JB/T 51125-1999 Quality classification of cylinder heads for internal combustion engines
Some standard content:
Mechanical Industry Standard of the People's Republic of China
JB/T51125—1999
Cylinder Head
Internal Combustion Engine
Product Quality Grading
(Internal Use)
Published on 1999-12-30
National Bureau of Machinery Industry
Implemented on 2000-06-01
JB/T51125—1999
This standard is a revision of JB/T51125.1~51125.3—94 "Product Quality Grading of Internal Combustion Engine Cylinder Head". Only editorial changes were made to the original standard during the revision, and the main technical content remained unchanged. This standard replaces JB/T51125.1~51125.3—94 from the date of implementation. This standard is proposed and managed by the National Technical Committee for Standardization of Internal Combustion Engines. The drafting unit of this standard is Shanghai Internal Combustion Engine Research Institute. The main drafter of this standard is Li Shaoqiu.
This standard was first issued in 1989 as JB/NQ199.1~199.3-89, and the standard number was adjusted to JB/T51125.151125.394 in September 1994.
1 Scope
Machinery Industry Standard of the People's Republic of China
Internal Combustion Engine Cylinder Head
Product Quality Classification
(Internal Use)
JB/T51125-1999
Replaces JB/T51125.1~51125.3-94
This standard specifies the product quality indicators, inspection methods and inspection rules for cast iron and cast aluminum cylinder heads (hereinafter referred to as cylinder heads) of reciprocating internal combustion engines with a cylinder diameter less than or equal to 200mm. This standard applies to the inspection and assessment of the quality of cylinder head products for internal combustion engines. 2 Cited standards
The provisions contained in the following standards constitute the provisions of this standard through reference in this standard. When this standard is published, the versions shown are valid. All standards will be revised, and parties using this standard should explore the possibility of using the latest versions of the following standards. GB/T228—1987
GB/T231—1984
GB/T1957—1980
GB/T1958—1980
GB/T2828—1987
GB/T3177—1997
GB/T 3934—1983
JB/T7945—1999
JB/T9742—1999
JB/T9766—1999
3 Quality indicators
Metal tensile test method
Metal Brinell hardness test method
Smooth limit gauge
Shape and position tolerance
Testing regulations
Counting sampling procedure and sampling table for batch inspection (applicable to inspection of continuous batches)Inspection of smooth workpiece dimensions
Ordinary thread gauge
Gray cast iron mechanical properties test method
Technical conditions for gray cast iron cylinder head and body castings for internal combustion enginesTechnical conditions for cast iron cylinder head for internal combustion engines
Products should be manufactured according to product drawings and technical documents approved through the prescribed procedures, and their technical requirements should comply with the provisions of this standard. Cylinder head products are classified into three grades according to their different quality indicators: qualified products, first-class products and superior products. 3.2
The mechanical properties of gray cast iron cylinder heads are classified according to Table 1. Table 1
Tensile strength MP
Hardness HBS
Hardness difference HBS
Qualified products
170-241
Note: Other quality requirements of castings shall comply with the provisions of JBT9742. Approved by the State Machinery Industry Bureau on December 30, 1999, first-class products
187-255
Superior products
Implemented on June 1, 2000
JB/T51125-1999
The mechanical properties of cast aluminum cylinder heads are classified according to Table 2. 3.3.2
Tensile strength MPa
Hardness difference HBS
Qualified products
3.4Tolerance zones of dimensions, shape and position tolerances, surface roughness, etc. of main parts of cylinder head
Excellent products
3.4.1The tolerance zone of aperture for installing valve guide and valve seat is H7, and the tolerance zone of thread for installing rocker arm shaft seat, injector, intake and exhaust pipe, water outlet pipe and glow plug is 6H.
