​Cold rolling refers to a material processing method in which the material is forged at normal temperature to make the thickness of the material gradually reduce.  The raw material of cold rolling is generally steel coil after heat treatment of[TJC STEEL] hot rolling.  In the process of cold rolling, the metastable austenite structure will undergo strain-induced martensitic transformation, which makes the strength and hardness of the steel increase, and the plasticity decrease, resulting in obvious work hardening.  
 
With the increase of forging passes, the total deformation rate of forging increases, the work hardening effect becomes more and more obvious, and the material becomes more and more hard.  Under the conventional heat treatment, the strength and hardness of the nickel-based superalloy are lower, and the plasticity is better, which is [TJC STEEL]good for forging.  If the superalloy is cold-rolled directly without heat treatment, the cost of material production can be greatly reduced.  The strength of the heat treated and hot rolled superalloys was analyzed, the test rolling process parameters were determined, and the mechanical properties of the test rolled products were compared.  
 
Feasibility analysis of direct cold rolling of superalloy without heat treatment  
 
1.1 Mechanical property analysis  
 
Samples of Hastelloy alloy in hot rolled state and hot rolled state were taken in production site, and the mechanical properties were tested and the results were compared.  Comparing the mechanical properties of the hot-rolled and hot-rolled nickel-based alloys, it can be seen that the average yield strength of the hot-rolled alloys [TJC STEEL]is 80.9 MPa higher, the average tensile strength is 40.7 MPa higher and the elongation is 5.7% lower than that of the hot-rolled alloys.  
 
From the point of view of mechanical properties, the strength of hot rolled nickel-based alloy plate has little difference before and after heat treatment, the hardening process of hot rolled material without heat treatment is a little faster [TJC STEEL]than that of heat treatment, but it is not obvious, and the load of cold rolling equipment has little change.  
 
Metallographic microstructure analysis The hot rolled and hot rolled nickel-based alloys were sampled, polished and corroded with HCl-FeCl3 solution.  It can be seen from the figure that the superalloy grains have completely recovered to [TJC STEEL]recrystallization after heat treatment.  Partial recovery also occurred in untreated superalloys.  
 
Hot rolled sheet technology of nickel-based alloy Hastelloy -1. PNG  
 
The dynamic grain recovery and dynamic recrystallization of Hastelloy alloys occur during hot rolling process, which causes the work [TJC STEEL]hardening to be released continuously.  
 
After hot rolling, because the steel coil still has a high temperature and lasts for a certain period of time in the high temperature state, grain recovery and recrystallization will occur in the material in this state, and the elongated grain will nucleate into equiaxed grain, and part of work hardening can be eliminated by [TJC STEEL]eliminating the microstructure and residual stress formed by the elongated grain.  After hot rolling and air cooling, strip steel has similar characteristics to that after heat treatment.  
 
Hot rolled sheet technology of nickel-based alloy Hastelloy -2. PNG  
 
Based on the mechanical properties, work hardening and microstructure, it is considered that the current field Ni-base alloy [TJC STEEL]Hastelloy superalloy can be cold-rolled directly without heat treatment.  
 
Cold rolling test for heat treatment of nickel-based alloy high temperature alloy for cold rolling, cold rolling mill roll system, the rigidity of twenty more roller base mill rolling mill, the forging process by adjusting the supporting roller crown and a middle roller axial control plate shape, putting-in-service proactively ACG system control the thickness of the material, appropriate to increase the flow of forging[TJC STEEL] lubricants at the same time,  To improve the cooling effect of the material in the forging process.  
 
 
Fearing **** passes, 6500 kN pressure, 300 kN higher than the pressure of ordinary heat treatment material, but the deformation rate is 2% lower than the ordinary heat treatment material, the subsequent passes, forging pressure is higher than the ordinary heat treatment material, but the deformation rate is low, the same forging total deformation rate, under the condition of the forging force is [TJC STEEL]not greatly improved,  The coil forged directly without heat treatment has one more forging pass than that of the heat-treated coil, which indicates that the deformation resistance of the hot rolled material without heat treatment is greater.  
 
Hot rolled sheet technology of nickel-based alloy Hastelloy -3. PNG  
 
The two cold-rolled materials were then treated by solution heat treatment at temperatures ranging from 1 050 ℃ to 1 150 ℃.  [TJC STEEL]The purpose of solid solution heat treatment is to dissolve the precipitated carbide into austenite again and restore the cold rolled strip structure to recrystallization.  
 
