Hastelloy forge piece and preparation method thereof

Abstract

The invention relates to a hastelloy forge piece and a preparation method thereof, and belongs to the technical field of hastelloy forge pieces. The method comprises the following steps: under a first set condition, carrying out destressing treatment on a red rotating cast ingot with set chemical components; carrying out homogenization treatment on the cast ingot subjected to the destressing treatment; carrying out forging treatment on the homogenized cast ingot for multiple times to obtain a forge piece; and under a second set condition, the forge piece is subjected to heat treatment, so that heat distribution of the forging area of the forge piece is uniform, and the hastelloy forge piece is obtained. According to the embodiment of the invention, under the synergistic effect of destressing treatment, homogenization treatment, forging and heat treatment after forging, the thermal stress and element segregation of the cast ingot are reduced, a precipitated phase is redissolved to the maximum extent, grain recovery and recrystallization are promoted, the machining deformation resistance is reduced, the structure is refined, and the plasticity of the hastelloy forge piece is improved.

Description

Technical Field

[0001] The present application relates to the technical field of Hastelloy forgings, and in particular to a Hastelloy forging and a preparation method thereof. Background Art

[0002] As a high-performance engineering material, C-276 Hastelloy forgings are widely used in chemical industry, marine engineering, electronics, aerospace, medical equipment and other fields. Its excellent corrosion resistance, high strength and good processability enable it to maintain stable performance in various extreme environments.

[0003] However, highly alloyed steels not only have segregation, but are also prone to cracking during pressure processing, which in turn has an adverse effect on the subsequent processing and performance of forged parts. The factor that has a greater impact on the forgeability of metals is the plasticity of the metal itself. The better the plasticity, the less likely it is to crack during forging. The plasticity of a metal is closely related to its structure. The finer the grains and the more uniform the structure, the better the plasticity. At the same time, in order for a metal material to be able to change shape without cracking during pressure processing, its deformation resistance needs to be reduced. Therefore, the better the plasticity and the smaller the deformation resistance, the better the forgeability of the metal, and vice versa. A method for preparing Hastelloy forgings is needed to reduce the adverse effects of segregation during forging, improve plasticity, and reduce deformation resistance, which is crucial to the development of C-276 alloy. Summary of the invention

[0004] The present application provides a Hastelloy forging and a preparation method thereof to solve the following technical problem: how to improve the plasticity of the Hastelloy forging.

[0005] In a first aspect, an embodiment of the present application provides a method for preparing a Hastelloy forging, the method comprising:

[0006] Under a first set condition, a red-transformed ingot having a set chemical composition is subjected to stress relief treatment;

[0007] homogenizing the ingot after stress relief treatment;

[0008] The homogenized ingot is subjected to forging treatment for multiple times to obtain a forging;

[0009] Under the second set condition, the forging is heat treated to uniformly distribute heat in the forging area of ​​the forging to obtain a Hastelloy forging.

[0010] Optionally, the first setting conditions include: temperature of 1100°C to 1120°C, and time of 1h to 2h.

[0011] Optionally, the second setting conditions include: temperature of 1120°C to 1150°C, and time of 1h to 2h.

[0012] Optionally, the homogenization process includes a first homogenization process and a second homogenization process; wherein,

[0013] The process parameters of the first homogenization treatment include: temperature of 1120°C to 1150°C and time of 1h to 2h;

[0014] The process parameters of the second homogenization treatment include: temperature of 1150° C. to 1180° C., and time of 3 h to 4 h.

[0015] Optionally, the process parameters of the forging treatment for multiple times include: the final forging temperature is ≥1050°C;

[0016] The reheating temperature is 1150℃~1180℃, and the reheating time is 40min~60min.

[0017] Optionally, the step of subjecting the red-transformed ingot having a set chemical composition to stress relief treatment under the first set condition comprises:

[0018] The raw materials are sequentially subjected to vacuum induction melting and electroslag remelting to obtain a red-cast ingot having a set chemical composition;

[0019] Under the first set condition, the red-transformed ingot with set chemical composition is subjected to stress relief treatment.

[0020] Optionally, the set chemical composition includes: Mo, Cr, Fe, W, C, Mn, Si, Co, V, and matrix element Ni; wherein, in parts by mass,

[0021] Mo is 15.0 to 17.0 parts, Cr is 14.5 to 16.5 parts, Fe is 4.0 to 7.0 parts, W is 3.0 to 4.5 parts, C is ≤0.02 parts, Mn is ≤1.0 parts, Si is ≤0.08 parts, Co is ≤2.5 parts, and V is ≤0.35 parts.

[0022] Optionally, the Hastelloy forging meets the following mechanical properties: tensile strength is ≥760MPa, yield strength is

[0023] ≥355MPa, elongation ≥40%, hardness 28HRC~36HRC.

[0024] In a second aspect, an embodiment of the present application provides a Hastelloy forging, which is prepared by the method described in any embodiment of the first aspect.

