Method for producing G20CrNi2MoA by adopting simple argon shield electroslag device

Abstract

The invention discloses a method for producing G20CrN i2MoA by adopting a simple argon-shielded electroslag device, which is characterized in that the simple argon-shielded electroslag device is added on the basis of a common electroslag furnace: after two semicircular protective cover upper covers (3) are closed, two semicircular aluminum silicate fibrous sealing plates (2) placed in the protective cover upper covers (3) are also closed at the same time; and the aluminum silicate fiber sealing plate pressing plate (1) is placed on the protective cover upper cover (3) to prevent gas leakage in the remelting process, and the simple argon protection electroslag device enables a common electroslag furnace to be rapidly converted into a protective atmosphere electroslag furnace. A corresponding electroslag remelting process is designed, the melting speed is set to be 6.5 kg / min to 7.5 kg / min, the current range is 7000 A to 15000 A, the voltage range is 50 V to 70 V, a binary pre-melting slag system CaF2: A < l > 2O3 = 70%: 30% is selected, the slag amount is 110 kg to 130 kg, and the electroslag melting speed is constant. The device has the advantages of being simple in structure, easy to construct and easy and convenient to operate; the equipment material manufacturing cost is low; and the product cost is greatly reduced.

Description

Technical Field

[0001] The invention belongs to the field of metal material metallurgy and relates to a method for producing G20CrNi2MoA by adopting a simple argon gas protection electroslag device. The finished product has a G20CrNi2MoA product for railway freight car bearing rings that meets oxygen content index requirements; the specifications are mainly Φ610mm electroslag ingots and Φ80mm-Φ130mm finished steel products. Background Art

[0002] China Railway Corporation Standard Q / CR593-2017 "Carburized Bearing Steel for Railway Freight Car Bearings" clearly requires that the oxygen content of carburized bearing steel G20CrNi2MoA used for railway freight car bearing rings should not exceed 20×10 -6 , due to the high oxygen content in the steel, it can significantly reduce the fatigue life of the bearing. Therefore, the oxygen content level has always been the core indicator for measuring the quality of G20CrNi2MoA products. In addition, due to the carbon-oxygen balance, the carbon content of carburized bearing steel is low, and it is very easy to increase oxygen during the smelting process, which is difficult to control; therefore, it is necessary to take certain measures during the smelting process to reduce the process oxygen increase and ensure that the product quality meets the relevant standards and usage requirements. Since electroslag steel products are significantly superior to vacuum degassed steel in terms of purity, carbide control, and organization, electroslag steel products are currently widely used in domestic railway freight car bearing rings. However, the electroslag remelting process is very easy to increase oxygen, causing the oxygen content of the finished product to exceed the standard. Domestic steel mills mostly introduce imported protective atmosphere electroslag furnaces from abroad to reduce process oxygen increase. However, imported protective atmosphere electroslag furnaces are usually very expensive, complex in structure, difficult to build, low in production efficiency, and impose technical blockades on domestic enterprises. Summary of the invention

[0003] The invention discloses a method for producing G20CrNi2MoA by adopting a simple argon protection electroslag device. On the basis of a common electroslag furnace, a simple argon protection electroslag device is added, and a corresponding electroslag remelting process is designed to achieve the same argon protection effect as that of an imported protective atmosphere electroslag furnace and reduce process oxygen increase.

[0004] The present invention adopts the following technical solution:

[0005] 1. The process flow is electric furnace + LF refining + VD vacuum degassing + die casting electrode rod + electroslag remelting + blanking + rolling + softening annealing + rough polishing.

[0006] 2. The chemical composition of G20CrNi2MoA is shown in Table 1.

[0007] Table 1

[0008]

[0009]

[0010] 3. If Figure 1 As shown, the protective cover body 5 of the simple argon protection electroslag device is placed on the upper part of the crystallizer, a slag feeding port 7 is set, a cooling water pipe 6 and an argon pipe 4 are connected, an aluminum silicate fiber sealing plate 2 is placed in the protective cover upper cover 3, and an aluminum silicate fiber sealing plate pressing plate 1 is placed on the protective cover upper cover 3; specifically, Figure 2 As shown, after the two semicircular protective cover upper covers 3 are closed, the two semicircular aluminum silicate fiber sealing plates 2 placed inside the protective cover upper covers 3 are also closed at the same time, and then the aluminum silicate fiber sealing plate pressing plate 1 is placed on the protective cover upper covers 3 to prevent leakage during the remelting process. The simple argon gas protection electroslag device allows the ordinary electroslag furnace to be quickly transformed into a protective atmosphere electroslag furnace. When in use, the simple argon gas protection electroslag device is fixed to the upper position of the crystallizer with bolts. After the electrode rod is placed in the crystallizer, the anti-leakage sealing plate in the protective cover upper cover 3 is attached to the electrode rod, and then argon gas and cooling water can be introduced for electroslag remelting.