Hot rolled sheet technology of nickel-based alloy Hastelloy alloy -4. PNG  
 
The elongation, yield strength and tensile strength of the cold rolled products in the hot rolled and hot rolled heat treatment state [TJC STEEL]are all up to the standard, but the elongation and strength of the cold rolled products in the hot rolled state are slightly lower and slightly higher.  
 
After cold rolling and solid solution treatment, the elongated fibrous structures in cold rolling process are nucleated and[TJC STEEL] recrystallized, and the grains are completely recovered. However, the grains of hot rolling untreated materials are finer.  
 
Hot rolled sheet technology of nickel-based alloy Hastelloy alloy -5. PNG  
 
Deposition process of the two solid solution and precipitation process is the same, but not direct cold rolling, heat treatment conditions hot rolling state of isometric into rectangular fibrous tissue, part of the deformation work at the same time in the form of lattice distortion and residual stress are preserved, form the recrystallization driving force, so the hot rolling without heat treatment after cold rolled steel coil easier to solid solution heat treatment;  On the other hand, the grain of hot rolled steel coil will grow up further during solution heat treatment.  Therefore, hot rolled materials without heat treatment are more likely to occur in the solution heat treatment after cold rolling, and the second is that the grain is more refined after heat treatment.  
 
1) Ni-base alloy hot-rolled unheat-treated steel coil can be cold-rolled directly, but the forging resistance is larger than that of hot-treated material.  
 
2) After cold rolling, the grain of untreated hot rolled nickel-based alloy coils can be completely recovered by solution heat treatment, and the grain size is relatively fine.  
 
Under the same conditions, the silicon consumption and lime consumption are almost the same, which can be used as a substitute for the steel and chromium scrap.  
 
3) Red mud ball.  The use of red clay balls in AOD furnace is essentially the same as that in electric furnace. Both of them use Si elements in pig iron and ferrochrome to reduce valuable metals such as Fe, Cr and Ni.  At present, the benefit estimated by AOD small batch test is 1 000 yuan /t. If the furnace entry condition can be optimized and the usage amount can be increased under the condition of excess temperature in the smelting process, the benefit will be further expanded.  
 
4) High nickel steel.  The experimental results and theoretical calculation of using high nickel steel in AOD furnace have a certain influence on silicon consumption and lime consumption. When 3 tons of high nickel steel is used in each furnace, the silicon consumption increases by 0.2 kg/t and the lime consumption increases by 1.0 kg/t, and the total impact cost is 377 yuan/furnace. The profit is better when the difference between scrap steel and slag steel is converted.  
 
5) high chromium steel.  It can completely replace the use of chromium scrap steel, has no obvious effect on the index, and the benefit is significant.  

​Hard alloy is a kind of or several refractory carbide (tungsten carbide, titanium carbide, etc.) powder as the main component, adding as an adhesive metal powder (cobalt, nickel, etc.), by powder metallurgy method and made of alloy.  It is mainly used in the manufacture of high-speed cutting tools and hard and tough material cutting tools, as well as the production of cold work die, measuring tools and high [TJC STEEL]wear-resistant parts that are not affected by impact and vibration.  The hardness, wear resistance and red hardness of high cemented carbides at room temperature hardness up to 86 ~ 93HRA, equivalent to 69 ~ 81HRC.  It can maintain high hardness at 900 ~ 1000℃ and has excellent wear resistance.  Compared with high speed tool steels, the cutting speed can be 4 ~ 7 times higher, the life can be 5 ~ 80 times longer, and the hardness can be cut up to 50HRC hard materials.  
 
When manufacturing cemented carbide, the raw material powder particle size is between 1 to 2 microns, and the purity is very high.  Raw materials according to the provisions of the composition of the proportion of the ingredients, add alcohol or other media in the wet ball mill wet grinding, so that they are fully mixed, crushed, after drying and screening to add wax or glue and other forming agents, and then [TJC STEEL]after drying, sieving the mixture.  Then, the mixture is granulated, pressed, heated to close to the melting point of the bonding metal (1300 ~ 1500℃), the hardening phase and the bonding metal will form eutectic alloy.  
Cemented carbide is also long used in the production of cold drawing die, cold punching die, cold extrusion die, cold pier die and other cold [TJC STEEL]die.  Moulds made of cemented carbide can better withstand impact and have better impact toughness, fracture toughness, fatigue strength, bending strength and wear resistance.  Usually, the cemented carbides used in the production of molds are medium and high cobalt and medium and coarse grain grades, such as YG15C, etc.  
 
