Prequenching inspection
1. The oil, rust, oxide and burr on the parts should be cleaned, and the surface roughness value should be lower than Ra6.4μm
2. The surface of the part shall not be decarbonized, and when necessary, the chemical composition and original organization shall be tested without abnormality
3. Shaft members should be tested for bending
Surface quality inspection after quenching
1. Surface cracks, overburning and other defects should be visually inspected
2. For important parts and parts with grooves, slots, holes, holes easy to quench cracks in single or small batch production should be non-destructive testing, batch or mass production should be in accordance with the process regulations, non-destructive testing
Hardness test after quenching and tempering
1. Hardness shall be tested by Rockwell and Vickers hardness. Quality arbitration shall be based on Vickers hardness test
2. The surface hardness of the parts after quenching (including self-tempering) should be greater than the lower limit of hardness specified in the drawing, and the hardness inspection proportion shall be carried out according to the process regulations. But each batch shall not be less than 5%~10%
3. The hardness test proportion after tempering shall not be less than 5%, the hardness test position is the position specified in the process document or the main working face, the edge of the hardening zone is not used as the test part, and the hardness fluctuation range should be within the range specified in the drawing
4. Hardness is generally tested on the physical or on the physical sample test
5. Large parts can be inspected with Shore hardness tester and Leeb hardness tester
6. For shaft and rod parts less than 150mm in length, the hardness can be tested at one point, but 3 points must be measured on the same section separated by 120º circumference, and the average value is taken. If two points are below or above the specified value of the drawing, the part is judged to be unqualified. The shaft member with a length of 150~500mm is tested at 2 hardness points on the main working face or vulnerable to failure. The shaft member with a length of more than 500mm is tested at 3 hardness points, and the part is judged to be unqualified if there is one hardness failure
7. Gear should measure the hardness of the tooth working surface at different circumferential positions, and the hardness of the tooth root, should meet the requirements of the drawing
8. The spline shaft allows the groove bottom hardness to be 3~5HRC lower than the tooth top hardness
9. Parts with complex shapes or difficult to test the hardness value and hardening zone location with a hardness tester are allowed to be tested with a medium and fine square file, the test method is shown in GB/T13321-91 "Steel Hardness file Test Method". When necessary, it can be cut and sampled, and retested with a hardness tester
Effective hardening depth test (DS)
1. Without special circumstances, the drawing requires the depth of the hardening layer, which can be considered to be the effective hardening layer depth
2. Effective hardening layer depth inspection according to GB5617-85 "Determination of effective hardening layer depth after induction hardening or flame quenching of steel", the sampling part is in the middle of the hardening zone
3. Effective hardened layer depth is measured by the hardness method, (HV1), and depth is the vertical distance from the surface to the hardness value. The hardness value is 0.8 times the lower limit of the surface hardness value specified in the drawing or technical document, and when the Vickers hardness load is less than 9.8N(kg), the hardness value is 0.9 times the surface lower limit hardness value
4. The transition zone is not part of the test for hardening depth
5. Hardening layer depth fluctuation value on the same part should be gentle transition, no sudden change, the transition length should be greater than 150mm, the same cross section transition length should be greater than 90º arc length
6. The effective hardening depth test method is also suitable for the determination of the induction hardening depth of ductile iron parts
7. Spline, gear bottom hardening layer depth should be greater than the drawing specified hardening layer 1/2
The depth of hardened layer was measured by microscopy
1. When GB5617-85 "Induction hardening of steel or determination of effective hardening layer depth after flame quenching" standard can not be implemented, JB2641-79 "Automobile induction hardening parts Metallography inspection standard" can still be temporarily used, but the quality arbitration should be implemented GB5617-85 standard
2. For pre-conditioned parts, the depth of the hardened layer is measured from the surface to the obvious sorbite, and no ferrite is allowed in the hardened layer. For pre-normalized parts, if the surface hardness is ≥55HRC, the depth of the hardened layer shall be measured from the surface to the martensite with a volume fraction of 50%; if the volume fraction of ferrite at martensite is greater than 20%, the depth of the hardened layer shall be measured from the surface to the core tissue half (sample amplified by 100×) when the surface hardness is less than 55HRC.
