CN1552928A - Ultrapure smelting process for nickel-base high-temperature alloy - Google Patents

Abstract

Process for melting Ni based high temperature alloy with super purity is carried out by degassing at first, purifying alloy elements and heating-up to 1600 - 1650 deg.C for 15 - 20 minutes, cooling to condense, next, heating-up to 1490 - 1540 deg.C for 20 - 30 minutes again, casting into ingots at 1500 - 1550 deg.C, then, melting degassed elements as raw materials to produce Ni based alloy with low carbon and gas contents. Because the raw material is degassed, no carbon is added, and melting time is not long, The Ni based alloy with low carbon and gas contents is obtained.

Description

Ultra-pure smelting method of nickel-based high-temperature alloy

Technical Field

The invention relates to a vacuum smelting technology, in particular to an ultra-pure smelting method for nickel-based high-temperature alloy with low gas and carbon contents by adopting common raw materials.

Background

The gas in the alloy can cause the alloy to generate pores and loose, and the pores and loose are usually used as fracture crack sources of the alloy. Therefore, reducing the gas content of the alloy is an important means for improving the strength of the high-temperature alloy. For some nickel-based high-temperature alloys, carbides are harmful phases, and excessive carbides can harm the performance of the alloys, so that an ultra-pure smelting method for simultaneously reducing the gas content and the carbon content needs to be invented.

The traditional high-temperature alloy vacuum smelting process generally adopts a carbon adding method to deoxidize. To smelt low-carbon high-temperature alloy, decarburization is needed while deoxidation is needed, which requires prolonging refining time and increasing refining temperature, but some volatile elements are difficult to controlunder vacuum, the decarburization and degassing effects are not ideal, the gas content cannot be reduced to a desired level, and low carbon and low gas content cannot be compatible. According to the traditional process, the purpose of low gas and carbon content can be realized by selecting high-purity raw materials, but the smelting cost is greatly increased.

Disclosure of Invention

The invention aims to provide an ultra-pure smelting method for nickel-based high-temperature alloy, which ensures low cost and realizes low carbon content and low gas content.

In order to achieve the above purpose, the technical scheme of the invention is as follows:

1) degassing treatment: and (3) cleaning the high-temperature alloy elements, heating to 1600-1650 ℃ for refining for 15-20 minutes, cutting off power, condensing thoroughly, heating to 1490-1540 ℃ for refining for 20-30 minutes, and heating to 1500-1550 ℃ after the refining for casting into ingots for later use.

2) The nickel-based high-temperature alloy is smelted by adopting the elements subjected to degassing treatment as raw materials: and after clearing, heating to 1490-1540 ℃, refining for 15-20 minutes at low temperature, cutting off power, condensing thoroughly, heating to 1500-1550 ℃, and pouring to obtain the nickel-based high-temperature alloy with low carbon content and low gas content.

Wherein: respectively adding 0.01-0.02% of carbon into the elemental nickel and cobalt alloy elements during degassing treatment; and respectively adding 40-60% of nickel into the elemental chromium and tungsten alloy elements during degassing treatment.

The invention has the following advantages:

1. has the characteristics of low gas content and low carbon content. The invention has the advantages that through a reasonable raw material treatment process (namely, a process of complete condensation exists during the treatment of the raw materials and the smelting of the alloy), the alloy elements have lower gas content, and the content of oxygen and nitrogen can reach below 5ppm generally; the invention does not add carbon during the smelting of the alloy, so that the alloy has lower carbon content which can reach below 30ppm generally.

2. Has the characteristic of low cost. The invention greatly reduces the smelting cost by adopting common raw materials.

3. The refining temperature of the alloy smelting is low, the refining time is short, and the alloy components are easy to control.

4. The invention is mainly applied to the nickel-based high-temperature alloy which requires low carbon and low gas content at the same time.

Drawings

FIG. 1 is a curve of the degassing treatment process of Ni, Co, Ni-Cr and Ni-W.

FIG. 2 is a nickel-based superalloy smelting process curve of an experiment of Ni75-Co5-W6-Cr6-A16-Ti2 according to an embodiment of the invention.

Detailed Description

The present invention will be described in detail below with reference to examples and the accompanying drawings.

Taking an experimental Ni-based high-temperature alloy of Ni75-Co5-W6-Cr6-A16-Ti2 as an example, firstly, the nickel, the cobalt, the chromium and the tungsten are degassed as follows:

respectively adding 0.015% of carbonized cleanerinto electrolytic nickel and electrolytic cobalt, heating to 1600 ℃, refining for 15 minutes at high temperature, cutting off power, condensing thoroughly, heating to 1490 ℃, refining for 20 minutes at low temperature, heating to 1500 ℃ after the low-temperature refining is finished, and casting into cast ingots for later use. See figure 1 for a process curve.

Respectively adding 50% electrolytic nickel into electrolytic chromium and tungsten strips, heating to 1650 ℃ for high-temperature refining for 20 minutes, cutting off power, condensing thoroughly, heating to 1540 ℃ for low-temperature refining for 30 minutes, heating to 1550 ℃ after low-temperature refining, and casting into nickel-chromium and nickel-tungsten binary alloy ingots for later use. See figure 1 for a process curve.

