JB/T 5944-1991 General technical requirements for heat-treated parts of engineering machinery
Some standard content:
Mechanical Industry Standard of the People's Republic of China
JB/T 5944-1991
Construction Machinery
General Technical Conditions for Heat-treated Parts
Published on December 12, 1991
Implementation by the Ministry of Machinery and Electronics Industry of the People's Republic of China on July 1, 1992
JB/T5944-1991
Subject Content and Scope of Application
Cited Standards
Technical Requirements
Test Methods
Inspection Rules
Marking, Packaging, Transportation, Storage
Appendix A
Metallographic Inspection Diagram (Reference)
Mechanical Industry Standard of the People's Republic of China
Construction Machinery
General Technical Conditions for Heat-treated Parts
Subject Content and Scope of Application
JB/T 59441991
This standard specifies the technical requirements, test methods, inspection rules, marking, packaging, transportation and storage of heat-treated parts in engineering machinery products.
This standard applies to heat-treated parts of carbon structural steel and alloy structural steel. Reference standards
ZBJ04005
ZBJ04006
JB4009
GB-4340
GB4341
GB1818
GB5617
GB9450
GB9451
GB6394
GB1979
ZBJ36009
JB2 849
JB2782
GB6397
GB2828
JB/T5947
3 Terminology
Penetrant testing method
Magnetic particle testing method for steel parts
Contact ultrasonic longitudinal wave direct flaw detection method
Metal Brinell hardness test method
Metal Rockwell hardness test method
Metal Vickers hardness test method
Metal Shore hardness test method
Method for testing Rockwell hardness of metal surface
Determination of effective hardened layer depth after induction quenching or flame quenching of steelDetermination and verification of effective hardened layer depth of carburizing and quenching of steel partsDetermination of total hardened layer depth or effective hardened layer depth of thin surface of steel partsDetermination method of metal average grain size
Determination method of decarburized layer depth of steel
Macrostructure defect rating chart of structural steel
Metallographic inspection of induction quenching of steel parts
Metallographic inspection of nitrided layer of steel parts
Metallographic inspection of carbonitrided gears for automobiles
Metal tensile test method
Metal tensile test specimens
Batch inspection counting sampling procedures and sampling tables (applicable to inspection of continuous batches)General technical conditions for packaging
Engineering machinery
Total hardened layer depth
The distance measured from the part surface in the vertical direction to the hardened layer with no change in microhardness or microstructure with the base metal. 3.2 Effective hardened layer depth
Approved by the Ministry of Machinery and Electronics Industry on December 12, 1991 and implemented on July 1, 1992
JB/T59441991
The distance measured from the part surface in the vertical direction to a certain microstructure boundary or a hardened layer with a specified microhardness 3.3 Soft spot
A small local area with low surface hardness after the steel or steel part is hardened by floating fire. 4 Technical requirements
4.1 Technical requirements for parts to be heat treated
General requirements
4. 1. 1. 1
Material test data
Supply status
Processing method
Preheat treatment type
The materials of parts to be heat treated shall comply with the requirements of the drawings and the provisions of relevant national standards and metallurgical industry standards. The original data of parts to be heat treated shall be indicated according to the items in Table 1. Table 1
Chemical skin
Mechanical properties"
Hardness test\
Permeability test\
Metallurgical structure and macroscopic defects
Hot rolling (hot extrusion)
Cutting method and measurement\
Cold pressing or drawing\
Cold rolling or cold extrusion"
Hot straightening or hot and cold straightening\
Welding (repair welding)
Normalizing or normalizing and tempering
Full annealing
Stress relief annealing
Note: 1) General parts can be omitted or all omitted. 4.1.1.3
The appearance of the parts to be heat treated shall meet the following requirements:
Grain size, decarburized layer, non-metal inclusions, macroscopic structure. Indicate cold forging or hot forging, and indicate forging ratio and grain size when necessary. Heavy cutting with large feed may cause cracks. Indicate hot and cold processing status
Forging welding. Indicate welding repair process and welding rod material used. Indicate heating temperature, holding time, cooling method. The rough parts are not allowed to have cracks, folds, oxide scale, looseness, slag holes and other defects that affect the quality of heat treatment. The machined surface is not allowed to have cracks, rust, serious bumps, burrs, iron chips and defects that affect the quality of surface heat treatment. The transition of mechanical processing should be rounded or chamfered. The size of the parts to be heat treated should have appropriate processing allowance for the parts that need to be machined after heat treatment. 4.1.1.4
4.1.2 Technical requirements for parts to be surface hardened and tempered, carburized, carbonitrided, and nitrided 4.1.2.1 Parts to be surface hardened and tempered should be normalized or quenched and tempered before quenching. 4.1.2.2 The surface of parts to be surface hardened and tempered should be clean, and burrs, iron filings, severe rust, scale, residues, impurities, and oil stains that may affect surface hardening are not allowed.
