This standard specifies the method, standard sample, instrument and calibration for measuring ferrite number. JB/T 7853-1995 Measurement of ferrite number in chromium-nickel austenitic stainless steel weld metal JB/T7853-1995 Standard download decompression password: www.bzxz.net

Mechanical Industry Standard of the People's Republic of ChinabZxz.net
Measurement of Ferrite Number in Chromium-Nickel Austenitic Stainless Steel Weld Metal
JB/T 7853--95
This standard adopts the international standard ISO 8249 "Measurement of Ferrite Number in Austenitic Weld Metal of Cr-Ni Steel Coated Electrode Fume Number" (1985 Edition) in a non-equivalent manner.
Subject Content and Scope of Application
This standard specifies the method, standard sample, instrument and calibration for measuring ferrite number. This standard is applicable to the measurement of ferrite number in weld metal and cladding metal in the as-welded state. It is also applicable to the case where ferrite undergoes a complete or partial non-avoidable transformation after post-weld heat treatment. The method specified in this standard is not applicable to the measurement of ferrite number in austenitic stainless steel castings and forgings. 2 Terminology
2.1 Ferrite
High-temperature ferrite formed directly by solidification and crystallization of liquid metal and retained at room temperature. 2.2 Ferrite Number (FN) An artificially selected standardized value used to represent the ferrite content of austenitic stainless steel weld metal. 2.3 Ferrite Number Grade Standard
Internationally used non-magnetic coating thickness standard, each primary standard gives the FN value of a certain equivalent magnetic weld metal, and is designated by the State Technical Supervision Bureau as a primary standard sample for calibrating primary standard instruments and secondary standards. 2.4 Weld Metal Secondary Standard
A small weld deposited metal sample made by cladding according to standard procedures, each group of at least eight samples, each with different ferrite content, is calibrated using a Magnimeter and a grade standard sample to determine the FN value of each sample. The ferrite number ranges from 2 to 27 FN, and is designated by the State Technical Supervision Bureau as a secondary standard sample for calibrating other ferrite measuring instruments. 3 Measurement of ferrite number
—General principles
The ferrite content in austenitic stainless steel weld metal is expressed by the measured ferrite number (FN). The ferrite number should be tested using a special ferrite measuring instrument based on the principle of magnetic attraction or magnetic permeability. The instrument for measuring the ferrite number should comply with the provisions of Appendix A (Supplement) of this standard. When measuring the ferrite number under any circumstances, the probe or magnetic needle of the ferrite measuring instrument should be kept perpendicular to the surface to be measured, and ensure that the contactor is in point contact with the surface to be measured.
If it is found that the ferrite distribution is very uneven during the measurement of the ferrite number, the average value, the highest value and the lowest value and their locations should be given in the measurement results.
3.2 Measurement of ferrite content in deposited metal by manual arc welding 3.2.1 Preparation of test specimens
Approved by the Ministry of Machinery Industry of the People's Republic of China on December 1, 1995 338
Implemented on July 1, 1996
JB/T7853--95
3.2.1.1 Use the electrode (or welding material) to be tested to build up the test specimen on the substrate in the shape and size shown in Figure 1. When building up the test specimen, two copper plates can be placed in parallel on the substrate and built up according to the parameters specified in Table 1. 210
Full plate: length × grams × height Tomm × 25
Measure within this range
Ferrite number (FN)
Figure 1 Schematic diagram of weld deposited metal specimen for measuring ferrite number Table 1 Welding parameters and surfacing dimensions
Electrode diameter
Welding current
90~100
120140
165~180
240~~260
Width W, mm
Length L, mm
3.2.1.2 When the substrate is Cr-Ni austenitic stainless steel, the minimum height H of the surfacing layer is 12.5mm. When the substrate is low carbon steel, the minimum height H of the surfacing layer is 18mm. For electrode diameter ≥4mm, each surfacing layer should consist of a single weld pass. For welding rods with a diameter less than 4mm, the width of the weld should not be greater than three times the core diameter, and each weld layer should consist of two or more welds. No contact with the plate is allowed. The arc length should be the same as the actual arc length used.
3.2.1.3 The arc should be started and extinguished at the beginning and end of the weld layer. Change the welding direction after each weld. 3.2.1.4 Use water cooling 20s after each weld, and the interlayer temperature between welds should be ≤100℃. Each weld of the last weld layer should be air cooled to below 425℃ before water cooling.
