CC BY
6ТЕХНИЧЕСКИЕ НАУКИ
УДК 669.13
Jumaev А.А.
PhD student, Navoi branch of the Academy of Sciences of the Republic of Uzbekistan Uzbekistan. c. Navoi
SELECTION OF THE OPTIMAL METHOD OF THE PURIFYING THE WHITE WEAR RESISTANCE OF IRON MAKE 300H32N2M2TL
Abstract: The article presents the results of studies of the etching of white wear-resistant cast iron with the help of various reagents and presents the optimal technology for etching white wear-resistant cast iron.
Key words: microstructure, nitric acid, ethyl alcohol, hydrochloric acid, picric acid, ferric chloride, impact-abrasive wear, carbide phase, abrasive wear, high-chromium white cast iron, structure, chemical composition, high-alloy cast iron.
The main structural components of white wear-resistant cast irons are carbides and a metal base. The main characteristics of carbides, which have a decisive influence on the wear resistance, mechanical and technological properties of white wear-resistant cast irons - the type of crystallographic lattice, morphology, quantity, size, orientation with respect to the wear surface [1].
Every year the operating conditions of machines that work in abrasive and hydroabrasive media become tougher. In this regard, increased requirements for the materials from which the cast parts of such machines and mechanisms are made [2]. Currently, the foundry of the Navoi Machine-Building Plant produces more than 117 tons of cast high-chromium white cast iron per month [3].
Research methods and materials used. For research, specimens with dimensions of 25x20x20 mm were cast from white wear-resistant cast irons, grade 300X32H2M2TL, on an IChT-2.5 induction furnace (Manufactured in Russia).
The chemical composition of the samples is determined by the emission spectral method on a Spectro-Lab instrument - M (Made in Germany).
Microshift prepared on the grinding and polishing machine "NERIS" (pr-in Latvia). For grinding the samples, sanding pads with a grain size of 180 to 1500 microns were used. The polishing of the surface of the microsections is carried out with the help of Diamond WC brand paste.
To identify the microstructure, microsections after polishing are subjected to chemical etching or electrochemical etching. The recommended application GOST 5639-82 provides the compositions and methods of etching.
Table 1. Reagents for detecting the microstructure of cast iron 300X32H2M2TL
Number Reagent name Chemical composition Etching method
1 Alcohol solution of picric and plyacid and ferric chloride, (A1) Picric acid 5gr, hydrochloric acid 2 ml,, ferric chloride 2 gr, ethyl alcohol 100 ml, Chemical
2 Vilella reagent, (A2) Hydrochloric acid 5 ml, picric acid 1 gr, Ethyl alcohol 100 ml. Chemical
3 Alcoholic solution of nitric acid, (A3) Nitric acid 15 ml, hydrochloric acid 15 ml and glycerin 15 ml. Chemical
Recently, much attention has been paid to improving the quality of products. In accordance with the technical requirements along with the chemical composition, the macrostructure and microstructure of cast iron 300X32H2M2TL are subject to mandatory control. The microstructure of cast iron grade 300H32N2M2TL held in accordance with GOST 5639-82.
The results and discussion. The results of the analysis are shown in table 1.
Table 1. The chemical composition of the investigated alloys.
Mark Elements, %
C Si Mn P S Cr Ni Mo Ti Cu
300H32N2M2TL Sample No. 1 2,67 1,20 0,60 0,045 0,018 31,58 1,93 0,37 0,30 0,06
300H32N2M2TL Sample No. 1 2,80 1,13 0,57 0,043 0,016 30,59 2,00 0,45 0,25 0,07
300H32N2M2TL Sample No. 1 2,92 1,23 0,68 0,048 0,015 31,80 2,05 0,35 0,35 0,07
However, in practice, the recommended etchants have several drawbacks, relatively long etching times, the detection of sulphide inclusions and the quality of the microstructure itself is difficult.
Using the recommended etchants to identify the structure, we obtained the microstructure shown in photos 1-3.
Figure 1. Micrograph of sample No. 1. Figure 2. Micrograph of sample number 2. Etching with a reagent A1, at T = 40-45 C Etching with a reagent A2. at t = 75-80 C Etching time 4-6 seconds. Etching time 16-20 seconds.
Figure 3. Micrograph of sample No. 1. Etching with reagent A1, at T = 60-65 C Etching time 9-10 seconds.
In order to determine the optimal composition of the etchant and improve the quality of etching, the experimental work was carried out in the CPL of the NMZ PO NMZ, with a change in the composition and methods of etching of samples of white wear-resistant cast iron 300X32H2M2TL.
As a result of the experimental work, an etchant (A3) was obtained to identify the structure of wear-resistant cast iron 300X32H2M2TL of the following composition: Nitric acid 15 ml, Hydrochloric acid 15 ml and glycerin 15 ml. The use of this reagent in a heated state at a temperature of 65-70 ° C, the etching time is reduced from 9 to 10 seconds. This improves the quality of micrographs. A micrograph of sample No. 3 etched with reagent A3 is shown in Figure 3.
Conclusion
For more qualitative and accelerated detection of the structure of samples from wear-resistant cast iron grade 300X32H2M2TL, it is advisable to use reagent A3 in a heated state at a temperature of 65 - 70 ° C.
References
1. A. A. Jumaev [2018] Comparative study of the structure of castings from white wear resistant cast iron // International Journal of Advanced Research in Science, Engineering and Technology. 12. 7575-7577.
