KR100766770B1 - Method for heat treatment adi - Google Patents

Abstract

A method for heat treatment of a high strength cast iron material is provided to improve physical properties of the high strength cast iron material and prevent the generation of environmental pollution due to use of wastewater by proceeding a quenching step through a first quenching step and a second quenching step and returning wastewater used during a washing process to the first quenching step. A method for heat treatment of a high strength cast iron material comprises the steps of: heating an ADI(austempered ductile iron) material into a cast article at an austenitizing temperature ranging from 850 to 950 deg.C in a heating chamber; first quenching the heated article at a temperature ranging from 250 to 430 deg.C in a first quenching vessel; second quenching the first quenched article at a temperature ranging from 190 to 380 deg.C in a second quenching vessel; and washing and drying the second quenched article. The method further comprises the step of supplying waste washing water of a neutral salt used in the washing process into the first quenching vessel, thereby increasing a cooling rate of the article.

Description

Heat treatment method of high strength cast iron {Method for heat treatment ADI}

1 is a schematic diagram illustrating a heat treatment method of a high strength cast iron according to the present invention;

2 is a process chart for explaining a heat treatment method of a high strength cast iron according to the present invention;

The present invention relates to a heat treatment method of a high-strength cast iron, more specifically, a high-strength cast made to perform a high-strength cast iron (ADI) heat treatment without additional components compared to the existing cast iron, to achieve a strength shape without increasing the material cost It relates to a method of heat treatment of steel.

In general, Austempered Duction Iron (ADI) is a material in which the structure of the nodular cast iron is strengthened by performing a heat treatment called austempering on the nodular cast iron.

ADI materials have the advantages of reducing production costs, flexibility in design, excellent processing characteristics, high specific strength, and improved toughness, abrasion resistance, and fatigue strength. It is comparable to cast steel, forged steel, welding materials, carburized steel, and aluminum parts, which are mainly used in the process. However, it is superior to these materials in consideration of economic and industrial aspects.

  In addition, ADI can take advantage of the many advantages of spheroidal graphite iron, which is a raw material, so that precision casting is possible, and it does not require much machining in the production of the product, and the heat treatment of the casting itself can be used as a finished product to further increase the economic value. Can be.

In addition, since ADI contains a relatively large amount of retained austenite, the toughness is high, so that little crack is generated during heat treatment, and since a large amount of graphite is present, the specific gravity is low and the wear resistance is excellent.

Due to these advantages, the scope of application is gradually being extended to automobile parts, other locomotive parts and tools, etc. Recently, as environmental regulations are strengthened, development of environmentally friendly automobiles is emerging. As the interest in light weight increases, the development of much lighter products while satisfying the same performance standards by providing excellent mechanical properties through improvement of the quality of existing materials along with efforts to replace lightweight metals such as Al and Mg with existing steel materials. It is done.

The mechanical properties of spheroidal graphite cast iron and ADI are mainly determined by the matrix structure, and the matrix of spheroidal graphite iron is composed of a mixture of pearlite and ferrite, and this structure is completely transformed from austenizing to austenite, and quenched. In the process of austempering, the ferrite and the high carbon stabilized austenite, called ausferrite, are transformed into an austerite, which is a main cause of the formation of high-strength and high-strength nodular cast iron. .

The heat treatment of the AID is performed in three steps, which are in the order of austenizing, quenching, and ostempering.

The austenizing is a casting heating step at an austenizing temperature in the range of 1500 to 1700 ° F. (815 to 927 ° C.), and the quenching is performed at a rate of 450 to 750 ° F. (232) at a rate sufficient to avoid the formation of pearlite. Quenching (cooling) to an ostempering temperature in the range of ˜400 ° C.), which is sufficient to produce an austerite matrix (stabilized austenite containing acicular ferrite and 2% carbon) at a suitable temperature. This is the step of ostempering the product for a time.

In the quenching step, Ni, Mo, Cu, etc. should be added as an additional component in order to improve the hardenability during the initial material casting in accordance with the product quenchability (curability) problem when quenched in the general salt.

This causes a significant increase in the heat treatment cost.

The present invention has been made in view of the above points, the heat treatment in the order of heating, quenching, washing, drying in the order of ADI material, while the quenching step proceeds to the first and second quenching step and also when washing It is an object of the present invention to provide a heat treatment method of high strength cast iron material that can be used for cooling by supplying the wastewater used in the first quenching step to improve the properties of the high strength cast iron material and to prevent the environmental pollution caused by the use of the waste water. .

