RU2226570C2 - Steel modifier - Google Patents

Abstract

FIELD: steelmaking. SUBSTANCE: modifier contains, wt %: powdered addition alloy of deoxidizer 20-40, powdered addition alloy with rare-earth metal 20-30, powdered addition alloy with alkali-earth metal 30-50, and fluxing additive 5-10. Above-mentioned addition alloy of deoxidizer is an iron-based fusible alloy including 5-10% aluminum, 30-50% silicon, and 5-10% manganese. Abovementioned fluxing additive is a mixture of fluorite and cryolite powders in ratio ranging from 5:1 to 1:5. Invention can be used when manufacturing cast blanks of steel parts operated at temperatures up to -60^o C. EFFECT: improved deoxidation, modifying, and fluxing capabilities of modifier reducing amount and degree of non-compactness of nonmetallic inclusions and improving mechanical strength of blank metal, in particular impact resistance factor at -60 C. 1 tbl

Description

The invention relates to metallurgy and can be used in foundry in the manufacture of cast billets for machines and mechanisms operating at temperatures up to -60 ° C.

The closest analogue of the inventive modifier is a deoxidizing modifier for improving the quality of steel and cast iron containing a deoxidizer, rare earth metals and alkaline earth metals [1]. The technical result of the invention is to improve the deoxidizing, modifying and fluxing ability of the modifier, which reduces the number and non-compactness of non-metallic inclusions and increases the mechanical properties of the metal castings, in particular, the impact strength at -60 ° C, ensuring its stability.

The technical solution is achieved by the fact that the steel modifier additionally contains a fluxing additive, and it contains a deoxidizer, REM and SCHM in the form of powder ligatures in the following ratio of components, wt.%: Deoxidant ligature powder 20-40; ligature powder with REM 20-30; ligature powder with ЩЗМ 30-50; fluxing additive 5-10, moreover, as a deoxidant ligature, it contains an alloy of A1, Si, Mn and Fe in the following ratio of components, wt.%: Al 5-10; S 30-50; Mn 5-10; Fe the rest, and as a fluxing agent - a mixture of fluorite powders with cryolite in a ratio of 1: 1.

The theoretical basis of the proposed solution was the study of the influence of nonmetallic inclusions (NMI) on the cold resistance of castings made of steel 25L [2-3].

It was found that with traditional methods of steel deoxidation, the impact strength of castings metal (KCU) at -60 ° C does not exceed 0.02 MJ / m and the values of this indicator depend on the amount and degree of non-compactness of the metal alloy, as well as on their morphology of topography. It was noted that during steel casting, the amount of HMB increases and the Mn content decreases as a result of re-oxidation of the melt.

The testing of the analog modifier in the calculation of the initiation by the oxides of the process for the separation of HMW with the aim of transferring them into the grain and preventing re-oxidation did not lead to the desired result. The number of HMWs increased, but their morphology changed, the degree of compactness increased, however, the impact strength at -60 ° C changed in the range 0.02-0.05 MJ / m, which indicates its low stability.

The known and proposed modifier compositions were tested in the manufacture of castings of a valve body made of steel 25L at OJSC “Ikar” at the Kurgan Pipe Fittings Plant.

Steel was smelted in an induction 4-ton furnace with an acid lining. Steel deoxidation was carried out in a furnace with additives of ferromanganese, ferrosilicon and aluminum, 0.1 each. Modifiers were introduced into casting ladles. Samples were cast in the form of a “gref” according to GOST 977-88 for testing for mechanical properties.

The test results of three samples at -60 ° C and a metallographic study of the amount and form of HMW (see table) using the known and proposed modifier compositions showed that the technical solution of the invention was achieved.

The impact strength index (KCU) at -60 ° C increased to 0.9-1.1 MJ / m. The stability of this indicator has increased: deviations as a percentage of the average value of the indicator are reduced from 75% to 25%. The total content of non-metallic inclusions decreased from 1200-1500 pcs / cm to 500-600 pcs / cm and the number of compact inclusions significantly increased from 78 - 82% to 85 - 98%.

Sources of information

1. RF patent No. 2164960, 04/10/2001 (prototype).

2. Minnekhanov G.N., Saburov V.P., Mokretsov S.V. The effect of modification of rare-earth metals on the cold resistance of carbon steel 25L. Foundry processes. - Magnitogorsk: MSTU, 2000, p.186-190.

3. The effect of non-metallic inclusions and structure on the cold resistance of low-carbon steel castings. Minnekhanov G.N., Saburov V.P., Mokretsov S.V. et al. Non-metallic inclusions of I gas in tin alloys. - Locking: ZDTU, 2000, p. 67-68.

Claims (1)

A steel modifier containing a deoxidizer, sharp earth metals (REM) and alkaline earth metals (ЩЗМ), characterized in that it additionally contains a fluxing additive, and it contains a deoxidizer, REM and ЩЗМ in the form of powder ligatures in the following ratio of components, wt.%: Deoxidant Ligature Powder 20-40 Ligature powder with REM 20-30 Ligature powder with ЩЗМ 30-50 Fluxing additive 5-10 in this case, as a deoxidant ligature, it contains a low-melting alloy, including aluminum, silicon, manganese and iron, in the following ratio of components, wt.%: Aluminum 5-10 Silicon 30-50 Manganese 5-10 Iron Else and as a fluxing additive, it contains a mixture of fluorite and cryolite powders in a ratio of 5: 1 - 1: 5.