[0025] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0026] The preparation method of the Hastelloy forging provided in an embodiment of the present application comprises: subjecting a red-turned ingot with a set chemical composition to stress relief treatment under a first set condition; subjecting the ingot after the stress relief treatment to homogenization treatment; subjecting the ingot after the homogenization treatment to forging treatment for multiple times to obtain a forging; and subjecting the forging to heat treatment under a second set condition to uniformly distribute heat in the forging area of ​​the forging to obtain a Hastelloy forging. The red-transformed ingot with set chemical composition is subjected to stress relief treatment under the first set conditions, which can reduce the element enrichment and shrinkage shrinkage of the head of the red-transformed ingot, as well as reduce the thermal stress concentration at the bottom of the red-transformed ingot; the ingot after stress relief treatment is subjected to homogenization treatment, which can eliminate the M6C carbide and the brittle intergranular precipitate μ phase in the ingot, thereby refining the grain of the ingot; the ingot after homogenization treatment is forged for many times, and the heat difference area is reduced by post-forging heat treatment in view of the defect of uneven heat distribution in the forging area, thereby reducing the cracking caused by partial stress concentration during the air cooling of the ingot. Therefore, under the synergistic effect of stress relief treatment, homogenization treatment, forging and post-forging heat treatment, the thermal stress and element segregation of the ingot are reduced, the precipitated phase is dissolved back to the maximum extent, the grain recovery recrystallization is promoted, the processing deformation resistance is reduced, the organization is refined, and the plasticity of the Hastelloy forgings is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0028] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0029] Figure 1 A schematic flow chart of a method for preparing a Hastelloy forging provided in an embodiment of the present application;

[0030] Figure 2 A schematic diagram of the internal temperature field of the electroslag remelting ingot of the C-276 alloy provided in Example 1 of the present application;

[0031] Figure 3 This is a DSC differential thermal analysis diagram of the C-276 alloy provided in Example 1 of the present application;

[0032] Figure 4 This is the EBSD morphology of the forged structure in the C-276 alloy provided in Example 1 of the present application;

[0033] Figure 5EBSD morphology of forged structure in C-276 alloy provided in comparative example 1 of this application

[0034] Figure 6 EBSD morphology of forging structure in C-276 alloy provided in Comparative Example 2 of the present application;

[0035] Figure 7 This is the EBSD morphology image of the forged structure in the C-276 alloy provided in Comparative Example 3 of the present application. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0037] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0038] In the present application, in the absence of any contrary description, the directional words used, such as "upper" and "lower", are specifically the directions of the drawings in the accompanying drawings. In addition, in the description of the present specification, the terms "including", "comprising", etc. refer to "including but not limited to". In this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. In this article, "and / or" describes the association relationship of the associated objects, indicating that there may be three relationships, for example, A and / or B, which can represent: A exists alone, A and B exist at the same time, and B exists alone. Wherein A, B can be singular or plural. In this article, "at least one" refers to one or more, and "plural" refers to two or more. "At least one", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of singular or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can all represent: a, b, c, ab (i.e. a and b), ac, bc, or abc, where a, b, and c can be single or multiple. "Parts" such as parts by weight, parts by mass, etc. represent the ratio between the components.

[0039] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0040] Hastelloy is a nickel-based alloy. It is mainly used to resist various corrosive environments and is a high-performance corrosion-resistant alloy. Its development stems from the urgent need in the industrial field for materials that can work stably and for a long time in harsh chemical environments. The embodiment of the present application focuses on Hastelloy C-276, which is a more famous one in the C series. The C series alloys have good tolerance to corrosive media in both oxidizing and reducing environments and are an all-round corrosion-resistant alloy. The reasonable combination of its chemical composition enables it to maintain a low corrosion rate in complex environments of various chemical media, such as mixed acids and chlorine-containing solutions in chemical production.

[0041] C-276 is an alloy with a high degree of alloying, and its hot working range is very narrow, making forging difficult. In the first aspect, the present application embodiment provides a method for preparing a Hastelloy forging. Figure 1 A schematic diagram of a process for preparing a Hastelloy forging provided in an embodiment of the present application; see Figure 1 , the method comprising:

[0042] S1. Under a first set condition, subjecting a red-transformed ingot having a set chemical composition to stress relief treatment;

[0043] In some embodiments, the first set condition includes: a temperature of 1100° C. to 1120° C. and a time of 1 h to 2 h.

[0044] In the embodiment of the present application, the first setting condition includes: the temperature can be 1100℃~1120℃, the time can be 1h~2h, which can fully reduce the element enrichment and shrinkage shrinkage of the head of the ingot, and reduce the thermal stress concentration at the bottom of the ingot; if the temperature in the first setting condition is higher than 1120℃ or the time is longer than 2h, it may aggravate the grain growth of the ingot and increase the difficulty of subsequent forging; if the temperature in the first setting condition is lower than 1100℃ or the time is shorter than 1h, it may accelerate the element enrichment and shrinkage deepening of the head of the ingot. Exemplarily, the temperature can be 1100℃, 1102℃, 1104℃, 1106℃, 1108℃, 1110℃, 1112℃, 1114℃, 1116℃, 1118℃, 1120℃, etc.; the time can be 1h, 1.2h, 1.4h, 1.6h, 1.8h, 2.0h, etc.

