CN114635023B - Production method of martensitic heat-resistant steel blank - Google Patents

Abstract

The invention relates to a production method of martensitic heat-resistant steel blank, belonging to the technical field of heat-resistant steel hot working. The production method of the invention comprises the following steps: 1) Homogenizing heat treatment of electroslag ingot, in order to reduce the thermal stress, design the specialized step type heating curve; 2) Forging and heating an electroslag ingot; 3) Upsetting and drawing forging are carried out for more than three times by adopting an upsetting device; 4) Annealing heat treatment; 5) And (5) tempering and heat treatment. According to the method for producing the martensitic heat-resistant steel blank, provided by the invention, the martensitic heat-resistant steel G115 blank with uniform structure, excellent performance and good welding process can be obtained through homogenization heat treatment, heating process, forging process, annealing process and tempering heat treatment process.

Description

Production method of martensitic heat-resistant steel blank

Technical Field

The invention belongs to the technical field of hot working, and mainly relates to a production method of a novel martensitic heat-resistant steel (G115) blank.

Background

Thermal power generation is an important component of energy structures in China, and the improvement of parameters of thermal power generating units is directly related to energy conservation and emission reduction. The most important parameters of the thermal power generating unit are the temperature and the pressure of steam, the parameters of the main thermal power generating unit in China are the ultra-supercritical unit at 600 ℃, the installed capacity of the ultra-supercritical unit is first in global ranking, but the unit with the parameters cannot meet the high-quality requirements of China on the beautiful China environment of green water and Qingshan, and the development of a new generation of high-parameter advanced ultra-supercritical unit is urgently required. Therefore, the construction of the ultra-supercritical unit at 630 ℃ is urgently brought up, for example, 370775 of Datang group, the ultra-supercritical demonstration power station at 630 ℃ in city has been approved by the national energy agency. The high requirements of the 630 ℃ ultra-supercritical unit on the materials are mainly expressed in high-temperature durable strength, stability of tissues after long-time high-temperature aging, oxidation resistance of high-temperature steam and the like. In view of the fact that the performance of the heat-resistant steel P92 of the existing 600 ℃ ultra-supercritical unit cannot meet the requirements of the 630 ℃ ultra-supercritical unit, under the condition, the novel martensitic heat-resistant steel of 9Cr-3W-3CoVNbCUBN with higher performance is applied, the brand of the martensitic heat-resistant steel is G115, the novel martensitic heat-resistant steel adopts a composite strengthening design concept, and has excellent high-temperature durable strength, long-time high-temperature aging structure stability and oxidation resistance, and the comprehensive performance of the martensitic heat-resistant steel is far better than that of P92; however, the excellent performance also brings certain processing difficulty, and the traditional P92-like hot processing and heat treatment process is not applicable to G115, so the invention provides a brand-new production method of martensitic heat-resistant steel G115 blank.

There are also related studies in the prior art involving G115, as follows:

the Chinese patent number CN103045962B is an invention patent of G115, mainly relates to the aspects of component design, reinforcement concept, manufacturing method, performance characteristics and the like of G115, and does not relate to a production method of G115 tube blanks/forgings.

Chinese patent CN108998650a relates to a method for manufacturing a seamless steel pipe with large caliber and thick wall by using a 630 ℃ ultra supercritical unit G115, which only relates to a pipe making process of the seamless steel pipe with large caliber and thick wall by using G115, no pipe blank production process is available, and the north heavy industry is one member of G115 research and development team, and mainly uses G115 pipe blank produced by using Wu Teye (original steel treasured special steel) to finish the production process of extruded pipe on a 3.6 ten thousand ton extruder.

Chinese patent CN108950148A relates to a method for improving radial organization and performance uniformity of G115 heavy caliber thick wall pipe, but does not relate to a method for producing G115 pipe blank/forging.

Chinese patent CN106119488A relates to a forging and heating process of P91 alloy steel, and does not relate to a process method related to G115 forging and heating, and has no reference value to the forging process of G115.