4. 1. 2. 3
For the surface induction heating quenching area with grooves or holes, copper bars should be used to inlay the grooves and holes flat to prevent local overburning, melting and cracking of the grooves and holes during quenching
JB/T5944—1991
4.1.2.4 The parts to be nitrided should be quenched, tempered, tempered and stress relieved, and the microstructure should be uniform granular sorbite or low-carbon martensite. After quenching and tempering, no blocky ferrite is allowed within 5mm of the surface of important parts, and the free ferrite within 5mm of the surface of general parts after quenching and tempering is allowed to be less than or equal to 5%.
4.1.2.5 The surface of the parts to be nitrided should be clean, without cracks, rust, scratches, bumps, sharp edges and corners, oxidation, decarburization, oil stains, iron filings, etc. 4.2 Classification of heat-treated parts
Classification by importance
Specially important parts: parts with high performance requirements, with special requirements for mechanical properties and metallographic structure after tempering; important parts: parts with high performance requirements, with mechanical properties and metallographic structure after tempering; general parts: parts with only hardness requirements. Classification by processing status
Rough parts: parts that have not been machined; Semi-finished parts: parts that are partially machined and partially machined after heat treatment. Finished parts: parts that are directly used without machining after heat treatment. Classification by weight
Small parts: parts weighing less than 5kg;
Medium parts: parts weighing 5 to 30kg;
Large parts: parts weighing more than 30kg. Technical requirements for heat-treated partswww.bzxz.net
Depending on the material, size, use conditions and heat treatment methods of the parts, they should meet the requirements of 1.3.1--4.3.6 respectively. 4.3.1 Annealing and normalizing
4. 3. 1. 1
4. 3. 1. 2
Appearance: No cracks or harmful scratches are allowed on the surface. Hardness: It should meet the specified range of the drawing or process and meet the requirements of Table 2. Table 2
Process type
Complete annealing
Incomplete annealing
4. 3. 1.4
The HBS.HV, HRB and HS values in the table are the values measured by various hardness testing machines, and there is no direct conversion relationship between them. The HS value is for reference only.
When the hardness deviation of large parts exceeds the requirements of Table 2, it should be resolved through negotiation between the supply and demand parties. The hardness deviation of a single piece is when a single piece is sampled.The non-uniformity of its surface hardness; the hardness deviation of the same batch of parts refers to the deviation of the surface hardness value of parts made of the same batch of materials under the same heat treatment conditions. Normalizing grade A is mainly suitable for cold deformation processing (referring to cold rolling, cold drawing, cold forging, etc.) steel; grade B is suitable for general cutting steel. Deformation: The deformation of parts should not affect the mechanical processing and use after heat treatment. Decarburization layer: should be less than 2/3 of the single-sided machining allowance. The non-machined surface shall be in accordance with the drawings or process requirements. The metallographic structure
Structural steel parts should be evenly distributed ferrite and lamellar pearlite; the grain size of structural steel should be 5 to 8, and large castings and forgings should be greater than or equal to 3. Quenching and tempering
JB/T59441991
Appearance: The surface of the quenched and tempered parts is not allowed to have cracks, serious bruises and harmful defects that affect the surface quality. Hardness: It should comply with the specified range of the drawing or process and meet the following requirements: The surface hardness of the quenched and tempered parts before high-temperature tempering after quenching should be greater than the upper limit of the hardness requirement; after quenching and high-temperature tempering of the quenched and tempered parts, the surface hardness of the parts should comply with the provisions of Table 3, Table 4, and Table 5. Deformation: The deformation of the quenched and tempered parts should not affect the subsequent mechanical processing and use. Table 3
Specially important parts
Specially important parts
Specially important parts
Important parts
4. 3. 2. 5
≤330
>50~70
≤330
>50~70
Surface oxidation and decarburization of quenched and tempered parts (machined before quenching) should be less than 1/3 of the single-sided machining allowance>70
Metallurgical structure after quenching and tempering: the section less than the critical diameter should be tempered troostite, and less than or equal to 5% free ferrite is allowed; the section larger than the critical diameter is allowed to have flakes in the core ferrite and ferrite, 4.3.2.6
Mechanical properties: should meet the requirements of the drawing or process. Appearance: cracks, melting, bruises, pits, rust, residues, and oil stains are not allowed on the surface of the parts. Hardness: should meet the specified range of the drawing or process, and meet the following requirements: the surface hardness value of the part after annealing and before tempering should be greater than the middle limit of the range required by the drawing or process; the surface hardness deviation of the annealed and tempered parts should meet Table 3 and Table 4 , Table 5: All heated and partially quenched parts or partially heated and quenched parts, the dimensional deviation of the hardened part: diameter less than or equal to 50mm, the allowable deviation is ±10mm; diameter greater than 50mm, the allowable deviation is ±15mm; d.
