A rolling process for difficult-to-deform alloy square and flat products

Abstract

The present invention discloses a rolling process for square flat materials of alloys that are difficult to deform. Through reasonable process control, the square flat materials with the same shape and size, transverse and longitudinal mechanical properties and microstructure can be produced. The technical process flow of the present invention is as follows: billet design and preparation → heating → rolling blanking → rolling forming → residual heat straightening → surface finishing → finished product inspection; the square flat material rolling process is mainly adopted, including two processes: rolling blanking and rolling forming. The process parameters for the design of blanking size, the basic distribution of rolling forming deformation, the requirements for final rolling temperature, and the state of surface and flatness are provided. The benefits of the present invention are as follows: the special process for rolling square flat materials is utilized to meet the shape, surface quality, mechanical properties and microstructure of the product; this type of square flat material can be used for the processing of blade products, and can replace the quality risks and costs caused by the continued forging process brought about by round steel. The process can be applied to the processing of square flat parts in more fields.

Description

Technical Field

[0001] The invention belongs to a special alloy hot processing technology, and in particular relates to a rolling process for a difficult-to-deform alloy square flat material. Background Art

[0002] Difficult-to-deform alloys mainly rely on strengthening methods such as solid solution strengthening, aging strengthening and phase transformation strengthening. The alloys have a narrow hot working window and are characterized by great difficulty in deformation, poor deformation plasticity, and many factors affecting performance. Summary of the Invention

[0003] The present invention discloses a rolling process for square and flat materials of alloys that are difficult to deform. Through reasonable process control, it can produce square and flat products with consistent shapes and sizes, transverse and longitudinal mechanical properties, and microstructures for small and medium-sized square and flat materials. The production process of square and flat materials of alloys that are difficult to deform is a short-process processing method with the characteristics of rapid production and low energy consumption. In the deformation process, it can replace the forging process of multiple heating combined with slow deformation by heating 1 to 2 times and distributing the deformation amount, which is more conducive to adapting to the problem of narrow recrystallization deformation range and improving dynamic recrystallization conditions. The steps of flat material rolling are generally divided into blanking and addition, which alleviates the cracks (surface cracks or core cracks) caused by excessive deformation exceeding the critical deformation and also provides conditions for grain recovery and uniform growth.

[0004] Technical solution of the present invention:

[0005] 1. Process

[0006] Billet design and preparation → heating → rolling and blanking → rolling and forming → residual heat straightening → surface finishing → finished product inspection.

[0007] ⑴ The design and preparation of the billet, combined with the characteristics of the square flat rolling mill equipment and the expected deformation of more than 25%, the cross-section of the billet should be 100mm~140mm×100mm~140mm, and the length should be 2000mm~3000mm, which is conducive to sufficient deformation while reducing the difference in organization and performance at both ends.

[0008] ⑵ Heating system. Heating behavior is a favorable condition for improving the deformation plasticity of the alloy and meeting the recrystallization temperature rolling. This is related to factors such as the melting point, hardness, and yield strength ratio of the processed product. The rolling temperature of the difficult-to-deform alloy is slightly higher than the forging heating temperature. The pre-design range can be 1100℃~1200℃, and the holding time is 3h~6h. The holding time is increased as temperature compensation during operation. It can be divided into preheating and soaking stages. It is suitable for iron, nickel, and cobalt-based deformation alloys and meets the requirements of the hot working plastic zone. The heating and holding conditions are controlled by temperature uniformity and rolling interval rate.

[0009] ⑶ Rolling blanking, the purpose is to accurately control the size and shape of the finished product before rolling, improve the deformation uniformity in the three directions of XYZ axis, and ensure the success rate of rolling forming and the designed deformation amount; 100mm~140mm×100mm~140mm cross section is blanked to 100mm~150mm×70mm~120mm, the deformation speed is 0.5m / s~8m / s, the deformation pressure direction is on the unidirectional Z axis, and the extension of the metal is on the X and Y axes; the deformation amount design of this step allows rolling after reheating on the basis of meeting the final deformation amount, and is mainly used for alloy varieties with large deformation resistance and narrow deformation range.

