GB/T 4336-2016Carbon and low-alloy steel—Determination of multi-element contents—Spark discharge atomic emission spectrometric method (routine method) (English PDF)

4.1 Excitation light source

The excitation light source shall be a stable spark excitation light source.

4.2 Spark room

The spark room is specially designed for use with argon, and the spark room is mounted directly on the spectrometer, with an argon flush spark bracket to place the flat sample and the rod-shaped counter electrode. The argon gas path in the spark chamber shall be able to replace the air in the optical path between the analysis gap and the condenser and provide an argon atmosphere for the analysis gap.

4.5 Spectrometer

Generally, for the spectrometer, the reciprocal of the first-grade spectral line dispersion of shall be less than 0.6 nm/mm, the focal length is 0.35 m ~ 1.0 m, the wavelength range is 165.0 nm ~ 410.0 nm, the vacuum of the spectrometer shall work below 3 Pa, or being filled with high-purity inert gas (the gas does not the absorb spectral line with a wavelength less than 200 nm, and the purity is not less than 99.999 %).

4.6 Photometric system

The photometric system shall include a photoelectric conversion detector for receiving a signal, an integrating capacitor capable of storing each of the output electrical signals, a measuring unit for directly or indirectly recording the voltage or frequency on the integrator, and a necessary switching circuit device provided for the desired timing.

5.1 Sampling

The sampling and sample preparation is carried out according to the specifications of GB/T 20066. When taking samples, it shall ensure that the analytical sample is taken evenly, without shrinkages and cracks. When taking casting samples, the molten steel shall be injected into the specified mold; when adopting aluminum deoxidation, the deoxidizer content shall not exceed 0.35 %; when taking samples form steel products, it shall select representative parts.

5.2 Sample preparation

Samples taken from the mold are usually cut in the height of 1/3 of the lower end. For uncut samples, the surface shall be removed by 1 mm in thickness. The cutting equipment used shall be the cutting machine with resin cutting blades, metal cutting machines, etc.

6.1 Standard samples

The standard sample is used to plot the calibration curve, its chemical properties and organizational structure shall be similar to those of the analytical samples, and shall cover the content range of the analytical elements and maintain the appropriate gradient; the content of the analytical elements shall be determined with accurate and reliable methods.

6.2 Standardization samples

The change in the state of the instrument may result in the deviation of the measurement results, to directly use the original calibration curve to obtain accurate results, 1 ~ 2 samples are used to standardize the instrument, these samples are called standardization samples. The sample shall be very uniform and have an appropriate content; the sample can be selected from standard samples or specially smelted. When using two-point standardization, the content is the content on each element calibration curve, respectively, near the upper and lower limits.

6.3 Control samples

The control sample is the uniform sample with similar metallurgical process, organizational structure and chemical composition to those of the analytical sample, being used for correcting the measurement results of the analytical sample or for type standardization correction.

7.1 Storage of instruments

The spectrometer, as recommended by the equipment manufacturer, shall be placed in shock-proof and clean laboratories, usually the indoor temperature maintains at 15 °C ~ 30 °C and the relative humidity shall be less than 80 %. In the same standardization cycle, the indoor temperature change does not exceed 5 °C.

7.2 Power supply

To ensure the stability of the instrument, the power supply voltage change shall be less than ± 10 %, the frequency change shall be less than ± 2 % and the AC power supply shall be the sine wave. According to the use requirements of the instrument, a dedicated ground line shall be equipped.

7.3 Excitation light source

In order to make the electrical part of the excitation light source work stably, before starting work, it shall be given the appropriate power time.

Use a voltage regulator or a voltage regulator device to adjust the power supply voltage to the desired value of the instrument.

7.6 Photometric system

After being shut down and then restarted, generally adequate power time shall be endured to make the photometric system work stably.

Select the appropriate pre-combustion time of the analytical element by making a pre-combustion curve. The integration time is determined by the test basing on the analytical accuracy.

8.1 Calibration curve method

Under the selected working conditions, activate a series of standard samples; in principle, use the standard samples of more than 5 levels, and activate at least 3 times per sample; plot a curve indicating the relation between the luminous intensity (or intensity ratio) and the content (or content ratio) of the analytical element as a calibration curve. Use this calibration curve to measure the element content in the sample.

8.2 Original calibration curve method

The original calibration curve method is to use the calibration curve method to plot the calibration curve. When temperature, humidity, vibration and other factors lead to displacement of the spectral line of the spectral instrument, or changes in luminous intensity leads to the calibration curve drifts, use the standardization sample to correct the drift of the calibration curve, to resume the strength of the corrected element to the strength when the calibration curve is initially established.

8.3 Control sample method

Due to the difference in the smelting process and the organizational structure between the analytical sample and the standard sample used to plot the calibration curve, the calibration curve is often changed.

9.1 Analysis conditions

The recommended analysis conditions of this Standard are as shown in Table 2, and the analytical lines and internal marking lines are listed in Table 3.

9.2 Analysis procedures

9.2.1 Prepare the instrument in accordance with the requirements in 7.2 to 7.6.

9.2.2 Before the analysis work, activate a piece of sample 2 ~ 5 times, to confirm that the instrument is in the best working condition.

9.2.3 Standardization of the calibration curve. under the selected working condition, activate the standardization sample, and each sample is activated at least 3 times to correct the calibration curve. When there are significant changes in the instrument or the original calibration curve exceeds the calibration range due to the drift, the calibration curve needs to be replotted.

9.2.6 Activate the analytical sample according to the working conditions selected by 9.2.2, each sample is activated at least 2 times (the sample is activated once to obtain an independent measurement result;