Preparation method of ultrafine carbon-iron alloy material

Abstract

A preparation method of ultra-micro carbon iron alloy material, high-carbon iron alloy blocks are pulverized, sprayed into a suspension roasting furnace in an oxygen-rich environment for spontaneous heating partial oxidation, the partially oxidized powder is cooled, and the carbon and oxygen element contents are detected, then the partially oxidized powder is mixed with un-oxidized high-carbon iron alloy powder according to the proportion, and the mixture is uniformly mixed, briquetted, and then put into a vacuum sintering furnace for deep decarburization and deoxidation, after the reaction is completed, the material in the furnace is cooled and discharged to obtain the ultra-micro carbon iron alloy material. The invention utilizes the combustible characteristics of elemental carbon and iron in high-carbon iron alloy material under certain conditions, accurately controls the decarburization and oxygenation conditions, and the material in the suspension state is not sintered, the decarburization is uniform without the need for secondary grinding, and no additional heat source is needed, thereby effectively reducing the production cost, improving the product quality, and producing the ultra-micro carbon iron alloy material after vacuum sintering.

Description

Technical Field

[0001] This invention relates to the field of metallurgical technology, and in particular to a method for preparing ultrafine carbon-iron alloy materials. Background Technology

[0002] High-carbon ferrochrome and high-carbon ferromanganese, as important ferroalloys, are widely used in the production of stainless steel and special steel. Ultrafine carbon ferroalloys, due to their unique low-carbon characteristics, have broad application value and an important strategic position in fields such as alloy optimization, cost reduction, material performance improvement, and powder metallurgy. The production of ultrafine carbon ferroalloys mainly involves vacuum solid-state decarburization. To reduce the carbon content in high-carbon ferroalloys, in addition to requiring a vacuum and high-temperature environment, it is also necessary to introduce an appropriate amount of oxygen. Traditionally, high-carbon ferroalloy powder is ground and then pre-oxidized by calcination in a rotary kiln. Because the calcined material becomes sintered lumps, it needs to be ground into powder again, and then unoxidized sintered high-carbon ferroalloy powder is added according to the carbon and oxygen ratio to ensure that carbon and oxygen combine and escape. This process has several drawbacks, such as the high energy consumption required for rotary kiln calcination, the high hardness of the sintered lumps, the difficulty of secondary grinding, and the complexity of the production equipment. To avoid the hassle of sintering, some production processes directly incorporate oxides. For example, patent CN1818105 grinds high-carbon ferrochrome into powder and then adds iron oxide or chromium oxide, while patent CN101260474 grinds high-carbon ferromanganese into powder and then adds iron oxide or manganese oxide before decarburizing in a vacuum sintering furnace. Both of these patents require the addition of additional oxidants. Adding iron oxide reduces the content of the main elements in the ferroalloy, affecting its value, while adding chromium oxide or manganese oxide is more expensive. Summary of the Invention

[0003] This invention provides a method for preparing ultrafine carbon-iron alloy materials to overcome the shortcomings of the prior art and solve the problem of the inconvenience of preparing traditional high-carbon ferrochrome and high-carbon ferromanganese powders.

[0004] In order to achieve the objectives of this invention, the following technologies are proposed:

[0005] A method for preparing ultrafine carbon-iron alloy materials includes the following steps:

[0006] Step 01: Crush and grind the high-carbon iron alloy block material;

[0007] Step 02: Preheat the suspension calcining furnace, introduce oxygen-enriched air, and turn off the heat source;

[0008] Step 03: High-carbon iron alloy powder is sprayed into the preheated suspension calcining furnace in step 02 for partial suspension self-combustion. After combustion, the powder is cooled and settled, and the carbon and oxygen content of the calcined powder is detected.

[0009] Step 04: According to the carbon and oxygen content in Step 03, add the high carbon iron alloy powder from Step 01 in the specified ratio, mix evenly, and press into shape.

[0010] Step 05: Place the shaped block material from Step 04 into a vacuum sintering furnace, evacuate the furnace, and raise the temperature to allow the carbon and oxygen elements in the material to combine into gas and be discharged. After maintaining the high temperature and vacuum state in the furnace for a certain period of time, cool down the furnace and remove the material to obtain ultrafine carbon-iron alloy material.

