JP2638298B2 - A method for determining the carbon equivalent, carbon content and silicon content of cast iron, as well as predicting its physical and mechanical properties - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention accurately measures a cooling curve of a cast iron by thermal analysis, and determines a carbon equivalent, a carbon content and a silicon content in the cast iron based on the measured cooling curve. The present invention relates to a measurement method for predicting physical and mechanical properties, sufficiently controlling the pre-furnace of a pre-casting process in a foundry, and measuring a molten metal from a blast furnace.

[Conventional technology]

The principle of the measurement of carbon equivalent is to simulate the initial heat stop temperature (primary crystal where it is the liquidus line) when the molten cast iron solidifies, and simulate the fundamentally ternary system of iron, carbon and silicon. The binary system has a carbon equivalent. There are various ways of expressing the carbon equivalent, but the most commonly used is C% + 1 /
3 (Si% + P%). Further, the eutectic temperature was measured, and the relationship between these and liquid, liquid + solid, and solid was examined to determine the silicon content,
It can determine the carbon content and predict the physical and mechanical properties of cast iron as a function of the time until solidification.These values are corrected according to changes in the actual casting shape and material, and analysis is performed. With the cup prepared by the technology prepared before pouring, it is quicker than any other analysis method, and it is possible to know the state of the molten metal accurately and manage it before casting. It is known that appropriate pre-processing can be performed when the composition and properties are different from the intended ones. Conventionally, there are U.S. Pat. No. 3,277,732 and U.S. Pat. No. 8,206,206 based on the above-mentioned known techniques, but none of them can sufficiently achieve this object.

[Problems to be solved by the invention]

Compared to the time when the prior art was proposed as described above, the current state of the casting industry has greatly expanded the range of choices of casting materials, and has enabled the development of compacted graphite cast iron (COMPACTED GRAPHITE IRO).
N, so-called CV cast iron) and Austemperd Ductile Iron (so-called ADI cast iron), etc., as well as advanced demands due to the development and development of alloy cast iron, etc., further quicker and more accurate on-site furnace Pre-molten metal management technology has been required. That is, iron and carbon are 2
It is a ternary system, iron, carbon, silicon, etc. are ternary systems, eutectic temperatures are constant in binary systems, eutectic temperatures are highest and lowest in ternary systems, and silicon content in cast iron The eutectic temperature increases for some elements and the eutectic temperature decreases for some elements, depending on the additional elements in the alloy cast iron. Iron, carbon (graphite), silicon-based stable solidification and iron: carbon (cementite) for ternary solidification of iron, carbon and silicon
-The two equilibrium of silicon-based metastable solidification exists.

Moreover, due to changes in the cooling rate and differences in the added elements, two equilibriums often occur alternately in the same molten metal.
Such a problem of double equilibrium complicates the solidification of the cast iron system. In recent years, the operation of cupolas has gradually shifted to electric furnace melting due to pollution regulations.In the current situation, changes in properties due to changes in molten metal due to elapsed time after melting, changes in composition of molten metal as well as oxygen in molten metal Quantity, oxide,
Alternatively, the problem of dissolved oxygen content is becoming a serious problem not only in steel but also in cast iron. For this reason, a situation that cannot be satisfied by the conventional thermal analysis method has appeared. Therefore, not only the primary crystallization temperature but also the eutectic temperature must be measured accurately, and the cooling curve must be measured in a safe white iron state (iron, cementite system), and measurement by metastable solidification is necessary. It is not only the cooling curve but other emission analysis methods,
It is becoming an essential condition for instrumental analysis samples such as X-ray analysis. The present invention focuses on this point, and as a paint such as chill wash in a measuring cup based on the patented invention as a method for adding a graphitization inhibiting element such as tellurium, bismuth, and boron as a metastable solidification accelerator of the prior art. Or addition of metallic tellurium powder in a cup, etc., but it is extremely doubtful that these are always added accurately at a constant ratio. It is a matter of whether the temperature is obtained or not, and in the method of obtaining a cooling curve as claimed in patent 820206, in which bismuth, boron, cerium,
Lead, magnesium and tellurium and their compounds and mixtures are added to hot water. Cerium, magnesium and the like are typical ductile iron spheroidizing reactants and spheroidizing stabilizers. This disturbs the equilibrium state of metastable solidification of iron and cementite, making it difficult to measure the temperatures of primary crystals and eutectics. The measurement of the primary crystal and the eutectic can be naturally obtained only after measuring the equilibrium state. Cerium, magnesium, etc. are always deoxidized, desulfurized and decarburized before spheroidizing graphite, so it is inconvenient to use elements that have a decarburizing effect when measuring carbon equivalent and carbon content. That is obvious.

[Means for solving the problem]

The present invention has succeeded in the development of the present invention as a result of various examination experiments in order to improve the above-mentioned disadvantages of the prior art, and the technical configuration of the present invention is used for measuring a cooling curve by thermal analysis of cast iron. At the inside of the cup for cooling curve measurement,
A powder compact or a sintered compact of a powder-particle mixture having a composition of 3 to 20% by weight of aluminum, 3 to 20% by weight of zinc, and the balance of tellurium is fixed, and a molten cast iron is poured into the measuring cup. Then, the primary crystal temperature and eutectic temperature based on the metastable solidification of iron, cementite, and silicon that appear on the cooling curve of cast iron,
There is a method of determining the carbon equivalent, carbon content, and silicon content of a casting and also predicting its physical and mechanical properties.

