A method of forging a die steel for continuous casting billet without upsetting

Abstract

The present application relates to a kind of forging method of continuous casting billet not rough production die steel, which can solve the problem of insufficient control of reducing carbon dioxide emission in conventional production die steel forging method, first control the deformation amount of oil press to make continuous casting billet into flat billet, then the flat billet is forged to the required size in two passes on the special upper and lower arc anvil, the shape of the intermediate billet is changed by the arc anvil, and then the core of the continuous casting billet is in a three-way compressive stress state, the compaction effect of the core of the continuous casting billet is increased, and at the same time, the pressure is maintained for a certain period of time after forging to the required size, to promote the welding of defects in the core of the continuous casting billet, and then meet the requirement of ultrasonic flaw detection.

Description

Technical Field

[0001] This invention belongs to the field of forging technology and relates to a forging method for producing die steel from continuously cast billets without upsetting, which can solve the problem of insufficient control of carbon dioxide emissions reduction in conventional methods for producing die steel forgings. Background Technology

[0002] When a continuously cast billet is pulled out of the crystallizer, it contains a liquid core. Within the continuous casting machine, it undergoes heat transfer, solidification, and forward movement, forming a long liquid cavity. Due to factors such as solidification and heat transfer, poor feeding of molten steel often occurs along the path of the liquid cavity. After the billet has completely solidified, defects such as porosity, shrinkage cavities, and microcracks are frequently found in certain areas along the axial direction of the billet, especially severe in large-diameter continuously cast billets with a diameter of Φ600mm or more. These defects are mainly addressed through the forging process. However, limited by the forging ratio, the production of die steel forgings using continuously cast billets typically employs a combination of upsetting and drawing processes, resulting in a long total forging time and hindering efforts to reduce carbon dioxide emissions. Summary of the Invention

[0003] The purpose of this invention is to address the problem that conventional methods for producing die steel forgings in the prior art are insufficient in controlling carbon dioxide emissions. This invention proposes a forging method for producing die steel from continuously cast billets without upsetting. Compared with conventional forging methods that use upsetting processes, this forging method can shorten production time by more than 5 hours and reduce carbon dioxide emissions.

[0004] The technical solution of this invention is implemented as follows: a forging method for producing die steel from continuously cast billets without upsetting, the forging steps are as follows: Step 1) Load the annealed continuous casting billet into the heating furnace. The heating furnace is heated at 600-750℃ for 4 hours, and then held at 1230℃±10℃ for 1.5 hours per 100mm section. Step 2) After heating and heat preservation of the billet, use a 3150-ton hydraulic press to draw the billet once on a 600mm upper and lower flat anvil, with a reduction of 20%-25%, and ensure at least 20% overlap between the anvils for every two anvils. Step 3) After flipping the billet from Step 2) by 90°, use a 3150-ton hydraulic press to draw it twice on a 600mm upper and lower special arc-shaped anvil to a certain size. The specific size is based on the finished product height, with a forging ratio of at least 1.5 to 2.0. The reduction in the first pass is controlled at 20 to 25%, and the reduction in the second pass is controlled at 35 to 40%. The anvil is fed in at full capacity, and at least 20% overlap is guaranteed between each two anvils. The billet is not flipped during the second drawing process. Step 4) Using a 3150-ton hydraulic press, the blank from Step 3) is stretched to the size after the second pressing in Step 2) using a 600mm upper flat anvil and a special arc-shaped anvil. Ensure that there is at least 20% overlap between the two anvils. Step 5) After flipping the billet from Step 4) by 90°, draw it on a 600mm upper and lower flat anvil to the same size as the second pressing in Step 2), ensuring at least 20% overlap between each two anvils; Step 6) After the billet from Step 5) is reheated in the furnace, it is stretched to the finished size using a 3150-ton hydraulic press on a 600mm upper and lower flat anvil.

[0005] In step 3), the reduction amount of the first and second passes is controlled at 20-25% and 35-40% respectively. The billet is not turned over during the second pass of drawing. The drawing height is based on the finished product height and reserves at least 1.5-2.0 forging ratio. The upper and lower special arc anvils satisfy the following relationships: the ratio of H1 / D is between 0.2 and 0.25, the ratio of H1 / H2 is between 0.8 and 1.1, and the ratio of H2 / H3 is between 0.2 and 0.25.

[0006] In steps 4) and 5), the pressure is maintained for 10 to 15 seconds after the billet is forged to the required size.

[0007] In step 6), the amount of reduction in the width direction during the blank rounding process shall not exceed 70mm.

[0008] The present invention has the following beneficial effects: 1. This invention discloses a forging method for producing die steel from continuously cast billets without upsetting. First, the deformation of the continuously cast billet is controlled by the hydraulic press to form a flat billet. Then, the flat billet is forged in two passes on a special upper and lower arc-shaped anvil to the required size. The shape of the intermediate billet is changed by the arc-shaped anvil, thereby putting the core of the continuously cast billet in a triaxial compressive stress state, increasing the compaction effect of the core of the continuously cast billet. At the same time, after forging to the required size, the pressure is maintained for a certain period of time to promote the welding of defects in the core of the continuously cast billet, thereby meeting the requirements of ultrasonic flaw detection.

