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Mechanical Industry Standard of the People's Republic of China
JB/T 6048-1992
Salt Bath Heat Treatment
Published on May 5, 1992
Implementation on July 1, 1993 by the Ministry of Machinery and Electronics Industry of the People's Republic of ChinaWww.bzxZ.net
Mechanical Industry Standard of the People's Republic of China
1 Subject Content and Scope of Application
JB/T 6048-1992
This standard specifies the equipment requirements, salt bath requirements, process operation, safety and environmental protection for salt bath heat treatment. This standard applies to the heating and cooling of metal workpieces in neutral salt baths or nitrate baths. 2
Reference standards
GB1298
JB3814
JB3877
JB4390
JB4406
JB5266
JB/T5093
ZB J36 007
ZB J71 001
QJ/Z124
3.1 Neutral salt bath
Carbon content analysis in steel and alloys
Carbon tool steel
Technical conditions
Normalizing and annealing of steel
Quenching and tempering of steel
High and medium temperature heat treatment salt bath corrector
General provisions for heat treatment safety technology
Indirect resistance furnace Part 12 RY series electric heating bath furnace Limits of harmful substances in heat treatment workshop gas Salt for heat treatment
General provisions for pollution control of harmful solid wastes in heat treatment salt bath Heat treatment of deformed aluminum alloys
Liquid medium formed by heating and melting neutral salt (such as alkali metal and alkaline earth metal chlorides, alkali metal carbonates or their mixed salts). 3.2 Nitrate salt bath
Liquid medium formed by heating and melting nitrates, nitrites or their mixed salts. 3.3 High temperature salt bath
Salt bath used above 950℃.
3.4 Medium temperature salt bath
Salt bath used between 650~950℃.
Low temperature salt bath
Salt bath used below 650℃.
Salt bath adjustment
Through salt bath calibration, slag removal and addition of new salt, the salt bath is made to have the performance that meets the process requirements. 3.7
Salt bath calibration
Adding a calibrant to the salt bath to remove oxides in the salt bath and prevent or reduce oxidation and decarburization of the workpiece. 3.8 Decarburization rate of foil
The percentage of the difference between the original carbon content of the foil before heating and the remaining carbon content after heating to the original carbon content of the foil before heating. Approved by the Ministry of Machinery and Electronics Industry on May 5, 1992 and implemented on July 1, 1993
Common Metal Materials
JB/T6048-1992
Carbon tool steel, alloy tool steel, high-speed tool steel, high-quality carbon structural steel, alloy structural steel, spring steel, chromium bearing steel, martensitic stainless steel, deformed aluminum alloy, etc. The technical conditions of the materials shall comply with the provisions of the relevant standards. 5
Salt bath furnace
Salt bath furnaces can be heated by electricity or fuel according to the conditions. Electric heating salt bath furnaces shall comply with the relevant provisions of JB5266. The insulation accuracy of the effective heating zone of the salt bath furnace shall meet the process requirements, and generally shall not exceed 15°C (suitable for heating steel parts) or 5°C (suitable for heating deformed aluminum alloy parts).
For electrode salt bath furnaces, it is recommended to adopt an embedded electrode structure, and appropriate rapid melting measures shall be taken according to the empty furnace heating time specified in JB5266.
The salt bath furnace should be equipped with an exhaust device.
The nitrate bath tank for cooling should have sufficient capacity and, if necessary, should be equipped with an appropriate stirring device
The salt bath in the bath tank should comply with the provisions of Chapter 6. 5.2 Cleaning device
The cleaning device should have sufficient capacity and workstations and be equipped with a resistance heating or steam heating device. The cleaning liquid and rust inhibitor should be replaced in time according to the usage. 5.3 Equipment maintenance
The equipment should be inspected and repaired regularly and records should be kept. 6
Composition of commonly used salt baths and quality requirements of salts 6.1.1
The composition ratio and operating temperature range of commonly used salt baths are shown in Table 1. Table 1
Type of salt bath
Neutral salt solution
Niter salt bath
Mass ratio of salt bath ingredients
100%BaCl
85%~95%BaCl,+15%~5%NaCl
70%~80%BaCl,+30%~20%NaCI
50%BaCI+50%NaCI|| tt | | |(Add 3%~5%H,0)
Melting temperature
760~850
635~700
Using temperature
1100~1300
900~1000
750~1000
700~900
720~950
580~880
350~600
350~600
230~550
150~550
150-360
JB/T6048-1992
6.1.2 The quality of salt shall comply with the provisions of ZBJ360076.1.3 Barium oxide, sodium chloride and potassium chloride new salt shall be dehydrated before use. Recommended dehydration treatment specification: barium chloride is 500℃×(3~4)h, sodium chloride and potassium chloride are 400℃×(2~4)h. 6.2 Performance requirements
6.2.1 The salt bath shall be clear, fluid and have low evaporation within the use temperature range, and the residual salt on the workpiece shall be easy to clean. 2 The salt bath shall not obviously oxidize or corrode the workpiece. 6.2.2
The decarburization performance of medium and high temperature salt baths is shown in Table 2. Table 2
Box decarburization rate △C
Medium temperature salt bath
High temperature salt bath
The cooling salt bath should have cooling performance that meets the process requirements. 6.2.4
6.3 Salt bath adjustment
Scope of application
Steel parts with strong decarburization sensitivity
Special and important parts with high surface quality requirements
General steel parts
6.3.1 Medium and high temperature salt baths should be calibrated strictly according to the calibration system. The calibration time interval for high temperature salt bath is generally 4~8h (should not exceed 4h in a humid environment), and for medium temperature salt bath is generally not more than 8h. 6.3.2
The salt bath calibrator used should comply with the provisions of JB4390. 6.3.3
The salt bath should be deslagging regularly.