Cemented carbide has good corrosion resistance, oxidation resistance and high temperature resistance.  Cutting tools made of [TJC STEEL]cemented carbide usually have good resistance to corrosion caused by atmosphere, acid, alkali, etc., are not prone to oxidation, and can remain hard at temperatures of 900 to 1000 degrees.  
 
The linear expansion coefficient of [TJC STEEL]cemented carbide is very small, which leads to its stable shape and size during machining.  

Cold rolling refers to a material processing method in which the material is forged at normal temperature to make the thickness of the material gradually reduce.  The raw material of cold rolling is generally steel coil after heat treatment of[TJC STEEL] hot rolling.  In the process of cold rolling, the metastable austenite structure will undergo strain-induced martensitic transformation, which makes the strength and hardness of the steel increase, and the plasticity decrease, resulting in obvious work hardening.  
 
With the increase of forging passes, the total deformation rate of forging increases, the work hardening effect becomes more and more obvious, and the material becomes more and more hard.  Under the conventional heat treatment, the strength and hardness of the nickel-based superalloy are lower, and the plasticity is better, which is [TJC STEEL]good for forging.  If the superalloy is cold-rolled directly without heat treatment, the cost of material production can be greatly reduced.  The strength of the heat treated and hot rolled superalloys was analyzed, the test rolling process parameters were determined, and the mechanical properties of the test rolled products were compared.  
 
Feasibility analysis of direct cold rolling of superalloy without heat treatment  
 
1.1 Mechanical property analysis  
 
Samples of Hastelloy alloy in hot rolled state and hot rolled state were taken in production site, and the mechanical properties were tested and the results were compared.  Comparing the mechanical properties of the hot-rolled and hot-rolled nickel-based alloys, it can be seen that the average yield strength of the hot-rolled alloys [TJC STEEL]is 80.9 MPa higher, the average tensile strength is 40.7 MPa higher and the elongation is 5.7% lower than that of the hot-rolled alloys.  
 
From the point of view of mechanical properties, the strength of hot rolled nickel-based alloy plate has little difference before and after heat treatment, the hardening process of hot rolled material without heat treatment is a little faster [TJC STEEL]than that of heat treatment, but it is not obvious, and the load of cold rolling equipment has little change.  
 
Metallographic microstructure analysis The hot rolled and hot rolled nickel-based alloys were sampled, polished and corroded with HCl-FeCl3 solution.  It can be seen from the figure that the superalloy grains have completely recovered to [TJC STEEL]recrystallization after heat treatment.  Partial recovery also occurred in untreated superalloys.  
 
Hot rolled sheet technology of nickel-based alloy Hastelloy -1. PNG  
 
The dynamic grain recovery and dynamic recrystallization of Hastelloy alloys occur during hot rolling process, which causes the work [TJC STEEL]hardening to be released continuously.  
 
After hot rolling, because the steel coil still has a high temperature and lasts for a certain period of time in the high temperature state, grain recovery and recrystallization will occur in the material in this state, and the elongated grain will nucleate into equiaxed grain, and part of work hardening can be eliminated by [TJC STEEL]eliminating the microstructure and residual stress formed by the elongated grain.  After hot rolling and air cooling, strip steel has similar characteristics to that after heat treatment.  
 
Hot rolled sheet technology of nickel-based alloy Hastelloy -2. PNG  
 
Based on the mechanical properties, work hardening and microstructure, it is considered that the current field Ni-base alloy [TJC STEEL]Hastelloy superalloy can be cold-rolled directly without heat treatment.  
 
Cold rolling test for heat treatment of nickel-based alloy high temperature alloy for cold rolling, cold rolling mill roll system, the rigidity of twenty more roller base mill rolling mill, the forging process by adjusting the supporting roller crown and a middle roller axial control plate shape, putting-in-service proactively ACG system control the thickness of the material, appropriate to increase the flow of forging[TJC STEEL] lubricants at the same time,  To improve the cooling effect of the material in the forging process.  
 