3.4.2 The shape and position tolerance classification shall be in accordance with the provisions of Table 3, Table 3
Flatness of bottom surface (joint surface with engine body)
Parallelism of item surface to bottom surface
Verticality of valve guide hole axis to bottom surface
Coaxiality of valve seat cone axis to guide inner hole axisQualified product
100:@0.10
Surface roughness (R. value) classification shall be in accordance with the provisions of Table 43.4.3
Bottom surface, guide hole, valve seat hole R
Top surface, combustion chamber hole and its stop surface R
Valve seat cone surface (before grinding) Ra
3.5 Casting defects and appearance quality
3.5.1 Unacceptable casting defects
Qualified products
100:006
Superior products
Superior products
a) Cracks, insufficient pouring, severe sand adhesion, and casting defects that reduce structural strength or affect cutting, positioning, and clamping are not allowed: b) No casting defects are allowed within the range of the combustion chamber surface, valve seat cone, spark plug hole, injection nozzle sealing surface, and cylinder bore diameter;
c) Sand adhesion, burrs, nodules, and other casting defects are not allowed in the intake and exhaust cavities: d) Seams and debris are not allowed in the waterway. 3.5.2 The classification of acceptable casting defects shall be as specified in Table 5. 2
Height of the residual root of the seam and pouring riser in mm
Number and size of individual holes on each surface
JB/T51125-1999
Qualified products
Unprocessed surface
Unprocessed surface
Processed surface
Note: Other provisions of holes shall comply with JB/T97422
Superior products
3.5.3 The surface of the product shall be clean, free of rust and bruises. The paint layer on the painted surface shall be smooth, free of bubbles and peeling, etc. 3.6 The product shall be tested for sealing without leakage. The water pressure or air pressure test shall be in accordance with the provisions of JB/T9766. The warranty period (service life) classification shall be in accordance with the provisions of Table 6. 3.7
Qualified products
Single cylinder machine
Multi-cylinder machine
4 Inspection methods
First-class products
Tensile strength test shall be in accordance with GB/T228, JB/T7945 and JB/T9742. 4.1
4.2 Hardness test shall be in accordance with GB/T231.
Superior products
4.3 For dimensional tolerance, use internal micrometer (in accordance with GB/T3177) and smooth plug gauge (in accordance with GB/T1957). For thread tolerance, use thread plug gauge (in accordance with GB/T3934). h
4.4 For shape and position tolerance, use flat plate, height gauge, micrometer or measuring stand with indicator, coaxial measuring gauge (in accordance with GB/T1958).
Surface roughness, using surface roughness specimens or surface roughness measuring instruments, 4.5
Water pressure or air pressure test, using a reservoir and a hydraulic press or air compressor and its device. Service life is mainly based on the main engine manufacturer's use report. Appearance quality, using visual assessment.
5 Inspection rules
5.1 Classification of unqualified products
According to GB/T2828, the quality characteristics of the inspected products that do not meet the requirements of the standards and drawings are called unqualified. According to their importance to product quality, unqualified products are generally divided into: Class A unqualified, Class B unqualified and Class C unqualified. The classification of unqualified quality of internal combustion engine cylinder head products is shown in Table 7.
Classification of unqualified products
2 Acceptable quality level AQL value
JB/T51125-1999
Tensile strength
Hardness and hardness difference
Hydraulic pressure (air pressure) test
Bottom surface flatness
Quality characteristics
Catheter hole size tolerance: in 1)
Catheter hole size tolerance: out 1)
Valve seat hole size tolerance: Enter 1)
Valve seat hole size tolerance: Row 1)
Perpendicularity of catheter hole to bottom surface: Enter 1)
Perpendicularity of catheter hole to bottom surface: Row 1)
Coaxiality of valve seat cone surface to catheter hole: Enter 1) Coaxiality of valve seat cone surface to catheter hole: Row 1 Parallelism of top surface to bottom surface
Bottom surface surface roughness
Top surface Surface roughness
Surface roughness of duct hole: Enter 1)
Surface roughness of duct hole: Row 1)
Surface roughness of valve seat hole: Enter 1)
Surface roughness of valve seat hole: Row 1
Surface roughness of valve seat cone: Enter 1)
Surface roughness of valve seat cone: Row 1)
Surface roughness of combustion chamber piercing and stopper: 1) Casting quality: Height of seam and pouring riser residual root on unmachined surface Number and size of single hole: Number and size of single hole on unmachined surface: Machined surface
