SU1588775A1 - Method of producing iron with spherical graphite for rolling-mill rolls - Google Patents

Abstract

This invention relates to metallurgy, in particular to the production of iron for rolling rolls. The purpose of the invention is to increase the wear resistance of the working layer of the roll. Magnesium is introduced into the processed melt in an amount of 0.13-0.21% by weight of the processed iron in a mixture with carbonate-containing material in a ratio of 1.0: (0.63-0.83), respectively. As carbonate-containing material, carbonate of rare-earth metals is used. 1 tab.

Description

The invention relates to metallurgy, mainly to foundry, and can be used in the manufacture of nodular cast iron (chsh) for casting large mill rolls.

The purpose of the invention is to increase the wear resistance of the working layer of the roll.

According to the invention, magnesium is introduced into the treated iron in an amount of 0.13-0.21% by weight of the metal in a mixture with a carbonate-containing material in a ratio of 1: (0.63-0.83), respectively, and carbonates are used as carbonate-containing material. REM

The cast iron is processed in the casting ladle by a mechanical mixture of metallic magnesium and carbonate of rare-earth metals, the general formula of which is (REM) (CO, g). Carbonates are fine powder (basic fraction 0.05 mm) and contain (Ce, La, Nd, Pr), (CO.) 96.98%, including Ce, (CO2) s 70-78%, impurities rest.

The mechanical mixture is placed in a bell for treating cast iron with magnesium and introduced into the melt to be treated. When the bell is lowered into the ladle, the evaporation of magnesium and the decomposition of the OCR carbonates occur with the formation of CO and RjfOu. The gaseous phase contributes to the mechanical distribution of the formed oxides of rare-earth metals throughout the volume of the melt. The affinity of REM oxides to sulfur is significantly higher than that of Magels.

CX) 00

sj

 U1

neither is higher than that of REMs. Therefore, when pig iron is produced, sulfur is neutralized due to its binding to oxysulfides of REM. The process takes place more intensively than with the introduction of magnesium and soda ash, without the time spent on the formation of oxides, as is the case with the processing of a ligature of rare-earth metals, the binding of sulfur to oxysulfides of rare-earth metals significantly reduces the amount of magnesium sulfoso-compounds responsible for the formation in the working layer of the rolls, unfavorable non-metallic inclusions, REM oxysulfides compared with sulfonates, magnesium has a higher density (2-3 and 5-6 g / cm, respectively), therefore they are almost not completely lyvayut in the ladle and can enter into the mold by pouring cast iron through the rotating bucket legs juice only with the last portions of the melt forming, the core roll. The deterioration of the coagulation and segregation conditions of non-metallic REM inclusions in density prevents their enlargement and concentration. Separate small oxysulfides of rare-earth metals that do not grow along the grain boundaries of cast iron do not have a significant negative effect on its durability compared to sulphate compounds of magnesium. In addition, rare earth oxysulfides do not manifest themselves as inoculators during the formation of graphite inclusions, which, together with a decrease in the concentration of magnesium, which increases the activity of carbon, contributes to the purification of the working layer from the inclusions of graphite. Residual oxides of rare-earth metals, which are not bound to oxysulfides, contribute to increasing the dispersion of the metal matrix, in particular, perlite.

Magnesium consumption within О, 13- 0.21% by weight of cast iron and the ratio of magnesium and carbonate-containing material 1: (0.63-0.83) was determined experimentally. At flow rates of less than 0.13% of magnesium, the degree of spheroidization of graphite in the necks and core, as well as the working layer of the rolls is not achieved, and at a flow rate of 0.21%, iron is re-modified, accompanied by a deterioration of the graphite shape factor. When the ratio of magnesium and carbonate-containing material is different from 1: 0.63 (for example, 1: 0.58), an increase in the dispersity of perlite is not achieved. When the ratio

0

. d e 5

0

0

five

0

the difference from 1: 0.83 (for example, 1: 0.88) no further increase in the dispersity of perlite is observed; however, the number of non-metallic inclusions increases in the iron.

Example, cast iron for casting rolls of the SSNHN-50 type, smelted in a flame furnace and containing, | wt.%: C 3.1, Si 1.5, Mp 0.5, P 0.2, S 0.03, 3, Ni 1,2 was discharged into a 30 t bucket. After the slag was removed, the bucket was placed in the chamber, when the melt reached a temperature of 1380 ° C, 25 kg of fluorspar was placed on the mirror and magnesium and carbonate-containing material were introduced into the bell. Melt processing time 2-3 min. After treatment, removal and removal of slag, molds were cast. When producing pig iron by a known method, magnesium and soda ash were injected on average 0.35% and 0.13%, which is 1: 0.37 in terms of. When producing cast iron using the proposed method, magnesium and light carbonate of rare-earth metals were introduced into the melt to be treated in a ratio of 1: 0.73 at a magnesium consumption of 0.11-0.23% and in a ratio of 1: 0.58; 1: 0.63; 1: 0.73; 1: 0.83; 1: 0.88 with a magnesium consumption of 0.17% in each experiment, respectively.

From the rolls cast from cast iron, obtained by the known and proposed methods, rings were selected during the machining process. The degree of spheroidizing graphite was evaluated on samples of cast iron of roll necks. The evaluation of the cast iron structure of the working layer was carried out on samples made from templates selected from the barrel (upper part) of the rolls. Samples were made from these rings for wear testing. The wear rate of cast iron was estimated by the standard method. Absolute wear was determined by the loss of mass of the test sample after 10,000 revolutions of the roller from Art. 3. The relative wear was calculated as the ratio of absolute wear to the initial mass of the sample. The relative wear of samples from rolls cast from cast iron, obtained by a known method, was taken as a unit of wear.

As follows from the research results (see table), in the working layer of the rolls cast from cast iron produced by the proposed method, a change in the distribution pattern is observed

non-metallic inclusions. At a depth of 5 mm from the working surface, there are not many different inclusions that are larger than to a depth of 10 mm, but their number is correspondingly smaller. In the working layer of the rolls, cast by a known method, the size of non-metallic inclusions at a depth of 5 mm is less than at a depth of 10 mm, but their number is correspondingly larger. The average number and average size of non-metallic inclusions in the cast iron, obtained by the proposed method, 1.5-2.0 times less than in the cast iron, obtained by a known method.

The dispersion of structural components, in particular, perlite, varies from 1.4 to 1.4 to 0.5, compared with 1.4-1.6 in iron, obtained by a known method. The form factor of graphite, with average magnesium consumption limits and an average ratio of magnesium to light carbonates of rare-earth metals, is 0.842 compared to 0.826.

in a cast iron obtained by a known method, the consumption of magnesium is 0.17 and 0.35%, respectively. The cast iron of the rolls obtained by the proposed method has a wear resistance of 22-28% Bbmie compared with the wear resistance of cast iron obtained according to the known way.

Claims (1)

Invention Formula A method of producing nodular cast iron for rolling rolls, including loading the charge, smelting, remelting the melt and tapping into the ladle, introducing a mixture of magnesium and carbonate-containing material, in order to improve the wear resistance of the working layer of the roll as carbonate-containing material, carbonates of rare-earth metals are used, which are introduced in a mixture with magnesium at a ratio of (0.63-0.83): while the amount of magnesium in the mixture is 0.13-0.21 by weight of the melt. The total number of 55 Prn salt of soda ash 0, I3Z by weight of cast iron.