The salt bath should be timely added with new salt or completely replaced according to the usage. 6.4 Salt bath inspection
The decarburization performance of medium and high temperature salt baths should be inspected regularly. The inspection method shall be carried out in accordance with Appendix A (Supplement). 6. 4.2
When necessary, the chemical composition of the nitrate salt bath should be inspected regularly, and the chloride ion content should generally not exceed 0.5%. 7
Heat treatment process
Preparation before treatment
Understand the material brand, technical requirements, pre-heat treatment conditions and heat treatment specifications of the workpiece. 7.1.2 Check the appearance quality of the workpiece. The workpiece surface should be free of defects such as oxide scale, rust spots, cracks and bumps. 7.1.3 Check whether the salt bath meets the provisions of Article 6.2. When the salt bath is working continuously, special attention should be paid to adjusting the salt bath according to the provisions of Article 6.3.
7.1.4 Check whether the measuring and controlling instruments are in the right position. Among them, for high-temperature salt baths measured by radiation temperature sensors, the furnace temperature should be regularly calibrated with thermocouples, and metallographic specimens should be used for verification if necessary. 5 Drying workpieces and fixtures.
7.2 Furnace loading
7.2.1 The workpieces should be placed in the effective heating zone of the furnace, and the number of furnaces loaded and the gap between the workpieces should be noted. 7.2.2
When the high-temperature salt bath is measured by radiation temperature sensors, the workpiece loading should not affect the correct measurement of the furnace temperature. 3
7.3 Process operation
7.3.1 Heating
JB/T6048-1992
a. The heating temperature and holding time should meet the requirements of the corresponding process. b. Medium and high alloy steels or workpieces with complex shapes or large cross-sectional dimensions should be preheated before quenching heating. If necessary, they should be preheated multiple times.
c. The workpiece should be tempered in time after quenching. When multiple tempering is required, the steel should be cooled to room temperature each time. 7.3.2 Cooling
When the workpiece is cooled in the salt bath, the temperature fluctuation of the salt bath should generally not exceed ±20℃ (suitable for graded quenching) or ±10℃ (suitable for isothermal quenching).
7.3.3 Cleaning and rust prevention
a: After the workpiece cools to room temperature according to the process requirements, the residual salt should be cleaned and dried in time. b. After salt bath heating quenching, the workpiece must be cleaned before entering the nitrate salt bath for tempering. c. If necessary, the workpiece should be rust-proofed after cleaning. 8 Quality inspection
The quality inspection of steel parts after salt bath heat treatment should be carried out in accordance with the relevant provisions of JB3877 or JB3814. The quality inspection of deformed aluminum alloy parts after salt bath heat treatment should be carried out in accordance with the relevant provisions of QJ/Z124. 9 Safety and environmental protection
9.1 Safety
9.1.1 The safe operation of salt bath heat treatment should be in accordance with the relevant provisions of JB4406. 9.1.2 It is strictly forbidden to bring nitrate salt into medium and high temperature salt baths. 9.1.3 Barium chloride is a highly toxic substance and nitrate salt is a toxic substance. They should be stored in a special place and kept by a special person in accordance with relevant regulations. It is strictly forbidden to heat closed hollow workpieces in a salt bath. Pay attention to the heating direction of workpieces with holes and tubular shapes. 9.1.4
9.2 Environmental protection
9.2.1 The pollution control of lock salt slag and nitrate salt slag shall comply with the relevant provisions of ZBJ71001. The content of harmful substances in the air at the salt bath heat treatment work site shall comply with the relevant provisions of JB/T5093. 9.2.2
3 Solid, gaseous or liquid wastes from salt bath heat treatment that exceed the standard of harmful substances shall be treated harmlessly and can only be discharged after meeting the relevant national emission requirements.
