This standard specifies requirements for salt-melting heating and cooling equipment, salt bath composition and properties, heating and cooling process operations, safety and health matters, and environmental impact. This standard applies to the heating and cooling of metal parts in neutral salt baths or nitrate salt baths. JB/T 6048-2004 Heating and cooling of metal parts in salt bath JB/T6048-2004 Standard download and decompression password: www.bzxz.net

ICs25.200
J36
Machinery Industry Standard of the People's Republic of China
JB/T6048—2004
Replaces JB/T6048—1992
Metal parts in Heating and Cooling in Salt Bath for Metallic Components Published on 2004-02-10
Implemented on 2004-06-01
Foreword published by the National Development and Reform Commission of the People's Republic of China
Scope
Normative references
Terms and definitions
Heated and cooled metal parts
S
6
7
8| |tt||9
Used heat treatment process
Equipment
Salt bath.
Salt bath heating and cooling process
Quality inspection||tt || FO |
Specimen (box piece)
A.2
Test equipment and heating specifications
Test step alliance,
A.3||tt| |A.4 Sample analysis..
A.5 Result calculation
Table 1 salt bath composition and operating temperature
Decarburization performance of high-temperature salt bath in Table 2|| tt||Table A.1
Box sheet heating specifications
JB/T6048—2004
ITI
Foreword
JB/T6048—2004|| tt||This standard is a revision of JB/T6048-1992 "Salt Bath Heat Treatment". When revising, reference was made to relevant domestic industry standards and relevant foreign standards and materials in recent years, and the original standards were revised and corresponding content was added. Compared with JB/T6048--1992, the main changes in this standard are as follows: The structure and format have been changed according to the requirements of GB/T1.1-2000 "Standardization Work Guidelines Part t: Standard Structure and Writing Rules", and added Table of Contents and Foreword:
The standard name has been changed to "Heating and Cooling of Metal Fabrication in Salt Baths": Provisions for the correct selection of salt baths have been added, and equipment and process requirements have been tightened. This standard replaces JB/T6048-1992 "Salt Bath Heat Treatment". Appendix A of this standard is an informative appendix.
This standard is proposed by China Machinery Industry Federation. This standard is under the jurisdiction of the National Heat Treatment Standardization Technical Committee. This standard was drafted by: Beijing Institute of Mechanical and Electrical Engineering. The main drafters of this standard: Fan Dongli, Jia Hongyan, and Ma Lan. The previous versions of the standard replaced by this standard are: JB/T6048--1992.
1 Scope
Heating and cooling of metal parts in salt bath JB/T6048—2004
This standard specifies the salt bath heating and cooling equipment, salt bath composition and properties , heating and cooling process operations, safety and health matters and environmental impact requirements
This standard applies to the heating and cooling of metal parts in neutral salt baths or nitrate salt baths. 2 Normative reference documents
The provisions in the following documents become provisions of this standard through reference in this standard. For dated reference documents, all subsequent amendments (excluding corrigenda) or revisions do not apply to this standard. However, parties to an agreement based on this standard are encouraged to study whether the latest versions of these documents can be used. . For undated referenced documents, the latest edition applies to this standard. GB/T223.1 Determination of carbon content in steel and alloys GB/T8121 Heat treatment process material terminology | Fire and annealing (egvJISB6911:1987) GB/T16924 Fire and tempering of steel parts (eqvJISB6913:1989) JB/T4390
High and medium temperature heat treatment salt bath correction agent
JB/T5073
JB/T5266
JB/T6047
JB/T9202
Limits of harmful substances in the air of heat treatment workshops Indirect resistance furnace RY series electric heating bath furnace||tt ||Heat treatment salt bath Hazardous solid waste harmless treatment method Heat treatment salt
JB/T9052
General provisions for the pollution management of hazardous solid waste in heat treatment salt bath HB/Z276
3 terms and definitions
Heat treatment of deformed aluminum alloy parts
The following terms and definitions established in GB/T8121 apply to this standard. 3.1
neutral saltbath
Neutral salt bath
Neutral salts (such as alkali metal and alkaline earth metal chloride salts, alkali metal carbonates or their mixed salts) are formed after heating and melting The liquid medium 3.2
Nitrate bath saltforlow-temperaturebath is a liquid medium formed after nitrate, nitrite or their mixed salts are heated and melted. 3.3 | 3.4
Salt carry-out loss saltloss
When metal parts are heated in a salt bath and then taken out for cooling, salt will adhere to the surface and grooves, causing salt loss. The latter depends on the viscosity of the salt bath, the adhesion of the salt to the metal workpiece, the shape and surface roughness of the workpiece. JB/T6048—2004
3.5
Covering agent coverture
A substance that covers the surface of the salt bath in order to avoid oxidation of salt and reduce surface heat loss. Generally, quartz sand, alumina blocks, silicon carbide, charcoal, coke or graphite powder (blocks) are used.
