Method for forging high-carbon stainless steel at low temperature through GFM radial forging machine

Abstract

The invention relates to a method for forging high-carbon stainless steel at low temperature, which overcomes the technical bottleneck by adopting a method of combining a large forging ratio, low-temperature forging and solution treatment. And the produced product has the characteristics of stable gas element content, pure and uniform internal structure, narrow chemical component range and high mechanical property consistency, and meets the market requirements.

Description

Technical Field

[0001] The present invention relates to the field of pressure processing, and particularly to a method for low-temperature forging of high-carbon stainless steel by a GFM radial forging machine. Background Art

[0002] High-carbon stainless steel forgings are mainly applicable to special fields of corrosion resistance and high temperature resistance. The production technology of this material is difficult and the process is complex.

[0003] The present invention provides a method for low-temperature forging by a radial forging machine to meet the market demand.

[0004] Since the requirements for internal gas and inclusions in this material are stringent, an electroslag process is considered. An atmosphere-protected electroslag furnace is used for production, with an ingot starter plate and arc starter chips of the same steel grade; the environmental humidity is <40°, and the oxygen content in the mold is <10%. The slag material is a mixed slag, the baking temperature of the slag material is ≥600°C, and the baking time is ≥4h to prevent gas in the auxiliary materials from entering the steel during melting.

[0005] Based on large-forging-ratio forged billets as the basic raw materials and the radial forging low-temperature forging process as the core technology, a production process is adopted. To achieve good internal structure and ensure that all technical indicators reach the expected goals, a two-heating and two-forging process is used. The first is high-temperature heating, followed by large-forging-ratio forging of the intermediate billet. The second is low-temperature heating and high-frequency forging, and finally a rapid solution process is adopted to achieve a uniform structure. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for low-temperature forging of high-carbon stainless steel by a GFM radial forging machine in view of the above problems.

[0007] The object of the present invention is achieved in the following way: A method for low-temperature forging high-carbon stainless steel by a GFM radial forging machine, comprising the following steps: Step 1: Electric furnace smelting of ingots: Ensure that the molten steel is completely melted, the smelting temperature is 1500°C - 1600°C, and the smelted ingot is used as the electrode blank for electroslag remelting; Step 2: Atmosphere-protected electroslag remelting: The electrode blank is processed by an atmosphere-protected electroslag furnace to obtain an electroslag ingot. The same steel-grade dummy bar and arc-starting chips are used. During the power-on stage, an arc is ignited to establish a molten slag pool. After the slag pool is formed, the electrode blank starts to melt and finally solidifies into an electroslag ingot. The environmental humidity < 40°, the oxygen content in the mold < 10%, a mixed slag is used, the slag material baking temperature is 600°C - 650°C, and the baking time is 4 - 5h; Step 3: Homogenization treatment: The temperature of high-temperature homogenization treatment is 1220 - 1240°C; Step 4: Large forging ratio blooming: Upsetting and drawing forging is adopted. The large forging ratio heating is divided into the first heating and the second heating. The first heating: First heat to 600 ± 10°C, hold for 3 - 4h, then increase the temperature at a heating rate of ≤ 100°C / h to 800 ± 10°C, hold for 5 - 6h, and then heat to 1230 - 1250°C, hold for 8 - 10h; The second heating: Heat to 1230 - 1250°C, hold for 3 - 5h; After forging, the cross-sectional area composite forging ratio from the electroslag ingot to the forged round steel reaches 5 - 10, and the forged blank specification is Φ360 ± 10mm; Step 5: Low-temperature forging into finished products by a radial forging machine: The Φ360 ± 10mm intermediate blank forged in Step 4 is subjected to low-temperature forging by a radial forging machine, and the temperature is increased to 1040 ± 10°C at a heating rate of ≤ 100°C / h, hold for 6 - 8h. The low-temperature forging adopts 3 - 5 passes, and the reduction per pass is 50 ± 5mm; Step 6: Solution treatment: The temperature is 1050 ± 10°C.

[0008] Specifically, for the solution treatment in Step 6, for the intermediate blank with a specification of φ195mm after low-temperature forging, the holding time is 90 - 100min, and the water cooling time after solution treatment is 30 - 40min; for the intermediate blank with a specification of φ150mm after low-temperature forging, the holding time is 60 - 70min, and the water cooling time after solution treatment is 20 - 30min.

[0009] The beneficial effects of the present invention are: After adopting the above scheme, the material has the advantages of stable gas element content, pure and uniform internal structure, narrow chemical composition range, high consistency of mechanical properties such as tensile and impact, and excellent shape, meeting the market demand. Brief Description of the Drawings

[0010] The present invention will be further described below with reference to the drawings.

[0011] Figure 1 It is the first heating curve graph of the ingot heating in the large forging ratio heating curve of the present invention.

[0012] Figure 2It is the second heating curve graph of the ingot heating in the large forging ratio heating curve of the present invention.