[0045] In some embodiments, the step of subjecting a red-transformed ingot having a set chemical composition to stress relief treatment under the first set condition comprises:

[0046] The raw materials (nickel plate, molybdenum bar, ferrotungsten, metallic chromium, pure iron, electrolytic manganese, ferrovanadium) are sequentially subjected to vacuum induction melting and electroslag remelting to obtain a red-cast ingot with a set chemical composition;

[0047] Under the first set condition, the red-transformed ingot with set chemical composition is subjected to stress relief treatment.

[0048] In the embodiments of the present application, vacuum induction melting is a smelting method that uses the principle of electromagnetic induction to generate an induced current in the metal raw material under a vacuum environment, thereby generating heat to melt the raw material. Vacuum induction melting can produce high-purity, high-quality liquid metal, providing a good foundation for the subsequent acquisition of high-quality ingots. Electroslag remelting is a process that uses the resistance heat generated when an electric current passes through a liquid slag pool to melt the consumable electrode (made of a metal ingot or billet obtained by vacuum induction melting), and re-solidifies the molten metal liquid into an ingot under the action of a water-cooled crystallizer. Electroslag remelting can significantly improve the purity and density of the ingot, improve the internal organizational structure of the ingot, make the grains of the ingot more refined and uniform, and thus improve the comprehensive performance of the ingot.

[0049] In some embodiments, the set chemical composition includes: Mo, Cr, Fe, W, C, Mn, Si, Co, V, and matrix element Ni; wherein, in parts by mass,

[0050] Mo is 15.0 to 17.0 parts, Cr is 14.5 to 16.5 parts, Fe is 4.0 to 7.0 parts, W is 3.0 to 4.5 parts, C is ≤0.02 parts, Mn is ≤1.0 parts, Si is ≤0.08 parts, Co is ≤2.5 parts, and V is ≤0.35 parts.

[0051] In the embodiment of the present application, the chemical composition is reasonably designed and set to ensure the mechanical properties of Hastelloy, and the set chemical composition is for C-276 Hastelloy. For example, the Mo can be 15.0 parts, 16.0 parts, 17.0 parts, etc.; Cr can be 14.5 parts, 15.5 parts, 16.5 parts, etc.; Fe can be 4.0 parts, 5.0 parts, 6.0 parts, 7.0 parts, etc.; W can be 3.0 parts, 3.5 parts, 4.0 parts, 4.5 parts, etc.; C can be 0.02 parts, 0.015 parts, 0.01 parts, etc.; Mn can be 1.0 parts, 0.9 parts, 0.8 parts, etc.; Si can be 0.08 parts, 0.07 parts, 0.06 parts, etc.; Co can be 2.5 parts, 2.4 parts, 2.3 parts, etc.; V can be 0.35 parts, 0.34 parts, 0.33 parts, etc.

[0052] S2, homogenizing the ingot after stress relief treatment;

[0053] In some embodiments, the homogenization process includes a first homogenization process and a second homogenization process; wherein,

[0054] The process parameters of the first homogenization treatment include: temperature of 1120°C to 1150°C and time of 1h to 2h;

[0055] The process parameters of the second homogenization treatment include: temperature of 1150° C. to 1180° C., and time of 3 h to 4 h.

[0056] In the embodiment of the present application, the process parameters of the first homogenization treatment include: the temperature can be 1120℃~1150℃, the time can be 1h~2h, and the M6C carbide can be eliminated as much as possible. If the temperature in the process parameters of the first homogenization treatment is higher than 1150℃ or the time is longer than 2h, the carbide may be melted back, but the grains become larger, increasing the difficulty of subsequent forging processing; if the temperature in the process parameters of the first homogenization treatment is lower than 1120℃ or the time is shorter than 1h, the M6C carbide may not be completely eliminated, which may easily lead to carbide aggregation at the grain boundary and cause ingot cracking. Exemplarily, the process parameter temperature of the second homogenization treatment can be 1120℃, 1130℃, 1140℃, 1150℃, etc.; the time can be 1h, 1.2h, 1.5h, 1.6h, 1.8h, 2h, etc.

[0057] The process parameters of the second homogenization treatment include: the temperature can be 1150℃~1180℃, the time can be 3h~4h, and the brittle intergranular precipitate μ phase can be eliminated as much as possible. If the temperature in the process parameters of the second homogenization treatment is higher than 1180℃ or the time is longer than 4h, the brittle intergranular precipitate μ phase may be dissolved back, but the grains will become larger, increasing the difficulty of subsequent forging; if the temperature in the process parameters of the second homogenization treatment is lower than 1150℃ or the time is shorter than 3h, the brittle intergranular precipitate μ phase may not be eliminated, causing the ingot to crack. Exemplarily, in the process parameters of the second homogenization treatment, the temperature can be 1150℃, 1160℃, 1170℃, 1180℃, etc.; the time can be 3h, 3.2h, 3.4h, 3.6h, 3.8h, 4h, etc.