4 Heated and cooled metal parts
Various structural steels, mold measuring steels, high-speed steels, spring steels, bearing steels, martensitic stainless steels, precipitation hardening stainless steels, solid solution Aged aluminum alloys, etc.
5 Applicable heat treatment processes
Austenitizing heating, isothermal or graded fire cooling and tempering of steel, solid solution treatment and aging of stainless steel and aluminum alloys 6 Equipment
6.1 High temperature salt bath furnace (above 950℃)
6.1.1 Suitable for austenitization of high-speed steel, hot and cold mold steel and solid solution treatment of high-strength stainless steel, usually an electrode type salt bath furnace 6.1.2 The thermal insulation accuracy of the effective heating zone should be guaranteed to be 10°C above soil. 6.1.3 In order to reduce the oxidation of salt and reduce heat loss, covering agent should be placed on the surface of the salt bath. 6.1.4 Photoelectric high temperature sensors and high-precision instruments must be used to measure and control the temperature. The temperature control accuracy should be guaranteed to be within 10°C. The photoelectric high-temperature sensing element should be directly facing the clean surface of the salt bath.
6.1.5 Check the furnace temperature uniformity twice a year according to GB/T9452. 6.2 Medium temperature salt bath furnace (650℃~950℃) 6.2.1 Suitable for austenitization of structural steel, tool molds and ductile iron and preheating of austenitization of tool and mold steel, usually externally heated crucible salt Bath furnace or internally heated electrode salt bath furnace.
6.2.2 The thermal insulation accuracy of the effective heating zone should be guaranteed to be ±10°C. 6.2.3 Use plug-in armored WRN or WRE type thermocouples and appropriate accuracy temperature measuring instruments. The thermal insulation accuracy should be guaranteed to be ±10°C. 6.2.4 According to GB/T9452, the furnace temperature uniformity of the effective heating zone should be tested twice a year. 6.3 Low-temperature salt bath furnace (below 650℃)
6.3.1 It is suitable for isothermal graded quenching, tempering and aluminum alloy solid solution treatment after austenitization of structural steel, tool and die steel, generally external heat Type-increased crucible furnace.
6.3.2 When used as isothermal or graded rate cooling, the furnace temperature uniformity in the effective heating zone should be guaranteed to be below 10°C. The thermal insulation accuracy when used for solution treatment of aluminum alloys should be guaranteed to be +3°C or meet process requirements. 6.3.3 Use plug-in armored WRF type thermocouples or armored WZP thermal resistors and appropriate precision temperature measuring instruments, and the insulation accuracy should be guaranteed to be within ±s°C.
