JB/T 7905-1999 This standard is a revision of JB/T 7905-95 "Sampling of sintered metal materials (excluding cemented carbide)". This standard specifies the sampling of test specimens for the inspection of dimensions, mechanical and physical properties and chemical composition of sintered metal materials (excluding cemented carbide). The standard was first issued on March 25, 1986 as GB 5957-86 and was adjusted to JB/T 7905-95 on April 14, 1996. JB/T 7905-1999 Sampling of sintered metal materials (excluding cemented carbide) JB/T7905-1999 standard download decompression password: www.bzxz.net

ICS77.160
Machinery Industry Standard of the People's Republic of China
JB/T7905-1999
Sintered metal materials (excluding hardmetals)-Sampling
Sintered metal materials, excluding hardmetals-Sampling1999-08-06 Issued
National Bureau of Machinery Industry
2000-01-01 Implementation
JB/T7905-1999
This standard is a revision of JB/T7905--95 "Sintered metal materials (excluding hardmetals)-Sampling". During the revision, only editorial changes were made to the original standard, and the main technical content remained unchanged. This standard replaces JB/T7905-95 from the date of implementation. This standard is proposed and managed by the Technical Committee for Standardization of Powder Metallurgy Products. The main drafting unit of this standard: Beijing Powder Metallurgy Research Institute. The main drafters of this standard are Wu Rongwei, Li Jian and Cao Baoxing. This standard was first issued on March 25, 1986 as GB5957--86, and the standard number was adjusted to JB/T790595 in April 1996.
Mechanical Industry Standard of the People's Republic of China
Sintered metal materials (excluding hard metals)-Sampling
Sintered metal materials, excluding hard metals-Sampling JB/T7905-1999
Replaces JB/T7905-95
This standard applies to the sampling method for testing the size, mechanical and physical properties and chemical composition of sintered metal materials (excluding hard metals).
The principle is that the acceptable quality level (AQL) of a batch of products can be determined by testing the performance of samples (parts). It is recommended to use the counting sampling method. Sampling should comply with the plan agreed upon by the relevant parties. 2 Terms
This standard adopts the following definitions.
2.1Batch
The number of unit products contained in the batch.
2.2Random sampling
A sampling method in which all unit products in the batch are equally likely to be sampled each time. 2.3Sample
The total number of sample units.
2.4Defectives
A unit product with one or more defects is called a defective product. 2.5·Unit product
A unit product is the basic unit divided for the purpose of implementing sampling inspection. For example: unit product, pair of products, a group of products, a component. 2.6Inspection
The process of comparing a unit product with the required conditions by measurement, test or other methods. 2.7Sampling plan
A sampling plan is a set of rules stipulated to determine the sample size and to judge whether the inspection batch is qualified. 2.8 Single sampling plan
Single sampling plan is to select only one sample from the batch, and judge the batch as qualified or unqualified based on the inspection results of the sample. 2.9 Two sampling plan
Two sampling plan is to judge the batch as qualified, unqualified or re-inspected based on the inspection results of the first sample: if re-inspection is done, the batch is judged as qualified or unqualified based on the results of the first and second sample inspections. 2.10 Normal inspection sampling plan
JB/T7905—1999
Sampling plan adopted when the process average is close to the qualified quality level. 2.11 Batch quality expression method
The quality of the batch is expressed by the number of unqualified products per 100 units of products or the number of defects per 100 units of products. 2.11.1 Number of defectives per 100 units
The total number of all defectives in the batch divided by the batch, multiplied by 100, that is: Number of defectives per 100 units - total number of defectives in the batch × 100 batch
2.11.2 Number of defects per 100 units
The total number of defects in all units in the batch divided by the batch, multiplied by 100, that is: Number of defects per 100 units - total number of defects in all units in the batch × 100 batch
2.12 Acceptable quality level (AQL)
In sampling inspection, the average upper limit of the process of consecutive inspection batches that are considered acceptable. AQL values ​​of 10 or less can be expressed as defective rate or number of defects per 100 units; those AQL values ​​exceeding 10 are expressed as number of defects per 100 units: 2.13 Provisions on sampling plan types
The types of sampling plans specified in this standard are: one-time sampling plan and two-time sampling plan. Regardless of the type of sampling plan used for inspection in this standard, as long as the specified inspection level and qualified quality level are the same, the judgment of batch quality is basically the same.