The G115 martensitic heat-resistant steel produced in the prior art has problems in terms of structural uniformity, tensile and impact properties, weld heat affected zone microscopic defect resolution and the like, cannot meet the actual relevant enterprise standards and industry standards, and cannot be applied to 630 ℃ ultra-supercritical demonstration power station engineering.

Disclosure of Invention

The invention aims to solve the technical problems of providing a production method of martensitic heat-resistant steel G115 blank, and comprehensively solving a series of problems encountered in large-scale industrialized mass production and engineering application of large-specification G115 blank/forging for the first time.

The invention is realized by the following technical scheme:

the invention provides a production method of martensitic heat-resistant steel blank, which comprises the following steps:

s1, carrying out homogenization heat treatment on an electroslag ingot of martensitic heat-resistant steel;

s2, forging and heating the product obtained in the step S1;

s3, forging the product obtained in the step S2 in a 6000 ton quick forging machine;

s4, carrying out annealing heat treatment on the product obtained in the step S3;

s5, carrying out tempering heat treatment on the product obtained in the step S4 to obtain the martensitic heat-resistant steel blank.

Preferably, the homogenizing heat treatment in step S1 specifically includes the following operations:

after the surface of the martensitic heat-resistant steel electroslag ingot is sprayed with the anti-oxidation coating, the temperature is raised to 600-650 ℃ at the speed of 50-80 ℃/h, the temperature is kept for 5-8 h, the temperature is raised to 1000-1050 ℃ at the speed of 50-80 ℃/h, the temperature is kept for 3-5 h, the temperature is raised to 1200-1250 ℃ at the speed of 50-80 ℃/h, the temperature is kept for not less than 80h, and after the temperature is kept, the furnace is cooled to 700-1000 ℃.

Preferably, the forging heating in step S2 specifically includes the following operations:

and (3) heating the product obtained in the step (S1) to 1140-1180 ℃ at a speed of 50-100 ℃/h, and keeping the temperature for not less than 0.5min/mm.

In the step S3, after the upper anvil and the lower anvil of the rapid forging machine are preheated to the anvil surface temperature not lower than 500 ℃, at least upsetting and drawing for 3 times, the forging temperature is controlled to be 1050-1100 ℃, and the final forging temperature is controlled to be 850-900 ℃.

In the step S3, upsetting is carried out at a reduction speed of 18-20 mm/S in each upsetting process, after upsetting is carried out to 1/2 of the original height of the electroslag ingot, drawing is started at a reduction of 50-70 mm each time, the reduction is increased to 100-120 mm by an increase of 10-15 mm each time, the reduction is carried out for 5-8 times, drawing is carried out to 900-1000 mm octagonal, furnace returning heating is carried out at 1140-1180 ℃, the heat preservation time is more than or equal to 3 hours, and finally, after upsetting at the last fire, the material is formed by rounding, and final forging is carried out at 850-900 ℃.

In the step S3, upsetting is carried out at a reduction speed of 18-20 mm/S in each upsetting process, after upsetting is carried out to 1/2 of the original height of the electroslag ingot, drawing is started at a reduction of 50-70 mm each time, the reduction is increased to 100-120 mm by an increase of 10-15 mm each time, the reduction is carried out for 5-8 times, drawing is carried out to 900-1000 mm octagonal, furnace returning heating is carried out at 1140-1180 ℃, the heat preservation time is more than or equal to 3 hours, and after the last upsetting, staggered anvil forging is adopted for final forging at 850-900 ℃.

Preferably, the annealing heat treatment in step S4 specifically includes the following operations:

and (3) annealing the product obtained in the step (S3) within 2 hours after forging, wherein the annealing temperature is controlled to be 750-850 ℃, the annealing time is not less than 1.5min/mm, and after annealing, cooling the furnace to below 100 ℃, cooling the furnace along with the furnace, and discharging and air cooling.

Preferably, the tempering heat treatment in the step S5 specifically includes the following operations:

heating the product obtained in the step S4 to 900-1000 ℃ at a speed of 50-80 ℃/h, preserving heat for at least 2h, continuously heating to 1050-1090 ℃ at a speed of 50-80 ℃/h, and normalizing for at least 0.6min/mm;

and heating the normalized product to 760-790 ℃ at the speed of 50-80 ℃/h, and tempering for not less than 1.6min/mm.