[0010] ⑷ Rolling forming: According to the required size of the final product, the design is heated once to meet the requirements of thermal deformation plasticity. The rolling process is divided into Z-axis rolling (three sets of flat rolls) and X-axis rolling (two sets of vertical rolls) (see Figure 1 ), the rolling deformation in two directions is combined and simultaneous, the purpose is to meet the requirements of diagonal symmetry and rectangular cross-sectional shape with four parallel sides, and it also reflects the requirements of uniform deformation of two groups of vertical sides to obtain the result of uniform tissue structure; the deformation amount is usually distributed as 3%~10%-3%~10%-10%~20%-4%~10%-4%~10%.

[0011] ⑸ Residual heat straightening. Using residual heat for straightening during rolling can avoid defects such as organizational changes and abnormal grain size growth caused by reheating. The temperature rise during rolling is caused by friction between metal atoms. Within the designed heating temperature range, the final rolling temperature is between 920℃ and 1010℃, and the straightening temperature can be between 900℃ and 1000℃, which can meet the straightening conditions for varieties with hardness HBW less than 230. If the hardness continues to increase, compensatory heating is required to improve the straightening conditions.

[0012] ⑹Surface finishing: the surface is shot blasted and pickled to remove defects, or it can be finished by planing, turning and milling. This method has a high metal loss rate and low processing efficiency. The products produced by the above rolling forming process have excellent surface quality and regular shape, and do not require mechanical processing to remove surface defects and complete the shape.

[0013] Description of the invention

[0014] This invention is based on a rolling process designed to produce flat, square, and rebar-resistant iron, nickel, and cobalt-based alloys suitable for applications in aviation, aerospace, and nuclear power. The process primarily utilizes a square, flat bar rolling process, encompassing both cogging and forming. The process parameters, including cogging size design, basic roll forming deformation distribution, final rolling temperature requirements, and surface and flatness control, provide significant practical value.

[0015] The present invention is beneficial in that:

[0016] A special process for rolling square flat steel is used to meet the product's shape, surface quality, mechanical properties and microstructure. This type of square flat steel can be used for blade product processing and can replace the quality risks and costs caused by continued forging processing due to round steel. It has been used in blades of aircraft engines and gas turbines. This process can be applied to more fields and the processing of square flat parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic diagram of the rolling direction of square flat steel in which the Y direction is the rolling direction;

[0018] Figure 2 This is a real picture of GH202 alloy 110mm×75mm flat square material;

[0019] Figure 3 This is the microstructure at the center of GH202 alloy 110mm×75mm flat square material;

[0020] Figure 4 It is the microstructure of the flat square center of GH131 alloy;

[0021] Figure 5 It is the flat square edge microstructure of GH131 alloy;

[0022] Figure 6 This is the rolling drawing of 108mm×72mm flat square material of C263 alloy. DETAILED DESCRIPTION

[0023] The following process is performed in conjunction with Example 1, Example 2, and Example 3:

[0024] 1. Normal blank selection: The length should be 2000mm~3000mm, which can meet the deformation of more than 25% and meet the lower limit requirement of 10% of critical deformation in the processing technology;

[0025] 2. Rolling and blanking: deformation speed 0.5m / s~8m / s, non-pass rolling Z-axis unidirectional reduction, reduction 20mm~40mm, rolling passes 1~3, rolling and blanking: 100mm~140mm×100mm~140mm cross section blanking to 100mm~150mm×70mm~120mm;

[0026] 3. Rolling forming: The rolling deformation speed is 0.5m / s~8m / s, the total rolling deformation (rolling blanking plus rolling forming) ranges from 25% to 80%, and the deformation force mode is three-dimensional deformation to meet the requirements of size and quality uniformity; the rolling is divided into 1 to 5 continuous rolling passes, and the rolling forming: from 100mm~150mm×70mm~120mm to 90mm~125mm×60mm~90mm;

[0027] 4. Residual heat straightening: The cooling rate of the product is affected by the contact medium and area, resulting in temperature differences and bending after rolling. Using residual heat straightening is an efficient process that reduces energy consumption and avoids structural changes. The straightening temperature is between 900℃ and 1000℃, and most deformable high-temperature alloys can undergo plastic deformation within this temperature range.

[0028] 5. Surface finishing, surface shot blasting to remove the surface oxide scale of iron-based or iron-nickel-based alloys, or adding pickling is suitable for removing the surface oxide structure and superficial defects of iron, nickel and cobalt-based alloys.

