The test piece material is 20 steel, length 200mm, width 300mm, and surface roughness is not more than 25μm. When the ambient temperature is -20℃ and the surface temperature of the test piece is -15℃, the winter glass water is applied to the surface of the test piece. It can be seen that the glass water can quickly wet the surface of the test piece in winter, as shown in Figure 1. , The formed film is continuous and covers the entire surface.

Figure 1 The surface state of the specimen during the wettability test

Choose a piece of pH test paper, immerse it in glass water for winter, take it out after half a second, and compare it with the standard color palette to get a pH of 9, and the result is qualified.

Add magnetic powder with a mass of (3±0.1) g into glass water for winter use, fully stir, at a stirring speed of 3000r/min, hold for 1 min, and pour it into a transparent measuring cup for visual observation. Visual observation revealed that the magnetic powder was uniformly distributed in the glass water used in winter without agglomeration, and the dispersibility test result was qualified.

The steel rod method was used to test the rust resistance of glass water in winter. Use a steel rod with a length of 100mm and a diameter of 20mm, and use a polisher to assemble a wire brush to perform surface treatment to make the surface roughness not greater than 25μm. The half length of the steel rod was immersed in winter glass water for 96 hours. After taking it out, it was placed in a room temperature environment. After 24 hours, the surface of the steel rod was observed. No obvious corrosion was found, and the corrosion resistance test was qualified.

Since the magnetic powder particles cannot be gathered and covered on the foam, the magnetic suspension is required to automatically eliminate the foam in a short time to ensure the validity of the test results. As shown in Figure 2, the test uses a 100mL graduated cylinder, filled with 70mL of winter glass water, covered the plug, and shaken up and down for 1min, the distance between up and down is about 1/3m, the shaking frequency is 100~120 times/min, and then it is still at room temperature. After leaving it for 10 minutes, it was observed that there was almost no residual foam on the liquid surface, and the defoaming test was qualified.

Put 50mL of winter glass water in a 100mL graduated cylinder, place it in a low temperature box at (-25±3)℃ and let it stand for 24 hours. After taking it out, let it stand at room temperature for 1 hour, as shown in Figure 3. It was observed that there was no delamination phase change phenomenon in the measuring cylinder, and the stability test result was qualified.

According to the industry standard NB/T 47013.4-2015, the mass concentration of non-fluorescent magnetic powder magnetic suspension is 10~25g/L.

The standard recommended mass concentration range is divided into 4 equal sections, and 4 different mass concentrations of 10, 15, 20, 25g/L are selected for preparation, and the volume fractions of the 4 magnetic suspensions are compared, and the results are respectively 0.9 %, 1.6%, 2.0% and 2.6%, the pear-shaped bottle precipitation test site is shown in Figure 4.

Because the density and viscosity of glass water in winter are different from those of other water carriers, the sedimentation rate is different. When the mass concentration is 10g/L and 25g/L, the volume fraction (solid content) cannot meet the standard requirements. Therefore, it is preliminarily confirmed that the mass concentration of the non-fluorescent magnetic powder aqueous magnetic suspension prepared with glass water as a carrier in winter is 15-20g/L.

Using the 4 groups of hydromagnetic suspensions with different mass concentrations, respectively, under the same testing conditions, the simulated crack defects of the magnetic particle inspection test block were detected, and the obtained crack marks are shown in Figure 5.

Through the sensitivity comparison test, it can be found that the appropriate mass concentration of the non-fluorescent magnetic powder magnetic suspension prepared with glass water in winter is 15-20g/L.

When the mass concentration of the magnetic suspension is 15-20g/L, the background display and the crack magnetic mark display are in strong contrast, the magnetic powder quickly accumulates on the crack surface, the outline of the crack magnetic mark is clear, and the details of the crack morphology are clearly displayed.

When the mass concentration of the magnetic suspension is less than 15g/L, the color of the crack marks is lighter, and the small cracks are not displayed, resulting in missed defects.

When the mass concentration of the magnetic suspension is greater than 20g/L, the background display color is too dark, causing many irrelevant displays and false displays, making it difficult to identify crack defects. It can be seen that the mass concentration is too low or too high, which is not conducive to magnetic particle detection.

In December 2020, a chemical plant in Xinjiang planned to conduct regular inspections on more than 10 pipelines, requiring magnetic particle inspection of pipeline welds. At this time, the outdoor temperature was below -25°C. Using winter glass water as the carrier to prepare a water magnetic suspension, the welds were tested, and 9 defects were successfully found, and the application effect was good. The appearance of some defects is shown in Figure 6.

Figure 6 Anatomy results of defects detected in a certain pipeline weld