HU190479B - Method for producing foundry alloy - Google Patents

Abstract

Graphite forming elements are mixed with part of a liquid, carbon contg. alloy, using a suitable gas to promote intensive mixing. The quantities added exceed the equilibrium condition. - Excess graphite and other non-metallic inclusions are removed by floatation, thus producing an alloy with low carbon, oxygen and sulphur content. The purified portion is then mixed with the rest of the melt producing an alloy for casting likely to achieve high purity sub-cooling, with a fine structure and small graphite elements.

Description

FIELD OF THE INVENTION The present invention relates to a process for producing cast iron alloys or castings of very favorable casting, metallo-metallic properties from carbon-bearing iron melt.

Recent industrial developments, due to rising commodity prices and increasing supply difficulties, have led to an increasing proportion of hot-melt smelters making use of steel pig iron, wastes that are difficult to control, and contain impurities that are unfavorable to product quality.

Difficulties in the supply of raw materials are particularly acute in iron and steel foundries. In recent years, blast furnaces have been producing less and less foundry crude acid. The reason for the decrease in production is that steel plants require more steel crude acid for oxygen intensification processes than before, and on the other hand the higher energy demand, production cost and less economical nature of cast iron production.

According to the experience of the foundry, cast iron casting is a basic, difficult to replace insert. The deposit is expected to cause, in whole or in part, an unfavorable change in casting quality, which can only be offset by costly complex measures and unique metallurgical technologies.

Various technological variants have been developed at the foundry to replace cast iron. The most typical are: partial or total replacement of cast iron pig iron with steel pig iron, production of synthetic cast iron pig iron from steel scrap or steel pig iron. Based on either option or combination thereof, the properties of the prepared liquid ferro-alloy are disadvantageous compared to practical ferro-alloys. Their common feature after freezing is the unfavorable, inhomogeneous tissue, mechanical properties. When used as a feedstock, it has unfavorable hereditary properties after remelting.

Utilizing the process of the present invention, casting alloys with favorable properties can be produced from liquid carbon-carbon alloys, independently of the insert components. The effect of the process is a complex operation consisting of several simultaneous operations; It consists of a localized alloying of a small proportion of the liquid iron alloy with graphite - forming elements in excess of equilibrium conditions, sometimes with additional micro - alloying, under intense flotation with a suitable gas.

The essence of the process is to introduce a small amount of liquid carbon-carbon iron alloy in the treatment vessel, which is well delimited by space, graphite-forming elements, preferably silicon and or calcium and or aluminum, metal, alloy or compound condition. An alloy limited to a given volume of a liquid alloy acts as if the carbon content of the alloy increases (the so-called "eutectic carbon content" of the iron alloy increases), the alloy becomes highly hyperexcited. Iron molten supersaturated with carbon can hold less than actual carbon in solution, and the excess crystallizes in the form of primary graphite (e.g., in the initially dissolved state

In an iron melt containing 4.3% by weight of carbon, 6% by weight of silicon can be left in solution, leaving only 2.4% by weight of carbon in the solution, precipitating as other graphite).

Removal of crystallized graphite from the melt by intensive flotation results in a lower carbon alloy near the alloying site compared to the rest of the melt. This lower carbon content of the melt blends with the residual equilibrium composition of the melt to reduce its carbon content when mixed with the intense flow during flotation. On the other hand, graphite does not crystallize, or only very small in small quantities, in the reduced carbon-carbon melt. Upon completion of the operations of the process, a homogeneous, prone to overheating iron melt is formed which, when solidified, contains more than average crystalline germs and results in a favorable modification of the fine-grained and fine-grained graphite casting without the addition of a modifying alloy.

A special advantage of the process is that during the sub-operations not only the graphite but also after coagulation other non-metallic inclusions are sulphides, oxides - a significant part of the flotation is removed from the iron melt, thus the oxygen and sulfur content of the melt decreases. Performing a separate deoxidizing, desulfurizing operation, or without the addition of deoxidizing, desulfurizing agents.

The process results in such an advantageous change in the properties of the ferrous melt that the casting alloy thus prepared is capable of producing castings without the need for a separate operation when the initial ferrous melt is dehydrated directly from the blast furnace.

Starting from a liquid steel pig iron, the process can be used to produce castings with a high inheritance, low sulfur and phosphorus content, low sulfur and phosphorus content, with a high saturation eutectic content of from 0.98 to 1.0, which are very advantageous for casting for solving the raw material supply of foundries.

The process can also be utilized in iron foundries with favorable results. Regardless of the nature of the material and the origin of the molten non-alloyed, weakly or moderately alloyed iron melt, homogeneous, favorable fabric, good mechanical properties, - vermiculoidal - spheroidal graphite castings can be manufactured with high security.

Some of the uses of the process of the present invention and the results achieved so far are described in the following examples.

Example 7

According to the process of the invention, liquid steel is blasted directly from a blast furnace

We made 190,479 liquid iron alloys from which we poured steel mills:

AC = 4.47%; Mn = 0.89%; Si = 0.91%; P = 0.072%; S = 4.5 kg / t ferrosilicon with intensive flotation with argon gas flowing through a porous plug embedded in a steel pig iron containing 0.021%; 0.75 kg / t of calcium silicon and 0.25 kg / t of aluminum were injected into the cauldron at a geometrically defined location. C = 4.00%, obtained after completion of the partial operations of the procedure; Si = 1.27%; Mn = 0.9%; P = 0.07%; S = 0.013%; O ₂ = 19 PPM; N ₂ = 31 PPM cast alloy steel castings. The typical fabric of the mold castings was ferrite - with small fibrous graphite - and the samples did not contain primary graphite.

