阅读说明：本技术 一种镍铁基合金的热加工工艺及应用 (Hot working process and application of nickel-iron-based alloy ) 是由 王常帅 吴云胜 秦学智 周兰章 于 2019-03-27 设计创作，主要内容包括：本发明属于耐热合金热加工技术领域,特别是涉及一种700℃超超临界火电机组用镍铁基合金的热加工工艺及应用,适用于镍铁基耐热合金的锅炉部件制造。该工艺包括锻造开坯和热挤压,其中：锻造开坯原料为经过均匀化退火的铸锭或电极棒,初锻温度为1150℃～1200℃,终锻温度在950℃以上,应变速率为0.01s<Sup>-1</Sup>～0.5s<Sup>-1</Sup>,工程应变在50％以下；热挤压的原料为开坯锻件,变形温度为1050℃～1200℃,应变速率为1.0s<Sup>-1</Sup>～10s<Sup>-1</Sup>,工程应变在70％以下。本发明根据热变形原料中晶粒组织的差异,选用不同的热变形参数,同时保证热变形组织的均匀性与热变形过程的低成本。经过锻造开坯和热挤压的合金未出现锻造裂纹、混晶等缺陷,组织均匀,再结晶比例高于95％,晶粒细小,动态再结晶平均晶粒尺寸不大于15微米。(The invention belongs to the technical field of heat-resistant alloy hot working, and particularly relates to a hot working process and application of a nickel-iron-based alloy for a 700 ℃ ultra-supercritical thermal power generating unit, which are suitable for manufacturing boiler parts made of the nickel-iron-based heat-resistant alloy. The process comprises forging cogging and hot extrusion, wherein: the forging and cogging raw material is ingot or electrode bar which is subjected to homogenizing annealing, the initial forging temperature is 1150-1200 ℃, the final forging temperature is more than 950 ℃, and the strain rate is 0.01s ‑1 ～0.5s ‑1 The engineering strain is below 50%; the hot extrusion raw material is a cogging forging, the deformation temperature is 1050-1200 ℃, and the strain rate is 1.0s ‑1 ～10s ‑1 The engineering strain is below 70%. The invention selects different thermal deformation parameters according to the difference of grain structures in thermal deformation raw materials and simultaneously ensures the uniformity of thermal deformation structuresAnd low cost of the thermal deformation process. The alloy after forging cogging and hot extrusion has no defects of forging cracks, mixed crystals and the like, has uniform tissue, the recrystallization proportion is higher than 95 percent, the crystal grains are fine, and the average size of the dynamic recrystallization crystal grains is not more than 15 microns.)

1. A hot working process of a nickel-iron-based alloy is characterized by comprising the following steps:

1) preparation of a Nickel-iron based alloy

The nickel-iron-based alloy comprises the following components: 0.01-0.12% of C, 18-26% of Cr, 15-26% of Fe, 0.8-2.6% of Mo, 0.7-1.5% of Nb, 0.3-1.5% of Al, 0.7-1.8% of Ti, 0.001-0.01% of B, 0.002-0.06% of P and the balance of Ni;

2) first step heat deformation

The first step of thermal deformation is forging cogging, the initial forging temperature is 1150-1200 ℃, the final forging temperature is more than 950 ℃, and the strain rate is 0.01s^-1～0.5s^-1Forming an cogging forging with the engineering strain below 50%;

3) second step thermal deformation

The second step is hot extrusion, the deformation temperature is 1050-1200 ℃, and the strain rate is 1.0s^-1～10s^-1The engineering strain is below 70%.

2. The hot working process of a nickel-iron based alloy according to claim 1, characterized in that the deformation temperature and strain rate of the first step hot deformation are different from those of the second step hot deformation.

3. The hot working process of a ferronickel-based alloy according to claim 1, wherein in the first step, the raw material for forging cogging is a homogenized annealed ingot or electrode bar; preferably, the initial forging temperature range is 1150-1200 ℃, the final forging temperature range is 950-1000 ℃, and the strain rate range is 0.01s^-1～0.2s^-1The engineering strain range is 10-50%.

4. The hot working process of the nickel-iron-based alloy according to claim 3, wherein the homogenizing annealing process comprises maintaining the temperature at 1150 ℃ ± 20 ℃ for 24-48 hours, furnace cooling to below 600 ℃, and air cooling to room temperature.