[0058] S3, forging the homogenized ingot for multiple times to obtain a forging;

[0059] In some embodiments, the process parameters of the forging treatment for multiple times include: the final forging temperature is ≥1050°C;

[0060] The reheating temperature is 1150℃~1180℃, and the reheating time is 40min~60min.

[0061] In the embodiment of the present application, the final forging temperature may be ≥1050°C, which can reduce the rapid precipitation of μ phase and carbide at the grain boundary, so that the ingot is in the forging hot working area; if the final forging temperature is lower than 1050°C, the ingot may quickly produce μ phase and carbide, directly reducing the hot working plasticity of the alloy and inducing cracking. Exemplarily, the final forging temperature may be 1050°C, 1055°C, 1060°C, 1065°C, 1070°C, etc.

[0062] The purpose of reheating is to restore the metal material to the appropriate forging temperature range after a certain forging deformation, and to perform the forging operation again. The reheating temperature can be 1150℃~1180℃, and the reheating time can be 40min~60min, so as to dissolve μ phase and carbide as much as possible, reduce or even eliminate element segregation, and improve the hot working plasticity of the ingot. If the reheating temperature is higher than 1180℃ or the time is longer than 60min, it may promote the internal grain growth of the ingot; if the reheating temperature is lower than 1150℃ or the time is shorter than 40min, a large amount of μ phase and carbide may be precipitated, missing the narrow processing range, and inducing cracking of the ingot. Exemplarily, the reheating temperature can be 1150℃, 1160℃, 1170℃, 1180℃, etc.; the reheating time can be 40min, 45min, 50min, 55min, 60min, etc.

[0063] Multiple forgings can gradually improve the organizational structure and performance of metal materials: the first forging can initially change the shape of the material, making it develop towards the outline of the final product, while breaking the coarse grains in the original cast structure and making the structure initially refined. With the increase in the number of subsequent forgings, the internal structure of the material is continuously optimized, impurities and defects are further eliminated or dispersed, and the internal stress distribution is more uniform. The number of forgings can be 3 to 5.

[0064] S4. Under the second set condition, the forging is heat treated to uniformly distribute heat in the forging area of ​​the forging to obtain a Hastelloy forging.

[0065] In some embodiments, the second set conditions include: a temperature of 1120° C. to 1150° C. and a time of 1 h to 2 h.

[0066] In the embodiment of the present application, the second setting condition includes: the temperature can be 1120℃~1150℃, the time can be 1h~2h, the ingot after homogenization treatment is forged for many times, and the heat distribution in the forging area is uneven, and the heat difference area is reduced by post-forging heat treatment, thereby reducing the cracking caused by partial stress concentration during the air cooling of the ingot. If the temperature of the second setting condition is higher than 1150℃ or the time is longer than 2h, it may cause the grain growth of the forging and affect the next rolling process; if the temperature of the second setting condition is lower than 1120℃ or the time is shorter than 1h, there may be some stress that cannot be eliminated, causing the forging to crack. Exemplarily, in the second setting condition, the temperature can be 1120℃, 1130℃, 1140℃, 1150℃, etc.; the time can be 1h, 1.2h, 1.3h, 1.5h, 1.7h, 1.8h, 2h, etc.

[0067] In some embodiments, the Hastelloy forging meets the following mechanical properties: tensile strength is ≥760 MPa, yield strength is ≥355 MPa, elongation is ≥40%, and hardness is 28HRC-36HRC.

[0068] The method for preparing the Hastelloy forging provided in the embodiment of the present application has the following advantages:

[0069] 1. Reduction of thermal stress and element segregation: Stress relief treatment alleviates the initial stress and uneven element distribution of the ingot from the source. Homogenization treatment further optimizes the element distribution and refines the grains. Although new stress will be generated during multiple forging processes, the organizational structure will also be continuously improved. The final post-forging heat treatment adjusts the uneven heat distribution and stress concentration generated by forging. These steps work together to effectively reduce the accumulation of thermal stress and element segregation in the ingot during the entire preparation process.

[0070] 2. Dissolution of precipitated phases and optimization of grains: The homogenization treatment dissolves some precipitated phases (such as M6C carbides) back into the matrix through high temperature. The high temperature and large deformation during the forging process promote the breakage and deformation of the grains, while the subsequent heat treatment helps the recovery and recrystallization of the grains, making the grains smaller and more uniform after a series of treatments, and optimizing the grain structure to the greatest extent;

[0071] 3. Reduction of processing deformation resistance and refinement of organization: The above steps work together to continuously refine the organization structure inside the ingot, and the originally coarse grains and uneven organization become more uniform and fine, which reduces the deformation resistance of the material in the subsequent processing process and is more conducive to further processing operations. At the same time, the refined organization also lays the foundation for improving the comprehensive performance of the forgings;

[0072] 4. Performance correlation analysis: The plasticity of Hastelloy forgings is finally improved through the synergistic effects of reducing thermal stress and element segregation, optimizing grain structure, and reducing resistance to processing deformation. The reduction of thermal stress and element segregation avoids premature failure of materials due to local stress concentration and uneven composition. The optimized grain structure enables the grain boundaries to better coordinate deformation when the material is deformed by force, hindering the generation and expansion of cracks. The lower resistance to processing deformation means that the material is more likely to deform uniformly during plastic deformation, and is less likely to crack due to local excessive deformation. In combination, the plasticity of the forgings is significantly improved, so that it can better withstand various external forces without damage in subsequent use.