[0013] Figure 3 It is the heating temperature curve graph of the radial forging at low temperature of the present invention. Specific embodiments

[0014] A method for low-temperature forging of high-carbon stainless steel by a GFM radial forging machine includes the following steps: Step 1: Electric furnace smelting of ingots: Ensure that the molten steel is completely melted and has good fluidity. The smelting temperature is 1500°C - 1600°C, serving as the electrode blank for electroslag remelting. The C content of the molten steel is 0.04 - 0.06%, and the remaining components meet the composition of 300 series stainless steel. Step 2: Atmosphere-protected electroslag remelting: The electrode blank is used to produce an electroslag ingot by an atmosphere-protected electroslag furnace. The same steel type ingot starter plate and arc ignition chips are used. During the power supply stage, the arc is ignited, and then a molten slag pool is established. After the slag pool is formed, the electrode blank starts to melt and finally solidifies into an electroslag ingot. The environmental humidity < 40°, the oxygen content in the mold < 10%. A mixed slag is used, that is, a combination of CaF2 + CaO is used. The slag material baking temperature is 600°C - 650°C, and the baking time is 4 - 5h. Step 3: Homogenization treatment: Through high-temperature homogenization treatment at 1220 - 1240°C, the as-cast segregation can be diffusively eliminated to achieve the purpose of refining the structure. Step 4: Large forging ratio blooming: Upsetting and drawing forging are adopted. The large forging ratio heating is divided into the first heating and the second heating. The first heating: First, heat to 600 ± 10°C and hold for 3 - 4h, then increase the temperature at a heating rate of ≤ 100°C / h to 800 ± 10°C and hold for 5 - 6h, then heat to 1230 - 1250°C and hold for 8 - 10h. The second heating: Heat to 1230 - 1250°C and hold for 3 - 5h. After forging, the cross-sectional area composite forging ratio from the electroslag ingot to the forged round steel should reach 5 - 10, and the forging blank specification is Φ360 ± 10mm. Step 5: Radial forging machine low-temperature forging into finished products: The forged Φ360 ± 10mm intermediate blank in Step 4 is subjected to low-temperature forging by a radial forging machine, and the temperature is increased to 1040 ± 10°C at a heating rate of ≤ 100°C / h and held for 6 - 8h. The forging adopts 3 - 5 passes, and the reduction per pass is 50 ± 5mm. Step 6: Solution treatment: The temperature is 1050 ± 10°C. For φ195mm, hold for 90 - 100min, and the water cooling time is 30 - 40min; for φ150mm, hold for 60 - 70min, and the water cooling time is 20 - 30min. Examples

[0015] 1. Process route: Electric furnace smelting of electrode blank → Atmosphere-protected electroslag remelting → Homogenization treatment → Large forging ratio blooming → Radial forging machine low-temperature forging into finished products.

[0016] 2. Process plan: 2.1 Electroslag remelting process: Produced by an atmosphere-protected electroslag furnace, using an ingot starter plate and arc-striking chips of the same steel grade; ambient humidity < 40°, oxygen content in the mold < 10%; using a mixed slag, the slag material baking temperature is 600 - 650°C, and the baking time is 4 - 5h. 2.2 Forging method: 2.2.1 The large forging ratio heating curve is shown in Figure 2 , upsetting and drawing forging is adopted, and the forging ratio should be not less than 5; the forged blank specification is Φ360mm. 2.2.2 Rotary forging low-temperature forging process: The heating temperature is shown in Figure 3 . The rotary forging low-temperature forging process is shown in Table 1.

[0017]

[0018] Solution treatment process: Temperature 1050°C, hold for 90 min at φ195mm and water-cool for 30 min; hold for 60 min at φ150mm and water-cool for 20 min.

[0019] The above are only specific embodiments of the present invention, but the structural features within the protection scope of the present invention are not limited thereto. Any changes or modifications made by those skilled in the art within the field of the present invention are covered by the patent scope of the present invention.

Claims

1. A method for low temperature forging of high carbon stainless steel by a GFM radial forging machine, characterized in that: The following steps are involved: Step 1: Smelting steel ingots in an electric furnace: Ensure that the molten steel is completely melted, the smelting temperature is 1500℃~1600℃, and the smelted steel ingots are used as electrode blanks for electroslag remelting; Step 2: Atmosphere protection electroslag remelting: The electrode blank is produced by an atmosphere protection electroslag furnace to obtain an electroslag ingot. The same steel grade ingot starter plate and arc starting scraps are used. The arc is ignited in the power supply stage to establish a molten slag pool. After the slag pool is formed, the electrode blank begins to melt and finally solidifies into an electroslag ingot. The ambient humidity is less than 40°, the oxygen content in the crystallizer is less than 10%, and mixed slag is used. The slag baking temperature is 600℃-650℃ and the baking time is 4-5h. Step 3: Homogenization: high temperature homogenization at 1220-1240°C; Step 4: Large forging ratio blanking: using upsetting forging, large forging ratio heating is divided into first fire heating and second fire heating, first fire heating: first heating to 600±10℃, keep warm for 3-4h, then heating to 800±10℃ at a heating rate of ≤100℃ / h, keep warm for 5-6h, then heating to 1230-1250℃, keep warm for 8-10h; second fire heating: heating to 1230-1250℃, keep warm for 3-5h; after forging, the composite forging ratio from electroslag ingot to forged round steel cross-sectional area reaches 5-10, and the forged blank specification is Φ360±10mm; Step 5: Low temperature forging of materials by radial forging machine: The Φ360±10mm intermediate billet forged in step 4 is forged by radial forging machine at low temperature, heated to 1040±10℃ at a heating rate of ≤100℃ / h, kept warm for 6-8h, and low temperature forging is performed for 3-5 times, with a reduction of 50±5mm for each time; Step 6: Solution treatment: temperature is 1050±10℃.

2. The method for low temperature forging of high carbon stainless steel by a GFM radial forging machine according to claim 1, characterized in that: The specific solution treatment process in step six is ​​as follows: the holding time of the intermediate billet with a specification of φ195mm after low-temperature forging is 90-100min, and the water cooling time after solution treatment is 30-40min; the holding time of the intermediate billet with a specification of φ150mm after low-temperature forging is 60-70min, and the water cooling time after solution treatment is 20-30min.

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