[0011] Furthermore, in step 01, the particle size of the high-carbon iron alloy after grinding is 10-50 μm.

[0012] Furthermore, in step 02, the preheating temperature of the suspension calcining furnace is 500-1000℃.

[0013] Furthermore, in step 02, the oxygen content of the oxygen-enriched air in the suspension calcining furnace is 30-90%, the temperature inside the calcining furnace is controlled at 500-1000℃, and the residence time of the powder is 3-30 seconds.

[0014] Furthermore, in step 03, the carbon:oxygen molar ratio in the calcined powder is controlled to be between 1:1.1 and 2.0.

[0015] Further, in step 04, the carbon:oxygen molar ratio in the mixture is 1:1.01 to 1.05.

[0016] Furthermore, in step 05, the vacuum degree inside the vacuum furnace is controlled to be 5-100 Pa, the temperature to be 1100-1600℃, and the holding time to be 1-12 hours.

[0017] Furthermore, in step 05, the carbon content in the ultrafine carbon-iron alloy material is ≤0.02%, and the oxygen content is ≤0.3%.

[0018] The advantages of the above technical solution are:

[0019] This invention utilizes the principle that elemental metals or carbon are easily combustible in powder form. By adjusting the powder particle size, the oxygen concentration in the combustion atmosphere, and the suspension residence time, carbon pre-oxidation is achieved. Compared with existing processes, no external heating source is required, saving the cost of calcination heat source. No oxides need to be added, which is beneficial to stabilizing the element ratio in the alloy and reducing the production cost of using high-priced oxides.

[0020] This invention utilizes suspension calcination technology to effectively avoid sintering of metal powder during combustion. After oxidation, the powder remains in a dispersed state, eliminating the need for secondary grinding as required by traditional rotary kiln sintering processes, thus reducing the process flow and operating costs. Detailed Implementation

[0021] Example 1

[0022] High-carbon ferrochrome (C=7.11%) is crushed and ground into powder with a particle size of 30-50 μm (90% content). A suspension roasting furnace with dimensions of φ400*5000mm is preheated to an internal temperature of 750℃, and oxygen is introduced to maintain an oxygen concentration of 40-45%. 100 kg of high-carbon ferrochrome powder is uniformly blown into the suspension roasting furnace from the bottom using oxygen-enriched air with an oxygen concentration of 40-45%. As the oxygen-enriched air moves upwards, the high-carbon ferrochrome powder undergoes spontaneous combustion, releasing heat. Simultaneously, the heat source of the suspension roasting furnace is turned off. The furnace temperature is maintained at 800-850℃ through the oxygen-enriched environment and the heat released from the spontaneous combustion of the high-carbon ferrochrome powder. After oxidation, the high-carbon ferrochrome powder leaves the suspension roasting furnace, and after cooling, 97.5 kg of oxidized powder is collected. The carbon content is measured to be 1.21%, and the oxygen content to be 2.42%. The oxide powder was mixed with 8.13 kg of high-carbon ferrochrome powder and pressed into φ30*20 mm blocks. After being kept in a vacuum of 10 Pa and a temperature of 1520 °C for 10 hours, the blocks were cooled to 100 °C and the furnace was removed to obtain ultrafine carbon ferrochrome alloy material. The carbon content was tested to be 0.0103% and the oxygen content was 0.1536%.

[0023] Example 2

[0024] High-carbon ferrochrome (C=7.11%) is crushed and ground to a particle size of 10-30μm (90% particle size). A suspension roasting furnace (φ400*5000mm) is preheated to 880℃, and oxygen is introduced to maintain an oxygen concentration of 35-38%. 100kg of high-carbon ferrochrome powder is uniformly blown into the suspension roasting furnace from the bottom using oxygen-enriched air (35-38% oxygen concentration). As the oxygen-enriched air moves upwards, the high-carbon ferrochrome powder undergoes spontaneous combustion, releasing heat. Simultaneously, the heat source of the suspension roasting furnace is turned off. The furnace temperature is maintained at 880-900℃ through the oxygen-enriched environment and the heat released from the spontaneous combustion of the high-carbon ferrochrome powder. After oxidation, 99.2kg of oxidized powder is collected from the suspension roasting furnace after cooling. The carbon content is measured to be 1.35%, and the oxygen content to be 3.07%. The oxide powder was mixed with 13.03 kg of high-carbon ferrochrome powder and pressed into φ30*20 mm blocks. After being kept in a vacuum of 50 Pa and a temperature of 1550 °C for 10 hours, the blocks were cooled to 100 °C and the furnace was dismantled to obtain ultrafine carbon ferrochrome alloy material. The carbon content was tested to be 0.0171% and the oxygen content was 0.1227%.