 
Fearing **** passes, 6500 kN pressure, 300 kN higher than the pressure of ordinary heat treatment material, but the deformation rate is 2% lower than the ordinary heat treatment material, the subsequent passes, forging pressure is higher than the ordinary heat treatment material, but the deformation rate is low, the same forging total deformation rate, under the condition of the forging force is [TJC STEEL]not greatly improved,  The coil forged directly without heat treatment has one more forging pass than that of the heat-treated coil, which indicates that the deformation resistance of the hot rolled material without heat treatment is greater.  
 
Hot rolled sheet technology of nickel-based alloy Hastelloy -3. PNG  
 
The two cold-rolled materials were then treated by solution heat treatment at temperatures ranging from 1 050 ℃ to 1 150 ℃.  [TJC STEEL]The purpose of solid solution heat treatment is to dissolve the precipitated carbide into austenite again and restore the cold rolled strip structure to recrystallization.  
 
Hot rolled sheet technology of nickel-based alloy Hastelloy alloy -4. PNG  
 
The elongation, yield strength and tensile strength of the cold rolled products in the hot rolled and hot rolled heat treatment state [TJC STEEL]are all up to the standard, but the elongation and strength of the cold rolled products in the hot rolled state are slightly lower and slightly higher.  
 
After cold rolling and solid solution treatment, the elongated fibrous structures in cold rolling process are nucleated and[TJC STEEL] recrystallized, and the grains are completely recovered. However, the grains of hot rolling untreated materials are finer.  
 
Hot rolled sheet technology of nickel-based alloy Hastelloy alloy -5. PNG  
 
Deposition process of the two solid solution and precipitation process is the same, but not direct cold rolling, heat treatment conditions hot rolling state of isometric into rectangular fibrous tissue, part of the deformation work at the same time in the form of lattice distortion and residual stress are preserved, form the recrystallization driving force, so the hot rolling without heat treatment after cold rolled steel coil easier to solid solution heat treatment;  On the other hand, the grain of hot rolled steel coil will grow up further during solution heat treatment.  Therefore, hot rolled materials without heat treatment are more likely to occur in the solution heat treatment after cold rolling, and the second is that the grain is more refined after heat treatment.  
 
1) Ni-base alloy hot-rolled unheat-treated steel coil can be cold-rolled directly, but the forging resistance is larger than that of hot-treated material.  
 
2) After cold rolling, the grain of untreated hot rolled nickel-based alloy coils can be completely recovered by solution heat treatment, and the grain size is relatively fine.  
 
Under the same conditions, the silicon consumption and lime consumption are almost the same, which can be used as a substitute for the steel and chromium scrap.  
 
3) Red mud ball.  The use of red clay balls in AOD furnace is essentially the same as that in electric furnace. Both of them use Si elements in pig iron and ferrochrome to reduce valuable metals such as Fe, Cr and Ni.  At present, the benefit estimated by AOD small batch test is 1 000 yuan /t. If the furnace entry condition can be optimized and the usage amount can be increased under the condition of excess temperature in the smelting process, the benefit will be further expanded.  
 
4) High nickel steel.  The experimental results and theoretical calculation of using high nickel steel in AOD furnace have a certain influence on silicon consumption and lime consumption. When 3 tons of high nickel steel is used in each furnace, the silicon consumption increases by 0.2 kg/t and the lime consumption increases by 1.0 kg/t, and the total impact cost is 377 yuan/furnace. The profit is better when the difference between scrap steel and slag steel is converted.  
 
5) high chromium steel.  It can completely replace the use of chromium scrap steel, has no obvious effect on the index, and the benefit is significant.  

4Cr3Mo2NiVNB steel code name is HD steel, is a kind of air-cooled hardening martensitic hot work die steel, is based on Sweden Udholm QRO-80 steel, by the Huazhong University of Science and Technology and other units[TJC STEEL] independently developed new hot work die steel.  

