This national standard specifies the method for determining the efficiency, metal recovery rate and deposition coefficient of coated electrodes for carbon steel and low alloy high strength steel with a diameter of 3.15 to 6.3 mm. The measurement accuracy specified in this national standard is sufficient in practical applications, because the properties of each batch of electrodes will always fluctuate to a certain extent. GB/T 3731-1983 Determination of efficiency, metal recovery rate and deposition coefficient of coated electrodes GB/T3731-1983 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Determination of the efficiency,metal recovery and deposition coefficient of coated electrodes
Covered electrodes - Determination of the efficiency,metal recovery and deposition coefficient1Content and scope of application
UDC 621.791
GB 3731-88
-ISO 2401 72 (E)
This national standard specifies the method for determining the efficiency,metal recovery and deposition coefficient of coated electrodes for carbon steel and low alloy high strength steel with a diameter of 3.15 to 6.3 mm.
The measurement accuracy specified in this national standard is sufficient in practical applications, because the properties of each batch of electrodes always fluctuate to a certain extent. Clause 4 of this national standard specifies the measurement of several different parameters. However, according to the specific items required to be measured, only the parameters required for calculating these items need to be measured.
2 Terms and meanings:
2.1 Nominal electrode efficiency
RN: The ratio of the weight of weld metal deposited by the electrode under the standard specification to the weight of the weld core melted according to the nominal diameter of the weld core is called the nominal electrode efficiency of the electrode.
2.2 Actual electrode efficiency
RE: The ratio of the weight of weld metal deposited by the electrode under the standard specification to the actual weight of the weld core melted is called the actual electrode efficiency of the electrode.
2.3 Electrode metal recovery rate
RG: The ratio of the weight of weld metal deposited by the electrode under the standard specification to the total weight of the tested electrode is called the metal recovery rate of the electrode.
2.4 Deposition efficiency
RD: The ratio of the weight of weld metal deposited by the electrode under the standard specification to the total weight of the weld core melted is called the deposition rate of the electrode. 2.5 Deposition coefficient
D: The weight of weld metal deposited per ampere minute by the electrode under standard specifications is the deposition coefficient of the electrode. When recording the test results, a supplementary symbol must be added after the abbreviations RN, RG, RE, Rp, D to indicate the type of current used to determine this value.
For example: DC positive polarity R
DC reverse polarity
8 test plates
3.1 Quantity
One test plate must be welded for each electrode diameter. 3.2 Specifications
The test plate shall be carbon steel plate (C<0.25%) with the following approximate dimensions: Issued by the National Bureau of Standards on June 21, 1983
Implemented from August to January, 1984
Width 75mm
Length 300mm
GB 3731-83
Thickness 12mm
In most cases, one test plate is long enough. If not, a second test plate of 150mm (or 300mm if necessary) can be placed end to end with the first test plate (see figure). 300
150 or 300
When two test plates are used, such a test plate may be divided into two pieces for the convenience of weighing after welding. The surface of the test plate shall be cleaned, such as by grinding or other suitable methods, to remove scale, rust, paint and oil stains. After cleaning and before welding, the test plate shall be weighed with an accuracy of ± 1 g.
4 Procedure
4.1 When testing a certain diameter of welding rod, three or five welding rods* shall be welded in separate passes on a test plate. Before welding, these welding rods shall be weighed with an accuracy of ± 1 g. The total weight of the three or five welding rods is called mE. In addition, three or five welding rods of the same batch shall be carefully removed from the coating. The total weight of these three or five welding cores is called mw. The total weight of these three or five welding cores can also be calculated by measuring the diameter and total length Lw of the welding core to be tested and taking the specific gravity of steel as 7.85 g/cm3. 4.2 The welding current I shall be about 90% of the maximum flat welding current indicated on the packaging by the welding rod manufacturer. The current value shall be measured with a damped ammeter of secondary accuracy of the electric measuring instrument. When using alternating current, the root mean square value of the current shall be measured. ** The welding machine specifications shall not be changed during the entire test process. To calculate the melting factor, the average value I of the root mean square value of the current measured during the test shall be used.
4.3 The arc length and welding procedure most commonly used for the electrode being tested shall be used. There shall be no obvious welding defects on the deposited weld. 4.4 Electrodes suitable for use only with direct current and electrodes for which the electrode manufacturer specifies that direct current should be used in preference, shall be tested with direct current, with the polarity determined by the manufacturer's recommendation.