The present invention for achieving the above object comprises the steps of: heating the ADI material to the austenizing temperature range of 850 ~ 950 ℃ in the heating chamber; First quenching the heated product in the first quenching bath in the range of 250 to 430 ° C .; Second quenching in a second quench bath in the range of 190 to 380 ° C .; It provides a heat treatment method of high-strength cast iron, characterized in that the step of washing and drying the second quenched product.

As a preferred embodiment, it is characterized in that the cooling rate is increased by supplying the wash water wastewater of the neutral salt used in the water washing to the primary sintering tank.

Hereinafter, the present invention will be described in more detail.

1 is a schematic diagram illustrating a heat treatment method of a high strength cast iron according to the present invention, and FIG. 2 is a process diagram illustrating a heat treatment method of a high strength cast iron according to the present invention.

The present invention eliminates the addition of Ni, Mo, Cu, etc. as an additional component in order to improve the hardenability during initial material casting in accordance with the problem of hardenability (hardening ability) in the quenching step, reducing material costs and properties of high-strength cast iron One point is to improve this.

First, a step of casting heating the ADI material at the austenizing temperature in the range of 850 ~ 950 ℃ in the heating chamber is carried out.

Next, the step of primary quenching the heated product in the range of 250 ~ 430 ℃ in the primary quenching tank and the second quenching in the range of 190 ~ 380 ℃ in the secondary quenching tank is in progress.

The heat treatment temperature range of each of the above austenizing and austempering is determined in order to obtain the desired structure considering the transformation temperature of the material. The actual temperature range and the heat treatment holding time are determined by many tests and analyzes. This is a very important factor in ADI heat treatment.

At this time, the wastewater of the neutral salt used for washing water is supplied to the first sintering tank, and by supplying the wastewater of the neutral salt generated during the washing process to the first sintering tank, it is possible to prevent environmental pollution due to the recycling of the wastewater. have.

Finally, the second quenched product is washed and dried to finish the heat treatment of the ADI product.

Hereinafter, the embodiment of the present invention will be described in more detail with a comparative example, but the present invention is not limited by the following examples.

Example

Casting heating the ADI material at an austenizing temperature in the range of 850-950 ° C .; First quenching the heated product in the first quenching bath in the range of 250 to 430 ° C .; Second quenching in a second quench bath in the range of 190 to 380 ° C .; Washing and drying the secondary quenched product; Heat treatment was performed on high-strength cast iron through the step of supplying the wastewater used for washing in the first quenching stage.

Comparative example

The ADI material was heat-treated by the conventional heat treatment method.

That is, in order to improve the hardenability during the initial material casting in accordance with the problem of product quenchability (hardening ability) in the first quenching step, Ni, Mo, Cu, etc. were added as an additional component and heat-treated.

Experimental Example

Physical properties of the high-strength cast iron of the present invention according to the embodiment, and the existing cast iron according to the comparative example was carried out by a conventional method, the results are shown in Table 1 below.

division Yield strength (Mpa) Tensile Strength (Mpa) Elongation (%) Hardness (HB) Existing cast iron material (Comparative example)  350  500  7-12  170-241 ADI development material (this invention)  550 ↑  850 ↑  12 ↑  280 ↑

As shown in Table 1 above, for example, by comparing the elongation, tensile strength, yield strength, fatigue strength, wear resistance and the like, the graph showing the physical properties showing the results that the high-strength cast iron of the present invention is more excellent Please present one vote.

As described above, according to the heat treatment method of the high-strength cast iron according to the present invention, while heating the ADI material in the order of heating, quenching, washing, drying, the quenching step proceeds to the first and second quenching step In addition, by supplying the wastewater used in the water washing in the first quenching step to cool the use, it is possible to improve the properties of the high-strength cast iron material and to prevent environmental pollution due to the use of wastewater.

Claims (2)

Casting heating the ADI material at an austenitic temperature in the heating chamber at a range of 850-950 ° C .; First quenching the heated product in the first quenching bath in the range of 250 to 430 ° C .; Second quenching in a second quench bath in the range of 190 to 380 ° C .; Washing and drying the secondary quenched product; Heat treatment method of a high-strength cast iron, characterized in that consisting of. The method of claim 1, wherein the cooling rate of the neutral salt used for washing the water is supplied to the primary sintering tank to increase the cooling rate.

Images