Forging process of vertical continuous casting billet of heat-resistant martensitic stainless steel 2Cr13

Abstract

This invention relates to a forging process for heat-resistant martensitic stainless steel 2Cr13 vertical continuous casting billets. The process involves fully heating the continuous casting billet and then using forging equipment to deform it at high temperatures with a large deformation amount. The billet is first drawn to a specified size using an integral elongation method, controlling the deformation amount in each pass to be 40%–50%. It is then repeatedly forged under large deformation by rotating it 90°, controlling the billet temperature between 980°C and 1150°C. The process involves repeated forging using upper and lower flat anvils, forging the ends first, then the middle, and finally forging the continuous casting billet with a hole in the core to heal it. This process opens up a new technical route for forging solid high-alloy steel products using continuous casting billets, reducing manufacturing costs and accelerating production efficiency. 2Cr13 high-alloy steel continuous casting billet forgings forged using this process can achieve a quality grade of 3 or higher according to ultrasonic testing standards (GB / T6402). Low-magnification testing according to GB / T226 generally achieves a quality grade of less than 1.0 for porosity and less than 1.5 for central porosity.

Description

Technical Field

[0001] This invention belongs to the field of stainless steel continuous casting billet forging technology, specifically relating to a forging process for heat-resistant martensitic stainless steel 2Cr13 vertical continuous casting billet that heals a central hole defect by forging. Background Technology

[0002] The chemical composition of heat-resistant martensitic stainless steel 2Cr13 conforms to GB / T1221 standard. Currently, continuous casting can be classified according to the shape of the casting machine into vertical continuous casting machines, vertical-bending continuous casting machines, arc continuous casting machines, elliptical continuous casting machines, and horizontal continuous casting machines. Currently, neither vertical nor arc continuous casting, nor other continuous casting methods, can solve the core defect problem of high-alloy steels such as 2Cr13. The produced continuously cast billets will inevitably have some degree of porosity in the center, making the continuous casting technology of high-alloy steel a global challenge. The larger the billet size, the more severe the core defect. Currently available vertical continuously cast billet sizes are 400mm, 600mm, and 800mm in diameter. A 400mm diameter billet has a porosity defect in the center within 60mm, a 600mm diameter billet has a porosity defect in the center within 120mm, and an 800mm diameter billet has a porosity defect in the center within 200mm, with the largest central hole reaching 10mm x 50mm.

[0003] Based on the current status of high-alloy steel continuous casting billets, 2Cr13 type high-alloy solid forgings are generally produced using ingot forging to ensure product quality, especially core quality. However, ingot forging suffers from low efficiency and low utilization, leading to high manufacturing costs. Currently, high-alloy continuous casting billets are generally used as electrode billets for electroslag remelting or for producing hollow forgings. To reduce manufacturing costs and improve market competitiveness, research is needed on forging processes. This requires the invention of a vertical continuous casting billet forging process for 2Cr13 type high-alloy steel to address the inherent porosity defects in continuous casting billets and to pave the way for continuous casting billet forging technology in producing high-alloy steel solid forgings. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a forging process for heat-resistant martensitic stainless steel 2Cr13 vertical continuous casting billets that can heal the core defects of the continuous casting billets, so as to open up the technical route of using continuous casting billet forging for high alloy steel solid forging products.

[0005] The objective of this invention is achieved as follows: A forging process for heat-resistant martensitic stainless steel 2Cr13 vertical continuous casting billets, wherein the forging process is carried out according to the following procedure: Step 1) Seal and weld the holes at both ends of the 2Cr13 continuous casting billet; Step 2) Heat the sealed continuous casting billet at a furnace temperature of 1200℃~1250℃ and hold for 15~20 hours. Step 3) Use a hydraulic press to roughen the continuous casting billet. The height after roughening is 50% to 60% of the original continuous casting billet height. The billet surface temperature is required to be 980℃ to 1150℃ during the roughing process. Step 4) Use a hydraulic press and upper and lower flat anvils to lightly press the roughed billet through two passes. First, forge 10% to 20% of the length at both ends, and then forge the middle. Control the reduction amount to 80mm to 100mm. Step 5) Reheat in the furnace at a temperature of 1200℃~1250℃ for 3~5 hours; Step 6) Using a hydraulic press, a rough plate is used on top and a platform is used below to cover the billet and elongate it. The billet is elongated to the size of the intermediate billet with a large deformation. The deformation is 40% to 50% per pass. Then, it is flipped 90° and pressed down, with a deformation of 40% to 45%. The size of the intermediate billet varies depending on the product specifications. The process of elongating the billet by covering it can be repeated by flipping it repeatedly for large deformation forging. This process requires the surface temperature of the billet to be 980℃ to 1150℃. If the temperature does not meet the requirements, the billet can be returned to the heating furnace for heating or cooling before forging. Step 7) Use a hydraulic press and upper and lower flat anvils to draw the billet to the finished product. First, forge 10% to 20% of the length at both ends, and then forge the middle. First, draw the billet to the square shape, and then repeatedly forge it by turning it 90°. The reduction is 100mm to 150mm. Then, turn it into an octagonal shape and finish it into a round billet. The final forging temperature is greater than 850℃.