The invention has the beneficial effects that:

the production method of the G115 tube blank/forging provided by the invention is a method which can be successfully implemented in industrial mass production, the macroscopic segregation of large-sized tube blanks and forgings and the microscopic massive segregation of tungsten-rich phases are effectively eliminated according to the G115 tube blank and forgings produced by the method, the G115 tube blank and forgings which are uniform in structure and excellent in performance and good in welding process are obtained, various performance indexes of the G115 tube blank and forgings meet the requirements of enterprise standard Q/OAPD 2753-2017 power stations on novel martensitic heat-resistant steel 08Cr9W3 VNCBn (G115) tube blanks and sectional materials, after tube blanks produced by the method are processed by tubes, the requirements of enterprise standard Q/OAPD 2253-2017 power stations on novel martensitic heat-resistant steel 08Cr9W3 VNCBN (G115) seamless steel tubes and industrial standard CSTM00017-2017 power stations on martensitic heat-resistant steel 08Cr9W3 VNCBN (G115) seamless steel tubes can be met, and the requirements of enterprise standard CSTM00017-2017 power stations on comprehensive performance and related industrial heat-resistant steel 08Cr9W3 VNCBN (G115) are evaluated, and the most-affected zone heat-affected zone welding critical performance is achieved by the method, and the critical defect of the G115 is overcome, and the critical defect is produced by the method is evaluated, and the critical defect is met.

Drawings

Other features, objects and advantages of the present invention will become more apparent upon reading of the detailed description of non-limiting embodiments, given with reference to the accompanying drawings in which:

FIG. 1 is a schematic diagram of a homogenizing heat treatment curve of an electroslag ingot in example 1 of the present invention;

FIG. 2 is a schematic diagram of a forging heating curve in example 1 of the present invention;

FIG. 3 is a schematic view showing the annealing heat treatment curve of a tube blank in example 1 of the present invention;

fig. 4 is a schematic diagram of a normalizing curve of the tempering heat treatment of the forging in the embodiment 4 of the invention;

FIG. 5 is a schematic drawing of tempering curves of the tempering heat treatment of the forging in the embodiment 4 of the invention;

FIG. 6 is a photograph of a low magnification tissue of example 1 of the present invention;

FIG. 7 is a photograph showing a metallographic structure in example 1 of the present invention;

FIG. 8 is a photograph of a morphology of a scanning electron microscope in example 1 of the present invention.

Detailed Description

The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the present invention, but are not intended to limit the invention in any way. It should be noted that variations and modifications could be made by those skilled in the art without departing from the inventive concept. These are all within the scope of the present invention.

A production method of martensitic heat-resistant steel G115 tube blank/forging comprises the following process flows:

1. homogenizing and heat-treating an electroslag ingot;

2. forging and heating an electroslag ingot;

3. forging by a 6000 ton quick forging machine;

4. annealing heat treatment after forging;

5. quenching and tempering heat treatment of the forging;

according to the production method of the G115 martensitic heat-resistant steel pipe blank/forging, preferably, the electroslag ingot homogenizing heat treatment comprises the following technical processes:

a. spraying the anti-oxidation coating, wherein the high-temperature homogenization temperature is high, the time is long, an oxide layer with the thickness of 10mm can be caused, the yield is influenced, and the oxide layer can be reduced to below 5mm after the anti-oxidation coating is sprayed;

b. charging steel ingot, and heating along with the furnace at a heating speed of 50-80 ℃/h;

c. heating to 600-650 ℃, preserving heat for 5-8 hours to ensure that the surface and the core are uniform in temperature and prevent the thermal stress from being overlarge;

d. continuously heating to 1000-1050 ℃ according to the heating rate of 50-80 ℃/h, and preserving heat for 3-5 hours to further homogenize the surface and core temperature and prevent the thermal stress from being overlarge;

e. continuously heating to the target temperature of 1200-1250 ℃ for homogenizing heat treatment according to the heating rate of 50-80 ℃/h, wherein the heat preservation time is more than or equal to 80 hours (according to the ingots with different specifications, the heat preservation time can be prolonged but not less than 80 hours);