[0011] The Φ470mm electrode is tumbled until there is no oxide scale on the surface. After the electroslag device is ready, argon is filled into the Φ610mm crystallizer for 15min to 25min. When the oxygen content in the crystallizer is not more than 6%, the Φ470mm electrode is used to start arc slag making. During the slag making process, argon is continuously filled into the crystallizer. The argon flow rate in the argon protective cover body 5 is 90L / min to 110L / min, and the argon flow rate in the protective cover upper cover 3 is 15L / min to 25L / min. After the slag making is completed, it is transferred to normal remelting. The oxygen content in the crystallizer is monitored to be not more than 200×10 -6 , after filling and cooling.

[0012] 4. A simple argon-protected electroslag furnace production process is adopted, the melting rate is set at 6.5kg / min~7.5kg / min, the current range is 7000A~15000A, the voltage range is 50V~70V, the binary pre-melted slag system CaF2:Al2O3=70%:30% is selected, the slag amount is 110kg~130kg, and the electroslag melting rate is constant.

[0013] 5. The rolling process is heated by a soaking furnace, the blanks are cut by a reciprocating rolling mill, and the finished products are rolled by a continuous rolling mill.

[0014] 6. Use a box-type annealing furnace for soft annealing, and the annealing temperature is 690℃~710℃.

[0015] 7. After annealing, the steel surface is roughly polished.

[0016] The invention points of the present invention:

[0017] (1) The sealing ring of the simple argon gas protection electroslag device is made of aluminum silicate fiberboard, which has certain strength and wear resistance, good sealing effect, and the material is easy to cut, easy to shape, and easy to operate. The simple argon gas protection electroslag device is equipped with an oxygen content meter to monitor the oxygen content in the crystallizer and the protective cover at all times. When the concentration is greater than 200×10 -6 The alarm is activated to remind the operator to control the seal to prevent oxygen from increasing during the electroslag remelting process.

[0018] (2) Based on the simple argon-shielded electroslag furnace device, the corresponding G20CrNi2MoA electroslag remelting process is innovatively proposed. The oxygen concentration in the crystallizer before the electroslag arc is standardized, and argon is required to be filled into the crystallizer before the arc is started. When the oxygen content in the crystallizer is not more than 6%, power is allowed. A simple argon-shielded electroslag furnace production process is adopted, the melting rate is set to 6.5kg / min~7.5kg / min, the current range is 7000A~15000A, the voltage range is 50V~70V, and the binary pre-melted slag system CaF2:Al2O3=70%:30% is selected, the slag amount is 110kg~130kg, and the electroslag melting rate is constant.

[0019] Advantages of the present invention:

[0020] The equipment has a simple structure, short production cycle, is easy to build, and occupies a small area. It can complete the upgrade and transformation of the electric slag furnace in the shortest time and improve the quality of G20CrNi2MoA electric slag steel products in time. It is easy to operate and operators can be trained and have operating capabilities in a short time.

[0021] The equipment material cost is low, the equipment can be assembled or disassembled, and can be reused on different electroslag furnaces of the same type; the accessories are easy to install and purchase, and can be replaced in time if they are found to be damaged, without affecting the production of G20CrNi2MoA; it can achieve the same air isolation function as the imported protective atmosphere electroslag furnace, greatly reducing the production cost of G20CrNi2MoA. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the overall appearance of a simple argon gas protected electroslag device;

[0023] Figure 2 It is a simple argon gas protection electroslag device protective cover upper cover and aluminum silicate fiber sealing plate;

[0024] Icon description: aluminum silicate fiber sealing plate pressure plate 1, aluminum silicate fiber sealing plate 2, protective cover upper cover 3, argon gas pipe 4, protective cover body 5, cooling water pipe 6, slag adding port 7. DETAILED DESCRIPTION

[0025] The present invention is further described in detail below by way of examples.

[0026] Embodiment 1, embodiment 2, embodiment 3 implement the process together:

[0027] 1. Electric furnace + LF refining + VD vacuum degassing + die casting electrode rod + electroslag remelting + 850 rolling mill billet + 750 rolling mill finished product + softening annealing + rough polishing.

[0028] 2. The tapping temperature of the electric furnace shall not be lower than 1600℃, and the tapping oxygen shall not be greater than 650×10 -6 , adopt the slag removal process; LF white slag time is not less than 20min; VD vacuum is maintained for 15min~20min, and the soft blowing time is 30min~60min; when pouring Φ470mm electrode, the electrode mold is filled with argon in advance to control the pouring speed.

[0029] 4. A simple argon-protected electroslag furnace production process is adopted, the melting rate is set at 6.5kg / min~7.5kg / min, the current range is 7000A~15000A, the voltage range is 50V~70V, the binary pre-melted slag system CaF2:Al2O3=70%:30% is selected, the slag amount is 110kg~130kg, and the electroslag melting rate is constant.

