Judgment Method of Forging Quality Grade

Quality classification of forgings is an important method to promote and improve the quality of forgings. It is stipulated in the National Level Standard for Machinery Industry Enterprises promulgated in 1987. It is pointed out that forgings are classified into first-class products and qualified products, and the proportion of first-class products in the total output value of enterprises of corresponding grades is stipulated. Therefore, it is helpful to further improve the quality of forgings to understand the classification standard of forgings, master the methods of forgings classification and the content of assessment. 

①. Relevant Standards for Forging Grade
1. Qualified steel free forgings
The internal quality and external quality of forgings are up to JB4385-87 《General Technical Conditions for Free Forging on Hammer》and meet the requirements of the contract.
The main shape size of forgings reaches JB4249-1986 《Machining Allowance and Tolerance of Steel Free Forging on Hammer》.
2. First-class steel free forgings
The internal and external quality meet the requirements of JM4385-87 《General Technical Conditions for Free Forging on Hammers》.
The main dimensions of the shape meet the requirements of DIN7527《Processing allowance and allowable deviation of steel free forgings》 (German standard).
3. Qualified products of steel die forgings
Structural design conforms to JB/Z295-87 《Die Forging Process Structural Elements》.
The internal quality and external quality are up to JB3835-1985《General Technical Conditions for Steel Die Forging》 and meet the requirements of the contract.
The main appearance dimensions meet the requirements of JB3834-1985 《Tolerance and Machining Allowance of Steel Die Forging》.
4. First-class steel die forgings
Structural design conforms to JB/Z295-87《 Die Forging Process Structural Elements》.
The appearance quality of forgings meets the German standard DIN7526-69.
The internal quality conforms to JB3835-1985 《General Technical Conditions for Steel Die Forging" and meets the requirements of the contract》.
The precision of forging appearance size is in accordance with DIN7526. 

②. Testing and testing methods
Forging structure design, appearance quality and shape dimension are checked by conventional measuring tools or templates; die forgings and complex forgings are checked by platform marking; surface defects are observed by naked eyes or checked by conventional surface defects such as pickling and magnetic powder according to need.
The quality and intrinsic quality of raw materials can be tested by chemical analysis, hardness test, low magnification test, fracture test, mechanical properties, impact test and metallographic test according to the requirements of the contract.

③. The Method of Determining Forging Grade
1. Sampling and Sealing Quantity
Free forgings on hammers are sampled at the production site according to the state of supply. The number of free forgings on hammers is not less than 10 pieces.
The number of samples for die forgings depends on the production site and stock situation, but not less than 5 kinds, and the number of samples for each variety is not less than 5 pieces.          
2. Judgment of quality grade of sample forgings
Sample forgings are tested and counted item by item according to the contract requirements and testing methods. After calculating the total item pass rate, the quality grade is determined according to the total item pass rate value.
3. For die forgings with inherent quality requirements, samples can be cut from the sampled forgings. The test results shall conform to the acceptance standards or technical agreements stipulated in the contract.