This standard specifies the requirements for raw materials, equipment, process and quality inspection during the heat treatment of malleable cast iron. This standard applies to the heat treatment of blackheart malleable cast iron, pearlite malleable cast iron and whiteheart malleable cast iron. JB/T 7529-1994 Malleable Cast Iron Heat Treatment JB/T7529-1994 Standard download decompression password: www.bzxz.net

Machinery Industry Standard of the People's Republic of China
JB/T7529-94
Heat Treatment of Malleable Cast Iron
Published on October 25, 1994
Ministry of Machinery Industry of the People's Republic of China
Implementation on October 1, 1995
Mechanical Industry Standard of the People's Republic of China
Heat Treatment of Malleable Cast Iron
1 Subject Content and Scope of Application
This standard specifies the requirements for raw materials, equipment, processes and quality inspection during the heat treatment of malleable cast iron. This standard applies to the heat treatment of Xixin malleable cast iron, special light malleable cast iron and white heart malleable iron. 2 Referenced Standards
GB5611
GB5612
GB7232
GB 9440
JB2122
Metal tensile test method
Metal Brinell hardness test method
Glossary of casting terms
Methods for indicating cast iron grades
Terms for metal heat treatment processes
Forgeable iron castings
Metallurgical standards for ferritic forgeable cast iron
3Grades and mechanical properties of forgeable cast iron
The method for indicating the grades of forgeable cast iron shall comply with the provisions of GB5612. The grades and mechanical properties of blackheart forgeable cast iron and pearlitic forgeable cast iron shall comply with the provisions of GB5612. The mechanical properties shall conform to the requirements of Table 1 Table 1
Grades and mechanical properties of blackheart malleable cast iron and pearlite malleable cast iron Brand
KTH300-062
KTH350-10
KTZ450-06
KTZ550-04
KTZ650-02
KTZ700-02
KTH330-08
KTH370-12
Previous: 1) Brand B series is a transitional brand. Specimen diameter
12 or 153
2) Brand KTH300-06 is suitable for airtight parts, tensile strength
yield strength
3) The trial diameter of 12mm is only suitable for castings with a main wall thickness of less than 10mm. Approved by the Ministry of Machinery Industry on October 25, 1994
JB/T 752994
Elongation 8
L,== 3d
Not more than 150
150~200
180~230
210~260
240~290
1995-10-01 implementation
JB/T7529-94
3.3 The grade and mechanical properties of whiteheart malleable cast iron shall comply with the requirements of Table 2. 2 Grades and mechanical properties of whiteheart malleable cast iron Sample diameter
KTB350-04
KTB380-12
KTB400-05
KTB450-07
Tensile strength
Filming strength
Note; 1) The diameter of the whiteheart malleable cast iron sample should be as close as possible to the main thickness of the same piece. 4 Heat treatment equipment
Clock length rate.
Not more than
4.1 Annealing furnace
4.1.1 The temperature of various annealing furnaces should meet the requirements of the heat treatment process, and can save energy, reduce pollution, and be easy to operate. The temperature of each zone of the continuous annealing furnace should be able to meet the requirements of the corresponding heat treatment stage, and the running speed of the casting in the furnace should be adjustable. 4.1.2 The flame of the fuel furnace cannot be directly sprayed onto the annealing box or castings. 4.1.3 The annealing furnace should be equipped with temperature measuring holes for optical pyrometers and potential couples and test piece sampling holes. The sampling holes should be located at a convenient position for extraction. The annealing furnace should be equipped with a device to adjust the cooling rate. 4.1.4
4.1.5 When annealing pearlite forgeable cast iron, a trolley furnace, a bell furnace or a continuous furnace is generally used. 4.2 Temperature measurement and recording instruments
4.2.1 It must be able to meet the temperature measurement requirements of various annealing processes and different positions of the furnace. 4.2.2
The periodic annealing furnace should be equipped with a device for recording temperature; each heating zone of the continuous annealing furnace should be equipped with such a device. Thermocouples and temperature recording instruments used for temperature measurement must be calibrated regularly. 4.2.3
4.3 Blower and spray device
The air volume of the blast device should be able to meet the cooling requirements. 4.3.1
4.3.2 The atomization degree and spray volume of the spray device should meet the cooling requirements. 4.4 Annealing box
Annealing box is generally made of white cast iron, high chromium cast steel or heat-resistant steel plate. 4.5 The ability of the pulverized coal machine
to crush coal blocks should meet the technical requirements. 4.5.1
4.5.2: The amount of pulverized coal sent to the furnace should be adjustable. 2
5 Heat treatment
5.1 Preparation
JB/T7529-94
5.1.1 The chemical composition, shape, size, weight, pouring condition and metallographic structure of raw material white cast castings must meet the technical requirements. Free stone wings are not allowed.