[0073] In a second aspect, an embodiment of the present application provides a Hastelloy forging, which is prepared by the method described in any embodiment of the first aspect.

[0074] The Hastelloy forging is realized based on the preparation method of the Hastelloy forging. The specific steps of the preparation method of the Hastelloy forging can refer to the above embodiment. Since the Hastelloy forging adopts part or all of the technical solutions of the above embodiment, it at least has all the beneficial effects brought by the technical solutions of the above embodiment, which will not be repeated here.

[0075] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are intended only to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods for the unrecorded specific conditions in the following examples are usually measured according to national standards. If there is no corresponding national standard, then carry out according to general international standards, normal conditions or according to the conditions recommended by the manufacturer.

[0076] Example 1

[0077] A method for preparing a Hastelloy C-276 forging, comprising:

[0078] The raw materials are sequentially subjected to vacuum induction melting and electroslag remelting to obtain a red-cast ingot with a set chemical composition; the set chemical composition, in terms of mass percentage, consists of the following components: Mo: 16.2%, Cr: 16.1%, Fe: 5.4%, W: 3.9%, C: 0.012%, Mn: 0.06%, Si: 0.06%, Co: 1.8%, V: 0.27%, the balance is Ni, and the rest are inevitable impurity elements;

[0079] Figure 2 Schematic diagram of the internal temperature field of the electroslag remelting ingot of the C-276 alloy provided in Example 1 of the present application; see Figure 2 During the solidification of the internal structure of the remelted steel ingot, the bottom cools the fastest, resulting in a large temperature gradient and large residual thermal stress; the head of the steel ingot solidifies last, so it is prone to shrinkage cavities and element segregation;

[0080] Under the first set condition, a red-cast ingot with a set chemical composition is subjected to stress relief treatment; the first set condition is a temperature of 1120° C. and a time of 1 hour;

[0081] The ingot after stress relief treatment was homogenized; the first homogenization treatment: temperature was 1150°C, time was 2h; the second homogenization treatment: temperature was 1180°C, time was 4h. Figure 3 DSC differential thermal analysis diagram of C-276 alloy provided in Example 1 of the present application; see Figure 3 , onset of precipitation (onset), end of precipitation (onset), peak maximum precipitation temperature, DSC differential thermal analysis diagram shows that C-276 alloy is prone to precipitation phase precipitation in the range of 1163℃~1288℃, so the μ phase and carbide in the ingot are dissolved back through homogenization treatment.

[0082] The homogenized ingot is forged several times to obtain forgings; the final forging temperature is 1063℃; specifically: the first forging deformation is 30%, and the forging process changes from cylindrical to hexagonal to avoid sharp angles and reduce corner cracks caused by large local temperature differences. When the bar is at 1053℃, it is returned to the 1180℃ furnace for heating and kept warm for 40 minutes. The second forging deformation is 20%, and the forging process continues from hexagonal to hexagonal. When the bar is at 1050℃, it is returned to the 1180℃ furnace for heating and kept warm for 40 minutes. The third forging deformation is 18%, and the forging process changes from hexagonal to round.

[0083] Under the second setting condition, the forging is heat treated to uniformly distribute heat in the forging area of ​​the forging to obtain a Hastelloy forging; the second setting condition is a temperature of 1150° C. and a time of 1 hour.

[0084] After heat treatment and air cooling, there are no obvious cracks on the surface of the forgings. The size of the forgings is Φ120×400mm. Figure 4 EBSD morphology of the forged structure of the C-276 alloy provided in Example 1 of the present application; see Figure 4 The EBSD morphology diagram visually observed that the grain size after forging was 18μm~23μm.

[0085] Example 2

[0086] A method for preparing a Hastelloy C-276 forging, comprising:

[0087] The raw materials are sequentially subjected to vacuum induction melting and electroslag remelting to obtain a red-cast ingot with a set chemical composition; the set chemical composition, in terms of mass percentage, consists of the following components: Mo: 15.6%, Cr: 16.1%, Fe: 4.5%, W: 3.8%, C: 0.010%, Mn: 0.07%, Si: 0.07%, Co: 1.3%, V: 0.31, the balance is Ni, and the rest are inevitable impurity elements;

[0088] Under the first set condition, a red-transformed ingot with a set chemical composition is subjected to stress relief treatment; the first set condition is a temperature of 1120° C. and a time of 1.5 h;

[0089] The ingot after stress relief treatment is homogenized; the first homogenization treatment: temperature is 1150°C, time is 2h; the second homogenization treatment: temperature is 1170°C, time is 3.5h;

[0090] The homogenized ingot is forged several times to obtain forgings; the final forging temperature is 1057℃; specifically: the first forging deformation is 25%, and the forging process changes from cylindrical to hexagonal to avoid sharp angles and reduce corner cracks caused by large local temperature differences. When the bar is at 1075℃, it is returned to the 1170℃ furnace for heating and kept warm for 50 minutes. The second forging deformation is 25%, and the forging process continues from hexagonal to hexagonal. When the bar is at 1082℃, it is returned to the 1170℃ furnace for heating and kept warm for 50 minutes. The third forging deformation is 18%, and the forging process changes from hexagonal to round.