5. The hot working process of a nickel-iron-based alloy according to claim 1, characterized in that in the second step, the raw material for hot extrusion is a cogging forging obtained in the first step; preferably, the deformation temperature range is 1100-1200 ℃, and the strain rate range is 1.0s^-1～10s^-1The engineering strain range is 30-70%.

6. The hot working process of a ferronickel-based alloy according to claim 1, wherein in the first step, the dynamic recrystallization proportion of the cogging forging is more than 85%, the proportion of small-angle grain boundaries is less than 25%, the average size of the dynamic recrystallization grains is not more than 20 μm, and the proportion of low-coincidence-position lattice grain boundaries is more than 15%.

7. The hot working process of a nickel-iron based alloy according to claim 1, wherein in the second step, the dynamic recrystallization ratio of the alloy after hot extrusion is more than 95%, the percentage of small angle grain boundaries is less than 5%, the average size of the dynamic recrystallization grains is not more than 15 μm, and the percentage of low-coincidence-position lattice grain boundaries is more than 30%.

8. Use of the ferronickel-based alloy according to any one of claims 1 to 7, wherein the ferronickel-based alloy billet produced by the hot working process of the ferronickel-based alloy is used to produce a boiler component.

9. Use of a nickel-iron-based alloy according to claim 8, characterized in that the boiler section is used in 700 ℃ ultra supercritical thermal power plants.

Technical Field

The invention belongs to the technical field of heat-resistant alloy hot working, and particularly relates to a hot working process and application of a nickel-iron-based alloy for a 700 ℃ ultra-supercritical thermal power generating unit, which are suitable for manufacturing boiler parts made of the nickel-iron-based heat-resistant alloy.

Background

The energy utilization efficiency of the thermal power generating set depends on two set parameters of steam pressure and steam temperature, and the improvement of the set parameters can not only save a large amount of coal energy, but also obviously reduce CO₂、SO_xAnd NO_xThe discharge amount of the waste water has important significance for the development of economy, society and environment. With the development of science and technology, thermal power generating units have been developed from ultrahigh pressure and subcritical to supercritical, ultra-supercritical and even advanced ultra-supercritical power generating units, and the thermal efficiency of the thermal power generating units is also improved from 35% of the ultrahigh pressure power generating units to more than 50% of the advanced ultra-supercritical power generating units.

With the development of the coal-fired generator set to 700 ℃ advanced ultra supercritical level, more severe service conditions are applied to the key high-temperature components of the power station, such as: the high and medium pressure rotor, cylinder, valve body, the over heater and the reheater in the boiler to and header and steam piping material of steam turbine put forward higher requirement, mainly show: (1) tissue stability at higher temperatures and excellent long-term strength; (2) good oxidation resistance and corrosion resistance; (3) good processability and the like. Under such temperature and pressure conditions, ferritic and austenitic heat-resistant steels have not been able to meet the requirements of strength and corrosion resistance, and nickel-based or nickel-iron-based alloys have been used. Currently, nickel-based or nickel-iron-based alloys such as Inconel 740H, Haynes 282, Nimonic 263, Inconel 617, GH984, etc. have become candidate materials for the key high-temperature components of 700 ℃ advanced ultra-supercritical power stations. The nickel-iron-based alloy has better economical efficiency and better application prospect.

The boiler tubes of the thermal power station are large in consumption and complex in thermal processing process, strip-shaped structures and mixed crystals are easy to appear in the alloy in the thermal deformation process, the overall performance of the material is deteriorated due to nonuniform structures, and the further thermal processing deformation process is influenced. Therefore, the reasonable thermal deformation process is of great importance, the defects of forging cracks, mixed crystals and the like can be effectively reduced or avoided, the hot working efficiency can be improved, and the hot working cost can be reduced.

Disclosure of Invention

The invention aims to provide a thermal processing technology and application of a nickel-iron-based alloy for a 700 ℃ ultra-supercritical thermal power generating unit, wherein different thermal deformation parameters are selected according to the difference of grain structures in thermal deformation raw materials, and the uniformity of the thermal deformation structures and the low cost of the thermal deformation process are ensured.

