JB/T 7951-1999 Test method for cooling performance of quenching medium JB/T7951-1999 Standard download decompression password: www.bzxz.net

ICS25.200
Machinery Industry Standard of the People's Republic of China
JB/T7951-1999
Testing method for cooling properties of quenching media
Testing method for cooling properties of quenching mediaPublished on 1999-06-24
JB/T 7951-1999
National Bureau of Machinery Industry
International Standard Download Network (www.bzxzw.com
Implementation on 2000-01-01
JB/T7951-1999
This standard is a revision of JB/T7951-95 "Testing method for cooling properties of quenching media". During the revision, only editorial changes were made according to relevant regulations, and the main contents remained unchanged.
This standard replaces JB/T7951-95 from the date of implementation. This standard is issued by the National Heat Treatment Standardization Administration The Technical Committee proposed and coordinated this standard. The responsible drafting unit of this standard: Beijing Electromechanical Research Institute. The responsible drafter of this standard: Wang Yue.
This standard was first issued on June 24, 1988 as GB9449-88, and was adjusted to JB/T7951-95 in April 1996. International Standard Download Network (www.bzxzw.com
Mechanical Industry Standards of the People's Republic of China
Mechanical Industry Standards of the People's Republic of China
Testing method for cooling properties of fire medium
Testing method for cooling properties of fire medium quendhingmedia This standard specifies the test method for the cooling performance of quenching media. This standard is applicable to the testing of oil-based quenching media and water-based quenching media. Cited standards
JB/T7951-1999
Replaces JB/T7951—95
The provisions contained in the following standards constitute the provisions of this standard through reference in this standard. When this standard was published, the versions shown were valid. All standards will be revised, and parties using this standard should explore the possibility of using the latest versions of the following standards. GB/T2614—1998 Nickel-chromium-nickel-silicon thermocouple wire 3 Definitions
This standard adopts the following definitions.
Oil Quenching medium
Quenching oil based on mineral oil or vegetable oil with appropriate additives. Water-based quenching medium
Quenching cooling medium made of water, alkali, inorganic salt or organic aqueous solution. Probe
Metallic test element equipped with thermocouple.
Cooling process curve
After the probe is heated to the specified temperature, it is put into the medium to be tested for cooling. The curve of the temperature change of the probe over time is used to characterize the temperature change of the probe over time.
Cooling characteristic curve
The cooling rate change curve of the probe core. The slope of the cooling process curve changes with the temperature of the probe core to characterize the cooling rate change of the probe at different temperatures. Film boiling period
The initial stage of putting the probe heated to the specified temperature into the quenching medium. Because the probe surface can provide enough heat to vaporize the surrounding liquid, a vapor film is formed on its surface. Bubble boiling period
When the probe temperature drops to a point where its heat is insufficient to maintain the formation of a vapor film on the surface, the stage where bubbles are constantly formed and burst on its surface.
Convection period
Approved by the State Bureau of Machinery Industry on June 24, 1999 and implemented on January 1, 2000
JB/T79511999
When the probe temperature is further reduced to a point where bubbles cannot form, the stage where only liquid heat convection occurs on its surface. 3.9
Characteristic temperature
The temperature at which the film boiling period transitions to the bubble boiling period is called the characteristic temperature. See 9.7 for the calculation method. Characteristic temperature seconds
The time to reach the characteristic temperature is called the characteristic temperature seconds, or T-seconds for short. See 9.7 for the calculation method. Maximum cooling rate
When the probe is cooled in the measured medium, the highest value displayed at a certain temperature on the cooling characteristic curve. 3.12 Repeatability
In the same laboratory, the same person uses the same device to test the same medium twice at different times, and the difference in the maximum cooling rate of the test results. 3.13 Reproducibility
In two different laboratories, different people use different devices to test the same medium, and the difference in the maximum cooling rate of the two test results is obtained. 4 Method Overview
The silver probe is heated to a specified temperature and quickly placed in a certain volume of the medium to be tested. The cooling process curve of the probe is recorded, or the cooling characteristic curve is made by computer data processing at the same time. The schematic diagram of the test device is shown in Figure 1. Manipulator
Tubular heating furnace
Medium to be tested
5 Probe
Structure and size
Starting point setter
Test recording system
Schematic diagram of the test device
The probe consists of a main body, a support tube, a fixing nut and a thermocouple. Its structural dimensions are shown in Figure 2. 2
TOF91
0.5K type thermocouple
24 ± 0.1
48 ± 0.1
78 ± 0.1
Silver body
JB/T79511999
Insulating porcelain tube
Support tube
Figure 2 Probe structure and dimensions
Fixing screw per
Inlay 0.8
The body and guide tube are made of pure silver (99.99%), the support tube is made of $10mm 1Cr18Ni9 stainless steel, the couple wire adopts Φ0.5mm K type thermocouple, which meets the Class II standard of GB/T2614 standard and has a length of 1m. 5.3 Manufacturing and assembly
Fix the thermocouple to the core of the main body by cold extrusion to maintain good electrical contact. 6 Test conditions
6.1 Heating equipment
6.1.1 The vertical tubular heating furnace should have at least a 60mm long effective heating zone, and its insulation accuracy should not exceed ±5°C. 6.1.2 During heating, the probe body should be placed in the effective heating zone. 6.1.3 The probe heating temperature is specified as (800 ± 5)°C, and the probe should be kept at temperature for 5 minutes after being heated to the temperature. 6.2 Quenching and cooling system
6.2.1 Prepare 3000mL of the medium to be tested. The container of the medium to be tested is specified as an 800mL standard beaker with a medium capacity of 700mL. The upper end surface of the silver body is immersed in the liquid surface by 20mm.