Quality of machined surfacebZxz.net
Quality of paint layer
The AQL values of three grades of internal combustion engine cylinder head products are specified as qualified products, first-class products and superior products, see Table 8~Table 12.3 Sampling plan
A normal inspection one-time sampling plan is adopted. The normal inspection sampling plan for the cylinder head of an internal combustion engine according to the number of cylinders is shown in Tables 8 to 12. In the table, Ac (qualified number) and Re (unqualified number) are calculated by the point method. 4
JB/T51125—1999
Table 8 Normal inspection sampling plan for single-cylinder cylinder head products Unqualified classification
Inspection level
Sample size code
Sample number n
Qualified products
First-class products
Superior products
Ac, Re
Table 9 Normal inspection sampling plan for double-cylinder cylinder head products Unqualified classification
Inspection level
Sample size code
Sample number n
Qualified products
First-class products
Superior products
Table 10 Normal inspection of three-cylinder cylinder head products. Unqualified classification
Inspection level
Sample size code
Number of samples n
Qualified products
First-class products
Superior products
N-26-50
N-26~50
N-26-50
21, 22
Unqualified classification||tt ||Inspection level
Sample size code
Number of samples n
Qualified products
First-class products
Superior products
Qualified products
First-class products
Superior products
Unqualified classification
Inspection level
JB/T51125-1999
Normal inspection sampling plan A for four-cylinder cylinder head products
Ac, Re
Sample size code
Number of samples n||t t||14，15
Sampling plan for normal inspection of six-cylinder cylinder head products A
Inspection batch M
21，22
N-26-50
21，22
N=26~50
30，31
The inspection batch N is specified to be 26~50, and the inspection batch shall not be less than the lower limit of the specified batch range. If it is greater than the upper limit of the specified batch range, the products shall be divided into several batches of 26~50, and one batch shall be randomly selected for sampling inspection. 5.5 Inspection level
For Class A non-conformity, special inspection level S-1 shall be adopted, and for Class B and C non-conformity, general inspection level II shall be adopted. 5 Sample extraction
Samples shall be extracted from user units and commercial departments, and at this time, they may not be restricted by the lower limit of the batch range. If there is no stock at the above locations, with the consent of the relevant departments, samples can be taken from the production line or from the products that have been put into storage recently (within half a year). At this time, the batch range specified in 5.4 must be strictly followed.
5.7 Product Quality Grade Assessment
5.7.1 Sample Inspection
JB/T51125-1999
The samples should be inspected and assessed according to the various types of non-conformities specified in Table 7 and the sampling plans specified in Tables 8 to 12, and in accordance with the provisions of Chapters 3 and 4.
5.7.2 Batch Assessment
After all samples have been inspected, if the number of non-conformities in a certain category in the sample is less than or equal to the Ac value, the category is judged as qualified. When the number of non-conformities in a certain category is greater than or equal to the Re value, the category is judged as unqualified. When the number of non-conformities in all categories is qualified, the batch of products is judged as qualified. 5.7.3 Quality Grade Assessment
5.7.3.1 After all samples have been inspected, if the number of unqualified items in each category in the sample is less than or equal to the Ac value of the superior product, the inspected product shall be assessed as a superior product: if the number of unqualified items in each category in the sample is less than or equal to the Ac value of the first-class product, the inspected product shall be assessed as a first-class product: if the number of unqualified items in each category in the sample is less than or equal to the Ac value of the qualified product, the inspected product shall be assessed as a qualified product: if the number of unqualified items in one category in the sample is greater than or equal to the Re value of the qualified product, the inspected product shall be assessed as an unqualified product. 5.7.3.2 If a product is assessed as an unqualified product, it is allowed to be re-inspected once after half a year. If the re-inspection is qualified, it can still be assessed as a qualified product, but it cannot be assessed as a first-class product or a superior product.