[0091] Under the second setting condition, the forging is heat treated to uniformly distribute the heat in the forging area of ​​the forging to obtain a Hastelloy forging; the second setting condition is a temperature of 1130° C. and a time of 1.5 h.

[0092] After heat treatment, the forgings are air-cooled and have no obvious cracks on the surface. The size of the forgings is Φ120×400mm. The grain size after forging is 20μm~25μm.

[0093] Example 3

[0094] A method for preparing a Hastelloy C-276 forging, comprising:

[0095] The raw materials are sequentially subjected to vacuum induction melting and electroslag remelting to obtain a red-cast ingot with a set chemical composition; the set chemical composition, in terms of mass percentage, consists of the following components: Mo: 16.3%, Cr: 15.9%, Fe: 4.1%, W: 3.7%, C: 0.014%, Mn: 0.06%, Si: 0.08%, Co: 1.45%, V: 0.36%, the balance is Ni, and the rest are inevitable impurity elements;

[0096] Under the first set condition, a red-cast ingot with a set chemical composition is subjected to stress relief treatment; the first set condition is a temperature of 1120° C. and a time of 2 hours;

[0097] The ingot after stress relief treatment is homogenized; the first homogenization treatment: temperature is 1120°C, time is 1h; the second homogenization treatment: temperature is 1160°C, time is 3h;

[0098] The ingot after homogenization treatment is forged several times to obtain forgings; the final forging temperature is 1061℃; specifically: the first forging deformation is 20%, and the forging process changes from cylindrical to hexagonal to avoid sharp angles and reduce corner cracks caused by large local temperature differences. When the bar is at 1100℃, it is returned to the 1160℃ furnace for heating and kept warm for 50 minutes. The second forging deformation is 18%, and the forging process continues from hexagonal to hexagonal. When the bar is at 1095℃, it is returned to the 1160℃ furnace for heating and kept warm for 50 minutes. The third forging deformation is 18%. When the bar is at 1051℃, it is returned to the 1160℃ furnace for heating and kept warm for 50 minutes. The fourth forging deformation is 20%, and the forging process changes from hexagonal to round;

[0099] Under the second setting condition, the forging is heat treated to uniformly distribute the heat in the forging area of ​​the forging to obtain a Hastelloy forging; the second setting condition is a temperature of 1140° C. and a time of 2 hours.

[0100] After heat treatment, the forgings were air-cooled and had no obvious cracks on the surface. The forging size was Φ120×400mm. The grain size after forging was 23μm~27μm.

[0101] Comparative Example 1

[0102] A method for preparing a Hastelloy C-276 forging, comprising:

[0103] Smelting process: the dried raw materials are subjected to vacuum induction melting and electroslag remelting to obtain red-cast ingots; the chemical composition of the C-276 alloy red-cast ingot is: Mo: 15.8%, Cr: 16.1%, Fe: 5.1%, W: 3.6%, C: 0.013%, Mn: 0.06%, Si: 0.08%, Co: 1.23%, V: 0.33%, the balance is Ni, and the rest are inevitable impurity elements;

[0104] No stress relief: C-276 alloy red-cast ingot is directly air-cooled out of the furnace.

[0105] Homogenization treatment: the C-276 alloy prepared in the above step is placed in a heating furnace, the temperature of the C-276 alloy is raised to 1100°C and kept at this temperature for 1 hour; the temperature is then raised to 1150°C and kept at this temperature for 3 hours;

[0106] Forging: Multiple forgings, the final forging temperature is not less than 1050℃. The first forging deformation is 20%. When the bar is at 1101℃, it is returned to the 1150℃ furnace for heating and kept warm for 40min. The second forging deformation is 18%, and the forging process continues from sixteen squares to sixteen squares. When the bar is at 1055℃, it is returned to the 1150℃ furnace for heating and kept warm for 40min. The third forging deformation is 16%. When the bar is at 1062℃, it is returned to the 1150℃ furnace for heating and kept warm for 40min. The fourth forging deformation is 16%. When the bar is at 1071℃, it is returned to the 1150℃ furnace for heating and kept warm for 60min. The fifth forging deformation is 12%, and the forging process changes from sixteen squares to rounds.

[0107] Post-forging heat treatment: heat the forged C-276 alloy to 1120℃ and keep it warm for 1h.

[0108] After cooling after heat treatment after forging, there is no obvious crack on the surface of the billet, and the size of the forging is Φ120×400mm. Figure 5 EBSD morphology of forging structure in C-276 alloy provided for comparative example 1 of this application; see Figure 5 , the grain size is 40~50μm.