Important parts are not allowed to have soft spots after quenching. Large parts (diameter or thickness greater than 80mm) and general parts are allowed to have a small number of soft spots. Deformation, the deformation of parts should comply with the drawings or process regulations, and meet the following requirements: The radial runout deformation of shaft parts over the entire length should not exceed 1/2 of the diameter allowance; b.
JB/T59441991
The flatness deformation of flat plate parts should not exceed 2/3 of the allowance: The carburizing and tempering deformation of gears and shafts is allowed to be 1/2 to 2,3 of the finished product tolerance. Effective hardened layer depth: It should comply with the drawings or process regulations; The effective hardened layer depth deviation should comply with the provisions of Table 6. 4.3. 3. 42
Effective hardened layer depth
Decarburized layer: After tempering, the surface decarburized layer of the part should be less than 1/3 of the single-sided machining allowance. Parts that require wear resistance are not allowed to have 4.3.3.5
Decarburized.
Metallographic structure; Generally, metallographic inspection is not performed after tempering, but the following requirements should be met: The martensite of the hardened layer of the part after quenching should be 1 to 4 levels, and the parts with little quenching cracking tendency can be 1--6 levels: There should be no abnormal structure after tempering.
4.3.3.7 Mechanical properties: For special parts and important parts, please refer to the drawing or process requirements. 4.3.4 Surface quenching and tempering
Surface quenching and tempering methods: surface induction heating quenching (medium and high cheeks); surface flame heating quenching. 4.3.4.1
Appearance; cracks, overburning, melting and bruises are not allowed on the surface of parts. 4. 3. 4. 2
Hardness: After surface quenching, the hardness should be greater than or equal to the middle limit of the specified value. After induction quenching and tempering, it should meet the following requirements: The surface hardness and the location and range of the hardened area of the quenched and tempered parts should comply with the requirements of the drawings or processes; The surface hardness deviation should comply with the provisions of Table 7, Table 8 and Table 9: The non-hardened area and soft zone of the surface induction quenching should comply with the provisions of Table 10; The surface induction quenching allows the proximal end face of the surface to have less than or equal to 5~8mm non-hardened, Table 7
Surface quenching and tempering parts
Surface quenching and tempering parts
≤500
Surface quenching and tempering parts
Important parts
Part categories
Partial induction fire
Step shaft
With hole or slot
With keyway
With empty knife slot
Spline shaft
≤10mm
Step shaft or
Flange
JB/T5944-1991
Allowed width of soft zone and unhardened zone
Tolerance of fire length±4mm
Unhardened zone at step
Distance of unhardened zone from hole or planting edge≤8mm
When there is no fillet at both ends of the groove bottom, 1≤8mm soft zone is allowed at both ends
A soft zone of/≤5mm is allowed at the empty knife slot. 6HRC lower than the top
A non-hardened area with a width of ≤8mm and a depth of 5mm is allowed at the sharp corners on both sides of the groove
A non-hardened area with a width of ≤8mm and a depth of 5mm is allowed at the sharp corners
When end face quenching, a non-hardened area with a circumference 5mm larger than the adjacent journal is allowed
Part category
Two right-angled planes
Parts with holes
Flat surface with precision
Wheels and large shafts
JB/T5944-1991
Continued Table 10
Allowed width of soft zone and non-hardened area
A tempered soft zone with a width of ≤8mm is allowed on one surface, or one of them is allowed-- The surface is not hardened within 5mm from the edge
The hole edge should be >6mm from the hardened surface, and the hole area is allowed to be unhardened. When the plane of the middle part of the two sides is a slender narrow strip, if its width is ≤8mm, it can be unquenched
When the inner hole hardening area is >200mm deep from the end face, a soft band of ≤10mm or no quenching is allowed
For the inner surface quenching of inner diameter D>200mm, if the height is ≤350mm, a soft band of ≤8mm is allowed at the intersection
When there is inner quenching, the groove is allowed to be unhardened
It cannot be quenched along the outer circle at one time, and when continuous quenching is used, a soft band of ≤20mm is allowed at the quenching intersection
It is allowed to be unhardened
JB/T 59441991
4.3. 4. 3
