A Comprehensive Guide to Nickel-based Alloy: Hastelloy B3 (UNS N10675)

What is Hastelloy B3?

Hastelloy B3 (UNS N10675/W.Nr. 2.4600/Alloy B3) is a nickel-molybdenum alloy with the addition of chromium, iron and other elements. It has excellent resistance to hydrochloric acid at all concentrations and temperatures. It also has good performance in sulfuric, acetic, formic and phosphoric acids, and other non-oxidizing media. Alloy B3 has excellent resistance to pitting corrosion, stress-corrosion cracking and to knife-line and heat-affected zone attack. Compared to Hastelloy B2, Hastelloy B3 has more superior thermal stability. It’s widely used in chemical processes, vacuum furnaces, and piping components in reducing environments.
Hastelloy B-3 (UNS N10675) is a solid solution strengthened, nickel-molybdenum alloy, typically used in extreme reducing conditions. Hastelloy B-3 has significantly lower carbon, silicon and iron compared to its’ predecessor, Hastelloy B (UNS N10001), making the alloy less susceptible to decreased corrosion resistance in the weld zone, in the as-welded condition. Controlling other alloying elements such as iron and chromium solved other issues concerning fabricability. Hastelloy B3 (n10675) is a nickel base superalloy composed of nickel, molybdenum, cobalt and other elements. The nickel content of Hastelloy B3 is about 65%. Hastelloy B3 (n10675) nickel base alloy is a new material based on Hastelloy B2, which improves the thermal stability and corrosion resistance of the material, and improves the hot forming and cold forming properties. In recent years, it has been more and more used in the production and manufacturing of chemical equipment.

Characteristics of Hastelloy B3 (UNS N10675)

• 1. Control of iron and chromium elements at the lowest levels, and prevent Beta phase Ni4Mo generated.
• 2. Excellent corrosion resistance to reductive environment.
• 3. Excellent resistance to corrosive medium concentration sulfuric acid and many non oxidizing acids.
• 4. Good resistance to chloride ion reduction stress corrosion cracking (SCC).
• 5. Excellent resistance to all kinds of organic acid corrosions. Hastelloy B-3 alloy is a new member of nickel molybdenum alloys has excellent corrosion resistance to hydrochloric acid at all temperature and the concentration . At the same time it also has good corrosion resistance to sulfuric acid, acetic acid, formic acid, phosphoric acid and other oxidizing medium. Because of its chemical composition adjustment, its thermal stability compared to the original Hastelloy B-2 alloy has improved significantly. Hastelloy B-3 alloy has high resistance to pitting corrosion, stress corrosion cracking, knife-line and heat-affected zone attacks,and etc.
• 6. Thermal stability superior to alloy B-2: compared to Hastelloy B-2, the biggest advantage of Hastelloy B-3 is maintaining excellent ductility during transient exposures to intermediate temperatures. The exposures regularly occur in the process of heat treatment processing. When a short exposure to the temperature of 700℃, B-2 alloy is very easy embrittlement, while B-3 alloy showed significant embrittlement resistance, and can make the show for a few hours. This provides a great convenience for the alloy provided in the form of complex, such as forming device components.

Hastelloy B3 Forged Elbow 1″ 3000#

Types of Hastelloy

• Hastelloy B-3 nickel molybdenum alloy has excellent corrosion resistance in reducing environment
• The upgraded version of Hastelloy B-3: B-3 has excellent corrosion resistance to hydrochloric acid at any temperature and concentration
• Hastelloy C-4: good thermal stability, good toughness and corrosion resistance at 650-1040 ℃
• Hastelloy C-22: has better uniform corrosion resistance than C-4 and C-276 in oxidizing medium and excellent local corrosion resistance
• Hastelloy C-276: good resistance to oxidizing and moderate reducing corrosion, excellent resistance to stress corrosion
• Hastelloy C-2000: the most comprehensive corrosion resistant alloy with excellent uniform corrosion resistance in oxidation and reduction environments
• Hastelloy G-35: the upgraded product of G-30 has better corrosion resistance and thermal stability, and has excellent performance in phosphoric acid and other strong oxidizing mixed acid media with high chromium content
• Hastelloy X: combined with the characteristics of high strength, oxidation resistance and easy processing, each of the above grades has its own specific chemical composition, mechanical properties and strong points, so we can’t generalize the characteristics of Hastelloy.