Mechanical Industry Standard
Internal Combustion Engine Cylinder Head
Product Quality Grading
(For Internal Use)
JB/T51125—1999
Published and Distributed by the China Academy of Mechanical Science
Printed by the China Academy of Mechanical Science
(No. 2 Shouti South Road, Beijing, Postal Code 100044)*
Format 880×1230
1/16 Printing Sheet 3/4 Word Count 16000
First Edition in April 2000
Print Quantity 1-500
First Printing in April 2000
Price 1500 Yuan
99-1269
Mechanical Industry Standard Service Network: http/kvwwJB.ac.cn6661s3 Sampling plan
Use a normal inspection single sampling plan. The normal inspection single sampling plan for internal combustion engine cylinder heads according to the number of cylinders is shown in Tables 8 to 12. In the table, Ac (qualified judgment number) and Re (unqualified judgment number) are calculated by the point method. 4
JB/T51125—1999
Table 8 Normal inspection single sampling plan for single-cylinder cylinder head products. Unqualified classification
Inspection level
Sample size code
Sample number n
Qualified products
First-class products
Superior products
Ac, Re
Table 9 Normal inspection single sampling plan for double-cylinder cylinder head products. Unqualified classification
Inspection level
Sample size code
Sample number n
Qualified products
First-class products
Superior products
Table 10 Normal inspection of three-cylinder cylinder head products. Unqualified classification
Inspection level
Sample size code
Number of samples n
Qualified products
First-class products
Superior products
N-26-50
N-26~50
N-26-50
21, 22
Unqualified classification||tt ||Inspection level
Sample size code
Number of samples n
Qualified products
First-class products
Superior products
Qualified products
First-class products
Superior products
Unqualified classification
Inspection level
JB/T51125-1999
Normal inspection sampling plan A for four-cylinder cylinder head products
Ac, Re
Sample size code
Number of samples n||t t||14，15
Sampling plan for normal inspection of six-cylinder cylinder head products A
Inspection batch M
21，22
N-26-50
21，22
N=26~50
30，31
The inspection batch N is specified to be 26~50, and the inspection batch shall not be less than the lower limit of the specified batch range. If it is greater than the upper limit of the specified batch range, the products shall be divided into several batches of 26~50, and one batch shall be randomly selected for sampling inspection. 5.5 Inspection level
For Class A non-conformity, special inspection level S-1 shall be adopted, and for Class B and C non-conformity, general inspection level II shall be adopted. 5 Sample extraction
Samples shall be extracted from user units and commercial departments, and at this time, they may not be restricted by the lower limit of the batch range. If there is no stock at the above locations, with the consent of the relevant departments, samples can be taken from the production line or from the products that have been put into storage recently (within half a year). At this time, the batch range specified in 5.4 must be strictly followed.
5.7 Product Quality Grade Assessment
5.7.1 Sample Inspection
JB/T51125-1999
The samples should be inspected and assessed according to the various types of non-conformities specified in Table 7 and the sampling plans specified in Tables 8 to 12, and in accordance with the provisions of Chapters 3 and 4.
5.7.2 Batch Assessment
After all samples have been inspected, if the number of non-conformities in a certain category in the sample is less than or equal to the Ac value, the category is judged as qualified. When the number of non-conformities in a certain category is greater than or equal to the Re value, the category is judged as unqualified. When the number of non-conformities in all categories is qualified, the batch of products is judged as qualified. 5.7.3 Quality Grade Assessment
5.7.3.1 After all samples have been inspected, if the number of unqualified items in each category in the sample is less than or equal to the Ac value of the superior product, the inspected product shall be assessed as a superior product: if the number of unqualified items in each category in the sample is less than or equal to the Ac value of the first-class product, the inspected product shall be assessed as a first-class product: if the number of unqualified items in each category in the sample is less than or equal to the Ac value of the qualified product, the inspected product shall be assessed as a qualified product: if the number of unqualified items in one category in the sample is greater than or equal to the Re value of the qualified product, the inspected product shall be assessed as an unqualified product. 5.7.3.2 If a product is assessed as an unqualified product, it is allowed to be re-inspected once after half a year. If the re-inspection is qualified, it can still be assessed as a qualified product, but it cannot be assessed as a first-class product or a superior product.
