Low-alloy ultrahigh-strength D406A steel forging method based on hot working diagram optimization
By controlling the deformation temperature and strain rate of the hot compression test and optimizing the forging parameters of D406A steel, the problems of uneven grain size and oxide scale during forging were solved, and high-performance low-alloy ultra-high-strength D406A steel was prepared, which is suitable for the load-bearing shell of solid rocket engines and other aerospace structural components.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- GUIZHOU UNIV
- Filing Date
- 2026-01-19
- Publication Date
- 2026-04-17
AI Technical Summary
During the forging process, D406A steel has a narrow deformation temperature range and high deformation resistance, which leads to uneven grains and the formation of mixed grain structure. In addition, the heating process is prone to oxide scale and cracks, which affect the performance of forgings.
By controlling the deformation temperature and strain rate of the hot compression test, the forging parameters of D406A steel were optimized. Specifically, the steel was heated to 850-1050℃ at a rate of 10℃/s, with a strain rate of 0.01-5s⁻1 and a true strain of 0.8-1.0. After holding at this temperature for 5 minutes, it was water quenched to prepare low-alloy ultra-high strength D406A steel.
Grain refinement was achieved, which improved the overall mechanical properties of the forgings, met the high-performance requirements of large annular components for solid rocket engine load-bearing shells, reduced production costs, and made them suitable for mass production.
Smart Images
Figure CN121869986A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of D406A steel forming and heat treatment technology, specifically relating to a forging method for low-alloy ultra-high strength D406A steel based on optimized heat treatment diagram. Background Technology
[0002] Solid rocket motors are the primary power source for various missile weapons today. The large annular component of the solid rocket motor's load-bearing casing, as a crucial structural part, must withstand high impact and strength loads during service. In recent years, a low-alloy ultra-high-strength steel, D406A (30Si2MnCrMoVE), has been widely used in structural components such as bulletproof steel plates, aircraft landing gear, and connecting shafts. This material boasts a room-temperature tensile strength of up to 1620 MPa, significantly higher than traditional 30CrMnSiA high-strength steel, and 4-6 times stronger than ordinary carbon steel. It also exhibits good impact toughness. However, during the upsetting and punching process of D406A steel, due to its narrow deformation temperature range and high deformation resistance, uneven deformation between the outer and inner annular parts of the forging leads to inconsistent dynamic recrystallization, resulting in uneven grain size and a mixed-grain structure. Furthermore, excessively long heating times or excessively high temperatures during forging can cause overheating, burning, decarburization, and oxidation. Heating can also cause oxide scale to form on the workpiece surface. If the oxide scale is not cleaned properly, it will be drawn into the workpiece during subsequent forging processes, disrupting the metal flow lines, reducing the workpiece's performance, and in severe cases, causing cracks during forging and rendering the entire ring forging unusable. Therefore, optimizing the forging parameters of D406A steel is one of the key issues that urgently needs to be addressed in the hot upsetting process of D406A steel to reduce forging defects in actual production.
[0003] Hot deformation parameters have a significant impact on the hot deformation behavior and microstructure of D406A steel. Hot working diagrams are considered an important means of evaluating the hot working properties of metals and alloys, and have been widely used to optimize the hot working processes of various alloy materials.
[0004] This invention optimizes the forging parameters of D406A steel by controlling the deformation temperature and strain rate of the hot compression test, aiming to solve the problem of mixed-grain structure in D406A steel during forging caused by the narrow deformation temperature range. Summary of the Invention
[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a forging method for low-alloy ultra-high strength D406A steel based on optimized hot working diagrams, in order to solve the problem of mixed grains in D406A steel forgings.
[0006] The technical solution of this invention is as follows: A forging method for low-alloy ultra-high strength D406A steel based on optimized hot working diagram, comprising the following steps: The forging method heats the D406A steel sample to a deformation temperature of 850-1050℃ at a rate of 10℃ / s, and then performs hot compression, with the hot compression strain rate set to 0.01-5s⁻ 1 The true strain is set to 0.8-1.0, and after holding at the temperature for 5 minutes, it is immediately water quenched and cooled to room temperature to obtain low alloy ultra-high strength D406A steel.