[0025] Example 3

[0026] High-carbon ferromanganese (C=7.54%) was crushed and ground to a particle size of 10-20 μm (95% purity). A suspension roasting furnace (φ400*5000mm) was preheated to 770℃, and oxygen was introduced to maintain an oxygen concentration of 60-65%. 100 kg of high-carbon ferromanganese powder was uniformly blown into the furnace from below using oxygen-enriched air (60-65% oxygen concentration). As the oxygen-enriched air flowed upwards, the powder spontaneously combusted, releasing heat. Simultaneously, the furnace heat source was shut off. The furnace temperature was maintained at 820-850℃ through the oxygen-enriched environment and the heat released from the spontaneous combustion of the powder. After oxidation, 96.5 kg of oxidized powder was collected from the furnace, after cooling. The carbon content was determined to be 1.89%, and the oxygen content 3.78%. The oxide powder was mixed with 11.74 kg of high-carbon ferromanganese powder and pressed into φ30*20 mm blocks. After being kept in a vacuum of 15 Pa and a temperature of 1500 °C for 15 hours, the blocks were cooled to 130 °C and the furnace was dismantled to obtain ultrafine carbon ferromanganese alloy material. The carbon content was tested to be 0.0093% and the oxygen content was 0.2587%.

[0027] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Obviously, those skilled in the art can make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention also intends to include these modifications and variations.

Claims

1. A method for preparing an ultrafine carbon-iron alloy material, characterized in that, Including the following steps: Step 01: Crush and grind the high-carbon iron alloy block material; Step 02: Preheat the suspension calcining furnace, introduce oxygen-enriched air, and turn off the heat source; The oxygen content of the oxygen-enriched air in the suspension calcining furnace is 30-90%, the temperature inside the calcining furnace is controlled at 500-1000℃, and the residence time of the powder is 3-30 seconds. Step 03: High-carbon iron alloy powder is sprayed into the preheated suspension calcining furnace in step 02 for partial suspension self-combustion. After combustion, the powder is cooled and settled, and the carbon and oxygen content of the calcined powder is detected. The carbon:oxygen molar ratio in the calcined powder should be controlled to be 1:1.1-2.0; Step 04: According to the carbon and oxygen content in Step 03, add the high carbon iron alloy powder from Step 01 in the specified ratio, mix evenly, and press into shape. The carbon:oxygen molar ratio in the mixture is 1:1.01-1.05; Step 05: Place the shaped block material from Step 04 into a vacuum sintering furnace, evacuate the furnace, and raise the temperature to allow the carbon and oxygen elements in the material to combine into gas and be discharged. After maintaining the high temperature and vacuum state in the furnace for a certain period of time, cool down the furnace and remove the material to obtain ultrafine carbon-iron alloy material.

2. The method for preparing ultrafine carbon-iron alloy materials according to claim 1, characterized in that, In step 01, the particle size of the high-carbon iron alloy block after grinding is 10-50 μm.

3. The method for preparing ultrafine carbon-iron alloy materials according to claim 1, characterized in that, In step 02, the preheating temperature of the suspension calcination furnace is 500-1000℃.

4. The method for preparing ultrafine carbon-iron alloy materials according to claim 1, characterized in that, In step 05, the vacuum level inside the vacuum furnace is controlled at 5-100 Pa, the temperature at 1100-1600℃, and the holding time at 1-12 hours.

5. The method for preparing ultrafine carbon-iron alloy materials according to claim 1, characterized in that, In step 05, the carbon content in the ultrafine carbon-iron alloy material is ≤0.02%, and the oxygen content is ≤0.3%.