f. in order to ensure the uniformity and accuracy of the temperature, a tracking thermocouple is required to be installed in each batch or new furnace for the first treatment, and the actual temperature of different positions of the blank and the comparison between the steel temperature and the furnace temperature are monitored;

g. after the heat preservation is finished, stopping the furnace for cooling (closing the burner and not opening the furnace door), and cooling the furnace to 700-1000 ℃;

according to the production method of the G115 martensitic heat-resistant steel pipe blank/forging, the forging and heating of the electroslag ingot in the second step preferably comprises the following technical processes:

a. the temperature rising speed is 50-100 ℃/h;

b. the heating temperature is 1140-1180 ℃;

c. the heat preservation time is determined according to the specification of the steel ingot (the heat preservation time is more than or equal to 0.5 min/mm), and the core temperature of the steel ingot is ensured to be uniform;

according to the production method of the G115 martensitic heat-resistant steel pipe blank/forging piece, the forging of the 6000 ton rapid forging machine in the third step preferably comprises the following technical processes:

a. preheating an upper anvil and a lower anvil, adopting scrap steel heated to above 800 ℃, and tightly attaching the upper anvil and the lower anvil, wherein the preheating is more than or equal to 20 minutes, and the temperature of the anvil surface is more than or equal to 500 ℃;

b. the forging temperature is 1050-1100 ℃, and the final forging temperature is 850-900 ℃;

c. upsetting by a first fire, wherein a special upsetting device (special steel patent number CN107552699A, a manufacturing method of a large upsetting device) is adopted in a 6000 ton rapid forging machine, and upsetting is carried out to 1/2 of the original height of an electroslag ingot; the special upsetting device is a disc-shaped device with a handle, has the thickness of 500-700 mm and the weight of about 20 tons, can ensure that the upper and lower surfaces of the steel ingot are smooth during upsetting, has even stress (the steel ingot is not required to be moved, and the upsetting of the steel ingot of 13.5 tons can be completed at one time), and does not have the defects of bending, tilting and the like;

d. the upsetting depressing speed is 15-25 mm/s;

e. drawing to an octagonal shape close to the diameter of the electroslag ingot, wherein the length of the octagonal shape is 1.8-2.5 times of the length of the electroslag ingot after upsetting, if the electroslag ingot is phi 1000, drawing to an octagonal shape of 980 mm;

f. repeatedly upsetting and drawing the tube blank/forging for more than three times so as to fully crush a large tungsten-rich phase and eliminate microscopic defects of a welding heat affected zone;

g. the heating temperature of each time of furnace returning is 1140-1180 ℃, and the heat preservation time is more than or equal to 3 hours (the specific time is determined according to the specification of the intermediate blank);

h. the tube blank is rounded to the specification of a finished product, and the dimensional tolerance is (-10 mm, +20 mm);

i. forging the forging piece into a specified shape according to the design specification of the drawing after upsetting and drawing, and forging the single-side stepped forging piece by adopting a staggered anvil forging mode;

j. and finally, the final fire is used for rounding the materials, the deformation is small, and the final forging temperature can be widened to 850 ℃.

According to the production method of the G115 martensitic heat-resistant steel pipe blank/forging, the post-forging annealing heat treatment in the fourth step preferably comprises the following technical processes:

a. after forging, annealing the furnace within 2 hours;

b. the annealing temperature is 750-780 ℃;

c. the heat preservation time is determined according to the size of the ingot shape (the annealing time is determined according to the length of not less than 1.5 min/mm);

d. after the heat preservation is finished, the furnace is cooled to below 100 ℃ (the burner is closed, the furnace door is not opened, and the furnace is cooled along with the furnace), and the furnace is taken out for air cooling.