CHEMICAL COMPOSITION（%）
C 0.35～0.45 Cr 2.50～3.00
Si ≤0.35 Mo 1.80～2.20
Mn ≤0.40 Ni 0.80～1.20
P ≤0.030 V 1.00～1.40
S ≤0.030 Nb 0.10～0.25

Citical Point  
AC1 =789℃, AC3 =910℃, MS =363℃  
 
Hot Forming
➣ HD Steel Forging Process Specification  
ITEMS STEEL INGOT BILLET
HEATING TEM℃ 1140～1180 1120～1160
FORGING TEM(BEGINNING)℃ 1080～1140 1060～1120
FORGING TEM(END)℃ ≥900 ≥850
COOLING METHOD[TJC STEEL] SAND OR PIT SLOW COOLING SAND OR PIT SLOW COOLING

Preliminary Heat Treatment  
Isothermal annealing of forging material: < 500℃ into furnace with furnace temperature rise, heating temperature 830 ~ 850℃, holding time (H) 1+1min/mm, isothermal temperature 730±10℃, holding time (H) 2+1min/mm, with furnace [TJC STEEL]cold to < 500℃ air cooling (HB≤250).  
 
Quenching Specification  
Quenching temperature is 1130±10℃, oil cold.  
➣ The Relationship Between Quenching Temperature And Hardness And Grain Size Of Hd Steel  
QUCHENING TEM/℃ HARDNESSHRC GRAIN SIZE/CLASS
1050 50.5 --
1100 53.5 11
1130 53.5 10
1160 56.0 8～9
1180 56.0 7～8
1200 56.5 7～8

➣ HD Stee’s Hardness Levels on Different Tempered Tem:
Tempered Tem/℃ HRC
HD Steel 3Cr2W8VSteel
300 52.5 51.0
400 52.0 51.0
500 52.5 51.4
530 53.5 52.3
560 54.0 51.5
590 53.8 51.8
620[TJC STEEL] 51.2 50.0
650 47.0 46.0
700 41.0 34.0

Mechanical Properties（Comparing with 3Cr2W8V Steel）

➣ HD Steel’s Mechanical Property under Different Room Tem:
Heat Treatments 1130℃ Quenching
650℃ Tempering 1130℃ Quenching
700℃ Tempering 
HD 3Cr2W8V HD 3Cr2W8V
σ0.2/MPa 1633 1463 1165 952
ψ（%） 32.4 41.8 45.7 41.9
αk/(J/cm2) 38.8 -- 48.8 --

➣ HD Steel’s Mechanical Property under Different Tem:
Test Tem 650℃ 700℃
HD 3Cr2W8V HD 3Cr2W8V
σ0.2/MPa[TJC STEEL] 536.9 414 405.3 235
ψ（%） 66.1 49.1 69.3 85.4
αk/(J/cm2) 56/54 -- 75/40 62/38

Note: The denominator in αk value is hardness value (HRC).  
 
Performance Characteristics:
On the basis of 4Cr3Mo3V steel, the toughness and thermal stability of 4Cr3Mo2NiVNb (HD) steel at room temperature and high temperature were improved by reducing the content of Mo and V and adding[TJC STEEL] the mass fraction of 1%Ni and 0.15%Nb. The hardness of 4Cr3Mo3V steel at 700℃ could still maintain 40HRC.  Under the same conditions of hardness, HD steel has 50% higher fracture toughness than 3Cr2W8V steel, 70% higher tensile strength at 700℃, 1 times higher cold and hot fatigue resistance and 50% higher hot wear resistance, respectively.  
 
Applications  
HD steel comprehensive performance is good, suitable for making heating temperature about 700 ℃, using strict hot-work mold, such as ferrous and non-ferrous materials of hot extrusion die, such as hot fine[TJC STEEL] forging die, in the steel tube hot extrusion convex die, the bottom of the copper alloy tube extrusion die and punch needle, hot extrusion convex die and concave die bearing ring, valve end of extrusion die and mold USES,  The service life of 3Cr2W8V steel is significantly improved.  

​Based on Inconel718 alloy, GH4169 nickel-based superalloy was designed in China.  GH4169 alloy properties **** The temperature range of GH4169 is -253 °C~650 °C. At this time, not only the strength and plasticity [TJC STEEL]are very high, but also the yield strength and durability are very high. At the same time, the radiation resistance, corrosion resistance and welding performance are also very good.  This makes this alloy since the launch of the beginning, by the attention of all walks of life, its current output can reach the total output of nickel-based high temperature alloy about 50%.  
 
In the application of GH4169 alloy, the application of key components of aeroengine is the main driving force for the development[TJC STEEL] of GH4169 alloy, and the alloy also ensures the stable operation of aeroengine.  
 