[0007] The aforementioned strain rate is 0.01-5 s⁻ 1 The relationship between work hardening rate and flow stress during the process; The aforementioned D406A steel sample was cylindrical with a diameter of 8 mm and a height of 12 mm.
[0008] The aforementioned deformation temperature is 975-1050℃.
[0009] Specifically, the aforementioned deformation temperature is 1050℃.
[0010] The aforementioned strain rate is 0.01-0.1 s⁻ 1 .
[0011] Specifically, the aforementioned strain rate is 0.01-0.056 s⁻ 1 .
[0012] The aforementioned true strain is set to 0.9.
[0013] The aforementioned application of low-alloy ultra-high strength D406A steel in the manufacture of aerospace structural components, including bulletproof steel plates, aircraft landing gear, and connecting shafts.
[0014] The aforementioned application of low-alloy ultra-high strength D406A steel in the manufacture of large annular components for the load-bearing shell of solid rocket motors.
[0015] Compared with the prior art, the present invention has the following beneficial effects: This invention controls the deformation temperature and strain rate in a hot compression test. Specifically, before deformation, the sample is heated to different deformation temperatures at a rate of 10℃ / s and held at that temperature for 5 minutes. The deformation temperatures are 850℃, 950℃, and 1050℃, and the strain rates are 0.01, 0.1, 1, and 5s⁻. 1 The true strain was set to 0.9, and water quenching was performed immediately after deformation. The optimal hot working window for D406A steel was successfully determined to be 975 to 1050℃ and 0.01 to 0.056 s⁻. 1 Specifically, at 1050°C and 0.01s⁻ 1 Under these conditions, the microstructure consists of finely dispersed martensite, and η>0.32, which helps to refine the grains.
[0016] The preparation process of this invention is simple, low-cost, and suitable for large-scale production. Attached Figure Description
[0017] Figure 1 The true stress-strain curves of D406A steel treated in Examples 1-3 at different strain rates are shown. Figure 2 The images show the hot working of D406A steel treated in Examples 1-3 at a true strain of 0.4. Figure 3 The images show the hot working of D406A steel treated in Examples 1-3 at a true strain of 0.5. Figure 4 The images show the hot working of D406A steel treated in Examples 1-3 at a true strain of 0.6. Figure 5 The image shows the hot working of D406A steel after treatment in Examples 1-3 at a true strain of 0.7. Detailed Implementation
[0018] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.
[0019] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.
[0020] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention.
[0021] The D406A steel billet used in the following examples is a D406A steel plate, cut from a large ring-shaped D406A steel component provided by Guizhou Guiyang Anda Aerospace Materials Engineering Co., Ltd. Its chemical composition is: C 0.31 wt.%, Si 1.62 wt.%, Mn 0.86 wt.%, Cr 1.14 wt.%, Mo 0.49 wt.%, V 0.12 wt.%, Ni 0.25 wt.%, Cu 0.05 wt.%, with the balance being Fe and unavoidable impurities.
[0022] Example 1 A forging method for low-alloy ultra-high strength D406A steel based on optimized hot working diagram is as follows: The D406A steel sample was heated to the deformation temperature of 850℃ at a rate of 10℃ / s, and then hot-compressed for 0.01, 0.1, 1, and 5 s⁻. 1 Four strain rates were used, with the true strain set at 0.9. After holding at this temperature for 5 minutes, the material was immediately water-quenched and then water-cooled to room temperature to obtain low-alloy ultra-high strength D406A steel.
[0023] Example 2 A forging method for low-alloy ultra-high strength D406A steel based on optimized hot working diagram is as follows: The D406A steel sample was heated to the deformation temperature (850-1050℃) at a rate of 10℃ / s, and then hot-compressed for 0.01, 0.1, 1, and 5 s⁻. 1 Four strain rates were used, with the true strain set at 0.9. After holding at this temperature for 5 minutes, the material was immediately water-quenched and then water-cooled to room temperature to obtain low-alloy ultra-high strength D406A steel.