A1 Test specimen (foil)
JB/T6048-1992
Appendix A
Test method for decarburization performance in medium and high temperature salt bath (supplement)
The raw material of the foil is specified to be a cold-rolled T10 steel strip with a thickness of 0.08±0.01mm and a width of 30mm. The chemical composition of the material shall comply with the provisions of GB1298.
A1.2 The foil cut from the steel strip shall be 120mm long per piece. A1.3 The foil shall be flat and smooth, without burrs, burrs, rust and oil stains. A1.4 Take two pieces of foil, make a small hole at one end in the length direction, clean with anhydrous ethanol and dry. Pass a wire through the small hole and tie it to a T-hook for use. In order to prevent the foil from floating in the salt bath, a heavy object can be hung on the wire. A2 Test equipment and heating specifications
The test equipment is the high or medium temperature salt bath to be tested. The salt bath should be in an unloaded state. A2.2 See Table A1 for foil heating specifications.
Salt solution type
High temperature salt bath
Medium temperature salt bath
Test steps
Temperature ℃
1230±10
850±10
Heating specifications
The salt bath is pre-calibrated with a thermocouple,
Then the prepared box is completely immersed in the effective heating area of the salt bath for heating, and the immersion depth is based on the upper end of the foil being about 80mm below the molten salt. After the foil is heated according to the heating specifications specified in Table A1, take out the quick water, carefully remove the foil, first wash off the residual salt on the surface with distilled water, then immerse it with anhydrous ethanol, dry it and store it in a desiccator for use. A4 Sample analysis
A4.1 Cut and mix two foils heated at the same time, and then analyze their carbon content according to GB223.1 (gas volumetric method). This carbon content is the residual carbon content of the foil.
A4.2 Take two unheated foils from the same steel strip and analyze their carbon content. This carbon content is the original carbon content of the foil. A5 Result calculation
The foil decarburization rate △Cp (%) is calculated according to formula (A1): ACp
Where: C. —Original carbon content of foil, %; C Residual carbon content of foil, %.
Additional instructions:
JB/T6048-1992
This standard was proposed and managed by the Beijing Electromechanical Research Institute of the Ministry of Machinery and Electronics Industry. This standard was drafted by the Beijing Electromechanical Research Institute. The main drafters of this standard were Liu Changgui and Wu Yue. China
People's Republic of China:
Mechanical Industry Standard
Heat Treatment
JB/T 60481992
Published and issued 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
Print Sheet 5/8
Word Count 10,000
First Edition in January 1993
First Printing in January 1993
Print Quantity 1-500
Price 10.00 Yuan
Mechanical Industry Standard Service Network: http://www.JB.ac.cn618092 Take two unheated foils from the same steel strip and analyze their carbon content. This carbon content is the original carbon content of the foil. A5 Result Calculation
The foil decarburization rate △Cp (%) is calculated according to formula (A1): ACp
Where: C. —Original carbon content of foil, %; C Residual carbon content of foil, %.
Additional Notes:
JB/T6048-1992
This standard was proposed and managed by the Beijing Electromechanical Research Institute of the Ministry of Machinery and Electronics Industry. This standard was drafted by the Beijing Electromechanical Research Institute. The main drafters of this standard were Liu Changgui and Wu Yue. China
People's Republic of China:
Mechanical Industry Standard
Heat Treatment
JB/T 60481992
Published and issued 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
Print Sheet 5/8
Word Count 10,000
First Edition in January 1993
First Printing in January 1993
Print Quantity 1-500
Price 10.00 Yuan
Mechanical Industry Standard Service Network: http://www.JB.ac.cn618092 Take two unheated foils from the same steel strip and analyze their carbon content. This carbon content is the original carbon content of the foil. A5 Result Calculation
The foil decarburization rate △Cp (%) is calculated according to formula (A1): ACp
Where: C. —Original carbon content of foil, %; C Residual carbon content of foil, %.
Additional Notes:
JB/T6048-1992
This standard was proposed and managed by the Beijing Electromechanical Research Institute of the Ministry of Machinery and Electronics Industry. This standard was drafted by the Beijing Electromechanical Research Institute. The main drafters of this standard were Liu Changgui and Wu Yue. China
People's Republic of China:
Mechanical Industry Standard
Heat Treatment
JB/T 60481992
Published and issued 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
Print Sheet 5/8
Word Count 10,000
First Edition in January 1993
First Printing in January 1993
Print Quantity 1-500
Price 10.00 Yuan
Mechanical Industry Standard Service Network: http://www.JB.ac.cn61809
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