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CN-121976122-A - Pull rod material for split forging ship and forging process thereof

CN121976122ACN 121976122 ACN121976122 ACN 121976122ACN-121976122-A

Abstract

The invention discloses a pull rod material for a split forging ship and a forging process thereof. The material is based on C, mn, cr, ni, is innovatively compatible with Mo, V, ti, nb, B and rare earth elements, and realizes the unification of toughness, grain refining and high cleanliness through three groups of microalloying designs with synergistic effect. The forging process adopts a single-diameter blank, and realizes the integrated welding-free precise forming of the pull rod in a pair of intelligent dies integrated with a cooling flow passage, a PVD coating and an embedded ultrasonic probe through the combination of sectional gradient heating, horizontal upsetting and flat forging pre-final forging. Meanwhile, a closed-loop control system for on-line detection and technological parameters is formed by using a machine vision and AI quality prediction model. The invention thoroughly eliminates the quality hidden trouble of the traditional welding process, and the manufactured pull rod has compact structure, complete streamline, high dimensional precision, excellent and stable mechanical property, and obviously improves the reliability and safety of the pull rod for the ship.

Inventors

  • HUANG JIANBO
  • GONG ZHAOYAN
  • HUANG JIANHUA
  • Gong Zhaosen

Assignees

  • 青岛布林瑞特机械有限公司

Dates

Publication Date
20260505
Application Date
20260211

Claims (8)

  1. 1. The pull rod material for the sub-forging ship is characterized by comprising the following chemical components in percentage by mass: C：0.18～0.25%,Si：0.20～0.40%,Mn：1.00～1.40%,P≤0.020%,S≤0.015%,Cr：0.80～1.20%,Ni：0.40～0.60%,Mo：0.15～0.25%,V：0.08～0.12%,Ti：0.04～0.06%,Nb：0.03～0.05%,B：0.001～0.004%, 0.02-0.06% of mixed rare earth, and the balance of Fe and unavoidable impurities; The mass ratio of Cr/Mo is 4.0-6.0:1, wherein the mixed rare earth comprises Ce and La, and the mass ratio of Ce/La=2/1; Wherein the mass ratio of V to (Ti+Nb) is 1 (0.7-1.2).
  2. 2. The tie rod material for a split forging ship according to claim 1, wherein the chemical components of the tie rod material are preferably ： C：0.22%, Si：0.30%, Mn：1.20%, P：0.015%, S：0.010%, Cr：1.05%, Ni：0.50%, Mo：0.20%, V：0.10%, Ti：0.05%, Nb：0.04%, B：0.002%, mixed rare earth in percentage by mass, 0.04% and the balance of Fe and unavoidable impurities.
  3. 3. A forging process for a tie rod material for a split forging ship according to claim 1 or 2, wherein a single gauge round steel blank is used to directly form the tie rod by integral non-welded precision segmented forging, comprising the steps of: s1, preparing a fixed-length round steel blank with the diameter of 24-28 mm; S2, sectional gradient heating, namely carrying out sectional heating on the blank by adopting medium-frequency induction heating, wherein the rod body section for forming the nodule is heated to 1150-1200 ℃, and the end section for forming the U-shaped fork head is heated to 1050-1100 ℃ by adopting multistage gradient heating; s3, precision segmented forging: s3.1, forming the knots, namely horizontally upsetting the heated rod body section to form the tie rod knots, wherein the forging ratio is controlled to be 2.0-3.0; S3.2, forming a U-shaped fork head, namely performing pre-forging and final forging integrated forging on the heated end section on a flat forging machine, wherein the pre-forging deformation is 30-40% to obtain a fork head rough blank, immediately performing final forging in a directional streamline forming die, forming the surface of a die cavity by adopting an additive manufacturing technology, coating AlCrN or similar PVD (physical vapor deposition) coating, and integrating a cooling runner in the die, wherein the final forging rate is controlled to be 5-8 mm/S, and the final forging temperature is not lower than 850 ℃ so that the dimensional tolerance of key parts of the U-shaped fork head is controlled to be +/-0.2 mm; S4, online intelligent detection and process control, namely embedding a miniature ultrasonic probe in the final forging die, and carrying out quick online nondestructive detection on a stress concentration area of the U-shaped fork head before demolding of the forging piece; And S5, finishing and temperature-control cooling, namely immediately performing finishing operations such as flash punching after forging and forming, and then transferring the forging into a heat-preservation environment at 650-700 ℃ for slow cooling or performing direct normalizing treatment by using waste heat after forging.
  4. 4. The forging process of the pull rod material for the split forging ship according to claim 3, wherein in the step S3.2, the PVD coating thickness of the directional streamline forming mold is 8-12 μm, the surface hardness of a mold cavity is more than or equal to 60 HRC, and the identification precision of the miniature ultrasonic probe on internal defects is not less than phi 0.1 mm.
  5. 5. The process for forging the pull rod material for the split forging ship according to claim 3, wherein in the step S4, the AI quality prediction and control system takes dimension data, ultrasonic signals, forging temperature and forging speed which are detected on line as input, dynamically analyzes the quality trend of the forging, and when the predicted grain size or defect risk exceeds a preset threshold, the system automatically and reversely regulates and controls the heating temperature in the step S2 or the forging speed parameter in the step S3.2, so that the closed-loop quality control of the forging process is realized.
  6. 6. The forging process of the pull rod material for the split forging ship according to claim 3, wherein in the step S5, the temperature-controlled cooling is specifically carried out by placing the finished forge piece in a 680-720 ℃ holding furnace, slowly cooling to below 400 ℃ along with the furnace, and then air-cooling.
  7. 7. The forging process of the pull rod material for the split forging ship according to claim 3, wherein in the step S2, the temperature rising rate of the medium-frequency induction heating is controlled to be 30-40 ℃ per minute, and in the step S3.2, the cumulative forging pressure ratio of the pre-forging and the final forging is controlled to be 1.2-1.5:1.
  8. 8. A marine pull rod is characterized by being manufactured by integrally forming a split forging marine pull rod material according to claim 1 or 2 through a forging process according to any one of claims 3 to 7, wherein the pull rod is an integral precision forging without a welded joint, the microstructure of the pull rod is uniform fine-grained ferrite, pearlite or tempered sorbite, the grain size is not lower than 8 levels, the critical dimensional tolerance of a U-shaped fork is +/-0.2 mm, the room-temperature mechanical property is met, the tensile strength is not less than 800MPa, the yield strength is not less than 650MPa, the elongation after break is not less than 18%, and the V-shaped notch impact energy at-20 ℃ is not less than 60J.