Hastelloy alloy is mainly divided into three series B, C and G. it is mainly used in iron-based Cr Ni or Cr Ni Mo stainless steel, non-metallic materials and other occasions with strong corrosive medium.
In order to improve the corrosion resistance and cold and hot working properties of Hastelloy, three major improvements have been made to Hastelloy:

• Series B: B → B-3 (00ni70mo28) → B-3
• Series C: C → C-276 (00cr16mo16w4) → C-4 (00cr16mo16) → C-22 (00cr22mo13w3) → C-2000 (00cr20mo16)
• G Series: G → G-3 (00cr22ni48mo7cu) → G-30 (00cr30ni48mo7cu)
• The most widely used materials are N10675 (B-3), N10276 (C-276), N06022 (C-22), N06455 (C-4) and N06985 (G-3)

Chemical Composition of Hastelloy B3 (UNS N10675)

C≤	Si≤	Mn≤	P≤	S≤	Cr≥	Ni≥	Mo≥	Cu≤
0.01	0.10	3.00	0.030	0.010	1.00-3.00	65.0	27.0-32.0	0.20
Nb/Ta≤	Al≤	Ti≤	Fe≤	Co≤	V≤	W≤	Ni+Mo	Ta≤
0.20	0.50	0.20	1.00-3.00	3.00	0.20	3.00	94.0-98.0	0.20

Equivalent Grades of Hastelloy B3 (UNS N10675)

Trademarks	GB	ASTM	UNS	DIN	W.Nr
Hastelloy B-3	NS3203	Hastelloy B-3	N10675	NiMo29Cr	2.46

Physical Properties of Hastelloy B3 (UNS N10675)

Density (g/cm3)	Melting Point (℃)	Electric resistivity  (µΩ·cm)	Coefficient of thermal expansion  10-6K-1(20-100℃)	Elastic modulus (GPa)	Hardness (Brinell)/HB	Operating temperature (°C )
9.22	1418	137	10.6	216	94	-200 – +400

Mechanical Properties of Hastelloy B3 (UNS N10675)

Annealed

• Heat Treatment: 2100°F (1150°C)
• Tensile Strength: 110 ksi (760 MPa) min 125 ksi (860 MPa) typ
• Suggested Operating Conditions: -300°F to 1800°F (-184°C to 900°C)

Product Forms and Standards of Hastelloy B3

Product Form	Standard
Sheet, Plate & Strip	ASTM B333
Billet, Rod & Bar	ASTM B335, B472
Coated Electrodes	DIN 2.4696
Bare Welding Rods & Wire	DIN 2.4695
Seamless Pipe & Tube	ASTM B622
Welded Pipe & Tube	ASTM B619, B626
Fittings	ASTM B366, B462
Forgings	ASTM B564, B462

Forming processing of Hastelloy B3 (UNS N10675)

