SU1118694A1 - Method of working cold-deformed steel blanks - Google Patents

Abstract

COLD PROCESSING METHOD STEEL BLANKS comprising nonoxidizing recrystallization annealing at 600-650 C in a molten salt eutectic containing sodium chloride and sodium metasilicate, and washing in hot water, about l m and q and u, and w and C in that, with In order to simplify the process, annealing is performed in the melt, additionally containing potassium chloride and sodium carbonate, in the following ratio of components, wt.%: Potassium chloride 30-41 Potassium chloride 20-30 sodium (L Metasnlikat0, 3-1.2 sodium Carbonate 32 , 8-44.7 sodium 00 od with 4

Description

The invention relates to the heat treatment of steels, in particular to the recrystallization annealing of steel billets subjected to cold deformation. In machine-building plants, where steel semi-finished products are subjected to multiple stretching, recrystallization annealing is carried out with an oxidizing atmosphere at 600-650 ° C p However, the steel surface is covered with a layer of strong scale, which in hot concentrated solutions of acids leads to hydrogenation of the workpieces. , contamination of the workshop with harmful vapors4 In addition, this method is characterized by low productivity and cumbersome equipment. The known method of recrystallization annealing of cold-formed steel billet in a protective atmosphere of C23 .. However, the method requires the organization of a gas host, sophisticated equipment, is very long. The closest in technical essence to the present invention is {the method of processing cold-deformed steel billets, including non-oxidative recrystallization annealing during bulat-bZO C in the eutectic melt of calcium and sodium with the addition of sodium metasilicate, exposure of the JB cooling process at 280-300 ° C to the eutect. with the addition of ferrocyanide excrement and washing in hot water C3J. The disadvantage of the known method is that when extracting blanks from the bath with molten salt of the substrate with a chloride-silicate film on the surface of the bath, the metal is prevented from oxidizing by air. heh, it is difficult to wash in hot water. Therefore, a second van with a melt of NaOH-KOH - K, CFe (CN) b at 280-300 ° C is required, in which the removal of the chloride-silicate film is provided. This complicates the processing. The aim of the invention is to simplify the process. : The goal is achieved by the fact that, according to the method of treating cold-deformed steel workouts, including recrystallization, “oxidation-free oxidation annealing at 600–650 ° C in eutectic salt containing sodium chloride and metasilicate sodium, and rinsing in hot water, annealing of the melt, additionally containing potassium chloride and sodium carbonate, in the following ratio, wt.%: Potassium chloride 30-41 Sodium chloride 20-30 Metasilicate. sodium 0.3 -1.2 sodium carbonate 32.8-44.7 The salt film that forms on the surface of the billet when it is removed from the KCI-NaCI-NagCOj-Na SiOg melt quickly hardens and protects the steel from oxidation in air. AT . At the same time, the presence of potassium chloride and sodium carbonate in the melt, as well as a reduced content of silicate, ensure good dissolution of film salts in hot (7080 ° C) water. Therefore, the use of an alkaline melt is not necessary. Thus, unlike the salt composition (CaCl2-NaCl). Na, SiO, which is very difficult to wash off with water from the surface of the blanks, the film of solidified melt KC1-NaC1-Naj, C03-Na, j, Si03 is washed off from the surface of the steel with hot water for 10-20 minutes. This is achieved due to properties the salt composition itself, i.e. it is easier to dissolve, and due to a significant reduction (approximately twice) in the thickness of the film formed. The concentration limits of salts in the melt are established empirically and are mainly due to the change in melting and viscosity of the melt. The proposed composition of the melt is melting at 565-580s. With the excess of the chloride content limit, the melting point and its viscosity increase sharply. Thus, the melts of the following composition, wt.%: KC1 45 24 31 34 NaCI 21 27 34 15 agCO, 33, 48 34 Na-jSiO 1 melt at 600-610 C. PosL) Lkyu recrystallization annealing of special steels, for example 10 GN and 11 SAA, when they are BOO-BZO C, the melts of the above composition are not harmful for this process (their working temperature is 650-700 0, i.e., higher than the temperature of operation, annealing). The sodium metasilicate in the proposed melt has the same function as in the known composition of the melt. However, its lower limit is higher, and its upper limit is lower than in the CaCI NaCI-NartSiO melt. To ensure non-oxidative annealing in a chloride-carbonate melt, 0.31.2% of NagSiO is sufficient. An increase in the silicate content above 1.2% only prolongs the washing of the salt film; a decrease in its concentration below 0.3% does not provide a qualitative oxidation-free annealing: a thin film of oxides is formed on the surface of steel n. Examples of the recrystallization annealing of special steels in the proposed melt are given in Table. In experiments 1-4, 7 and 8, sample 4 of steel 11 JA was used, in experiments 5 and 6, samples of steel 10 GN. The duration of exposure of the samples in the melt from steel 11 JAA 20 min, from steel 10TH 90. min. After extraction from the melt, the samples were cooled in air to 250–300 ° C, and then subjected to washing with hot (70 ° C) water for 10–20 min. The monitoring of the completion of the washing was performed visually, as well as by chemical analysis for chloride. When performing recrystallization annealing in the KCl – NaCI – Naj CO –Na.SiOj melt within the proposed concentrations of components, the surface of the steel after cooling, lathering and washing is light, without scale. With an increased content of silicate, a poor salt capture is observed, with a reduced 944 surface oxidation (Table 1, examples 7 and 8). The viscosity of the proposed melt is much lower than what is known, therefore the removal of salts with the preforms decreases approximately by half. In tab. 2, specific data are given before the removal of salts in the most low-melting composition of the proposed melt (containing, wt.%: KC1 35.4, NaCI 27, 0.6, NajCO 37.0, and in the known containing, wt.%: CaClj 66, NaCI 32.5,. Although the thickness of the KC1-NaCINa-CO-Naa SiOj melt liquid film formed on the blanks is half as much as in the case of the melt (CaClg -NaCI) ed, however, it solidifies faster. This is due to the lower overheating of the proposed melt melting point -. Thus, the melting point of the known melt offered is 565-580 ° C. Thus, for solidification films of the proposed melt annealed billet should be cooled at 20-35 ° C to harden the film of a known melt at 95-145 ° C. At the same given cooling rate, the film of the proposed melt hardens faster and prevents diffusion of oxygen to the steel surface. Technical and economic efficiency of the proposed method process, which is to simplify the process, is determined by the exception of the alkaline melt from the technological process for washing the salt film on the workpieces, reducing the duration of the technological process for 8–15 min, cheaper melt (KC1 and, cheaper than CaCl2) and also a decrease in the specific removal of salts by 2 times. . The melt can be introduced at machine-building plants, which process, convolve, stretch billets by cold deformation .;

Table 1

44.7

0.3

25

thirty

32.4

1.6

36

thirty

Prototype

Clean, light, free from salt and scale

Also

eleven

Salt casting is full, surface color is dark, uneven

Salt washing incomplete

table 2

0.98

0.78

Offered easily1118694

8 Continuation of table 2

Claims (1)

COLD PROCESSING METHOD STEEL BLANKS comprising nonoxidizing recrystallization annealing at 600-650 C ⁱⁿ a molten salt eutectic containing sodium chloride and sodium metasilicate, and washing in hot water, characterized in that, in order to simplify the process, annealing produce a melt, additionally containing potassium chloride and sodium carbonate, in the following ratio, wt. X: Potassium chloride Sodium chloride Metasilicate · sodium Sodium carbonate