of the martensitic needle (see length 1). The martensitic rating diagram is shown in national 1 ~ Figure 6,
5.3. Martensite is evaluated by metallographic comparison method: the inspection shall not be less than 3 fields of view, and the field of view with the longest martensitic needle shall be evaluated against the rating diagram of the corresponding steel grade:
5.4 When there is a dispute, the maximum length of the martensitic needle or the grain size can be measured. The grain size determination shall be in accordance with the provisions of GB6394. 5.5 Generally, the martensite rating of hot working dies is preferably 2 to 4, and the hoop strength level is -10 to 7. Approved by the Ministry of Machinery Industry on September 13, 1996
1997-07-8 [Implementation
5CrNiMo
Sfr4w5Mo2V
3cr2w8v
3Cr3M03W2V
4CrSMosiV
ACr3Ma2NiVNB
JB/T $420-96
Table 1 Microstructural characteristics of hot working die and maximum length of martensite needles Martensite type
Microstructural characteristics
Martensite + fine pearlite + ferrite
Hidden needle martensite + very little retained austenite Dimensional needle martensite + a small amount of retained austenite
Needle martensite + retained austenitebzxZ.net
Coarse martensite + relatively high retained austenite Coarse needle martensite + strong residual austenite Martensite + pearlite + a small amount of carbide
Hidden needle Martensite + very small amount of retained austenite + residual fine martensite + a small amount of residual martensite + carbide needle-shaped martensite + retained austenite + relatively large carbides Needle-shaped martensite + more retained austenite + large carbides Needle-shaped martensite + more retained austenite + carbides Needle-shaped martensite + more retained austenite + large carbides Needle-shaped martensite + more retained austenite + large carbides Needle-shaped martensite + fine pearlite + a small amount of carbides Needle-shaped martensite + very small amount of retained austenite + sputtered fine martensite + a small amount of retained austenite + carbides Needle-shaped martensite + retained austenite + relatively large carbides Needle-shaped martensite + more retained austenite + large carbides Martensite, a large amount of residual austenite, a carbide martensite, fine pearlite + a small amount of carbides
hidden martensite + a very small amount of retained austenite + a small amount of carbides, fine needle martensite, a small amount of basic residual austenite + a small amount of magnetite, needle-shaped martensite + retained austenite + a small amount of pad carbon, relatively large needle-shaped martensite + more residual huitrite + a very small amount of carbides, a large amount of residual austenite + a very small amount of carbon-free martensite + upper bainite
hidden needle martensite + a very small amount of lamellar austenite
needle martensite + a small amount of residual austenite
Special martensite + residual austenite
Coarse martensite + more residual austenite Coarse needle-shaped martensite + a large amount of retained austenite Martensite + fine spheroidal ferrite + needle-shaped ferrite + a small amount of carbide Needle-shaped martensite + a small amount of retained austenite + carbide Fine needle-shaped martensite + a small amount of retained austenite + carbide Needle-shaped martensite + retained austenite + carbide Large lamp-shaped martensite + more residual austenite + Coarse needle-shaped martensite + a large amount of retained austenite + carbide Maximum length of martensite needles
JB/T 842096
Figure 12 Grade
JB/T8420-96
Figure 1-Grade
Figure 1.66 Grade
Figure 15CrNi steel martensite rating diagram ×500JB/T 8420 -96
Figure 211 Grade
盈2-2 Grade
Figure 2-53 Grade
JB/T 8420 -96
Figure 266 Grade
Figure? 504WM?2V steel martensite rating diagram
IB/T 8420 96
Figure 3-1 Level 1
Zone 3-22 Level
Figure 8-83 Level
JB/T 842096
Figure-44 Level
Figure 5-5 Line
[Figure 33℃2w8V steel martensite rating diagram]00JB/T 8420--96
Figure 1-Level
JB/T 8420-96
Figure 4-4 Level 4
Figure 45 Level
Figure 4-5 Level
Figure 43Cr3Mr3W2V steel martensite wrinkle rating diagram
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