[0029] Example 1

[0030] GH202 alloy 110mm×75mm hot-rolled square flat products;

[0031] GH202 alloy is a nickel-based aging alloy. The main chemical components of the product are as follows: carbon: 0.067%, tungsten: 4.5%, molybdenum: 4.5%, nickel: 47%, aluminum: 1.32%, titanium: 2.64% by mass.

[0032] Finished product specifications: 110mm×75mm.

[0033] The billet size is 120mm×120mm, and the equipment used is WF540 model rolling mill, the heating temperature is 1170℃, the insulation is 5h, and then the rolling and forming are started, with a rolling rate of 2.25m / s; the rolling and forming process is: 120mm×120mm billet 128mm×100mm, rolling and forming 128mm×100mm→129mm×95mm→120mm×97.6mm→121mm×79mm→115mm×77.8mm→110.8mm×75.3mm; the final rolling temperature is 940℃, the head bend is straightened, and the finished product length reaches 7m.

[0034] The mechanical properties test results are shown in Table 1, which meet the standard requirements.

[0035] Table 1 Mechanical properties of GH202 alloy flat square

[0036]

[0037] The surface of the product is shot blasted, such as Figure 2 .

[0038] Microstructure Figure 3 .

[0039] Example 2

[0040] GH131 alloy 93mm×78mm hot-rolled square flat products;

[0041] GH131 alloy is an iron-based solid solution alloy. The main chemical components of the product are as follows: carbon: 0.04%, chromium: 20.5%, tungsten: 5.42%, molybdenum: 3.14%, niobium: 0.98%, nickel: 28% by mass.

[0042] Finished product size: 93mm×78mm.

[0043] The billet size is 105mm×105mm, and the equipment used is WF540 model rolling mill, the heating temperature is 1150℃, the insulation is 4h, and the rolling and forming are carried out in six passes, the rolling rate is 0.88m / s, and the rolling process is: 105mm×105mm billet to 115mm×85mm, rolling and forming 115mm×85mm→115.8mm×80mm→102mm×87.4mm→100.2mm×80mm→93mm×82.7mm→93.4mm×78.5mm; the final rolling temperature is 920℃, the billet has good flatness and does not require straightening.

[0044] There are fine cracks on the surface oxide scale and right angles of the product, which are cleaned after shot blasting and pickling.

[0045] The room temperature mechanical properties are shown in Table 2.

[0046] Table 2 Room temperature tensile properties of GH131 alloy

[0047] NO. R0.2 / MPa Rm / MPa A / ％ Z / ％ A 414 830 42 50 B 420 836 40 45 C 406 842 35.7 48 D 410 840 36 46

[0048] Microstructure Figure 4 、 Figure 5 .

[0049] Example 3

[0050] C263 alloy 108mm×72mm hot rolled square flat steel;

[0051] C263 alloy is a chromium-cobalt-nickel based alloy. The main chemical components of the product are as follows:

[0052] Carbon: 0.058%, Chromium: 20.5%, Cobalt: 20.13%, Molybdenum: 5.95%, Nickel: 51.1%; Aluminum: 0.44%, Titanium: 2.30%;

[0053] Finished product size: 108mm×72mm.

[0054] The billet size is 115mm×115mm, the length is 1800mm~3200mm, and the equipment used is WF540 rolling mill, the heating temperature is 1170℃, the heat preservation is 4h, the rolling is performed in six passes, the rolling speed is 1.21m / s, the rolling opening is: 115mm×115mm to 128mm×100mm, the rolling forming is: 128mm×100mm→129mm×95mm→119.6mm×99mm→123.3mm×78mm→111.2mm×79mm→108.6mm×72.8mm; the final rolling temperature is 950℃, and the two ends are bent. Figure 6 ; After residual heat straightening, the straightness reaches 4mm / m, the surface and dimensional quality meet the ASTMB164 standard, shot blasting is used, and the surface inspection is qualified.

[0055] The mechanical properties test results are shown in Table 3.