According to the production method of the G115 martensitic heat-resistant steel pipe blank/forging, preferably, the quenching and tempering heat treatment of the forging in the step e comprises the following technical processes:

a. the modulating heat treatment of the forging comprises two working procedures of normalizing and tempering;

b. the normalizing temperature rising speed is 50-80 ℃/h, the temperature rises to 900-1000 ℃ and is kept for more than or equal to 2 hours, then the temperature continues to rise to the normalizing target temperature 1050-1090 ℃ at the temperature rising speed of 50-80 ℃/h, the temperature keeping time is determined according to the maximum section of the workpiece (the normalizing time is determined according to not less than 0.6 min/mm), and the workpiece is cooled after being discharged;

the tempering temperature rising speed is 50-80 ℃/h, the temperature rises to the tempering target temperature 760-790 ℃, the tempering time is determined according to the maximum section of the workpiece (the tempering time is determined according to not less than 1.6 min/mm), and the air cooling is carried out after the discharging.

Example 1

Adopting an electroslag ingot of phi 1200, uniformly spraying an anti-oxidation coating on the surface, airing, charging into a furnace, charging into the furnace according to a homogenization heat treatment curve of figure 1, heating to 640-660 ℃ at a heating rate of 60-70 ℃/h, preserving heat for 6 hours, heating to 990-1010 ℃ at a heating rate of 70-80 ℃/h, preserving heat for 4 hours, heating to 1230-1250 ℃ at a heating rate of 70-80 ℃/h, preserving heat for 90 hours, cooling to 800 ℃ and discharging.

After 12 hours of incubation at 800 ℃, the temperature was raised and heated according to the forging heating curve shown in fig. 2. The temperature rising speed is 80-90 ℃/h, the temperature rises to 1160+/-10 ℃, the heat is preserved for 10 hours, and the first fire is discharged from the furnace for forging.

And preheating an upper anvil and a lower anvil of a 6000-ton quick forging machine for 20 minutes by using scrap steel with the temperature of 900 ℃ before discharging and forging, and measuring the temperature of the anvil surface to be 550 ℃ after the preheating is finished. The first fire upsetting, the upsetting to 1/2 of the original height of electroslag ingot, the upsetting depressing speed to 18-20 mm/s, the temperature to 1080 deg.c measured after the falling of oxide skin, the drawing after upsetting, the initial depressing amount controlled at 50-70 mm each time, the gradually increased depressing amount to 100-120 mm, the drawing to 1000mm octagon and the length of 2.2m. The final forging temperature is 900 ℃. And (5) returning to the furnace for heating, wherein the heat preservation temperature is 1150-1170 ℃, and the heat preservation time is 3 hours.

The second fire and the first fire adopt the same process, upsetting to 1/2 of the original height, drawing to 1000mm octagonal, and final forging temperature is 900 ℃. And (5) returning to the furnace for heating, preserving heat for 3 hours at 1150-1170 ℃, discharging and forging the third fire.

And upsetting to 1/2 of the original height by using a third fire, drawing to 920mm octagon, and then rounding to phi 900 (-10 mm, +20 mm) pipe blank. The final forging temperature is 850 ℃.

Annealing in an annealing furnace for 1.5 hours after forging is completed, heating according to an annealing heat treatment curve shown in fig. 3, wherein the annealing temperature is 760-780 ℃, the heat preservation time is 25 hours, the furnace is cooled to 100 ℃, and the total time is 50 hours, and the furnace is taken out for air cooling.

The results of the low-power inspection of the tube blanks are shown in Table 1, the inclusions are shown in Table 2, and the grain sizes are shown in Table 3. Fig. 6, 7, 8. FIG. 6 is a photograph of a macroscopic structure of a tube blank, which shows that the macroscopic structure of the tube blank is uniform and compact, and no center segregation, ingot segregation, dot segregation and other defects are visible visually; FIG. 7 is a photograph of a metallographic structure of a tube blank 100 times, and as can be seen from the figure, the tube blank is a typical tempered martensite structure, the prior austenite grain size is 3.5-4.5 grade, and the microstructure is uniform; fig. 8 is a photograph of secondary electron phase morphology of a tube blank by a scanning electron microscope, and shows that no obvious precipitated phase is gathered and the tissue is uniform.

