Abstract: F304 steel is an austenitic stainless steel commonly used in the manufacturing of valves. In this study, a Ø500 mm electroslag remelted ingot of F304 steel with an optimized chemical composition was forged with a forging ratio of 2.4. This was followed by a solution treatment at 1,050 °C for 3 hours with water cooling, and then a sensitization treatment at 670 °C for 1 hour followed by air cooling. The microstructure and mechanical properties of the forgings were evaluated. The results indicate that the mechanical properties meet the required standards, exhibiting good strength and toughness. The intergranular corrosion resistance also complies with the relevant technical specifications.

 

F304 steel is one of the most widely used austenitic stainless steels. It contains alloying elements such as nickel and chromium and is extensively applied in industries including aerospace, chemical processing, nuclear power, and automotive manufacturing. This paper investigates the effects of optimized chemical composition, forging techniques, and heat treatment processes on the microstructure and mechanical properties of F304 steel valve body forgings.

 

The electrode is melted using a +150 mm × 800 mm AOD (Argon Oxygen Decarburization) process. Raw materials are carefully selected to prevent the introduction of low-melting-point impurities into the electrode base metal. The electrode is then subjected to electroslag remelting to produce a +500 mm electroslag ingot. Due to the high alloy content and stringent corrosion resistance requirements for valve body forgings, the chemical composition must be carefully optimized to ensure the final product meets all performance standards. The chemical composition of the electroslag ingot is presented in Table 1. The ingot is blanked using a 2000-ton hydraulic press at an initial forging temperature of (1,180 ± 20) °C. After blanking, forging is performed, followed by air cooling.

 

Forging is carried out on a 2000-ton hydraulic press, with strict control over the initial and final forging temperatures (1,180 °C and 850 °C, respectively) as well as the forging ratio at each stage. Before forging, the steel ingot is heated to 1,180 °C and held at this temperature for 4 to 7 hours. The specific heating process is illustrated in Figure 1. The Ø500 mm electroslag remelted ingot is initially forged into a 280 mm × 280 mm × 580 mm billet, achieving a forging ratio of 2.4. This billet is then further forged to the final dimensions of 175 mm × 200 mm × 1,150 mm (L = 3 + S). The forging process yields three finished forgings along with additional test specimens. Air cooling is applied after forging.

 

Figure 2 illustrates the solution treatment process for F304 steel valve body forgings.

 

Table 1 Chemical Composition of F304 Steel Forgings

 

Figure 1 Heating process prior to forging the ingot

 

Figure 2 Solution treatment process for valve body forgings

 

After solution treatment at 1,050 °C, samples were extracted from the extended section of the forged body. The sampling location is shown in Figure 3. The tensile specimens had a gauge length of 50 mm and a diameter of 12.5 mm. The impact specimens were V-notch Charpy samples. Tensile and impact tests were performed using a WDW20E electronic universal testing machine and a JB-B (300 J) semi-automatic impact tester, respectively.

Figure 3 Schematic diagram of specimen extraction from the forging

 

Figure 4 shows the microstructure of the F304 steel valve body forging after solution treatment. The microstructure consists primarily of uniform, single-phase austenite with a grain size of 4. Thanks to the optimized steel composition, the post-treatment microstructure remains single-phase austenite, which reduces the electrode potential differences between matrix phases and further improves corrosion resistance. Table 2 presents the mechanical properties of F304 steel forgings following solution treatment. After water-cooled solution treatment at 1,050 °C, the forgings demonstrate mechanical properties and hardness at both room and elevated temperatures that not only meet but significantly exceed the specified technical requirements.

Figure 4 Microstructure of F304 steel forging after solution treatment (×200)

 

Table 2 Mechanical Properties of F304 Steel Forging After Solution Treatment

 

Samples were extracted from the forgings and subjected to sensitization treatment following ASTM A262 Practice E. Specifically, the specimens were heated to 670 °C, held at that temperature for 1 hour, and then air-cooled. Intergranular corrosion testing was performed in accordance with ASME Section II, Part A, SA-262: Practice for Determining the Susceptibility of Austenitic Stainless Steels to Intergranular Attack. As a result, no cracks were observed after bending the sample 180°, indicating that the intergranular corrosion resistance of F304 steel meets the required standards following solution treatment at 1,050 °C.

 

The composition-optimized F304 steel valve body forgings were manufactured through a carefully designed smelting process, appropriate hot forming, and an effective solution treatment. The resulting forgings meet all mechanical property requirements, exhibiting good strength and toughness. Furthermore, their intergranular corrosion resistance conforms to the relevant technical standards.