• (1) The elongation of Hastelloy B3 is higher, which creates favorable conditions for cold forming.
• (2) Hastelloy B3 is harder than austenitic stainless steel and has more obvious work hardening tendency, so it needs more pressure or step-by-step forming in cold forming.
• (3) When the cold forming deformation rate of Hastelloy B3 is less than 10%, the corrosion resistance of the machined parts will not be affected, but the existence of residual stress may cause hot cracks in the weld. Therefore, the influence of residual stress should be eliminated as much as possible for the workpiece to be welded in the later stage.
• (4) Cold forming with severe deformation can improve the yield ratio of Hastelloy B3, and increase the sensitivity of stress corrosion and crack. Intermediate and final heat treatment processes are often used.
• (5) Hastelloy B3 is very sensitive to oxidizing medium, sulfur, phosphorus, lead and other low melting point metals at high temperature.
• (6) In the temperature range of 600-800 ℃ and too long heating time, brittle phase will be produced in Hastelloy B3 alloy, which will lead to the decrease of elongation. Moreover, hot cracking is easy to occur in this temperature range when the external force or deformation is limited. Therefore, the temperature must be controlled above 900 ℃.
• (7) Before the processing and pressing of Hastelloy B3 material, the mold surface contacting with the workpiece shall be cleaned; during cold working, lubrication method can be adopted, and degreasing treatment or alkali cleaning shall be carried out immediately after forming.
• (8) After the workpiece is discharged from the furnace and cooled, the oxide film on the surface is relatively thick, which should be fully acid washed. If there is residual oxide film, cracks may occur during the next pressing; if necessary, sandblasting can be carried out before pickling.

Welding of Hastelloy B3 (UNS N10675)

• (1) Before the forming process, if the raw blank needs to splice the weld, it is better to choose the GTAW welding method, so as to better protect the weld from oxidation. If manual arc welding method is adopted, it is easy to cause the intermediate weld bead to be oxidized. Even if each layer is polished and cleaned, it is difficult to ensure the thorough cleaning, and there is a small residual oxide layer, which may also form the weld Processing performance is affected. Before welding, the attachment and oxide layer on groove and base metal surface must be removed, because the existence of oxide film and impurities will affect the performance of weld and HAZ. It is better to use small current to avoid too slow speed and swing. The interlayer temperature should be controlled below 100 ℃. The front and back sides should be protected by argon to avoid high temperature oxidation and burning of alloy elements. Before pressing, the weld surface shall be polished smooth, and the thick oxide layer on the weld surface shall be removed and acid pickling shall be supplemented. Because the oxide layer of Hastelloy B3 weld is very hard, it is difficult to remove it by direct acid pickling. It is easy to produce fine cracks in the process of pressing forming, which will affect the performance of weld.
• (2) The advantage of hot forming is that it can be formed at one time and can avoid work hardening. If the forming temperature can be controlled well, heat treatment can be avoided. However, the temperature changes greatly in the hot forming process, and each region is different, and even the surface directly contacting with the die may be far lower than the temperature inside the metal, which is difficult to measure and control. Once the local material enters the sensitive temperature region during the processing, the micro cracks and other defects will be difficult to eliminate in the later solution heat treatment. The cold forming process was selected based on the experience of the processing plant. Molding is preferred for pressing method. When spinning must be adopted, cold spinning or warm spinning with temperature no more than 400 ℃ shall be adopted.
• (3) In the cold forming process, the step-by-step forming process should be adopted when the deformation rate is large. The intermediate heat treatment should be carried out for the step forming, and the solution heat treatment should be selected, and the temperature should be controlled above 1000 ℃. The solution heat treatment process was selected and the temperature was 1060 ~ 1080 ℃. After the final pressing of the workpiece, a solution heat treatment should be carried out to eliminate the residual stress and avoid affecting the subsequent welding quality.

Heat treatment of Hastelloy B3 (UNS N10675)