[0024] Example 3 A forging method for low-alloy ultra-high strength D406A steel based on optimized hot working diagram is as follows: The D406A steel sample was heated to the deformation temperature (850-1050℃) at a rate of 10℃ / s, and then hot-compressed for 0.01, 0.1, 1, and 5 s⁻. 1 Four strain rates were used, with the true strain set at 0.9. After holding at this temperature for 5 minutes, the material was immediately water-quenched and then water-cooled to room temperature to obtain low-alloy ultra-high strength D406A steel.
[0025] Figure 1 The true stress-strain curves of D406A steel treated in Examples 1-3 at different strain rates are shown. At a given strain rate, the flow stress gradually decreases with increasing deformation temperature. This is because high temperature reduces the deformation resistance of D406A steel by enhancing atomic motion.
[0026] Figure 2 The images show the hot working of D406A steel treated in Examples 1-3 at a true strain of 0.4. The optimal heat treatment range is 945–1050°C, with a strain rate of 0.01–0.056 s⁻. 1 .
[0027] Figure 3 The images show the hot working of D406A steel treated in Examples 1-3 at a true strain of 0.5. The optimal heat treatment range is 930–1050°C, with a strain rate of 0.01–0.1 s⁻. 1 .
[0028] Figure 4 The images show the hot working of D406A steel treated in Examples 1-3 at a true strain of 0.6. The optimal heat treatment range becomes 940–1050°C with a strain rate of 0.01–0.096 s⁻ 1 .
[0029] Figure 5 The images show the hot working conditions of D406A steel treated in Examples 1-3 at a true strain of 0.7. The optimal heat treatment range is narrowed down to 975–1050°C with a strain rate of 0.03–0.11 s⁻ 1 .
[0030] Taking the intersection of the optimal heat treatment ranges, the optimal heat treatment range is determined to be 975 to 1050℃ and 0.03 to 0.056 s⁻ 1 .
[0031] Experimental Example 1: Room Temperature Tensile, Impact, and Fracture Toughness Tests: The heat treatment will be carried out at 1050℃ for 0.01s⁻ 1 and 97℃, 0.056s⁻ 1 Low-alloy ultra-high strength D406A steel treated under two different conditions was subjected to room temperature tensile, impact, and fracture toughness tests. Room temperature tensile testing was performed using an XforceK universal testing machine with a uniaxial tensile rate set to 1 mm / min. The parallel section dimensions of the tensile specimen were 26.5 × 1.5 × 1.8 mm. 3 The test results are shown in Table 1.
[0032] Table 1 Results of room temperature tensile, impact and fracture toughness tests Table 1 shows the tensile strength, yield strength, elongation, reduction of area, and impact toughness of the treated low-alloy ultra-high strength D406A steel. As can be seen from Table 1, after heat treatment at 97℃ for 0.056s⁻ 1 and 1050℃, 0.01s⁻ 1The plasticity of low-alloy ultra-high strength D406A steel was significantly improved after treatment under both conditions.
[0033] Due to the large size of the load-bearing ring component in a solid rocket motor's load-bearing shell, uneven deformation during the ring rolling process can easily lead to inhomogeneous microstructure, resulting in lower overall mechanical properties of the ring component. Currently, the mechanical properties of the prototype D406A steel large ring component are as follows: σ b =1500MPa; σ 0.2 =1200MPa; δ=6%; ψ=25%; Impact energy A Ku2 =28J; K IC =70MPa·m 1 / 2 This cannot meet the high-performance requirements of large annular components in the load-bearing shell of high-thrust solid rocket motors. The elongation at room temperature (EL) of the treated D406A steel is 10.5% and 13.0%, respectively, far exceeding that of the prototype D406A steel. For large annular components in the load-bearing shell of solid rocket motors, low yield strength and elongation at break cause premature failure of the alloy during service, resulting in catastrophic losses. However, the D406A steel treated by the low-alloy ultra-high-strength D406A steel forging process based on the optimized hot working diagram meets the requirements of high strength and high plasticity in both yield strength and elongation at break. This allows the large annular components in the load-bearing shell of solid rocket motors to withstand more extreme service environments. One of the core goals of modern high-strength steel is to maintain high strength while avoiding a decrease in plasticity and toughness. Therefore, sufficient plasticity is a necessary condition for ensuring structural reliability, and its value far exceeds the limited benefits brought by simply pursuing strength indicators.