6.3.4 The isothermal graded rate cold salt bath must be equipped with a water jacket or serpentine pipe for water cooling and propeller stirring facilities. The salt bath for solid solution treatment of aluminum alloys should also have stirring facilities
6.3.5 The effective heating zone shall be tested twice a year in accordance with GB/T9452. 6.4 Other technical conditions
6.4.1 The electric salt bath furnace should comply with the regulations of JB/T5266. 6.4.2 An exhaust or side exhaust system should be equipped to improve the working environment, 6.4.3 Various salt bath furnaces, especially low-temperature nitrate salt furnaces, must be equipped with over-temperature power-off and alarm facilities 7 Salt bath
7.1 Salt bath composition and quality requirements
2
7.1 .1
The recommended salt bath ingredients and operating temperature range are shown in Table 1. JB/T6048—2004
The impurities of various single salts in the mixed salt bath, especially the sulfate content, must meet the regulations in JB39202. 7.1.2
7.1.3BaCl>, NaCI and KCI must be dehydrated before preparing a new salt bath, BaCl500C×(3~4)h. NaCI, KC1400℃×(2~4)h, 7.1. 4. Medium and high temperature salt baths should ensure the performance requirements for steel decarburization listed in Table 2. Salt bath correction
7.2
7.2.1

The medium-temperature salt bath shall be calibrated once per production shift, and the high-temperature salt bath shall be calibrated twice per production shift. After calibration, it shall be adjusted appropriately and table 1. Salt bath composition and operating temperature
Types of salt baths
mediumbzxz.net
sex
salt
bath
nitrate
salt
bath
100%BaCls
Salt bath or mass distribution ratio
85%~95% BaCl,+15%~5%NaCi
70%~80% BaCI+30%~20%NaCI| |tt||50% BaCl+50% NaCI
50% KCI+50%NaCI
50% BaCI,+30% KCI +20% NaCI
100%KNO,| |tt||100%NaNO
50% KNOg+50% NaNO;
50% KNO,+50% NaNO
55%KNO,+45%NaNO(additional 3% 5%H:O) melting temperature
c
960
760850
635~700
640
670||tt| |560
337
317
218
140
137
Dephosphorization performance of high temperature salt bath in Table 2|| tt||Box sheet decarburization rate AC,
(w%)
Medium temperature salt bath
≤30
≤50
High temperature salt bath| |tt||≤40
60
7.2.2
The salt bath calibrator should be selected according to JB/T4390. Scope of application
Steel parts with strong sensitivity to decarburization
Specially important steel parts with high surface quality requirements General steel parts
7.2.3 Use long-acting salt containing correction agent in supplementation The salt bath can be calibrated when new salt is added, but the slag must be removed frequently. 7.3 Inspection
7.3.1 The decarburization performance of steel in medium and high temperature salt baths should be tested regularly according to the method specified in Appendix A. 7.3.2 The C ion content (generally <0.5%) of isothermal and graded cold nitrate salt baths should be checked regularly. 8 Salt bath heating and cooling process
8.1 Pre-production preparation
8.1.1 Check whether the workpiece material, technical requirements and heat treatment specifications are correct 8.1.2 Check the surface condition and defects of the workpiece. 8.1.3 Check whether the composition of the salt bath meets the workpiece process requirements, 8.1.4
Check whether the equipment and instruments are normal, whether the thermocouple is calibrated regularly, whether the temperature-one millivolt correspondence is normal, and whether the use temperature
ItD0~130(5
900-1100
7501000
700900
720950
580~880
350~600||tt ||350~600
230550
150550
150~360
3
JB/T6048—2004
8.1.5 inspection Whether the drying tools and fixtures are in good condition. 8.2 Loading the furnace
B.2.1 Put the dried small workpieces into baskets, tie small batches of medium and small workpieces with wires, and lift large workpieces into the furnace with fixtures. The position in the furnace should not exceed the range of the effective heating zone. 8.2.3 When the workpiece is heated in a high-temperature salt bath, its position in the furnace should not affect the temperature measurement of the photoelectric high-temperature sensor-type high-precision instrument. 8.3 Heating||tt| |8.3.1 The heating temperature and holding time of the workpiece are strictly implemented in accordance with the process regulations. 8.3.2 The heating time of the steel parts in the medium temperature salt bath is calculated as 0.7 minutes per millimeter of diameter or thickness, and the heating time of the high, medium and low temperature salt baths is calculated. Calculated as 1:3:5.
8.3.3 Workpieces of medium and high alloy steel or with complex shapes or large cross-sections should be preheated multiple times when necessary. .
8.3.4 The workpiece should be tempered in time after being tempered. When multiple temperings are required, it should be cooled to room temperature after each tempering.
