Abstract: According to the industrial and mining conditions of the high temperature section of the continuous casting roll, compared with the imported welding wire, the flux-cored wire 414N for continuous casting roll surfacing was developed, and the performance of the developed flux-cored wire was tested. By comparison, it can be seen that the developed 414N Flux cored wire can completely replace imported wire.
0 Preface
With the needs of economic construction, in the past ten years, China has successively built and put into operation a large number of modern continuous casting and rolling mills. Their performance and service life are bound to have a major impact on the national policy and social and economic benefits of energy conservation and materials. The continuous casting surfacing technology has been developed in China for more than ten years. According to the general steel mill, the entire continuous casting roll consists of three parts: the supporting guide roller, the fan segment and the horizontal segment. The supporting guide roller is composed of a close-packed roller, and the slab is transformed into a circular arc by multi-point bending. After the roll blank is pulled out from the crystallizer, although a certain section is formed, the center of the roll is still in a liquid state, the thickness of the shell is generally 12-20 mm, and the surface temperature of the slab is as high as 1200 °C. Due to the action of high temperature and cooling water, the roll surface is prone to high temperature oxidation and corrosion, and the diameter of the foot roll and the support guide roll is small, and the bending deformation is easily caused by the difference in rigidity. Therefore, the continuous casting rolls in this section should be made of Cr13 type martensitic stainless steel with high Ni and Mo contents which are resistant to corrosion, high temperature oxidation and considerable heat. At present, the more advanced surfacing materials at home and abroad are ultra-low carbon nitrogen alloyed 0Cr13Ni4MoN (414N) flux-cored wire, which can significantly improve the high temperature oxidation resistance and corrosion resistance of the surfacing layer by nitrogen-based carbon. Significant improvements can be made. A series of tests were carried out by comparing the British welding alloy company CHROMECORE 414N-O flux-cored welding wire. We have developed a 414N flux-cored wire suitable for supporting the guide rolls, and have achieved good application in production.
1 N role in deposited metal
The developed 414N flux-cored wire can be made by submerged arc and open arc self-protection. Table 1 lists the chemical composition of 414N deposited metal.
Table 1 Chemical composition of 414N flux-cored wire deposited metal (%)
Table1 Chemical compositions of 414N flux-cored wire deposited matal
Surfacing usability C Cr Ni Mo Mn Si S P N
SA 0.031 13.54 4.34 0.89 1.48 0.23 0.0052 0.021 0.06
OA 0.035 12.98 3.80 0.87 0.75 0.84 0.012 0.018 0.08
CHROMECORE414N-O 0.06 12.59 4.01 0.80 0.79 0.55 0.021 0.022 0.09
It can be seen from Table 1 that compared with the typical Cr13 alloy, the content of impurities such as S and P of the flux-cored wire deposited metal is further reduced, on the one hand, the thermal crack resistance is improved, and on the other hand, the toughness is improved. The grain is refined to improve the cold and heat fatigue resistance. The decrease of C content further improves the thermal crack resistance of the material, but the decrease of C content will inevitably lead to the weakening of the material strengthening effect, and the addition of N solves this problem well. N mainly exists in the deposited metal. The following effects:
1) In the Cr13 series alloy, the γ phase region is enlarged, which is a strong element for forming and stabilizing austenite, inhibits the formation of ferrite, and improves the resistance to cold and heat fatigue, and its effect is about 20 times that of nickel. [1], under certain limits, a part of nickel can be used in steel; 2) appropriate nitrogen is added to form a stable nitride with chromium, vanadium, titanium, etc. in the alloy, which promotes the effective action of microalloying elements. To improve the high temperature yield strength of the material, the nitride is highly dispersed in the weld overlay layer, which greatly increases the hardness, strength, especially fatigue strength, wear resistance and high temperature corrosion resistance of the weld overlay layer, while inhibiting the material The high temperature creeps and the plasticity does not decrease.
2 performance of the surfacing layer
The performance of the developed 414N flux-cored wire was tested. A total of five layers were deposited. After welding, it was kept in a furnace at 585 °C + 10 °C for 10 hours, and then cooled to room temperature with the furnace. According to GB2649-82 and GB2650-89, 15 samples were processed into normal temperature tensile impact and high temperature tensile test pieces. The experimental instrument was INSTRON-5500R electronic universal testing machine. The experimental data is shown in Table 2, which is equivalent to the imported welding wire.
Table 2 Mechanical properties of 414N flux-cored wire surfacing layer
Table2 Mechanical properties of 414N flux-cored wire depositied metal
No. Temperature/°C σb/Mpa σ0.2/MPa δ5/% Ψ/% AKV/J Hardness/HRc
1 24 874.9 812.6 13.94 48.16
2 24 903.7 769.5 15.00 43.24
3 24 914.1 799.6 14.79 43.75
4 500 709.5 645.6 16.10 52.39
5 500 667.3 603.3 15.63 49.23
6 500 643.4 578.4 17.72 49.23
7 650 269.2 222.93 44.63 59.36
8 650 269.2 218.95 49.51 68.35
9 650 297.6 249.8 44.87 76.23
10 750 176.8 131.5 37.97 52.39
11 750 178.1 134.1 37.25 45.60
12 750 154.2 122.5 30.70 39.93
13 24 21.5 31
14 24 23.0 30
15 24 22.0 31
3 metallurgical structure of surfacing metal
The microstructure of the surfacing metal of the 414N flux-cored wire is very uniform and fine low-carbon martensite, as shown in Figure 1. It is basically consistent with the microstructure of the imported wire surfacing layer (Fig. 2).
4 Conclusion
After experiment, the 414N flux-cored wire suitable for the high temperature section of continuous casting rolls was developed and its performance was tested. It can be seen from the test data that the developed 414N flux-cored wire is consistent with the imported wire and can completely replace the imported wire. Welding wire.
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