[0034] in conclusion: The D406A steel of this invention exhibits significantly different properties under different deformation conditions. At low strain rates (0.01 s⁻¹), it shows particularly good performance. 1 and 0.1s⁻ 1 At the true stress-strain curves, the softening effect is more significant than the hardening effect after reaching the peak stress. Therefore, the rheological resistance decreases, exhibiting typical DRX characteristics. In contrast, at higher strain rates (1 s⁻¹), the softening effect is more pronounced than the hardening effect. 1 and 5s⁻ 1 Under these conditions, the hardening and softening effects remain in dynamic equilibrium after reaching peak stress. As a result, the true stress value tends to stabilize, and the curve exhibits typical DRV characteristics.
[0035] As can be seen from the hot working diagram of D406A steel in this invention, with the increase of strain, the unstable region gradually expands from the low-temperature region to the high-temperature region and becomes increasingly obvious. Therefore, during hot working, the unstable region (gray area) should be avoided, and regions with high power dissipation efficiency should be selected instead. The hot working region is divided into two areas: the stable region (white) and the unstable region (shaded region). The stable region usually appears in the high strain rate region, while the unstable region appears in the strain rate below 0.1 s⁻ 1 The peak dissipation efficiency occurs in the region of high temperature and low strain rate, which may be due to dynamic recovery (DRV) and dynamic recrystallization (DRX).
[0036] Specifically, at 1050°C and 0.01s⁻ 1 Under these conditions, the microstructure consists of finely dispersed martensite, and η>0.32, which helps to refine the grains.
[0037] The third aspect of this invention provides the above-mentioned low-alloy ultra-high strength D406A steel based on optimized hot working diagrams for use in structural components such as large annular parts of solid rocket engine load-bearing shells, bulletproof steel plates, aircraft landing gear, and connecting shafts. The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.
Claims
1. A forging method for low-alloy ultra-high strength D406A steel based on hot working diagram optimization, characterized in that: Includes the following steps: The forging method involves heating the D406A steel sample to a deformation temperature of 850-1050℃ at a rate of 10℃ / s, followed by hot compression. The hot compression strain rate is set to 0.01-5s⁻ 1 The true strain is set to 0.8-1.0, and after holding at the temperature for 5 minutes, it is immediately water quenched and cooled to room temperature to obtain low alloy ultra-high strength D406A steel.
2. The forging method for low-alloy ultra-high strength D406A steel based on hot working diagram optimization according to claim 1, characterized in that: The strain rate is 0.01-0.5 s⁻ 1 The relationship between work hardening rate and flow stress.
3. The forging method for low-alloy ultra-high strength D406A steel based on hot working diagram optimization according to claim 1, characterized in that: The D406A steel sample was cylindrical with a diameter of 8 mm and a height of 12 mm.
4. The forging method for low-alloy ultra-high strength D406A steel based on hot working diagram optimization according to claim 1, characterized in that: The deformation temperature is 975-1050℃.
5. The forging method for low-alloy ultra-high strength D406A steel based on hot working diagram optimization according to claim 1 or 4, characterized in that: The deformation temperature is 1050℃.
6. The forging method for low-alloy ultra-high strength D406A steel based on hot working diagram optimization according to claim 1, characterized in that: The strain rate is 0.01-0.1 s⁻ 1 .
7. The forging method for low-alloy ultra-high strength D406A steel based on hot working diagram optimization according to claim 1 or 6, characterized in that: The strain rate is 0.01-0.056 s⁻ 1 .
8. The forging method for low-alloy ultra-high strength D406A steel based on hot working diagram optimization according to claim 1, characterized in that: The true strain is set to 0.
9.
9. The application of the low-alloy ultra-high strength D406A steel as described in any one of claims 1-8 in the manufacture of structural components for the aerospace field, characterized in that: The structural components in the aerospace field include bulletproof steel plates, aircraft landing gear, and connecting shafts.
10. The application of the low-alloy ultra-high strength D406A steel as described in any one of claims 1-8 in the manufacture of large annular components for the load-bearing shell of solid rocket motors.