3. Daily production allows the use of corrosion method, rough to see the depth of the layer, but not as a basis for final judgment
Hardening zone position and dimension inspection
1. Daily production, hardening zone size can be measured according to the color of the hardening zone with steel ruler or vernier. Quality arbitration or full-time inspection department should be based on the hardness measurement
2. Hardness measurement: According to the carbon content of carbon steel, the hardness value of the end of the hardening zone can be referred to the hardness value of the hardening layer in Table 9-57, and the hardening zone of 45 steel is measured to about 45HRC. The hardness value of the alloy steel boundary should be the lower limit hardness value specified in the drawing, and the distance between the two boundaries is the size of the hardening zone
3. Microscopic measurement: The sample is measured to the semi-martensite at the edge of the hardened area under a microscope magnified 100 times, and the distance between the martensite points at both ends of the hardened area is the length of the hardened area
4. Table 9-32 describes the hardening zone position errors
Metallographic examination
1. According to ZBJ36009-88 "Induction hardening Metallographic inspection of steel parts", the test is carried out, and the structure of the pole is described in Table 9-54
2. In mass production, the first piece must be checked, and the first piece of metallographic organization can be produced normally according to the process
3. Daily production, at least 1 to 2 pieces of physical inspection per batch, the number of physical anatomy should be controlled in 1/500 to 1/1000
4. When the minimum hardness stipulated by the pattern is ≥55HRC, the microstructure is qualified at grade 3 to 7; when the minimum hardness stipulated by the pattern is <55HRC, the microstructure is qualified at grade 3 to 8, and the important parts are qualified at grade 4 to 7. Worm allows 3~8 grade qualified
5. Pre-conditioned parts, normalizing parts, surface and interior metallographic structure should meet the process requirements
6. For parts with surface hardness ≥55HRC, ferrite and trostenite are not allowed in the hardened layer. For parts with hardness less than 55HRC, a small amount of ferrite is allowed in the hardened layer
7. When the decarburization layer of cold-drawn steel is greater than the grinding allowance, it should be carbonized and then induction heating quenching
8. The sample should not be tempered
9. During arbitration, the microstructure shall be tested at 400 times and shall be tested at the surface of the effective hardened layer. Daily production can be tested at 450 times
10. After induction hardening, the nodular iron parts are inspected according to the provisions of ZBJ36010-88 "Induction hardening Metallographic inspection of pearlitic nodular iron parts" for microstructure inspection, generally 3~6 grades qualified, and the specific structure is described in Table 9-55
Distortion test
1. For parts that are not grinding after quenching and tempering, the distortion control shall be checked according to the technical requirements
2. Shaft and rod parts, according to the pattern of the inspection straightness and radial runout, the pattern is not clearly specified, the allowable radial runout is 1/2 of the unilateral grinding allowance, flat, plate parts of the warp is less than the grinding allowance of 2/3
3. The distortion of gear parts should be controlled within the scope required by the drawing or technical document
4. The number of distortion inspection according to the pattern or process documents, the general long shaft member should be inspected, the excess straightening, the same batch of quenched gear, the sampling number of each batch shall not be less than 3 pieces
Reworked parts
1. When the hardness is less than 2HRC or 20HV specified in the pattern, the size deviation of the hardening zone is more than 2mm (small and medium-sized parts), the depth of the hardening layer is less than 0.5mm specified in the pattern, or the microstructure is underheated (grade 9 to 10), overheating, allowing after low temperature annealing, the extraction process quenching and tempering
2. The inspection quantity of the repaired parts is 2 to 3 times that of the original regulations, and the inspection is complete when necessary
3. Induction hardening parts are only allowed to be reworked once