Mechanical Industry Standard
Internal Combustion Engine Cylinder Head
Product Quality Grading
(For Internal Use)
JB/T51125—1999
Published and Distributed by the China Academy of Mechanical Science
Printed by the China Academy of Mechanical Science
(No. 2 Shouti South Road, Beijing, Postal Code 100044)*
Format 880×1230
1/16 Printing Sheet 3/4 Word Count 16000
First Edition in April 2000
Print Quantity 1-500
First Printing in April 2000
Price 1500 Yuan
99-1269
Mechanical Industry Standard Service Network: http/kvwwJB.ac.cn6661s3 Sampling plan
Use a normal inspection single sampling plan. The normal inspection single sampling plan for internal combustion engine cylinder heads according to the number of cylinders is shown in Tables 8 to 12. In the table, Ac (qualified judgment number) and Re (unqualified judgment number) are calculated by the point method. 4
JB/T51125—1999
Table 8 Normal inspection single sampling plan for single-cylinder cylinder head products. Unqualified classification
Inspection level
Sample size code
Sample number n
Qualified products
First-class products
Superior products
Ac, Re
Table 9 Normal inspection single sampling plan for double-cylinder cylinder head products. Unqualified classification
Inspection level
Sample size code
Sample number n
Qualified products
First-class products
Superior products
Table 10 Normal inspection of three-cylinder cylinder head products. Unqualified classification
Inspection level
Sample size code
Number of samples n
Qualified products
First-class products
Superior products
N-26-50
N-26~50
N-26-50
21, 22
Unqualified classification||tt ||Inspection level
Sample size code
Number of samples n
Qualified products
First-class products
Superior products
Qualified products
First-class products
Superior products
Unqualified classification
Inspection level
JB/T51125-1999
Normal inspection sampling plan A for four-cylinder cylinder head products
Ac, Re
Sample size code
Number of samples n||t t||14，15
Sampling plan for normal inspection of six-cylinder cylinder head products A
Inspection batch M
21，22
N-26-50
21，22
N=26~50
30，31
The inspection batch N is specified to be 26~50, and the inspection batch shall not be less than the lower limit of the specified batch range. If it is greater than the upper limit of the specified batch range, the products shall be divided into several batches of 26~50, and one batch shall be randomly selected for sampling inspection. 5.5 Inspection level
For Class A non-conformity, special inspection level S-1 shall be adopted, and for Class B and C non-conformity, general inspection level II shall be adopted. 5 Sample extraction
Samples shall be extracted from user units and commercial departments, and at this time, they may not be restricted by the lower limit of the batch range. If there is no stock at the above locations, with the consent of the relevant departments, samples can be taken from the production line or from the products that have been put into storage recently (within half a year). At this time, the batch range specified in 5.4 must be strictly followed.
5.7 Product Quality Grade Assessment
5.7.1 Sample Inspection
JB/T51125-1999
The samples should be inspected and assessed according to the various types of non-conformities specified in Table 7 and the sampling plans specified in Tables 8 to 12, and in accordance with the provisions of Chapters 3 and 4.
5.7.2 Batch Assessment
After all samples have been inspected, if the number of non-conformities in a certain category in the sample is less than or equal to the Ac value, the category is judged as qualified. When the number of non-conformities in a certain category is greater than or equal to the Re value, the category is judged as unqualified. When the number of non-conformities in all categories is qualified, the batch of products is judged as qualified. 5.7.3 Quality Grade Assessment
5.7.3.1 After all samples have been inspected, if the number of unqualified items in each category in the sample is less than or equal to the Ac value of the superior product, the inspected product shall be assessed as a superior product: if the number of unqualified items in each category in the sample is less than or equal to the Ac value of the first-class product, the inspected product shall be assessed as a first-class product: if the number of unqualified items in each category in the sample is less than or equal to the Ac value of the qualified product, the inspected product shall be assessed as a qualified product: if the number of unqualified items in one category in the sample is greater than or equal to the Re value of the qualified product, the inspected product shall be assessed as an unqualified product. 5.7.3.2 If a product is assessed as an unqualified product, it is allowed to be re-inspected once after half a year. If the re-inspection is qualified, it can still be assessed as a qualified product, but it cannot be assessed as a first-class product or a superior product.
Mechanical Industry Standard
Internal Combustion Engine Cylinder Head
Product Quality Grading
(For Internal Use)
JB/T51125—1999
Published and Distributed by the China Academy of Mechanical Science
Printed by the China Academy of Mechanical Science
(No. 2 Shouti South Road, Beijing, Postal Code 100044)*
Format 880×1230
1/16 Printing Sheet 3/4 Word Count 16000
First Edition in April 2000
Print Quantity 1-500
First Printing in April 2000
Price 1500 Yuan
99-1269
Mechanical Industry Standard Service Network: http/kvwwJB.ac.cn6661scn6661scn6661s
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