8.4.1 The workpiece should be cooled in a salt bath. The temperature fluctuation of the salt bath should generally not exceed ±20°C (applicable to graded rate cooling) or ±10°C (applicable to isothermal rate cooling)
8.4.2 In the active salt bath (including C). The heated workpiece cannot be isothermally cooled or cooled in nitrate salt. 8.5 Cleaning and rust prevention
8.5.1 The residual salt should be cleaned and dried in time after the workpiece is cooled to room temperature according to the process requirements. 8.5.2 Salt bath heating rate. Finally, the workpiece must be cleaned before entering the nitrate salt bath for tempering. 8.5.3 If necessary, the workpiece should be subjected to anti-rust treatment after cleaning. 9. Quality inspection of steel parts after salt bath heat treatment. The quality inspection of deformed aluminum alloy parts after salt bath heat treatment shall be carried out in accordance with the relevant provisions of HB16924 or GB/T16923. 9.2 When there are regulations, the distortion of the workpiece after cooling or aging must be determined. Carry out the measurement. Safety and Environmental Protection
10
10.1 Safety
10.1.1 The safe operation of salt bath heat treatment should comply with the relevant regulations of GB15735. 10.1.2 It is strictly prohibited to bring salt salt into people. Medium and high temperature salt baths. 10.1.3 Chloride and nitrate salts are toxic and should be stored in special places and kept by dedicated personnel in accordance with relevant regulations. 10.1.4 It is strictly prohibited to heat closed hollow workpieces in a salt bath. Pay attention to the heating direction for holes and tubular workpieces. 10.1.5 It is strictly prohibited to transfer workpieces that have been liquid carburized in cyanide salt to nitrate salt for isothermal or graded rate cooling. 10.2 Environmental Protection
10.2.1 The pollution control of salt slag and nitrate salt slag shall comply with the relevant provisions of JB/T9052 and JB/T6047. 10.2.2 The content of harmful substances in the air at the salt bath heat treatment work site should comply with the relevant provisions of JB/T5073. 10.2.3 The solid, gas or liquid waste of salt bath heat treatment with excessive harmful substances should be treated harmlessly and meet the relevant national emission standards. Only then can it be discharged.
A.1 sample (foil)
Appendix A
(informative appendix)
Test method for medium and high temperature salt bath decarburization performance JR/T6048 —2004
A.1.1 The box sheet material is stipulated to be cold-rolled T10 steel strip with a thickness of (0.08±0.01) mm and a width of 30mm. The chemical composition of materials should comply with the regulations of GB/T1298.
A.1.2 Foil pieces cut from steel strips, each piece is 120mm in length. A.1.3 The foil should be flat, smooth and free of flash, burrs, rust and oil stains. A.1.4 Take two box pieces, punch a small hole at one end of the length direction, clean them with absolute ethanol and dry them. Thread wire through the hole and place on a T-hook. In order to prevent the box pieces from floating in the salt bath, a weight can be hung on the iron wire. A.2 Test equipment and heating specifications
The test equipment is a high-temperature or medium-temperature salt bath to be inspected. The salt bath should be in an unloaded state: A.2.1
A.2.2
The box piece heating specifications are shown in Table A.1.
Table A.1
Foil heating specifications
Salt solution types
High temperature salt bath
Medium temperature salt device
A.3 test steps
temperature
1230±10
850±10
time
min
3
20| |tt||The salt bath is calibrated with a thermocouple in advance, and then the entire prepared box piece is immersed in the effective heating area of ??the salt bath for heating. The immersion depth is based on the upper end of the foil being approximately 80mm below the molten salt. After the foil is heated according to the heating specifications specified in Table A1, take it out and quickly cool it with water. Carefully remove the foil from the box. Wash the residual salt on the surface with distilled water first, then soak it in absolute ethanol, dry it and store it in a desiccator. spare. A.4 Sample analysis
A.4.1 Cut and mix the two foils heated at the same time, and then analyze their carbon content according to GB/T223.1 (gas volumetric method). This carbon content is the remaining carbon content of the box piece.
A.4.2 Take two unheated foils from the same steel strip: analyze their carbon content. This carbon content is the original carbon content of the foil. A.5 results calculation
decarburization rate AC of the foil. (%) Calculated according to formula (A.1): ACp
Where:
Original carbon content of one foil, %:
Co
One foil Remaining carbon content of the slice, %.
C
Co-C
Co
X100%
(At)
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