The lifetime of the molds thus produced, on average, was 30% higher than previously produced, with significant cost savings and energy savings.

Example 2

According to the process of the present invention, an iron alloy used as a liner in a foundry was made from blast-iron-blasted steel.

AC = 4.31%; Mn = 0.73%; Si = 1.06%; S = 0.048%; P = 0.071%; 3.5 kg / t of CaCN ₂ , 0.3 kg / t of Al and 1.5 kg / t of ferrosilicon were injected locally into the composite pig iron by intense flotation through a porous plug . Completion of process operations following the process, after removal of the slag and of non-metallic impurities in the slag

C = 4.00%; Si = 1.16%; Mn = 0.71%; S = 0.022%; P = 0.07%; N ₂ = 36 PPM; O ₂ = 18 PPM foundry alloy was obtained which was cast into alloy ingots. Blocks with a low S and O ₂ content without the appearance of primary graphite, which can be advantageously used after curing, were used as an insulator in an induction furnace.

Hydraulic control valve castings were made from the ferrous alloy produced by the process, without the use of cast iron, and from the cast iron insert, which was made of steel scrap. As a result of the favorable inheritance properties of the high carbon carbon iron alloy used as the insert, the fabric of tensile strengths of 280-320 N / mm ² and hardness of 220-240 HB was pure perlite with fine graphite without the appearance of ledeburit.

with intense flotation. Dotation was performed with inert gas flowing through a porous plug.

C = 3.78%; Si = 1.95%; Mn = 0.31%; S = 0.019%; P = 0.11%; N ₂ = 38 PPM; An iron alloy of O ₂ = 9 PPM was obtained and cast into blocks. These were used as filler material for the production of ductile iron castings. The low oxygen and sulfur content of the iron alloy produced by the process enabled the molten cast iron to be solidified into spheroidal graphite fabric with 30% less treatment material than before.

Example 4

A favorable result is the application of this process to the production of ferroalloys for the production of castings for temperature-operated parts.

Liquid C = 4.21%; Si = 0.68%; Mn = 0.42%; S = 0.046%; In an alloy of P = 0.097%, 20 kg / t of aluminum and 0.5 kg / t of calcium silicon were alloyed locally by injection while the melt was intensively flotated with neutral gas. Upon completion of the procedure, C = 3.81%; Al = 1.97%; Mn = 0.41%; P = 0.096%; S = 0.027%; O ₂ = 12 PPM; N ₂ = 33 PPM melt. This casting was further combined with 0.6 kg / t of mixed metal. The castings, even with a small amount of mischmetal, were frozen with pure spheroidal graphite.

Example 5

Founded as a mildly alloyed core of molten chromium, nickel and molten chromium, nickel in a foundry blend, found in a melt containing 3.52% carbone, 1.62% silicon and 0.58% manganese, locally 0.3% calcium silicon and 0.05% Al was combined with intensive flotation. After completion of the process operations, the main constituents, in addition to nickel and chromium, were cast iron castings from the liquid iron containing 3.44% carbon, 1.73% silicon and 0.58% manganese without any modifications or modifications. The castings were cured with pure perlite fabric containing fine fibrous graphite. The strength of the castings was 10% higher than that of castings of similar composition cast after special modification.

Example 3

The process according to the present invention provides an iron alloy which is advantageously used as a foundry insert from a blast iron blast furnace.

The composition of the starting liquid steel pig iron C = 4.06%; Mn = 0.32%; Si = 1.14%; S = 0.032%; P = 0.11%.

Topically, 12 kg / t of ferrosilicon was introduced into the melt; 0.2 kg / t aluminum was alloyed with a submersible bell.

Claims (2)

Claims A process for the production of an ore alloy from a liquid carbonic iron alloy comprising the step of combining a defined volume of the liquid carbonic alloy with graphite-forming elements in an intense flotation using gas to produce an excess of carbon at the equilibrium state. Crystallizing 190,479 earths, graphite and a substantial part of the other non-metallic inclusions created by removing the flotation low carbon, sulfur and melt containing oxygen, it is mixed with the rest of the melt with high purity tends to undercooling, fi ⁵ my wife metallic fabric, obtained solidifying small graphite alloy . 2. A method according to claim 1, characterized in that in addition to locally intense average composition, pig iron melt flotation ⁰ 0.5-4.0 kg / t CaCN _? 0.1-0.7 kg / t Al, optionally 0.5-2.0 kg / t CaSi and or 0.5-5.0 kg / t ferrosilicon. 3. A method according to claim 1, characterized in that the liquid containing zet vasötvö- ⁵ carbon is - pig iron - a proportional part of an intensive flotation time 1.0 to 20.0 kg / t of FeSi, 0.5 to 5.0 kg / t of calcium silicon, 0.1-0.5 kg / t of aluminum, occasionally 0.3-2.0 kg / t of magnesium, and or 0.5-10 kg / t of cerium topically mixed. The process according to claim 1, characterized in that the local alloy in the iron melt is 6-22 kg / t aluminum, 1.0-8.0 kg / t silicon, optionally 0.5-1.0 kg / t magnesium, and or 1.0 to 10.0 kg / t of cerium. 5. A process according to claim 1, wherein the non-alloyed or low-alloyed C * 2.6-4.0%, Si = 1.4-3.0% Mn = 0.2-2.0%, sometimes Cr = 0.2-2.5%, Ni = 0.2-4.0% Mo = 0.12-1.0% as impurity In the iron melt containing S and P with intense flotation 0.5 to 5.0 kg / t ferrosilicon silicate and or 0.5-5.0 kg / t of calcium silicon is topically alloyed.