It is very important to keep the workpiece clean and pollution-free before and during heat treatment of Hastelloy B3 (n10675) Hastelloy alloy. In the heating process, the workpiece should not contact with sulfur, phosphorus, lead and other low melting point metals, otherwise the properties of the alloy will be damaged and the alloy will become brittle. The heating furnace should be electric furnace. If gas or oil fired furnace is used, the lower the sulfur content in the fuel, the better. According to the recommendation of material manufacturers, the total sulfur content in natural gas and liquefied petroleum gas is not more than 0.1% (V), the sulfur content in city gas is not more than 0.25 g / m3, and the sulfur content in fuel oil should be less than 0.5% (W).
The furnace gas must be clean and suitable for micro reduction. The fluctuation between oxidizability and reducibility of furnace gas should be avoided, and the heating flame cannot directly contact the workpiece. Before entering the furnace, the workpiece must be protected from high temperature deformation. The heating speed of the workpiece should be as fast as possible, and the workpiece can not be put into the furnace until the furnace temperature reaches the heat treatment temperature. After being discharged from the furnace, the water should be cooled quickly, and the immersion method or the whole area should be sprayed evenly. It is strictly forbidden to use water pipes for pouring, so as to prevent abnormal deformation or tearing due to uneven cooling and heating.

Application areas of nickel-based alloy Hastelloy B3 (UNS N10675)

An Alloy B3 90DEG Elbow 6″ SCH80S extruded from the UNS N10675 seamless pipe.

Hastelloy B3 (UNS N10675) is widely used in the chemical, petrochemical, energy manufacturing and pollution control related processing and equipment , especially in the processes dealing with various acids (sulfuric acid, hydrochloric acid, phosphoric acid, acetic acid and so on. Some of the more common uses of Hastelloy B3 include:

• Wire wound resistors.
• Bimetal contacts.
• Electric and electronic applications.
• Marine engineering.
• Chemical and hydrocarbon processing equipment.
• Gasoline and freshwater tanks.
• Crude petroleum stills.
• De-aerating heaters.
• Boiler feed water heaters and other heat exchangers.
• Pumps, shafts and fasteners.
• Industrial heat exchangers.
• Chlorinated solvents.
• Crude oil distillation towers.
• Meter and valve parts.
• Screw machine products.
• Oil refinery piping.
• Heat exchangers.
• Nuclear fuel production.
• Generator tubing.
• High temperature heating coils.
• Crude oil transfer piping.
• Propeller and pump shafts.
• Piping system.
• Heat exchange tubes.
• Pipe fittings.
• Flanges.
• Valves.

Variety specifications and supply status of Nickel-based alloy: Hastelloy B3 (UNS N10675)

Variety classification:

Yaang Pipe Industry can produce various specifications of Hastelloy B3 seamless pipe, Hastelloy B3 steel plate, Hastelloy B3 round bar, Hastelloy B3 forgings, Hastelloy B3 flange, Hastelloy B3 pipe fittings, Hastelloy B3 welded pipe, Hastelloy B3 steel strip, Hastelloy B3 wire and supporting welding materials. 

Delivery status:

• Seamless pipe: solid solution + acid white, length can be set;
• Plate: solid solution, pickling, trimming;
• Welded pipe: solid solution acid white + RT% flaw detection;
• Forging: annealing + car polish; Bars are forged and rolled, surface polished or car polished;
• Strips are delivered after cold rolling, solid solution soft state, and deoxidized;
• Wire rods are finely ground in solid solution pickled disk or straight strips, solid solution straight strips Delivery in light state.

Forming process of Hastelloy B3 dish head

The technical characteristics and forming process of Hastelloy B3 were analyzed, and the forming process of Hastelloy B3 dish head was tested. The results indicate that using cold processing methods such as molding or spinning, the forming quality of the dish head fully meets the design requirements, and the forming process is simple, reasonable, and feasible.

0. Introduction

Hastelloy B3 is a new material improved on the basis of Hastelloy B2, which improves the thermal stability of the material, thereby improving corrosion resistance and also improving the hot and cold forming properties. In recent years, it has been increasingly applied in the production and manufacturing of chemical equipment.
However, in China, the experience of forming and processing Hastelloy B3 needs to be more mature, especially for the forming of Hastelloy B3 dish heads. Many processing plants in China need reliable processing techniques and experience. According to investigation and analysis, the most common defects in the forming process of Hastelloy B3 dish head are surface cracking, peeling, and deformation, making it difficult to ensure the success of the forming process. Therefore, analysis and research were conducted on the forming process of the Hastelloy B3 dish head, and a reliable forming process method for the Hastelloy B3 dish head was found through experiments.