4.5 For electrodes suitable for use with both alternating and direct current, the test shall be made with alternating current. In this case, the welding transformer shall comply with the following provisions:
The no-load voltage of the welding transformer shall not be more than 10 V higher than the minimum no-load voltage indicated in the electrode instructions, a.
b. For the set of specifications used for welding, the current waveform factor provided by the transformer in the short-circuit state shall be within the following range: 1.11F1.2.
Note: For each value of alternating current, the waveform factor F is the ratio of its root mean square value to its average value. The range given above corresponds to the range observed when the welding transformer is short-circuited. The waveform factor F is determined either by a recording instrument or by two ammeters in series, one of which has a scale for the rms value of the current and is not very sensitive to changes in the waveform (e.g., magnet type or thermal type) and the other has a scale for the average value of the current (e.g., magnetoelectric type with rectifier). 4.6 Each electrode should be welded in the flat welding position and the welding should be continuous without interruption until the remaining welding tip is 50 mm long (it is recommended to mark the required electrode tip length on the electrode before welding). 4.7 The arc burning time of each electrode shall be measured to the nearest ± 0.2 s and the total burning time of three or five electrodes shall be calculated in minutes. * If the weight of the deposited metal of one electrode is greater than 100 g, it is allowed to use only three electrodes. ** The rms value of the current is the value measured by the magnet type AC ammeter. 89
GB 3731-83
4.8 After welding a pass, the test plate can be cooled in water, but before re-starting welding, the water on the test plate must be completely dried. Before welding the next few passes, carefully clean off the slag and spatter adhering to the test plate. The interlayer temperature cannot exceed 100℃. 4.9 After each weld, the electrode head must be retained to prevent the loss of unmelted coating on it. After cooling, measure three or five electrode heads as follows:
Weigh with an accuracy of ±1g and determine the total weight ms Weigh after carefully removing all remaining coating and determine the total weight mws 1b.
Measure the length of each welding core head (accuracy ±1mm) and calculate the total length of the welding core head Ls. c.
4.10 After all welding is completed, the test plate should be cooled to room temperature. After removing all slag and flying objects adhering to the test plate (if water cooling is used, wait until all water has dried up), weigh the test plate with an accuracy of ±1 g. The difference between this weight and the original weight of the test plate determined in 4.1 is the total weight of the molten metal mD. 4.11 The total length of the three electrode heads shall be between 144 and 156 mm, and the total length of the five electrode heads shall be between 240 and 260 mm. If the total length of the electrode heads is outside this range, the test shall be repeated. 5 Calculation of electrode efficiency and metal recovery rate
5.1 The total nominal weight of the three or five welding cores, mcN, can be calculated based on the nominal diameter and nominal length of the three or five welding cores minus the measured length Ls of their welding core heads (accuracy ±1 m). Take the specific gravity of steel as 7.85 g/cm2. 5.2 The actual total weight of the melted length of three or five electrode cores mce is calculated by the following formula: mce = mw
where mw-
the total weight of the core, g,
the total measured length of the core head, mm
Lw-the total measured length of the core, mm.
Or it can be calculated by the following formula:
mCE=mw\
where mws
the total weight of the core head.
5. The following ratio gives the nominal electrode efficiency
where mp
the weight of the molten weld metal,
the nominal weight of the core melted.
5.4 The following ratio gives the actual electrode efficiency
5.5 The following ratio gives the electrode metal recovery RG% =
Where: me
Total weight of the electrode tested.
5.6 The following ratio gives the melting rate
Where: ms
-Total weight of electrode head.
× 100
me -ms
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GB3731-83
The coefficient values ​​and recovery rates calculated according to 5.3 to 5.6 must be expressed as integers, without decimals (e.g. 93.4% strain is 93%, 93.5% strain is 94%).
6 Melting coefficient calculation
The deposition coefficient (g/A·min) is given by the following ratio: D
Where, mp is the weight of deposited metal, g,
I, — welding current, A,
t — arc burning time, min.
indicates that the above calculation should retain two digits after the decimal point, such as 0.164g/A·min strain is 0.16g/A·min, 0.165g/A·min strain is 0.17g/A·min.
Additional remarks:
This standard is proposed by the Ministry of Machinery Industry of the People's Republic of China. This standard is drafted by Harbin Welding Research Institute. The main drafter of this standard is Tu Naiming.
Harbin Welding Research Institute is entrusted with the interpretation of this standard.
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