5.1.2 According to the quality requirements, furnace loading and the original condition of the castings, formulate the corresponding heat treatment process. 5.1.3 Check or clean all equipment used. 5.1.4 When annealing cast iron, it is generally necessary to pack it in boxes. When packing, it should be carried out according to certain requirements based on the shape, size, weight, etc. of the parts, and a certain gap should be left between the castings. a.www.bzxz.net
A certain amount of decarburizer should be placed in the annealing box of self-core forgeable iron. When using solid decarburizer, the box cover and the box body should be sealed with fire mud. If decarburizing atmosphere is used as the heating medium, the box cover is not necessary. e.
The annealing box of spherical forgeable castings does not need to be sealed. A certain number of samples and random inspection specimens in front of the furnace should be placed in each furnace. d.
5.1.5 Furnace loading requirements
The annealing box containing castings should have gaps between the front, back, left, right, and right of the furnace, and partitions between the top and bottom, and a certain distance from the furnace top and furnace top.
The test specimens for inspection in front of the furnace and the annealing box containing samples should be placed in representative positions in the furnace. b.
When using a periodic annealing furnace, the furnace door should be sealed. c.
5.2 Heat treatment process
5.2.1 When heating, attention should be paid to the heating speed, and 1 to 2 stage heating methods can be adopted. 5.2.2 The holding time should be determined according to the process and the test piece in front of the furnace: the temperature of the first stage graphitization annealing of blackheart malleable cast iron and pearlite malleable cast iron is 850~960℃, and that of whiteheart malleable cast iron is a.
930~1050℃,
b. The holding time of the first stage annealing is determined according to the annealing process regulations and the fracture color selection and morphology of the test piece in front of the furnace or the degree of graphitization of the metallographic structure.
The second stage graphitization annealing of blackheart malleable cast iron is slowly cooled from 760℃ to 650℃. According to the process regulations and the fracture color or metallographic structure of the test piece in front of the furnace, decide whether to extend the holding time. 5.2.3 The cooling method should be determined according to the type of malleable cast iron produced: a.
After the first stage of blackheart galvanized cast iron is completed, it is required to quickly reduce the furnace temperature to near the eutectoid temperature, and then slowly cool with the furnace to implement the second stage of graphitization annealing. After the second stage is completed, the annealing box can be pulled out of the furnace and cooled to below 400℃ by blast or mist. b. After the first stage of pearlite malleable cast iron is completed, the workpiece can be taken out of the furnace for cooling. c. After the first stage of whiteheart malleable cast iron is completed, it is cooled with the furnace to about 65G℃, and then taken out of the furnace for air cooling. 5.3 Heat treatment record
Necessary matters during the heat treatment process should be recorded and a spare set should be kept. 6 Further heat treatment of pearlite cast iron According to the performance requirements, pearlite cast iron can also be subjected to isothermal annealing, tempering, induction annealing, flame annealing and other potential treatments. 7 Quality inspection
7.1 Surface quality
Use visual inspection to check the surface quality of castings one by one, and no oxide scale is allowed to remain. 7.2 Distortion
The geometric shape and size of the castings shall meet the technical requirements. The deformation produced during the heat treatment process can be eliminated by correction. Frequency 3
JB/T7529-94
Correction is usually carried out at room temperature, and heat correction can be used in special cases. 7.3 Mechanical properties
7.3.1 The mechanical properties of malleable cast iron are based on the tensile strength and elongation of the specimen as the acceptance basis. The mechanical properties of the specimen shall comply with the provisions of Table 1 and Table 2.
7.3.2 When there are requirements for strength and hardness, they shall comply with the provisions of Table 1 and Table 2 after agreement between the supplier and the buyer. 7.3.3 When there are requirements for other properties (such as compression, bending, torsion, impact, elastic modulus, etc.), an agreement shall be reached at the time of ordering. 7.3.4 The tensile specimen and tensile test method must comply with the provisions of GB9440. The composition, casting method, thickness, etc. of the specimen shall be representative of the actual casting and shall be carried out under the same conditions. 7.3.5.The hardness test is carried out in accordance with GB231. When measuring the hardness at the position determined by the sample or casting, it is necessary to remove 1 to 2 mm of the surface before conducting the test.
7.4 Gold pat test
Blackheart malleable cast iron is carried out in accordance with GB2122. Its normal structure is ferrite matrix and flocculent graphite. b. The normal structure of pearlite malleable cast iron is lamellar pearlite and clustered graphite. The normal structure of whiteheart malleable cast iron should comply with the provisions of GB9440. e.
7.5 Destructive test
Destructive test is only carried out when the demander makes a request, and the judgment standard of whether it is qualified or not is agreed upon by the supply and demand parties when placing an order. 7.6 The evaluation, re-inspection and revision of the test results shall be carried out in accordance with the provisions of GB9440.
8 Other requirements
Marking and certification, surface protection, packaging, transportation and storage, acceptance and rejection shall be carried out in accordance with the provisions of GB9440. Additional Notes:
This standard was proposed and managed by the National Technical Committee for Heat Treatment Standardization. This standard was drafted by the Shanghai Mechanical Manufacturing Technology Research Institute. The main drafters of this standard are Mei Zhiqiang and Shi Yiren.
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