Example 2

Adopting an electric slag ingot of phi 1000, uniformly spraying an anti-oxidation coating on the surface, airing, charging into a furnace, carrying out homogenization heat treatment, heating to 640-660 ℃ at the heating rate of 70-80 ℃/h, preserving heat for 5 hours, heating to 1010-1030 ℃ at the heating rate of 70-80 ℃/h, preserving heat for 3 hours, heating to 1220-1240 ℃ at the heating rate of 70-80 ℃/h, preserving heat for 85 hours, cooling to 900 ℃ and discharging.

After the heat preservation is carried out for 10 hours at 900 ℃, the temperature is raised, the temperature raising speed is 90-100 ℃/h, the temperature is raised to 1150-1170 ℃, the heat preservation is carried out for 9 hours, and the first fire is discharged from the furnace for forging.

And preheating an upper anvil and a lower anvil of a 6000-ton quick forging machine for 20 minutes by using scrap steel with the temperature of 900 ℃ before discharging and forging, and measuring the temperature of the anvil surface to be 560 ℃ after the preheating is finished. The first fire upsetting, the upsetting to 1/2 of the original height of electroslag ingot, the upsetting depressing speed to 20-22 mm/s, the temperature to 1070 deg.c, the actual steel temperature to be measured after falling oxide skin, the upsetting to start drawing, the initial depressing amount to 50-70 mm each time, the gradually increasing depressing amount to 100-120 mm, the drawing to 900mm octagon and the length to 2.3m. The final forging temperature is 900 ℃. And (5) returning to the furnace for heating, wherein the heat preservation temperature is 1150-1170 ℃, and the heat preservation time is 3 hours.

The second fire and the first fire adopt the same process, upsetting to 1/2 of the original height, drawing to 900mm octagonal, and final forging temperature is 900 ℃. And (5) returning to the furnace, heating, preserving heat for 3 hours at 1160+/-10 ℃, discharging and forging the third fire.

And upsetting to 1/2 of the original height by using a third fire, drawing to 900mm octagon, and then rounding to phi 850 (-10 mm, +20 mm) pipe blank. The final forging temperature is 850 ℃.

Annealing in annealing furnace for 1.5 hours after forging, wherein the annealing temperature is 750-770 ℃, the heat preservation time is 22 hours, the furnace is cooled to 100 ℃, and the common time is 47 hours, and the furnace is discharged for air cooling.

The results of the low-power inspection of the tube blanks are shown in Table 1, the inclusions are shown in Table 2, and the grain sizes are shown in Table 3.

Example 3

Adopting an electroslag ingot of phi 900, uniformly spraying an anti-oxidation coating on the surface, airing, charging into a furnace, carrying out homogenization heat treatment, heating to 640-660 ℃ at the heating rate of 70-80 ℃/h, preserving heat for 5 hours, heating to 1010-1030 ℃ at the heating rate of 70-80 ℃/h, preserving heat for 3 hours, heating to 1210-1230 ℃ at the heating rate of 70-80 ℃/h, preserving heat for 80 hours, cooling to 900 ℃ and discharging.

After the heat preservation is carried out for 8 hours at 900 ℃, the temperature is raised, the temperature raising speed is 90-100 ℃/h, the temperature is raised to 1160-1180 ℃, the heat preservation is carried out for 8 hours, and the first fire is discharged from the furnace for forging.

And preheating an upper anvil and a lower anvil of a 6000-ton quick forging machine for 20 minutes by using scrap steel with the temperature of 900 ℃ before discharging and forging, and measuring the temperature of the anvil surface to be 550 ℃ after the preheating is finished. The first fire upsetting, the upsetting to 1/2 of the original height of electroslag ingot, the upsetting depressing speed to 22-24 mm/s, the temperature to 1080 deg.c measured after the falling of oxide skin, the drawing after upsetting, the initial depressing amount controlled at 50-70 mm each time, the gradually increased depressing amount to 100-120 mm, the drawing to 900mm octagon and the length of 2.0m. The final forging temperature is 900 ℃. And (5) returning to the furnace for heating, wherein the heat preservation temperature is 1160-1180 ℃, and the heat preservation time is 3 hours.