[0109] Comparative Example 2

[0110] A preparation method of Hastelloy C-276 forgings, comprising: a smelting process: subjecting dried raw materials to vacuum induction melting and electroslag remelting to obtain a red cast ingot; the chemical composition of the C-276 alloy red cast ingot is: Mo: 15.9%, Cr: 16.1%, Fe: 4.6%, W: 3.9%, C: 0.008%, Mn: 0.065%, Si: 0.06%, Co: 1.13%, V: 0.29%, the balance is Ni, and the rest are inevitable impurity elements;

[0111] Stress relief: C-276 alloy red-cast ingot is heated to 1120℃ and kept at this temperature for 1h.

[0112] Homogenization treatment: the C-276 alloy in the above step is recharged, the temperature of the C-276 alloy is raised to 1110°C, and kept at this temperature for 1 hour; then the temperature is raised to 1140°C, and kept at this temperature for 2 hours;

[0113] Forging: Multiple forgings, the final forging temperature is not less than 1050℃. The first forging deformation is 18%. When the bar is at 1112℃, it is returned to the 1150℃ furnace for heating and kept warm for 60min. The second forging deformation is 18%, and the forging process continues from sixteen squares to sixteen squares. When the bar is at 1075℃, it is returned to the 1150℃ furnace for heating and kept warm for 60min. The third forging deformation is 18%. When the bar is at 1054℃, it is returned to the 1150℃ furnace for heating and kept warm for 60min. The fourth forging deformation is 12%. When the bar is at 1066℃, it is returned to the 1150℃ furnace for heating and kept warm for 60min. The fifth forging deformation is 10%, and the forging process changes from sixteen squares to rounds.

[0114] Post-forging heat treatment: heat the forged C-276 alloy to 1120℃ and keep it for 1h.

[0115] After cooling after heat treatment after forging, there is no obvious crack on the surface of the billet, and the size of the forging is Φ120×400mm. Figure 6 EBSD morphology of forging structure in C-276 alloy provided for comparative example 2 of this application; see Figure 6 , the grain size is 30μm~40μm.

[0116] Comparative Example 3

[0117] A preparation method of Hastelloy C-276 forgings, comprising: a smelting process: subjecting dried raw materials to vacuum induction melting and electroslag remelting to obtain a red cast ingot; the chemical composition of the C-276 alloy red cast ingot is: Mo: 16.1%, Cr: 16.3%, Fe: 4.4%, W: 3.7%, C: 0.009%, Mn: 0.059%, Si: 0.07%, Co: 1.08%, V: 0.32%, the balance is Ni, and the rest are inevitable impurity elements;

[0118] Stress relief: C-276 alloy red-cast ingot is heated to 1120℃ and kept at this temperature for 1h.

[0119] Homogenization treatment: the C-276 alloy in the above step is recharged, the temperature of the C-276 alloy is raised to 1120°C, and kept at this temperature for 1 hour; then the temperature is raised to 1150°C, and kept at this temperature for 3 hours;

[0120] Forging: Multiple forgings, the final forging temperature is not less than 1050℃. The first forging deformation is 25%. When the bar is at 1063℃, it is returned to the 1150℃ furnace for heating and kept warm for 50min. The second forging deformation is 18%, and the forging process continues from sixteen squares to sixteen squares. When the bar is at 1069℃, it is returned to the 1150℃ furnace for heating and kept warm for 50min. The third forging deformation is 18%. When the bar is at 1062℃, it is returned to the 1150℃ furnace for heating and kept warm for 50min. The fourth forging deformation is 18%. When the bar is at 1054℃, it is returned to the 1150℃ furnace for heating and kept warm for 50min. The fifth forging deformation is 10%, and the forging process changes from sixteen squares to rounds.

[0121] No heat treatment after forging: The ingot after forging in the above steps is not subjected to post-forging heat treatment.

[0122] After forging, it is air-cooled and there is no obvious crack on the surface after cooling. The forging size is Φ120×400mm. Figure 7 EBSD morphology of forging structure in C-276 alloy provided for comparative example 3 of this application; see Figure 7 , the grain size is 25μm~30μm.

[0123] The performance data of Hastelloy C-276 prepared in Examples 1 to 3 and Comparative Examples 1 to 3 are shown in Table 1:

[0124] Table 1 Performance test data

[0125] project Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Elongation after break / % 45 42.5 40.3 26 32 29 Hardness / HRC 30 32 36 47 41 45 Tensile strength MPa 885 914 956 1150 1013 1059 Yield strength MPa 619 641 675 805 709 742

[0126] Hardness is a mechanical property index that measures the hardness of metal materials. It indicates the ability of a local volume on the metal surface to resist deformation. There is an approximate corresponding relationship between the various hardness values ​​of metal materials and between the hardness value and the strength value. Generally speaking, the higher the strength of the material, the higher the resistance to plastic deformation, and the higher the hardness value, and vice versa.