Effective hardened layer: It should comply with the specified range of the drawing or process; the effective hardened layer depth deviation should comply with the provisions of Table 6. The effective hardened layer depth and deviation of complex and large parts can be agreed upon by the supplier and the buyer. Gear hardened layer distribution: For non-carburized gears with a modulus less than or equal to 4, the depth of the tooth bottom hardened layer shall not be less than 0.5mm, whether it is tooth mat hardening or full tooth hardening. For gears with a modulus greater than 4, the tooth surface shall have an itchy hardened area of not less than 2/3 of the tooth height. 4.3.4.4 Deformation: The deformation of the parts shall not affect the subsequent machining quality and performance. 4.3.4.5 Metallographic structure: When the hardness of the part is greater than or equal to 55HRC, its structure shall be martensite 4 to 7; less than or equal to 5% of martensite is allowed, but ferrite is not allowed. When the hardness of the part is less than 55HRC, its structure should be martensite level 3 to 7; the hardened layer area is allowed to have less than or equal to 5% ferrite, but the hardness must meet the specified requirements. 4.3.4.6 Mechanical properties shall be in accordance with the provisions of Article 4.3.3.7, and for special important parts and important parts, they shall be in accordance with the drawings or process requirements. 4.3.5 Carburizing and carbonitriding
4.3.5.1 Appearance: The surface of the parts after carburizing and carbonitriding treatment and quenching and tempering shall be free of cracks, peeling, chipping, bumps, oxide scale, rust, pitting and other defects.
The surface hardness of the unfired parts after carburizing and carbonitriding or the local anti-seepage area after quenching and tempering is generally not greater than that of the parts after quenching and tempering. The surface hardness of the parts after carburizing and carbonitriding shall comply with the specified range of the drawing or process, and its hardness deviation shall comply with the provisions of Table 11, Table 12, Table 13 and Table 14. 4.3.5.3 Deformation: The deformation of the parts shall comply with the provisions of the drawing or process. 4.3.5.4 Layer depth: After carburizing and carbonitriding treatment and quenching and tempering, the effective hardened layer depth of the parts shall be in accordance with the requirements of the drawing or process, and the depth deviation shall comply with the requirements of Table 15.
Carburizing and carbonitriding parts
Important parts
Carburizing and carbonitriding parts
Important parts
Carburizing and carbonitriding parts
≤500
Carburizing and carbonitriding parts
Hardened layer depth
Effective hardened layer depth
Parts of the same batch
Metallographic structure
JB/T5944-1991
Total hardened layer depth
For the same batch of parts
Partial carburizing and carbonitriding parts, the measurement position after quenching and tempering should not be at the boundary of the carburized layer
The surface hardened layer depth is the measured depth value
3.2 or more hardened layer depths meet the hardened layer deviation requirements, and are calculated according to the average value. The metallographic structure of the carburized and carbonitrided parts after slow cooling (equilibrium state) is pearlite + a small amount of carbides or carbonitrides; the network carbides or carbonitrides shall not exceed level 4; the grain size of the core of important parts: level 48. b.
Organization.
Carburized and carbonitrided parts carburized layer depth: carbon cable structural steel measured from the surface to 1/2 of the transition zone; alloy steel measured from the surface to the original carburized layer gradient: hypereutectoid layer + eutectoid layer is not less than 50% to 75% of the total depth. Surface concentration of carburized layer: carbon concentration 0.70%~1.05%; nitrogen content 0.15%~0.40%. The technical requirements of gears after carburizing and carbonitriding and quenching and tempering shall comply with the provisions of Table 16. Table 16
Heat treatment method
Effective hardened layer depth
Martensite and residual austenite
Central ferrite
Carbon ammonia nitrogen compounds
Black structure
Decarburized layer
Nitriding (nitriding)
Technical requirements
Should be free of defects such as cracks, melting, bruises, rust, pitting, peeling, etc. 58~64 HRC
Module ≤833~45HRC, module>829~45HRC is allowed to occupy 1/2~2/3 of the finished product tolerance according to the drawing or process requirements
1~6 levels
Module ≤51~4 levels,
Often gear
Shift gear
Module>5
1~6 levels
1~5 levels
1~5 levels
Carbonitriding
33~48HRC
1~5 levels
1~5 levels
1~4 levels
1~2 levels
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