6.2.2 The water-based medium to be tested should be measured at (25±2)℃, and the oil-based medium to be tested should be measured at (50±2)℃: if there are special requirements, it can be specified separately.
6.2.3 Unless otherwise specified, the medium to be tested should remain static. 6.2.4 The speed of the probe entering the medium is (5±1)m/min. 6.2.5 Start recording when the hot spot of the probe thermocouple is at the liquid surface. 7 Surface treatment of the probe
7.1 Before use, the new probe should be pre-treated as follows: after polishing according to 7.3, it should be predicted in the calibration liquid (see Chapter 8) for no less than three times, and the results should meet the requirements of 3.12 and the corresponding technical documents. 7.2 After each test, when the probe temperature is below 80℃, the probe is removed from the medium, then cooled to below 40° in clean water, scrubbed with detergent, rinsed with clean water, and wiped dry with finger-free gauze. 7.3 If there is obvious attached film on the probe surface, use 600 metallographic sandpaper to remove it, and polish it appropriately to reveal the metallic luster, then clean and dry it. 7.4
Before reuse, it should be pre-treated again according to the provisions of 7.1. There are 3 pages left to read. Do you want to continue reading? This document was shared by which person on 2012-04-278
Calibration quenching liquid
JB/T 79511999
The calibration quenching liquid is specified as (25±2)℃ distilled water. Test procedure
Preparation of the medium to be tested
Prepare the medium according to the provisions of 6.21, and heat it on an electric furnace according to the test temperature specified in 6.2.2, and stir it continuously. Test preparation
Turn on the power of the measurement system and check whether all instruments are normal. Heating the probe
Heat the probe that has been calibrated and pre-treated (Chapter 6 and Chapter 7) to the specified temperature and keep it for 5 minutes. 9.4 Yuan
Entering the medium
Put the sample of the medium to be tested on the test bench, cut off the power supply of the heating furnace, and let the probe enter the medium to be tested according to 6.2.4. 9.5
When the probe is put into the measured liquid, all measuring and recording instruments will start immediately. When the oil base is 250℃ and the water base is 80℃, the recording can be stopped.
9.6 Cleaning
After the test, the probe should be removed from the medium according to 7.2. Cleaning is carried out as required. 9.7
Determination of characteristic temperature
Extend the straight line of the film boiling period of section A of the cooling process curve (see Figure 3) and the extended line of the straight line of section B of the bubble boiling period, and intersect them at point C. Draw parallel lines of T and T axes through point C to obtain characteristic temperature T. , characteristic temperature second T. . 10
Test report
After the test is completed, a report with the contents specified in Table 1 should be submitted, with the test curve attached. n℃
Cooling process curve
Medium name
Probe number
Average value
Characteristic temperature
JB/T 79511999
Quenching medium cooling performance test report (with test curve)Test number
Temperature second
Maximum cooling rate
Medium temperature
Maximum cooling rate
Temperature where degree
800-400C
Test date
Operator
Cooling time
800-300C
300-100'℃
People's Republic of China
Mechanical industry standard
Quenching medium cooling performance test method
JB/T 7951 1999
Published by the Machinery Standardization Research Institute of the Ministry of Machinery Industry Printed by the Machinery Standardization Research Institute of the Ministry of Machinery Industry (No. 2 Shouti South Road, Beijing
Postal Code 100044)Www.bzxZ.net
Format 880X1230
Print Sheet 1/2 Word Count 12000
First Edition in October 1999
First Printing in October 1999
Print Quantity 1-500
Price 500 Yuan
6661561
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