This standard specifies the terminology, product classification, technical requirements, test methods, inspection rules and marking, packaging, transportation and storage of semi-hydrated gypsum powder. This standard applies to semi-hydrated gypsum powder for ceramic molds. QB/T 1639-1992 Gypsum powder for ceramic molds QB/T1639-1992 Standard download decompression password: www.bzxz.net

Light Industry Standard of the People's Republic of China
Gypsum Powder for Ceramic Moulds
Subject Content and Scope of Application
QB/T 1639- 1992
This standard specifies the terminology, product classification, technical requirements, test methods, inspection rules and marking, packaging, transportation and storage of semi-hydrated gypsum powder. This standard applies to semi-hydrated gypsum powder for ceramic moulds. 2 Reference standards
GB/T2828 Count sampling procedure and sampling table for batch inspection (applicable to inspection of continuous batches) GB/T2829 Count sampling procedure and sampling table for periodic inspection (applicable to inspection of stability of production process) GB/T 5000
Terms and terms of daily-use ceramics
QB/T1640 Test method for physical properties of gypsum powder for ceramic molds QB/T 1641
3 Terms
3.1 Standard consistency
Chemical analysis method for ceramic stone
Under the conditions specified in QB/T1640, when the free expansion diameter of gypsum slurry reaches (220±5) mm, the percentage of water added to the amount of gypsum powder.
3.2 Other terms shall be implemented in accordance with GB/T5000.
4 Product classification
According to the product crystal form, it is divided into α-hemihydrate gypsum powder and β-hemihydrate gypsum powder. 5 Technical requirements
5.1 White color (except modified gypsum), no impurities and lumps. 5.2 Free water content shall not be greater than 0.5%.
5.3 Physical properties shall comply with the provisions of Table 1.
5.4 Chemical composition shall comply with the provisions of Table 2.
5.5 Classification of first-class products and qualified products according to product quality Table 1
Physical properties
Sieve residue.%
Standard consistency.%
0. 15 mm aperture
0.090 mm aperture
Approved by the Ministry of Light Industry of the People's Republic of China on January 15, 1993 436
Quasi-hot compaction
Implemented on September 1, 1993www.bzxz.net
Physical properties
Initial setting time, min
Final setting time·min
2 h Wet flexural strength, MPa
45C dry flexural strength.MPa
Chemical composition
Crystallized water
Acid insoluble matter
Test method
6.1 Physical properties shall be determined in accordance with QB/T1640.
QB/T1639—1992
Table 1 (end)
Chemical composition and free water shall be determined in accordance with QB/T1641. 6.2
7 Inspection rules
7.1 Product inspection is divided into delivery inspection and type inspection. Quality products
Qualified products
Qualified products
7.2 Each batch of products can be shipped only after passing the inspection, and must be accompanied by documents proving the quality of the products when leaving the factory. 7.3 Delivery inspection
7.3.1 Delivery inspection items are the contents specified in Articles 5.1 and 5.3. %
7.3.2 Products are batched according to the same variety and grade. Samples are randomly drawn. 7.3.3 Delivery inspection shall be carried out in accordance with GB/T2828. The classification of non-conformity, qualified quality level, inspection level and sampling plan of each inspection item are shown in Table 3.
Inspection items
Non-conformity classification
Qualified quality level
Inspection level
Scheme type and strictness
Special inspection-sub-sampling plan
7.3.4 Sample units, if any one of the specified inspection items is unqualified, the sample unit shall be judged as unqualified. 7.3.5 When a batch is judged as unqualified after inspection, the batch of products shall be reprocessed and graded by the delivery party before it can be submitted for inspection again. 7.4 Type inspection
7.4.1 Type inspection shall be carried out once a year. Type inspection shall also be carried out in any of the following circumstances. a.
New product trial production and identification:
After formal production, when there are major changes in structure, materials and processes; 437
Quasi-heating real net
Quasi-running material room
When the product resumes production after a long period of suspension;
QB/T1639—1992
d When the superior supervisory department proposes a requirement for type inspection. The items of type inspection are the contents specified in Articles 5.1 to 5.4. 7.4.2
7.4.3 The samples for type inspection shall be drawn from the products produced within this cycle and qualified by the manufacturer. 7.4.4 Type inspection shall be carried out in accordance with GB/T2829. The classification of non-conforming items, non-conforming quality level, discrimination level, sampling plan and sample size are shown in Table 4.
Inspection items
Non-conforming classification
Non-conforming quality level
Discrimination level
Sampling plan
Sample size
7.4.5 Sample unit. If one item in the inspection items is unqualified, the sample unit shall be judged as unqualified; if it is judged as an unqualified batch after inspection, the batch of products shall be reprocessed and graded by the delivery party before it can be submitted for inspection again. 8 Marking, packaging, transportation, storage
8.1 All products shall be packed in moisture-proof bags before leaving the factory. The weight error of each bag shall not exceed 2% of the marked weight. The bag shall have the product name, manufacturer name, moisture-proof mark and product grade, validity period and export date card. 8.2 During transportation, it is strictly forbidden to be damp to prevent loose packages and mixed impurities. When storing, it must be placed in a ventilated and dry place. Additional remarks:
This standard is proposed by the Quality Standards Promotion Department of the Ministry of Light Industry. This standard is under the jurisdiction of the National Ceramic Standardization Center. This standard is drafted by the Ceramic Industry Science Research Institute of the Ministry of Light Industry. The main drafters of this standard are Li Miaoliang, Shen Wei, Huang Cai'e, and Li Feng. From the date of implementation of this standard, the original Ministry of Light Industry standard QB904-1983 "Gypsum powder for daily ceramic molds" will be invalidated. 438
Quasi-heating network
Four standard road material costs
Tip: This standard content only shows part of the intercepted content of the complete standard. If you need the complete standard, please go to the top to download the complete standard document for free.