3.2.1.5 Each weld must be cleaned before the next weld can be welded. 3.2.1.6 After welding, use a 35mm coarse-tooth file to file the weld surface flat. The file axis should be perpendicular to the length of the weld. The flat surface should have enough ferrite measurement points. When the chain cutter applies pressure, it should be pushed forward steadily so that the filed surface extends along the length of the weld bead. The principle is to file a sufficient length and width. The weld bead must not be filed crosswise.
The filed surface should be smooth and free of weld ripples. The surface should be continuous along the length of the weld bead and the width should not be less than 5mm. 3.2.2 Measurement of ferrite number
3.2.2.1 On the chain-leveled cladding layer surface, use a ferrite measuring instrument to measure a total of 6 to 10 ferrite numbers along the length of the weld bead. The measuring points are 339
JB/T 7853—95
with a spacing of 5 to 10mm. Then take the average of the 6 to 10 ferrite numbers measured as the measurement result of the sample. 3.2.2.2 If the reading of the ferrite measuring instrument is not FN but a percentage (%), it can be converted into ferrite number according to Figure 2. 14
Ferrite number (FN)
Note: This figure is only applicable to ferrite measuring instruments designated by the State Administration of Technical Supervision. 121314
Figure 2 Conversion curve between ferrite percentage and ferrite number 3.3 Preparation and measurement of weld metal samples for other welding processes Preparation of weld metal samples and measurement of ferrite number for other welding processes (such as TIG welding, MIG welding and submerged chlorine welding) can refer to the relevant provisions of the above-mentioned manual arc welding. The width and thickness of the male welding layer should be appropriately increased according to the increase in the specification. The saw plates on both sides can be placed according to the process characteristics.
3.4 ​​Measurement of ferrite number of welding products
3.4.1 The measurement of ferrite number in the weld metal and cladding metal of welding products can be sampled or directly measured from the welding test piece provided for inspection of the product, or it can be directly measured on the weld or cladding layer of the product. The measuring instrument shall comply with the provisions of Chapter 4, and the measuring procedure shall comply with the provisions of 3.2.
3.4.2 When measuring the ferrite number in the weld metal and overlay metal of welded products, the measuring position shall be specified in the product technical conditions or agreed upon by the parties. Generally, the measured surface shall be filed flat. If the surface processing of the weld can cause changes in corrosion resistance or other specific properties and affect the product quality, whether the surface of the weld (including overlay metal) of such products is filed flat when measuring the ferrite number shall be agreed upon by the parties. At the selected measuring position, an FN value shall be measured every 5 to 10 mm, and a total of more than 6 FN values ​​shall be measured, and the average value shall be taken as the ferrite number of the measuring position.
3.4.3 For long welds and large-area overlays, the ferrite number shall be sampled at a certain ratio, and the ratio and position of the sampled measurement shall be agreed upon by the parties. The sampled measurement position shall be representative. The measuring points shall be evenly distributed within the range of the selected measurement position. When the welding operator is replaced, the welding parameters are changed, the plate thickness is changed or the cooling conditions are changed, the ferrite number should be re-measured in time. 3.4.4 When measuring the ferrite number of the transition layer according to the technical requirements, the overlap area of ​​the two outermost welds should be used as the measurement location. 340
JB/T 7853-95
3.4.5 When measuring the ferrite number of the stainless layer weld of the stainless composite plate and the thinner stainless steel cladding layer, if the thickness of the weld and cladding layer is less than 3mm, the influence of the ferromagnetic substrate on the measurement result shall not exceed 5% of the measured value. 4 Calibration of ferrite measuring instrument
4.1 Regular calibration
The ferrite measuring instrument should be calibrated regularly (usually not more than one year) by the designated unit of the State Technical Supervision Bureau on the basis of normal maintenance using international standard samples or weld metal secondary standard samples. Such calibration records should be archived. The results of regular calibration are qualified within the allowable error range specified in Table 2, and the calibration certificate will be issued by the responsible unit. When the instrument fails to meet the requirements specified in Table 2, it is considered unqualified. The instrument should be stopped from use and returned to the manufacturer for processing. Table 2 Maximum allowable error between the calibration point and the calibration curve when calibrating with the secondary standard sample of weld metal Ferrite number range (FN)
>10~15
4.2 Daily calibration
Maximum allowable error (FN)
Before measuring, the ferrite measuring instrument shall be calibrated by the user using the calibration block attached to the instrument. The error shall meet the requirements of Table 3 before it can be used. Otherwise, the instrument shall be calibrated and verified by the designated unit of the State Administration of Technical Supervision using the primary standard sample or the secondary standard sample of weld metal, and the calibration certificate shall be obtained before it can be used. If the calibration fails, it shall be stopped and returned to the manufacturer for repair. Table 3 Maximum allowable error of the calibration block
Ferrite number range (FN)
>10～~15
5Others
Maximum allowable error (FN)
5.1 Any other ferrite measuring instrument that can be calibrated with one of the primary or secondary standards or can prove that there is a correspondence of 11±0.05 between them and the standard instrument is a qualified and usable ferrite measuring instrument; otherwise, it is an unqualified and unusable ferrite measuring instrument. In case of any dispute over the measurement results of the ferrite measuring instrument, the measurement results of the standard instrument designated by the State Administration of Technical Supervision shall prevail.