1. Material analysis

Hastelloy B3 (UNS designation N10675) is a Ni-Mo alloy with extremely low carbon and silicon content, and its main chemical composition is shown in Table 1. The mechanical properties of Hastelloy B3 plate in a solid solution state are shown in Table 2. The physical properties of Hastelloy B3 at room temperature are shown in Table 3.
According to the experimental data provided by Haynes Company for the Hastelloy B3, as the heating temperature increases, its tensile strength, yield strength, and elastic modulus decrease, while the elongation, thermal expansion coefficient, thermal conductivity, and specific heat slightly increase; As the cold deformation rate increases, its hardness, tensile strength, and yield strength increase, while its elongation decreases.
Table.1 Chemical Composition% of Hastelloy B3 Material

Element	Content
Ni	≥65
C	≤0.01
Co	≤3
Cr	1.0–3
Mo	27.0–32
Cu	≤0.2
Fe	1.0–3
Si	≤0.1
Mn	≤3
Al	≤0.5
S	≤0.01
P	≤0.03
W	≤3
Ti	≤0.2
Nb	≤0.2
Ta	≤0.2
V	≤0.2
Zr	≤0.1
Ni+Mo	94.0–98

Table.2 Mechanical Properties of Hastelloy B3 Plate in Solid Solution State

Project	Plate thickness t/mm	Minimum tensile strength Rm/MPa	Minimum yield strength ReL/MPa	Minimum elongation (50.8 mm)/%	Maximum Rockwell hardness HRB
Numerical Value	≤63.5	760	350	40	100

Table.3 Physical properties of Hastelloy B3 at room temperature

Project	Numerical Value
Relative density/g.cm–3	9.22
Melting temperature range (melting point)/℃	1371-1420
resistivity μ/ω.Cm	137
21 ℃ thermal expansion coefficient/m.(m.℃)-1	10.6×10-6
Thermal conductivity coefficient/W.(m.℃)-1	11.2
Elastic modulus/GPa	216
Specific heat/J.(kg.℃)-1	373

2. Forming and processing technology

2.1 Forming and processing characteristics
After analysis, the forming and processing characteristics of Hastelloy B3 mainly include:

• (1) The elongation of Hastelloy B3 is relatively high, creating favorable conditions for cold pressing forming;
• (2) Hastelloy B3 is harder than austenitic stainless steel and has a more pronounced tendency to work hardening, so it requires greater pressure or step-by-step forming during cold forming;
• (3) When the cold-forming deformation rate of Hastelloy B3 is less than 10%, it will not affect the corrosion resistance of the processed parts. However, in welding processing, the presence of residual stress may cause hot cracks in the weld seam. Therefore, for workpieces that require welding and processing in the later stage, the influence of residual stress should be eliminated as much as possible;
• (4) Cold forming with severe deformation can increase the yield strength ratio of Hastelloy B3 and also increase the sensitivity to stress corrosion and cracking. Intermediate and final heat treatment processes are often used;
• (5) Hastelloy B3 is highly sensitive to oxidizing media, sulfur, phosphorus, lead, and other low melting point metals at high temperatures;
• (6) In the temperature range of 600-800 ℃, if the heating time is too long, Hastelloy B3 alloy will produce brittle phases, leading to a decrease in elongation. Moreover, when external forces or deformation are limited in this temperature range, hot cracks are prone to occur. Therefore, when using hot forming, the temperature must be controlled above 900 ℃;
• (7) Before processing and pressing Hastelloy B3, clean the surface of the mold in contact with the workpiece. During cold processing, lubrication methods can be used, and immediately after forming, degreasing treatment or alkaline cleaning is required;
• (8) After the processed parts are cooled by water, the surface oxide film is thick and should be thoroughly pickled. If there is a residual oxide film, it may cause cracks during the next pressing process. If necessary, sandblasting can be performed before pickling.