[0009] 2. The technical solution of this invention shortens the process flow. By designing a special arc-shaped anvil to change the size of the precast billet to meet the requirements of ultrasonic testing, it reduces gas consumption and carbon dioxide emissions.

[0010] 3. The technical solution of this invention eliminates the upsetting process and shortens the process flow. By designing a special arc-shaped anvil to change the size of the precast billet, the defective part of the continuous casting billet core is placed in a triaxial compressive stress state during forging deformation, which promotes the forging of defects, meets the requirements of ultrasonic flaw detection, and ultimately reduces gas consumption and carbon dioxide emissions. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the continuously cast billet of the present invention.

[0012] Figure 2 This is a cross-sectional view of the upper arc-shaped anvil of the present invention.

[0013] Figure 3 This is a cross-sectional view of the lower arc-shaped anvil of the present invention.

[0014] Figure 4 This is a schematic diagram of the intermediate billet of the present invention. Detailed Implementation

[0015] The present invention will be further described and illustrated below with reference to specific embodiments.

[0016] Example 1: Steel grade: 50CrMnMo; Continuous casting billet: φ800mm; Die steel width and height: 1200mm×280mm. Production was carried out using a 3150-ton hydraulic press with a 30-ton operating mechanism, employing 600mm upper and lower flat anvils and 600mm upper and lower special arc anvils. The specific forging steps are as follows: Step 1) The annealed φ800mm continuous casting billet is loaded into the heating furnace. The heating furnace is heated at 600~750℃ for waiting for the material, then heated for 4 hours, and held at 1230℃±10℃ for 12 hours before being taken out of the furnace for forging. Step 2) After heating and heat preservation, the billet is drawn to a thickness of 600mm using a 3150-ton hydraulic press with upper and lower flat anvils of 600mm. At least 20% overlap between the two anvils is guaranteed. Step 3) After flipping the billet from Step 2) by 90°, use a 3150-ton hydraulic press to lengthen it on a special arc-shaped anvil with an upper and lower diameter of 600mm. Press it down to 750mm in the first pass and to 500mm in the second pass. Feed it into the anvil at full capacity, ensuring at least 20% overlap between the two anvils. Do not flip the billet during the second lengthening pass. Step 4) Using a 3150-ton hydraulic press, the arc portion of the billet from Step 3) is drawn to 500mm on an upper flat anvil and a lower special arc anvil. At least 20% overlap between the two anvils is ensured. After drawing to the desired size, the pressure is held for 10-15 seconds. Step 5) After flipping the billet from Step 4) 180°, use a 3150-ton hydraulic press on an upper flat anvil and a lower special arc-shaped anvil to stretch the arc part to 500mm. Ensure that there is at least 20% overlap between the two anvils. After stretching to the required size, hold the pressure for 10-15 seconds. Step 6) Return the billet from Step 5) to the furnace for heating at a furnace temperature of 1200±10℃. After holding at this temperature for 2-3 hours, use a 3150-ton hydraulic press to stretch the billet on a flat anvil with a diameter of 600mm to the finished size of 1400mm×350mm. Note that the amount of reduction in the width direction during the rounding process should not exceed 80mm.

[0017] The die steel forgings obtained in this example, after subsequent annealing and inspection, showed good surface quality, and the ultrasonic testing met the GB / T4162-2008 Class B standard.

Claims

1. A forging method for producing die steel from continuously cast billets without upsetting, characterized in that: The forging steps are as follows: Step 1) Load the annealed continuous casting billet into the heating furnace. The heating furnace is heated at 600-750℃ for 4 hours, and then held at 1230℃±10℃ for 1.5 hours per 100mm section. Step 2) After heating and heat preservation of the billet, use a 3150-ton hydraulic press to draw the billet once on a 600mm upper and lower flat anvil, with a reduction of 20%-25%, and ensure at least 20% overlap between the anvils for every two anvils. Step 3) After flipping the billet from Step 2) by 90°, use a 3150-ton hydraulic press to draw it twice on a 600mm upper and lower special arc-shaped anvil to a certain size. The specific size is based on the finished product height, with a forging ratio of at least 1.5 to 2.

0. The reduction in the first pass is controlled at 20 to 25%, and the reduction in the second pass is controlled at 35 to 40%. The anvil is fed in at full capacity, and at least 20% overlap is guaranteed between each two anvils. The billet is not flipped during the second drawing process. Step 4) Using a 3150-ton hydraulic press, the blank from Step 3) is stretched to the size after the second pressing in Step 2) using a 600mm upper flat anvil and a special arc-shaped anvil. Ensure that there is at least 20% overlap between the two anvils. Step 5) After flipping the billet from Step 4) by 90°, draw it on a 600mm upper and lower flat anvil to the same size as the second pressing in Step 2), ensuring at least 20% overlap between each two anvils; Step 6) After the billet from Step 5) is reheated in the furnace, it is stretched to the finished size using a 3150-ton hydraulic press on a 600mm upper and lower flat anvil.

2. The forging method for producing die steel from continuously cast billets without upsetting, as described in claim 1, is characterized in that: In steps 4) and 5), after the billet is forged to the required size, the pressure is maintained for 10 to 15 seconds.

3. The forging method for producing die steel from continuously cast billets without upsetting, as described in claim 1, is characterized in that: In step 6), the amount of reduction in the width direction during the blank rounding process shall not exceed 70mm.

Images