5.2 Influence of nearby ferromagnetic materials
During measurement, it shall be ensured that the strong ferromagnetic materials near the instrument are excluded from the influence on the measurement results. For example, low carbon steel and cast iron. For instruments such as the magnimeter that use standard magnets, the ferromagnetic materials must be 18mm away from the magnet. For other probe-type instruments, the minimum distance that should be controlled shall be determined by experiment.
5.3 The calibration block attached to the ferrite measuring instrument is provided by the instrument manufacturer to the user for routine calibration. The calibration block must be calibrated and qualified by the technical coordination unit designated by the State Administration of Technical Supervision using the secondary standard sample (or the primary standard instrument) and obtain a certificate of qualification. The number of calibration blocks should be no less than one for each range (each sub-level of Table 3 and Table 4). 341
JB/T7853—95
Appendix A
Regulations on instruments, standards and calibration
(Supplement)
A1 Magnimeter, NTR-I, TCY-I and 1.054 ferrite measuring instruments are recommended as ferrite measuring instruments that meet the requirements of this standard. A2 The internationally recognized primary ferrite number standards, secondary weld metal standards and primary standard instruments (Magnimeter) are uniformly stored in the National Welding Materials Testing Center (Harbin Welding Research Institute, Ministry of Machinery Industry), which undertakes: a. Standardization (measurement), transfer and comparison of domestic weld metal ferrite number: regular calibration and verification of ferrite measuring instruments: b.
Arbitration test and decision of measurement results.
Any department or unit that purchases or owns the primary standard sample of ferrite number, the secondary standard sample of weld metal and the primary standard instrument shall be approved by the State Technical Supervision Bureau and issued a certificate, and shall be filed with the National Welding Material Testing Center before it becomes effective. A3 Magni meter can only be calibrated with the primary standard sample, the secondary standard sample must be calibrated with the primary standard sample and Magni meter, and other ferrite measuring instruments must be calibrated with the secondary standard sample of weld metal; the calibration block attached to the ferrite measuring instrument must be calibrated with the secondary standard sample of weld metal and the standard instrument designated by the State Technical Supervision Bureau.
A4 From the date of implementation of this standard, all ferrite measuring instruments in use must be calibrated and verified by the technical coordination unit designated by the State Technical Supervision Bureau with the primary standard sample or the secondary standard sample of weld metal, and can only be used after obtaining the calibration certificate. A5 About the application of Schefler organization chart and Delong organization chart. These two organization charts are relatively effective for semi-quantitatively predicting the structure of weld metal. However, it is impossible to accurately measure the quantity of each organization with them. Because, a large number of tests and investigations have shown that the influence of comprehensive factors such as welding process factors, chemical analysis errors of weld components and errors in the organization diagram itself will cause a large deviation between the calculated value and the measured value. Therefore, this standard recommends using ferrite measured values ​​instead of ferrite calculated values. Additional Notes:
This standard was proposed and coordinated by the National Welding Standardization Technical Committee. This standard was drafted by the Harbin Welding Research Institute of the Ministry of Machinery Industry. 342
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