2.2 Welding and Forming
Before forming and processing, if the raw material needs to be spliced with welds, it is best to choose the tungsten argon arc welding (GTAW) welding method to protect the welds from oxidation better. If the manual arc welding method is used, it is easy to cause oxidation of the intermediate weld bead. Even if each layer is polished and cleaned, it isn’t easy to ensure thorough cleaning. There are small residual oxide layers, which may also affect the forming and processing performance of the welds.
Before welding the workpiece, it is necessary to remove the attachment and oxide layer on the groove and base metal surface, as the presence of oxide film and impurities can affect the performance of the weld and heat-affected zone. It is best to choose a small current for welding to avoid too slow speed and not swing. The interlayer temperature should be controlled below 100 ℃ and argon gas protection should be used on the front and back sides to avoid high-temperature oxidation and burning of alloy elements.
Before pressing, the surface of the weld seam should be polished smooth to remove the thicker oxide layer on the surface of the weld seam and supplemented by acid washing. Because the oxide layer on the weld seam of Hastelloy B3 is very hard and difficult to remove by direct acid washing, it is easy to produce small cracks during the pressing process, which affects the performance of the weld seam.
The advantage of hot forming is that it can be formed in one go, avoiding work hardening. If the forming temperature can be controlled well, it can also avoid heat treatment. However, during the hot forming process, the temperature changes greatly, and each region has its differences. Even the surface in direct contact with the mold may be much lower than the temperature inside the metal, making it difficult to measure and control. Once local materials enter sensitive temperature zones during the processing, micro-cracks and other defects are generated, which are difficult to eliminate in later solid solution heat treatment. Drawing on the experience of processing plants, the cold-forming process was chosen. The preferred pressing method is molding, and when spinning is necessary, cold spinning or warm spinning at a temperature not exceeding 400 ℃ should also be used.
During the cold forming process, when the deformation rate is high, a step-by-step forming process should be used. Intermediate heat treatment is required for step-by-step forming, and solid solution heat treatment should be selected, with a temperature controlled above 1000 ℃. Choose a solid solution heat treatment process with a temperature of 1060-1080 ℃. After the final pressing and forming of the machined part, another solution heat treatment is required to eliminate residual stress and avoid affecting the subsequent welding quality.
2.3 Heat treatment
It is very important to always keep the workpiece clean and pollution-free before and during heat treatment.
During the heating process, the workpiece should not come into contact with sulfur, phosphorus, lead, or other low melting point metals, as this will damage the performance of the alloy and make it brittle. The heating furnace is preferably an electric furnace, such as a gas or oil-fired furnace. The lower the sulfur content in the fuel, the better. According to the material manufacturer’s recommendation, the total sulfur content in natural gas and liquefied petroleum gas should not exceed 0.1% (V), the sulfur content in urban gas should not exceed 0.25g/m³, and the sulfur content in oil should be less than 0.5% (W), which is better. The furnace gas must be clean and suitable for microreduction, and fluctuations between oxidation and reduction should be avoided. The heating flame should not directly contact the workpiece. Before entering the furnace, the workpiece must be supported to avoid adverse deformation at high temperatures. The heating speed of the workpiece should be as fast as possible, and the workpiece must wait until the furnace temperature reaches the heat treatment temperature before entering the furnace. After being discharged from the furnace, rapid water cooling should be carried out using the immersion method or full-area uniform spraying. It is strictly prohibited to use water pipes for pouring to prevent uneven cooling and heating, which may cause abnormal deformation or tearing.