In order to achieve the purpose, the invention adopts the technical scheme that:

a hot working process of a nickel-iron-based alloy comprises the following steps:

1) preparation of a Nickel-iron based alloy

The nickel-iron-based alloy comprises the following components: 0.01-0.12% of C, 18-26% of Cr, 15-26% of Fe, 0.8-2.6% of Mo, 0.7-1.5% of Nb, 0.3-1.5% of Al, 0.7-1.8% of Ti, 0.001-0.01% of B, 0.002-0.06% of P and the balance of Ni;

2) first step heat deformation

The first step of thermal deformation is forging cogging, the initial forging temperature is 1150-1200 ℃, the final forging temperature is more than 950 ℃, and the strain rate is 0.01s^-1～0.5s^-1Forming an cogging forging with the engineering strain below 50%;

3) second step thermal deformation

The second step is hot extrusion, the deformation temperature is 1050-1200 ℃, and the strain rate is 1.0s^-1～10s^-1The engineering strain is below 70%.

According to the hot working process of the nickel-iron-based alloy, the deformation temperature and the strain rate of the first-step thermal deformation are different from those of the second-step thermal deformation.

In the hot working process of the nickel-iron-based alloy, in the first step, the raw material for forging and cogging is an ingot or an electrode bar which is subjected to homogenization annealing; preferably, the initial forging temperature range is 1150-1200 ℃, the final forging temperature range is 950-1000 ℃, and the strain rate range is 0.01s^-1～0.2s^-1The engineering strain range is 10-50%.

The hot working process of the nickel-iron-based alloy comprises the following steps of carrying out heat preservation at 1150 +/-20 ℃ for 24-48 hours, carrying out furnace cooling to below 600 ℃, and carrying out air cooling to room temperature.

In the second step of the hot working process of the nickel-iron-based alloy, the hot extrusion raw material is the cogging forging obtained in the first step; preferably, the deformation temperature range is 1100-1200 ℃, and the strain rate range is 1.0s^-1～10s^-1The engineering strain range is 30-70%.

In the first step of the hot working process of the ferronickel-based alloy, the dynamic recrystallization proportion of the cogging forging is more than 85%, the small-angle grain boundary proportion is less than 25%, the average size of the dynamic recrystallization grains is not more than 20 microns, and the low-coincidence-position lattice grain boundary proportion is more than 15%.

In the second step, the dynamic recrystallization proportion of the alloy after hot extrusion is more than 95%, the small-angle crystal boundary proportion is less than 5%, the average size of the dynamic recrystallization crystal grains is not more than 15 microns, and the lattice crystal boundary proportion at the low coincident position is more than 30%.

The application of the ferronickel-based alloy is to utilize the ferronickel-based alloy blank prepared by the hot working process of the ferronickel-based alloy to prepare the boiler part.

The application of the ferronickel-based alloy, the boiler part is used for 700 ℃ ultra-supercritical thermal power generating units.

The invention has the advantages and beneficial effects that:

according to the difference of the grain sizes in the two-step thermal deformation raw materials, different thermal deformation parameters are selected, so that the uniformity of a deformation structure is ensured, and the cost of the thermal deformation process for preparing the boiler tube is reduced. The alloy after forging cogging and hot extrusion has uniform deformation structure, does not have the defects of forging cracks, mixed crystals and the like, has the recrystallization proportion of more than 95 percent, fine crystal grains and the average size of recrystallized crystal grains of not more than 15 microns.

Drawings

FIG. 1 shows the grain structure of the cast ingot after the nickel-iron based alloy of the invention is adopted for homogenizing annealing.

Fig. 2 is a thermal processing diagram (true strain 0.7) of an ingot after the homogenizing annealing of the nickel-iron-based alloy of the present invention. In the figure, the abscissa Temperature represents Temperature (. degree. C.), and the ordinate (left)Representing the natural logarithm of the strain rate, ordinate (right)

Representative of strain rate(s)^-1)。

FIG. 3 shows the cast ingot of the nickel-iron-based alloy of the invention after being annealed uniformly at 1150 ℃/0.01s^-1Fully recrystallized structure after lower deformation.

FIG. 4 is a hot working drawing (true strain 0.7) of a wrought product forged by cogging the nickel-iron-based alloy of the present invention. In the figure, the abscissa Temperature represents Temperature (. degree. C.), and the ordinate (left)Representing the natural logarithm of the strain rate, ordinate (right)

Representative of strain rate(s)^-1)。

FIG. 5 shows that the forging piece is cogging with the ferronickel base alloy of the invention at 1150 ℃/10s^-1Fully recrystallized structure after lower deformation.

Detailed Description

The present invention will be further described with reference to the following embodiments.