[0056] Table 3 Mechanical properties of C263 alloy flat square

[0057]

Claims

1. A rolling process for hard-to-deform alloy square flat products, characterized in that: Process flow: billet design and preparation → heating → rolling and blanking → rolling and forming → residual heat straightening → surface finishing → finished product inspection; The billet is designed and prepared in accordance with the characteristics of the square flat rolling mill and the expected deformation of more than 25%, with a cross section of 100mm to 140mm x 100mm to 140mm and a length of 2000mm to 3000mm; The heating and rolling temperature are higher than the forging heating temperature, the design range is 1100℃~1200℃, and the holding time is 3h~6h; Heating and holding conditions are controlled by temperature uniformity and rolling interval rate; The rolling process is to roll the cross section of 100mm-140mm×100mm-140mm into 100mm-150mm×70mm-120mm at a deformation speed of 0.5m / s-8m / s; The rolling forming process satisfies the requirements of hot deformation plasticity through one heating. The rolling process is divided into Z-axis rolling, i.e., three sets of flat rolls, and X-axis rolling, i.e., two sets of vertical rolls. The rolling deformation in the two directions is combined and simultaneous. The rolling deformation speed is 0.5m / s to 8m / s. The total deformation range of the rolling blanking and rolling forming is 25% to 80%, and the deformation distribution is 3% to 10% - 3% to 10% - 10% to 20% - 4% to 10% - 4% to 10%, and the area is rolled from 100mm to 150mm × 70mm to 120mm to 90mm to 125mm × 60mm to 90mm. The residual heat straightening, within the designed heating temperature range, has a final rolling temperature of 920°C to 1010°C and a straightening temperature of 900°C to 1000°C, which can meet the straightening conditions for varieties with a hardness of less than 230 HBW. If the hardness continues to increase, compensatory heating is required to improve the straightening conditions. The surface finishing comprises removing defects by shot blasting and pickling, or finishing by planing, turning and milling.

2. The rolling process of a difficult-to-deform alloy square flat material according to claim 1, characterized in that: The hard-to-deform alloy is GH202 nickel-based aging alloy, and the finished product specifications are: 110mm×75mm hot-rolled square flat; Blank size 120mm×120mm; Heating temperature 1170℃, keep warm for 5h; Entering the rolling process of blanking and forming, the equipment WF540 model rolling mill is used with a rolling rate of 2.25m / s; the rolling forming process is: 120mm×120mm blanking 128mm×100mm, rolling forming 128mm×100mm→129mm×95mm→120mm×97.6mm→121mm×79mm→115mm×77.8mm→110.8mm×75.3mm; Final rolling temperature 940℃; The bent part of the head is straightened; the finished product length reaches 7m.

3. The rolling process of the difficult-to-deform alloy square flat material according to claim 1, characterized in that: The hard-to-deform alloy is GH131 iron-based solid solution alloy, and the finished product specifications are: 93mm×78mm hot-rolled square flat steel; Blank size 105mm×105mm; Heating temperature 1150℃, keep warm for 4h; The rolling process is as follows: 105mm×105mm billet to 115mm×85mm billet, then rolling to form 115mm×85mm→115.8mm×80mm→102mm×87.4mm→100.2mm×80mm→93mm×82.7mm→93.4mm×78.5mm. Final rolling temperature 920℃; The straightness of the blank is good and does not require straightening; there are fine cracks on the surface oxide scale and right angles of the product, which are cleaned after shot blasting and pickling.

4. The rolling process of the difficult-to-deform alloy square flat material according to claim 1, characterized in that: The hard-to-deform alloy is C263 chromium-cobalt-nickel based alloy, and the finished product specifications are: 108mm×72mm hot-rolled square flat steel; Blank size: 115mm×115mm, length: 1800mm~3200mm; Heating temperature 1170℃, keep warm for 4h; The process of rolling blanking and forming is six passes in total. The equipment used is WF540 rolling mill with a rolling speed of 1.21m / s. The rolling blanking is from 115mm×115mm to 128mm×100mm. The forming process is from 128mm×100mm→129mm×95mm→119.6mm×99mm→ 123.3mm×78mm→111.2mm×79mm→108.6mm×72.8mm; Final rolling temperature 950℃; The two ends are bent and straightened with residual heat, and the straightness reaches 4mm / m. The surface and dimensional quality meet the ASTMB164 standard. Shot blasting is used and the surface inspection is qualified.

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