The decarburization and degassing principle of the invention is as follows:

the decarburization and the deoxidation in the refining period are both metal oxides reduced by carbon at high temperature, so that a Boolean reaction occurs, and the process can be represented by the following reaction formula:

(1)

(2)

(3)

namely two steps of CO reduction MeO and gasification of carbon.

The principle of the condensation degassing is as follows, in which a gas is dissolved in the metal in atomic state alone in the solubility range, and the standard free energy of dissolution of the gas in the metal (in the case of oxygen) can be represented by the following formula:

${\mathrm{\&Delta;<figure-callout\; id="0"\; label="G\; T"\; filenames="A0313353300061.png"\; state="\{\{state\}\}">G</figure-callout>}}_T^{}={\mathrm{\&Delta;H}}_{298}^0-\mathrm{T\&Delta;}{S}_{298}^0=A+\mathrm{BT}---\left(4\right)$

namely:

${\mathrm{<figure-callout\; id="0"\; label="log\; C"\; filenames="A0313353300061.png"\; state="\{\{state\}\}">log</figure-callout>}C}_0=\frac{1}{2}{\log P}_{O_2}-\frac{A^{\&prime;}}{T}-B^{\&prime;}---\left(5\right)$

in the formula:

$A^{\&prime;}=\frac{A}{2.303R}=\frac{{\mathrm{\&Delta;H}}_{298}^0}{2.303R}$

$B^{\&prime;}=\frac{B}{2.303R}=\frac{-\mathrm{\&Delta;}{S}_{298}^0}{2.303R}$

as can be seen from equation (5), the concentration of oxygen dissolved in the alloy is determined by the partial pressure of oxygen within the system, and thus reducing the system pressure (i.e., drawing a vacuum) reduces the solubility of oxygen in the alloy. In addition, since the dissolution process of oxygen in the alloy is an endothermic reaction, the temperature decrease may also decrease the solubility of oxygen in the alloy. Similarly, lowering the system pressure and temperature reduces the solubility of other gases such as nitrogen in the alloy. In the process of the invention, the alloy temperature is continuously reduced and the system pressure is also continuously reduced in the condensation process, so that the gas content is continuously reduced, and the purpose of degassing is achieved.

The gas content of the raw materials treated by the above method was significantly reduced, and table 1 shows the gas content comparison before and after the treatment of several raw materials.

TABLE 1 comparison of gas content before and after treatment of several raw materials

	Ni		Ni-Cr		Co		Ni-W
									O(ppm)	N(ppm)	O(ppm)	N(ppm)	O(ppm)	N(ppm)	O(ppm)	N(ppm)
	Before treatment	42	1	328	1199	80	10	28									5
After treatment									7	1	77	74	10	1	12	2

The raw materials can be used for smelting Ni75-Co5-W6-Cr6-A16-Ti2 experimental nickel-based high-temperature alloy adopted in the embodiment after degassing treatment, and the specific smelting process is as follows:

taking 63% of degassed nickel, 5% of cobalt, 12% of nickel-tungsten and 12% of aluminum and 2% of titanium according to alloy components, adding the mixture into the mixture, heating to 1500 ℃, refining for 20 minutes at low temperature, cutting off power, condensing thoroughly, heating to 1550 ℃, and pouring to obtain the nickel-based high-temperature alloy with low carbon content and low gas content. See figure 1 for a process curve. Table 2 shows the comparison of the gas and carbon contents of the alloy of this example when the process of the present invention is used for smelting with the conventional process.

TABLE 2 comparison of the results of the inventive process with the conventional process

	C(ppm)	O(ppm)	N(ppm)
				The invention	25	4	3
Conventional process	150	15	10

Therefore, the invention can realize the purpose of simultaneously reducing the carbon content and the gas content at low cost.

Claims (2)

1. An ultra-pure smelting method of nickel-based superalloy is characterized by comprising the following steps: 1) degassing treatment: cleaning high-temperature alloy elements, heating to 1600-1650 ℃, refining for 15-20 minutes at high temperature, cutting off power, condensing thoroughly, heating to 1490-1540 ℃, refining for 20-30 minutes at low temperature, heating to 1500-1550 ℃ after the low-temperature refining is finished, and casting into ingots for later use;

2) the nickel-based high-temperature alloy is smelted by adopting the elements subjected to degassing treatment as raw materials: and after clearing, heating to 1490-1540 ℃, refining for 15-20 minutes at low temperature, cutting off power, condensing thoroughly, heating to 1500-1550 ℃, and pouring to obtain the nickel-based high-temperature alloy with low carbon content and low gas content.

2. The method according to claim 1, characterized by comprising: wherein: respectively adding 0.01-0.02% of carbon into the elemental nickel and cobalt alloy elements during degassing treatment; and respectively adding 40-60% of nickel into the elemental chromium and tungsten alloy elements during degassing treatment.

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