An alloy with good properties must be inseparable from its chemical composition and structure, GH4169 alloy is no exception.  Its chemical composition is shown in Table 1. The strengthening phase is mainly γ 'phase and γ "phase, which are Ni3(Al,Ti,Nb) and Ni3Nb phase respectively.  GH4169 alloy generally contains [TJC STEEL]more than a dozen chemical elements, which are located in different positions in the crystal structure of the alloy. Based on these elements, they can be divided into the following three categories:  
The **** type of elements are solid solution strengthening elements, including nickel, iron, chromium, cobalt, tungsten and[TJC STEEL] molybdenum from groups V, VI and VII, which are selected to form the austenite matrix (γ ').  
The second type of elements are precipitation-strengthening elements, including niobium, aluminum, titanium, hafnium and[TJC STEEL] molybdenum from groups III, V, VI, etc., which are distributed into the formation of γ "precipitate phase.  
The third type of elements is interstitial elements, including boron, zirconium and carbon from groups II, III and IV, which tend [TJC STEEL]to segregate at grain boundaries.  
 
For 3D printing and laser cladding processes, the sphericity, oxygen content, fluidity and hollow sphere ratio of the powder have a decisive effect on the performance of the final molded parts.  The spherical degree of GH4169 superalloy powder for 3D printing produced by Guanda Technology is more than 90%, the oxygen content can be kept within 100ppm, and the Hall flow rate is 15.6s, which [TJC STEEL]can meet the requirements of 3D printing process.  
 
GH4169 Powder Particle Size Distribution for 3D Printing  
The microstructure of GH4169 alloy is particularly sensitive to the hot working process. The processor needs to master the phase precipitation and melting law in the alloy and the relationship between the[TJC STEEL] microstructure and the process and the properties, so as to develop a feasible process, so as to produce parts that meet different strength levels and use requirements.  The disk, ring, blade, shaft and shell parts of GH4169 are used in the next generation rocket engine components.  
 
GH4169 nickel-based deformed superalloy  
Chinese brand number: GH4169/GH169, GH169 (GH4169)  
U.S. brand: INCONEL 718/UNS NO7718  
French brand number: NC19FENB  
   
The GH4169 alloy is a nickel-based superalloy precipitated by γ" phase with a body center square and γ" phase with a face center cubic.  It has good comprehensive properties in the temperature range [TJC STEEL]of -253 ~ 700℃, and the yield strength below 650℃ ranks first in the deformation superalloy, and has good fatigue resistance, radiation resistance, oxidation resistance, corrosion resistance, as well as good processing performance, welding performance and long-term organizational stability. It can manufacture various complex shapes of parts.  It is widely used in aerospace, nuclear energy and petroleum industries in the above temperature range.  
 
Another characteristic of the alloy is that the alloy structure is particularly sensitive to the hot working process, grasp the alloy phase precipitation and dissolution law and the relationship between the structure and process, performance, can be used for different requirements to develop a reasonable and feasible process rules, can be obtained to meet the different strength levels and use [TJC STEEL]requirements of various parts.  The products we supply are forgings, forging bars, rolling bars, cold rolling bars, round cakes, ring pieces, plates, belts, wires, pipes and so on.  It can be made into disk, ring, blade, shaft, fastener, elastic element, plate structure, casing and other parts and components for long-term use in aviation.  
     
Material grade GH4169(GH169)  
1.2 GH4169 was investigated similar brand Inconel 718 (USA), NC19FeNb (France)  
Technical standard for 1.3GH4169 material  
The chemical composition of the alloy can be classified into three categories: standard composition, high quality composition, and high purity composition, as shown in Table 1-1.  High quality components on the basis of standard components to reduce the amount of niobium carbide, reduce the number of fatigue sources and increase the number of strengthening phase, improve the fatigue [TJC STEEL]resistance and material strength.  At the same time reduce harmful impurities and gas content.  High purity components are based on high quality standards to reduce the content of sulfur and harmful impurities, improve the purity and comprehensive properties of materials.  
 
For the GH4169 alloy used in nuclear energy, the boron content shall be controlled (other elements shall remain[TJC STEEL] the same), and the specific content shall be determined by the supply and demand parties through negotiation.  When ω (B) ≤0.002%, to distinguish with the aerospace industry GH4169 alloy, alloy grade for GH4169A.