[0030] 5. Use a soaking furnace for heating, with a heating temperature of 1260℃~1280℃; use the 850 rolling mill for billet production and the 750 rolling mill for finished products.

[0031] 6. Use a box-type annealing furnace for soft annealing, and the annealing temperature is 690℃~710℃.

[0032] 7. Roughly polish the steel surface.

[0033] Example 1

[0034] The rough polished product specification is Φ120mm.

[0035] 3. Use a simple argon gas protection electroslag device, Φ470mm electrode rolling treatment until the surface is free of oxide scale, after the electroslag preparation is completed, fill argon gas into the Φ610mm crystallizer for 15 minutes, when the oxygen content in the crystallizer is not more than 6%, use the Φ470mm electrode to start arc slag making, and continue to remelt argon gas into the crystallizer during the slag making process, where the argon gas flow rate in the argon shield is 90L / min, and the argon gas flow rate in the upper cover 3 of the shield is 15L / min. After the slag making is completed, it will be turned to normal remelting, and the oxygen content in the crystallizer should be monitored to be no more than 200×10 -6 , after filling and cooling.

[0036] 4. Oxygen content control effect: A total of 12 oxygen content samples were calibrated for the finished product, and the oxygen content results were (9-11)×10 -6 , meet the requirements of Q / CR593-2017 "Carburized bearing steel for railway freight car bearings" with an oxygen content of no more than 20×10 -6 requirements.

[0037] Example 2

[0038] Roughly polished product specification: Φ95mm.

[0039] 3. The Φ470mm electrode is tumbled until the surface is free of oxide scale. After the electroslag preparation is completed, argon is filled into the Φ610mm crystallizer for 20 minutes. When the oxygen content in the crystallizer is not more than 6%, the Φ470mm electrode is used to start arc slag making. During the slag making process, argon is continuously remelted into the crystallizer. The argon flow rate in the argon shield is 100L / min, and the argon flow rate in the protective cover 3 is 20L / min. After the slag making is completed, it is turned to normal remelting. The oxygen content in the crystallizer is monitored to be not more than 200×10 -6 , after filling and cooling.

[0040] 4. Oxygen content control effect: A total of 12 oxygen content samples were calibrated for the finished product, and the oxygen content results were (9-12)×10 -6 , meet the requirements of Q / CR593-2017 "Carburized bearing steel for railway freight car bearings" with an oxygen content of no more than 20×10 -6 requirements.

[0041] Example 3

[0042] The rough polished product specification is Φ90mm.

[0043] 3. The Φ470mm electrode is tumbled until the surface is free of oxide scale. After the electroslag preparation is completed, argon is filled into the Φ610mm crystallizer for 25 minutes. When the oxygen content in the crystallizer is not more than 6%, the Φ470mm electrode is used to start arc slag making. During the slag making process, argon is continuously remelted into the crystallizer. The argon flow rate in the argon shield is 110L / min, and the argon flow rate in the protective cover 3 is 25L / min. After the slag making is completed, it is turned to normal remelting. The oxygen content in the crystallizer is monitored to be not more than 200×10 -6 , after filling and cooling.

[0044] 4. Oxygen content control effect: A total of 12 oxygen content samples were calibrated for the finished product, and the oxygen content results were (8-11)×10 -6 , meet the requirements of Q / CR593-2017 "Carburized bearing steel for railway freight car bearings" with an oxygen content of no more than 20×10 -6 requirements.

Claims

1. A simple argon gas protected electroslag device, characterized in that: The protective cover body ⑸ of the simple argon gas protection electroslag device is placed on the upper part of the crystallizer, a slag adding port ⑺ is set on the protective cover body ⑸, and the cooling water pipe ⑹ and the argon gas pipe ⑷ are connected. The aluminum silicate fiber sealing plate ⑵ is placed in the protective cover upper cover ⑶, and the aluminum silicate fiber sealing plate pressure plate ⑴ is placed on the protective cover upper cover ⑶; the simple argon gas protection electroslag device is fixed to the upper position of the crystallizer with bolts.

2. According to claim 1, a simple argon gas protection electroslag device is characterized in that: The specific assembly is to close the two semicircular protective cover upper covers ⑶, and then close the two semicircular aluminum silicate fiber sealing plates ⑵ placed inside the protective cover upper covers ⑶ at the same time, and then place the aluminum silicate fiber sealing plate pressure plate ⑴ on the protective cover upper covers ⑶ to prevent air leakage during the remelting process.

3. A method for producing G20CrNi2MoA using a simple argon gas protected electroslag device according to claim 1 or 2, characterized in that: The melting rate is set to 6.5kg / min~7.5kg / min, the current range is 7000A~15000A, the voltage range is 50V~70V, the binary pre-melted slag system CaF2:Al 2O3=70%:30% is selected, the slag amount is 110kg~130kg, and the electroslag melting rate is constant.

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