The second fire and the first fire adopt the same process, upsetting to 1/2 of the original height, drawing to 900mm octagonal, and final forging temperature is 900 ℃. And (3) returning to the furnace for heating, preserving heat for 3 hours at 1160-1180 ℃, discharging and forging the third fire.

And upsetting to 1/2 of the original height by using a third fire, drawing to 850mm octagon, and then rounding to phi 820 (-10 mm, +20 mm) pipe blank. The final forging temperature is 850 ℃.

Annealing in an annealing furnace for 1.5 hours after forging, wherein the annealing temperature is 750+/-10 ℃, the heat preservation time is 21 hours, the furnace is cooled to 100 ℃, and the total time is 46 hours, and the furnace is taken out for air cooling.

The results of the low-power inspection of the tube blanks are shown in Table 1, the inclusions are shown in Table 2, and the grain sizes are shown in Table 3.

Example 4

Adopting an electric slag ingot of phi 1000, uniformly spraying an anti-oxidation coating on the surface, airing, charging into a furnace, carrying out homogenization heat treatment, heating to 640-660 ℃ at the heating rate of 70-80 ℃/h, preserving heat for 5 hours, heating to 1010-1030 ℃ at the heating rate of 70-80 ℃/h, preserving heat for 3 hours, heating to 1220-1240 ℃ at the heating rate of 70-80 ℃/h, preserving heat for 85 hours, cooling to 900 ℃ and discharging.

After the heat preservation is carried out for 10 hours at 900 ℃, the temperature is raised, the temperature raising speed is 90-100 ℃/h, the temperature is raised to 1150-1170 ℃, the heat preservation is carried out for 9 hours, and the first fire is discharged from the furnace for forging.

The upper anvil and the lower anvil of a 6000 ton quick forging machine are preheated for 20 minutes by scrap steel with the temperature of 900 ℃ before discharging and forging, and the temperature of the anvil surface is measured to be 570 ℃ after the preheating is finished. The first fire upsetting, the upsetting to 1/2 of the original height of electroslag ingot, the upsetting depressing speed to 20-22 mm/s, the temperature to 1100 deg.c, the actual steel temperature to be measured after falling of oxide skin, the drawing after upsetting, the initial depressing amount controlled to 50-70 mm each time, the increasing depressing amount to 100-120 mm, the drawing to 900mm octagon and the length of 2.3m. The final forging temperature is 900 ℃. And (5) returning to the furnace for heating, wherein the heat preservation temperature is 1150-1170 ℃, and the heat preservation time is 3 hours.

The second fire and the first fire adopt the same process, upsetting to 1/2 of the original height, drawing to 900mm octagonal, and final forging temperature is 900 ℃. And (5) returning to the furnace for heating, preserving heat for 3 hours at 1150-1170 ℃, discharging and forging the third fire.

Upsetting by third fire to 1/2 of the original height, drawing to 900mm octagonal, and final forging at 900 ℃. And (5) returning to the furnace for heating, preserving heat for 3 hours at 1150-1170 ℃, discharging and forging the fourth fire.

And the fourth fire is further used for drawing and forging to obtain a flat blank with the thickness of 700mm and the width of 1100mm, wherein the final forging temperature is 900 ℃. And (3) returning to the furnace for heating, preserving heat for 3 hours at 1150-1170 ℃, discharging and forging the fifth fire.

And fifthly, forging the unilateral step type forging by adopting a staggered anvil forging mode. The final forging temperature is 870 ℃.

Annealing in an annealing furnace for 1.5 hours after forging, wherein the annealing temperature is 770+/-10 ℃, the heat preservation time is 18 hours, the furnace is cooled to 100 ℃, and the total time is 44 hours, and the furnace is taken out for air cooling.

Normalizing according to the normalizing curve of the quenching and tempering heat treatment of the forging shown in fig. 4, wherein the heating speed is 60-70 ℃/h, heating to 940-960 ℃ and preserving heat for 2 hours, heating to 1070-1090 ℃ at the heating speed of 70-80 ℃/h, preserving heat for 7 hours, and discharging and air-cooling to room temperature.