3 MethodsWww.bzxZ.net
3.1 General principles
Before sampling inspection, the relevant parties should agree on the following points: a) items, indicators and allowable deviations to be inspected; b) test methods;
c) determine an attribute sampling plan and specify acceptance and rejection criteria. Note: The relevant parties can also agree on different sampling plans (including experience sampling plans), but the statistical power of these plans should be the same. Samples should be randomly selected from the batch to be inspected, and each item should be counted separately. The number of unqualified items should be counted and measured with acceptance and rejection criteria.
3.2 Dimensional inspection
Dimensional inspection is carried out in accordance with the general principles specified in 3.1, using normal attribute sampling plans, including single sampling plans and double sampling plans, the plans are as follows:
a) Single sampling plan uses Figure 1 and Table 2:
b) Double sampling plan uses Figure 2 and Table 3.
3.2.1 Single sampling plan
The number of products n to be inspected shall be equal to the sample specified in the plan. If the number of unqualified products d found in the sample inspection is equal to or less than the acceptable number c, the batch of products shall be accepted. If the number of unqualified products d found in the sample inspection is equal to or greater than the rejection number r, the batch of products shall be rejected.
3.2.2. Double sampling plan
JB/T7905-1999
The number of products to be inspected shall be equal to the sample of the first sampling given in the plan. If the number of failures d in the first sample is equal to or less than the first acceptable number ci, the batch of products should be accepted. If the number of failures d in the first sample is equal to or greater than the first rejection number r, the batch of products should be rejected. If the number of failures d in the first sample is between the first acceptable and rejection numbers, the second sampling sample given in the plan should be tested. The number of failures d in the first sample and the number of failures d in the second sample, the two failures added together are d+d. If the total number of failures is equal to or less than the second acceptable number c3, the batch of products should be accepted; if the total number of failures is equal to or greater than the second rejection number r3, the batch of products should be rejected. 3.3 Mechanical properties, physical properties and chemical composition inspection Since mechanical properties, physical properties and chemical determinations are usually more complex and have the characteristics of destructive samples, it is often inappropriate to extract the same number of samples as the number of samples generally used for dimensional inspection. The sampling method should be agreed upon by the relevant parties. Table 1 is the recommended minimum sample selected from each inspection batch, which is used to conduct various performance tests. The items to be inspected and the details of acceptance or rejection of a batch of products shall be agreed upon by the relevant parties. More than one performance test is allowed on the same sample without affecting the test results.
The performance test method shall be in accordance with the provisions of the current standards. Number of pieces in a batch N
Take n sample units from the product
Accept in batch
Figure 1 Sampling plan for one time
Reject in batch
Performance to be tested
Other mechanical properties
Porosity
Metallurgical structure
Chemical composition
For mechanical properties, the following points should be considered: JB/T7905-1999
Table 1 Minimum samples for inspection batch
Minimum number of products taken in each inspection batch Required sample weight for each element to be analyzed 1 For the determination of mechanical properties of a batch of materials, samples should generally be taken directly from the inspected products and then processed into the specified mechanical properties test specimens; when samples cannot be taken directly from the products due to product size or other reasons, the sampling method shall be agreed upon by the relevant parties. 2 When it is required to inspect the actual performance of a batch of product components, special tests on actual use shall be carried out directly on these components, and the test method shall be agreed upon by the relevant parties.
Number of batches N
First sample n, sample units
First inspection n, units
A)d,≤c
B)c,
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