[0127] Compared with Examples 1 to 3, smelting, stress relief, homogenization treatment, forging and post-forging heat treatment within a reasonable range are helpful to obtain a C-276 alloy with high elongation and good plasticity. Compared with Example 1, Examples 2 and 3 reduce the heat treatment time of the steel ingot after forging, which can sacrifice the elongation and increase the hardness, but the range is still within the standard. Compared with the comparative examples, the examples do not have stress relief (Comparative Example 1), lower temperature and shorter time pre-forging heat treatment leads to an increase in the number of fire forgings (Comparative Example 2), and no post-forging heat treatment (Comparative Example 3). These comparative examples require multiple fire forgings in the process engineering, increase costs, small elongation, increased deformation resistance, increased hardness, and low plasticity. Compared with Example 1, the C-276 alloy of Comparative Example 1 does not add a stress relief process, increases the element enrichment and shrinkage shrinkage of the remelted ingot head, and the thermal stress concentration at the bottom; increases the number of tempering in the subsequent forging process, and also makes the alloy have the worst elongation, the highest hardness, and the largest grain size (40 to 50 μm). Compared with Example 1, the C-276 alloy of Comparative Example 2 has a lower temperature and a shorter time for pre-forging heat treatment, a short homogenization time, an increase in the probability of μ phase and carbide precipitation at the grain boundary, and then an increase in the number of tempering times in the subsequent forging process, affecting the hardness and plasticity of the ingot, and the organization grain size is larger (30-40μm). Compared with Example 1, the C-276 alloy of Comparative Example 3 is not heat-treated after forging, and the heat distribution in the forging area is uneven, which increases the partial stress concentration during the air cooling of the ingot, increases the hardness, reduces the plasticity, and has a larger organization grain size (20-30μm). Therefore, suitable stress relief, homogenization treatment, forging reduction and post-forging heat treatment can reduce the thermal stress and element segregation of the ingot, dissolve the precipitated phase to the maximum extent, promote the recovery of grains and recrystallization, reduce the resistance to processing deformation, refine the organization, and improve the plasticity of the C-276 alloy.

[0128] One or more technical solutions in the embodiments of the present application also have at least the following technical effects or advantages:

[0129] (1) The preparation method of the Hastelloy alloy forging provided in the embodiment of the present application reduces the thermal stress and element segregation of the ingot, dissolves the precipitated phase to the maximum extent, promotes grain recovery and recrystallization, reduces the resistance to processing deformation, refines the structure, and improves the plasticity of the C-276 alloy;

[0130] (2) The preparation method of Hastelloy forgings provided in the embodiment of the present application shortens the long-term high-temperature operation of the heating furnace, saves energy and reduces emissions, and promotes enterprises to further reduce costs and increase efficiency through reasonable heat treatment processes before, during and after forging.

[0131] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A method for preparing a Hastelloy forging, the method comprising: Under a first set condition, a red-transformed ingot having a set chemical composition is subjected to stress relief treatment; homogenizing the ingot after stress relief treatment; The homogenized ingot is subjected to forging treatment for multiple times to obtain a forging; Under the second set condition, the forging is heat treated to uniformly distribute heat in the forging area of ​​the forging to obtain a Hastelloy forging.

2. The method according to claim 1, characterized in that The first setting conditions include: temperature of 1100° C. to 1120° C., and time of 1 hour to 2 hours.

3. The method according to claim 1, characterized in that The second setting conditions include: temperature of 1120° C. to 1150° C., and time of 1 hour to 2 hours.

4. The method according to claim 1, characterized in that: The homogenization process includes a first homogenization process and a second homogenization process; wherein, The process parameters of the first homogenization treatment include: temperature of 1120°C to 1150°C and time of 1h to 2h; The process parameters of the second homogenization treatment include: temperature of 1150° C. to 1180° C., and time of 3 h to 4 h.

5. The method according to claim 1, characterized in that: The process parameters of the forging treatment include: the final forging temperature is ≥1050°C; The reheating temperature is 1150℃~1180℃, and the reheating time is 40min~60min.

6. The method according to claim 1, characterized in that The step of subjecting the red-transformed ingot having a set chemical composition to stress relief treatment under the first set condition comprises: The raw materials are sequentially subjected to vacuum induction melting and electroslag remelting to obtain a red-cast ingot having a set chemical composition; Under the first set condition, the red-transformed ingot with set chemical composition is subjected to stress relief treatment.

7. The method according to claim 1, characterized in that The set chemical composition includes: Mo, Cr, Fe, W, C, Mn, Si, Co, V, and matrix element Ni; wherein, by mass, Mo is 15.0 to 17.0 parts, Cr is 14.5 to 16.5 parts, Fe is 4.0 to 7.0 parts, W is 3.0 to 4.5 parts, C is ≤0.02 parts, Mn is ≤1.0 parts, Si is ≤0.08 parts, Co is ≤2.5 parts, and V is ≤0.35 parts.

8. The method according to claim 1, characterized in that The Hastelloy forging meets the following mechanical properties: tensile strength is ≥760MPa, yield strength is ≥355MPa, elongation is ≥40%, and hardness is 28HRC-36HRC.

9. A Hastelloy forging, wherein the Hastelloy forging is prepared by the method according to any one of claims 1 to 8.

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