Tempering heat treatment is carried out according to the tempering heat treatment tempering curve of the forge piece shown in fig. 5, the heating speed is 60-70 ℃/h, the temperature is raised to 760-780 ℃, the heat is preserved for 19 hours, and the forge piece is discharged from the furnace and cooled to room temperature.

The low-power inspection result of the forging is shown in table 1, the inclusions are shown in table 2, the grain size is shown in table 3, and the mechanical properties are shown in table 4.

Table 1 results of the low power test of each example

	General porosity	Center porosity	Ingot segregation	Dot segregation	Other defects visible by visual inspection
						Example 1	0.5	0	0	0	0
Example 2	0.5	0	0	0	0
						Example 3	0.5	0	0	0	0
Example 4	0.5	0	0	0	0

Table 2 inclusions of examples

Table 3 grain size of each example

Table 4 mechanical properties of the forgings of example 4

It is specifically noted that the above embodiments are merely illustrative of the technical solution of the present invention and are not limiting. While the invention has been described in detail with reference to the preferred embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents substituted for elements thereof without departing from the scope of the invention, which is to be encompassed by the appended claims.

Claims (1)

1. A method for producing a martensitic heat-resistant steel blank, comprising the steps of:

s1, carrying out homogenization heat treatment on a G115 martensitic heat-resistant steel electroslag ingot,

the homogenizing heat treatment specifically comprises the following operations:

after spraying an anti-oxidation coating on the surface of the martensitic heat-resistant steel electroslag ingot, heating to 600-650 ℃ at the speed of 50-80 ℃/h, preserving heat for 5-8 h, continuously heating to 1000-1050 ℃ at the speed of 50-80 ℃/h, preserving heat for 3-5 h, continuously heating to 1200-1250 ℃ at the speed of 50-80 ℃/h, preserving heat for not less than 80h, and cooling to 700-1000 ℃ after the heat preservation is finished;

s2, forging and heating the product obtained in the step S1,

the forging heating specifically comprises the following operations:

heating the product obtained in the step S1 to 1140-1180 ℃ at a speed of 50-100 ℃/h, and keeping the temperature for not less than 0.5min/mm;

s3, forging the product obtained in the step S2 in a 6000-ton quick forging machine,

in the step S3, after the upper anvil and the lower anvil of the quick forging machine are preheated to the temperature of the anvil surface not lower than 500 ℃, upsetting and drawing for at least 3 times, controlling the forging temperature to 1050-1100 ℃ and the final forging temperature to 850-900 ℃,

in the step S3, upsetting is carried out at a reduction speed of 18-20 mm/S in each hot upsetting process, after upsetting is carried out to 1/2 of the original height of an electroslag ingot, drawing is started at a reduction of 50-70 mm each time, the reduction is increased to 100-120 mm by an increase of 10-15 mm each time, the reduction is carried out for 5-8 times, drawing is carried out to 900-1000 mm octagonal, furnace returning heating is carried out at 1140-1180 ℃, the heat preservation time is more than or equal to 3 hours, and finally, round-break forming is carried out after upsetting at the last hot or staggered anvil forging is carried out, and final forging is carried out at 850-900 ℃;

s4, carrying out annealing heat treatment on the product obtained in the step S3,

the annealing heat treatment specifically comprises the following operations:

annealing the product obtained in the step S3 within 2 hours after forging, controlling the annealing temperature to be 750-850 ℃, controlling the annealing time to be not less than 1.5min/mm, cooling the furnace to be below 100 ℃ after annealing, cooling along with the furnace, and discharging and air cooling;

s5, carrying out tempering heat treatment on the product obtained in the step S4 to obtain the martensitic heat-resistant steel blank,

the tempering heat treatment specifically comprises the following operations:

heating the product obtained in the step S4 to 900-1000 ℃ at a speed of 50-80 ℃/h, preserving heat for at least 2h, continuously heating to 1050-1090 ℃ at a speed of 50-80 ℃/h, and normalizing for at least 0.6min/mm;

and heating the normalized product to 760-790 ℃ at the speed of 50-80 ℃/h, and tempering for not less than 1.6min/mm.