[0006] The positive effects of this invention are as follows: The forging process of this invention effectively solves the forging problem of difficult healing of core void defects in 2Cr13 continuously cast billets; it opens up a technical route for forging solid high-alloy steel products using continuously cast billets, significantly reducing manufacturing costs, accelerating production efficiency, and improving product market competitiveness. 2Cr13 high-alloy steel continuously cast billet forgings produced using this process, when tested according to the ultrasonic flaw detection standard GB / T6402, can achieve a quality grade of 3 or higher; when tested according to the low magnification standard GB / T226, the quality grade generally achieves a porosity grade of 1.0 or lower, and a center porosity grade of 1.5 or lower. Detailed Implementation

[0007] To fully understand the inventiveness of this invention, the forging process of heat-resistant martensitic stainless steel 2Cr13 vertical continuous casting billet will be described in detail in the embodiments to fully illustrate the invention.

[0008] A forging process for heat-resistant martensitic stainless steel 2Cr13 vertical continuous casting billets: The forging process is as follows... Art Performance: The heat-resistant martensitic stainless steel 2Cr13 forging has a billet diameter of 475mm and a length of 4800mm. The continuous casting billet weighs 7.6 tons and has dimensions of Ф785mm*2000mm.

[0009] Step 1) Seal and weld the holes at both ends of the 2Cr13 continuous casting billet. A hole defect was found 163 mm from the center of the end. Step 2) Heat the sealed continuous casting billet, hold at 400-450℃ for 4 hours, raise the temperature to 600-750℃ for 5 hours, raise the temperature to 1230℃ for 15 hours. Step 3) Use a 3150-ton hydraulic press to roughen the continuously cast billet to H=1000mm (~Ф1100mm). During the roughing process, the initial forging temperature of the billet was measured to be 1105℃ and the final forging temperature was 984℃. Step 4) Using a 3150-ton hydraulic press and an 800mm flat anvil, lightly press the roughed billet throughout. First, forge the two ends with a length of 150mm each, then forge the middle. Lightly press twice, with a pressing amount of 80mm to 100mm per pass, to lengthen the billet to Ф920mm. Step 5) Return the billet to the furnace for reheating, and hold at 1230℃ for 5 hours; Step 6) Using a 3150-ton hydraulic press, a Ф1800mm forging plate, and a Ф2000mm platform to cover the billet and elongate it, first pressing it to H=550mm. During this process, the initial forging temperature of the billet was measured to be 1085℃ and the final forging temperature was 962℃. Step 7) Return the billet to the furnace for reheating, and hold at 1230℃ for 3.5 hours; Step 8) The billet is flipped 90º (at this time the width extends to about 1000mm), and a 3150-ton hydraulic press, a Ф1800mm forging plate, and a Ф2000mm platform are used to cover the billet and elongate it until H=600mm. During this process, the initial forging temperature of the billet is measured to be 1102℃ and the final forging temperature is 968℃. Step 9) Using a 3150-ton hydraulic press and a 500mm upper and lower flat anvil, the billet is drawn to the finished product. First, the length of each end is forged to about 800mm, and then the middle is forged. The billet is first drawn to a square length of 470mm, and then repeatedly forged by turning it 90º, with a reduction of 100mm to 150mm. Then, it is turned into an octagon and finished to a hot Ф482mm. During this process, the initial forging temperature of the billet was measured to be 1121℃ and the final forging temperature was 861℃. Ultrasonic testing and low-magnification inspection were performed on the 2Cr13 forgings. The testing standard was GB / T6402, and the test results met the requirements of quality grade 3. The low-magnification inspection standard was GB / T226, and the test results were grade 0.5 for general porosity and grade 1.0 for central porosity.

Claims

1. A forging process for heat-resistant martensitic stainless steel 2Cr13 vertical continuous casting billets, characterized in that: The forging process is carried out according to the following procedure: Step 1) Seal and weld the holes at both ends of the 2Cr13 continuous casting billet; Step 2) Heat the sealed continuous casting billet at a furnace temperature of 1200℃~1250℃ and hold for 15~20 hours. Step 3) Use a hydraulic press to roughen the continuous casting billet. The height after roughening is 50% to 60% of the original continuous casting billet height. The billet surface temperature is required to be 980℃ to 1150℃ during the roughing process. Step 4) Use a hydraulic press and upper and lower flat anvils to lightly press the uptaked billet through two passes. First, forge 10% to 20% of the length at both ends, and then forge the middle. The reduction should be controlled at 80mm to 100mm. Step 5) Reheat in the furnace to a temperature of 1200℃~1250℃ and hold for 3~5 hours; Step 6) Using a hydraulic press, the billet is covered by an upsetting plate on top and a platform on the bottom for drawing and elongating. The billet is drawn with a large deformation to the size of the intermediate billet, with a deformation of 40% to 50% per pass. It is then flipped 90° and pressed down, with a deformation of 40% to 45%. The size of the intermediate billet varies depending on the product specifications. The billet is drawn and elongated by covering it with the platform, and the large deformation forging is repeated by flipping the billet repeatedly. This process requires the surface temperature of the billet to be 980℃ to 1150℃. If the temperature does not meet the requirements, the billet is returned to the heating furnace for heating or cooling before forging. Step 7) Use a hydraulic press and upper and lower flat anvils to draw the product to its finished length, first forging 10% to 20% of the length at both ends. During the subsequent forging process, the billet is first drawn into a square shape, then repeatedly forged by turning it 90°, with a reduction of 100mm to 150mm. The billet is then finished into a round shape using an octagonal forging process, with a final forging temperature greater than 850℃.