As described above, the inventor has a sufficient deoxidizing effect and has a primary crystallization temperature of cast iron, even in a small amount and remaining as an alloy element,
Focusing on aluminum from this point of view without affecting the eutectic temperature, the effect of the metastable solidification accelerator of tellurium, bismuth and boron can be enhanced, and at the same time, a small amount of heat generated by the deoxidation reaction of aluminum By adding a small amount of zinc to suppress the phenomenon, the heat generation is offset by latent heat of vaporization to further enhance the effect of metastable solidification, and completely remove the effects of oxides or dissolved oxygen, and remove tellurium, bismuth Mixing powders such as boron and powders of zinc and aluminum with powder and powder compacting, or fixing as a sintering mold inside the cup for measuring the cooling curve and reacting well with the molten cast iron to be poured It is intended to quickly and accurately measure the carbon equivalent, carbon content, and silicon content of the cast iron and also determine the physical and mechanical properties of the cast iron.

Cup (1) for measuring a cooling curve shown in FIGS. 1 and 2
Was used to carry out the method of the present invention. The measuring cup (1)
A ring-shaped molded body of the present invention (2) surrounding the thermocouple (3) is provided on the inner bottom surface. The compact (2) is formed by compacting or sintering a metal powder such as tellurium, bismuth, boron, zinc, or aluminum or a mixture thereof, and the preferable composition range is as described above. The range is as follows.

Aluminum: 3 to 20% by weight Zinc: 3 to 20% by weight Tellurium balance Further, up to 50% by weight of one part of the tellurium content can be replaced with bismuth or boron.

Experimental results confirm that the intended purpose of the present invention is not achieved if these composition component ranges are less than the above ranges, and that if the added amount exceeds the upper limit, only expensive elements are wasted. Was done.

The arrangement relationship of the molded body (2) in the measuring cup shown in the drawing is the best mode, and the arrangement of the molded body in the measuring cup is not limited to the illustrated one. .

Example 1 Composition of compacted body Aluminum 7.3% by weight Zinc zinc 9.7% by weight Ter Remainder Compaction molding conditions The above-mentioned composition and granules were mixed uniformly, and the mixed particles were filled in a powder metallurgy die of a predetermined size. Then, a ring-shaped molded product having a thickness of about 1 mm was formed by a press for powder metallurgy. No binder is used for the powder at this time, but a small amount of volatile binder may be used depending on the mixing ratio. As shown in the figure, a pocket suitable for the outer diameter and thickness of the green compact is provided in the center bottom of a shell sand measuring cup as shown in the figure, and the compact is pressed in and fixed. . Of course, since the inner diameter is slightly larger than the outer diameter of the thermocouple protection tube and molded, there is no problem in inserting the thermocouple.
When the cast iron to be measured having a molten metal temperature of 1400 to 1405 ° C. was poured into the cup according to each composition, the following results were obtained.

Example 2 Aluminum 6.94 wt% Zinc 9.72 wt% Bismuth 10.50 wt% Ter The remaining mixture was used as a molded body in the same manner as in Example 1 to perform a similar measurement operation. Was obtained. In addition, almost the same results were obtained when part of tellurium was replaced with boron.

The actions and effects of the present invention are listed as follows: (1) The measurement range is wide, and it is possible to measure the alloy cast iron from the hypoeutectic side to the hypereutectic side.

(2) Unlike the conventional method of applying metal powder particles such as chill wash and tellurium on the inner surface of a measuring cup, an additive having a constant composition can always be correctly added. As in the case of chill wash, the amount of tellurium or the like in each measuring cup is high or low, and the measurement often becomes difficult due to the appearance of cooling, a so-called re-brightness phenomenon, on the cooling curve. With the development of these composite additives, the lower limit of the ternary temperature can be properly captured and the primary and eutectic temperatures always stable in the metastable solidification region of iron and cementite. I can do things.

(3) As described above, according to the present invention, the amount of the green compact or sintered compact added to the cast iron is 0.2-1.0% by weight.
Can achieve the purpose sufficiently, and the measurement result is ± 0.05% in carbon equivalent, ± 0.05 in carbon amount, and ± 0 in silicon amount.
Almost 100% can be measured accurately within 15%, and it can fully demonstrate its ability as a method of managing molten metal in the front of a furnace in a casting factory, and further develop casting technology in the future It will contribute to the management technology of the melting operation corresponding to.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of a cooling curve measuring cup used in the method of the present invention, and FIG. 2 is a longitudinal sectional view taken along the line II-II of FIG.

DESCRIPTION OF SYMBOLS 1: Measurement cup 2: Molded body 3: Thermocouple

Claims (2)

(57) [Claims] In a method for measuring a cooling curve of a cast iron by thermal analysis, a powder having a composition comprising 3 to 20% by weight of aluminum, 3 to 20% by weight of zinc and the balance tellurium is provided on the inner surface of a cup for measuring the cooling curve. After fixing the green compact or sintered compact of the mixture, the molten iron of the cast iron is poured into the measuring cup, and the iron, cementite, and silicon based on the metastable solidification of the iron, cementite, and silicon clearly defined on the cooling curve of the cast iron are fixed. A method in which the crystallization temperature and the eutectic temperature appear to determine the carbon equivalent, carbon content, and silicon content of cast iron, as well as its physical and mechanical properties. 2. The method according to claim 1, wherein part of tellurium, which is a component of the green compact or sintered compact, is replaced with bismuth or boron.
A method of determining the carbon equivalent, carbon content, and silicon content of the cast iron described, and also predicting its physical and mechanical properties.