Description

Pull rod material for split forging ship and forging process thereof Technical Field The invention relates to the technical field of manufacturing of ship accessories, in particular to a pull rod material for a split forging ship and a forging process thereof. Background The marine pull rod is a core fastener for guaranteeing the safety of cargoes of the container ship. The traditional production process adopts two materials with different diameters (such as phi 24mm rod body and phi 55mm fork head material) to be respectively processed and welded into a whole by friction welding. The process has the inherent defects that 1) the welding quality is greatly influenced by the batch differences of equipment, personnel and materials, the strength and toughness of a welded junction are difficult to ensure stably, ultrasonic flaw detection and destructive stretching verification are required to be carried out on each product, the cost is high, 2) the forging ratio of a fork head part is too large (from phi 55mm to about phi 24 mm), coarse grains and internal folding cracks are easy to cause, the dimensional tolerance is large (+ -0.5 mm or more), and the quality hidden trouble is large. These drawbacks are the important cause of failure of the tie rod under severe sea conditions, causing container fall accidents. In recent years, attempts to improve the forging process are made, but the problem of cooperative improvement of strength, toughness, precision and stability is not solved from the aspects of material source and process intelligent control. Therefore, a new material system and manufacturing method are urgently needed to thoroughly eliminate the hidden trouble of welding and realize high-performance, high-consistency and low-cost manufacturing. Disclosure of Invention The invention aims to overcome the defects of the prior art, and provides low-carbon alloy structural steel for a pull rod for a split forging ship and a forging process thereof, and the integrated near-net forming and the accurate performance regulation and control of the pull rod are realized through the combination of material innovation and process innovation. The technical scheme is that the pull rod material for the split forging ship comprises the following chemical components in percentage by mass: C：0.18～0.25%,Si：0.20～0.40%,Mn：1.00～1.40%,P≤0.020%,S≤0.015%,Cr：0.80～1.20%,Ni：0.40～0.60%,Mo：0.15～0.25%,V：0.08～0.12%,Ti：0.04～0.06%,Nb：0.03～0.05%,B：0.001～0.004%, 0.02-0.06% of mixed rare earth, and the balance of Fe and unavoidable impurities; the mixed rare earth comprises Ce and La, and the mass ratio of Ce/La=2/1; Wherein the chemical composition comprises the following three groups of microalloying element combinations with synergistic performance: The first synergistic component is Cr, ni and Mo, wherein the Cr and the Ni jointly improve the hardenability, the toughness and the low-temperature toughness of the material, the Mo and the Cr form composite carbide to improve the fatigue resistance, and the mass ratio of Cr/Mo is 4.0-6.0:1; Mn and Si mainly play a solid solution strengthening role and improve forging plasticity, V, ti and Nb strongly inhibit austenite grain growth in the forging and heat treatment processes by forming fine carbonitrides, and grain refinement is realized, wherein the mass ratio of V to (Ti+Nb) is 1 (0.7-1.2); The third synergistic component is B and mixed rare earth, wherein B element is biased to grain boundary to further improve hardenability and strengthen the grain boundary, and the rare earth element is used for deep desulfurization, deoxidization and spheroidizing inclusion to improve material cleanliness and isotropy. Preferably, the chemical components of the alloy are ： C：0.22%, Si：0.30%, Mn：1.20%, P：0.015%, S：0.010%, Cr：1.05%, Ni：0.50%, Mo：0.20%, V：0.10%, Ti：0.05%, Nb：0.04%, B：0.002%, mixed rare earth 0.04 percent by mass, and the balance of Fe and unavoidable impurities. A forging process of a pull rod material for a separate forging ship comprises the following steps: s1, preparing a fixed-length round steel blank with the diameter of 24-28 mm; S2, sectional gradient heating, namely carrying out sectional heating on the blank by adopting medium-frequency induction heating, wherein the rod body section for forming the nodule is heated to 1150-1200 ℃, and the end section for forming the U-shaped fork head is heated to 1050-1100 ℃ by adopting multistage gradient heating; s3, precision segmented forging: s3.1, forming the knots, namely horizontally upsetting the heated rod body section to form the tie rod knots, wherein the forging ratio is controlled to be 2.0-3.0; s3.2, forming a U-shaped fork head, namely performing pre-forging and final forging integrated forging on the heated end section on a flat forging machine, wherein the pre-forging deformation is 30-40% to obtain a fork head rough blank, immediately performing final forging in a directional streamline forming die, forming the surface of a die