3. Dish head forming test

The δ10 ASME SB333 N10675 plate (solid solution state) was used for the forming test of the head. The standard and specification of the head is JB/T 4746-2002 EHB219X10, and the deformation rate after forming will reach 21.8 %.
According to the process in Section 2 of the text, the original blank of the dish head is spliced with 2 plates, and the cutting size is ∅ 310, as shown in Figure 1. Before forming, grind the weld seam flat, remove the oxide layer, and clean the surface.
The hardness of the base metal and weld seam on both the positive and negative surfaces was measured, and the average values of 9 points were randomly measured, as shown in Table 4. The hardness of the weld seam is lower than that of the base material. It does not exceed the upper limit of hardness (HB250) specified in the Hastelloy B3 standard, indicating that the state of the weld seam is relatively ideal.

Figure.1 The original blank of the head is spliced with 2 plates
Table.4 Hardness values of the base material and weld seam of the dish head raw material

Hardness Value (HB)	Front	Back
Base Material	197	217
Weld Seam	142	146

Perform cold pressing and performing on the original blank of the dish head, with a maximum deformation rate of about 14%. After processing and forming, clean and measure the hardness of the base metal and weld on the front and back surfaces. The results are shown in Table 5.
Table.5 Hardness Values of Preformed Dish Head

Hardness Value (HB)	Front (outer) surface	Reverse (inside) surface
Base Material	241	270
Weld Seam	218	221

From Table 5, it can be seen that the hardening of the formed material is still quite obvious, and the hardness values of multiple parts have exceeded the upper limit of hardness specified in the material standard (HB250). A dyeing inspection was conducted on the inner and outer surfaces of the dish head (see Figure 2), and no abnormalities were found. Subsequently, solid solution heat treatment was performed, and the furnace temperature was set at 1070 ℃. Immediately quench with water to cool, acid wash, clean, and remove the surface oxide layer upon discharge. The hardness of the base material and weld seam was tested, and the results are shown in Table 6.

Figure.2 A dyeing inspection was conducted on the inner and outer surfaces of the dish head
Table.6 Hardness values of dish head after solid solution

Hardness Value (HB)	Front (outer) surface	Reverse ( inside ) surface
Base Material	139	130
Weld Seam	153	150

From Table 6, it can be seen that after solid solution treatment, the hardness values of the dish head base material and weld seam are greatly reduced, and the hardness of the base material is lower than that of the weld seam. No abnormalities were found during the appearance inspection of the dish head. After cleaning, the dish head was reshaped. Retest its hardness, and the results are shown in Table 7.
Table.7 Hardness values after secondary forming of the dish head

Hardness Value (HB)	Front (outer) surface	Reverse ( inside ) surface
Base Material	204	216
Weld Seam	223	204

PT was performed on the inner and outer surfaces of the dish head, and no abnormalities were found, as shown in Figures 3.

Figure.3 PT was performed on the inner and outer surfaces of the dish head, and no abnormalities were found
To investigate whether delayed cracking may occur, no secondary solid solution was performed. Two days later, PT was performed again, and no issues were found. However, considering the impact on later welding, it is still recommended to perform solid solution treatment after secondary forming during actual manufacturing.
Subsequently, samples were taken from the dish head and a 20% boiling hydrochloric acid corrosion test was conducted. The average annual corrosion rate was about 0.3mm, and the results were consistent with the data provided by the material manufacturer.

4. Conclusion

• (1) The experiment proves that the cold forming process method of using one intermediate forming and two final forming for hastelloy B3 material dish head is feasible;
• (2) Cold forming can increase the yield strength ratio of materials, increase the sensitivity to stress corrosion and cracking, and require intermediate and final solution heat treatment processes;
• (3) Recently, two more sets of dish heads have been pressed according to the above process. One set is molded, and the other set is spun due to non-standard diameter. Both have undergone two cold-forming and solid solution treatments; no problems have been found through inspection;
• (4) The article only focuses on the forming of the dish head, and the rolling of the cylinder is also a forming process, with a lower deformation rate compared to the dish head. Considering the impact of residual stress on weld quality, when the deformation rate of the cylinder is greater than 2%, especially for some rolled nozzles, it is also recommended to undergo a solid solution treatment.

Author: Lu Guangxian