 

ASTM A182 F92 is susceptible to surface cracking under improper forging due to its high alloy content. Additionally, its high chromium (Cr) and tungsten (W) content significantly reduces the effectiveness of conventional flame-based defect detection methods, which in turn reduces production efficiency. Severe surface cracks may render the product non-compliant with quality standards. Therefore, optimizing the forging process for F92 large valve is essential.

 

ASTM A182 F92 complies with ASTM A182/A182M-2018, the standard for forged or rolled alloy steel and stainless steel components used in high-temperature applications. It is a martensitic heat-resistant steel. The increased tungsten (W) and molybdenum (Mo) content enhances its high-temperature corrosion resistance, low-cycle thermal fatigue resistance, and creep rupture strength. The chemical composition of F92 is detailed in Table 1. The high alloy content of F92 increases resistance to hot deformation, narrows the forging temperature range, and raises the risk of surface cracking. Grain size control during forging is essential to maintaining material quality. Therefore, strict forging process control is essential for producing high-quality F92 large valve body forgings.

 

After upsetting the steel ingot, the WHF (Weight Hammer Forging) center compaction method, wide anvil feed, and a minimum 20% reduction in forging are applied to shape the blank. This ensures effective plastic deformation of the forging blank core under three-dimensional compressive stress, refining the coarse as-cast structure and eliminating internal cavity defects. Using the forging of a 15-ton steel ingot as an example, the forging process design is outlined as follows:

• Step 1: Perform chamfering, secure the workpiece, and ensure a dry surface.
• Step 2: Upset the ingot to a height of 865 mm and a diameter of 1500 mm. Use a 900 mm wide anvil for stretching, maintaining an anvil width ratio of 0.6 to 0.8. Refer to Table 2 for pressure control parameters, and rotate the ingot 90° sequentially.

 

During forging, the F92 steel billet may develop surface cracks under high forging pressure, which can occur during both the upsetting process (Figure 1a) and the stretching process (Figure 1b). In severe cases, these cracks can disrupt the forging process, potentially rendering the billet unusable.

(a) Surface cracking during upsetting (b) Surface cracking during stretching
Figure 1: Surface Cracking

 

Therefore, forging process optimization aims to minimize surface cracking in large F92 steel billets while enhancing core deformation, refining the coarse as-cast structure, and eliminating internal cavity defects to achieve a uniform microstructure.

 

 

 

Strain Rate: Strain rate refers to the rate of deformation per unit time and is measured in s⁻¹.

According to Gleeble thermal deformation tests at 1200°C, the stress-strain curve for ASTM A182 F92 under different strain rates is shown in Figure 2. As the strain rate increases, the material's flow stress also increases. Therefore, when significant deformation is required during forging, the strain rate must be strictly controlled. To optimize forging conditions, maintain the strain rate at or below 0.5 s⁻¹.

Figure 2: High-Temperature Stress-Strain Curve of F92 at 1200°C Under Different Strain Rates

 

As illustrated in Figure 3, the high-temperature stress-strain curve of F92 at a strain rate of 0.005 s⁻¹ under different temperature is shown. As the temperature increases, the deformation resistance of F92 decreases, while the softening effects of recovery and recrystallization become more pronounced. When the temperature exceeds 1000°C, the material's deformation resistance reduces to below 110 MPa. To achieve significant deformation during forging, maintain the forging temperature above 1000°C whenever feasible. Based on this analysis, the following process improvements are proposed:

• Reduce the degree of upsetting. After upsetting, briefly reheat the forging billet in the furnace to increase its surface temperature.
• Control the deformation rate by increasing the anvil feed, reducing the forging reduction to 15–20%, and increasing the number of forging passes. This ensures that the overall forging ratio remains unchanged while lowering the deformation rate and ensuring effective core forging.

 

Figure 3 High-temperature stress-strain curves of F92 steel at different temperatures at a strain rate of 0.005 s⁻¹

 

Using a 15-ton steel ingot as an example, and considering the reduced upsetting and reduction during the lengthening process, the optimized forging process design is as follows:
Step 1: Chamfer the ingot, clamp it, and remove surface moisture.
Step 2: Upset to H = 990 mm and 1400 mm. Use upper and lower plates to shape the ingot into a square according to the specifications in Table 3 for the first and second passes, followed by brief reheating in the furnace.
Step 3: Use a 1200 mm wide anvil for drawing, maintaining an anvil width ratio of 0.8–1.1. Apply the pressure settings shown in Table 3 (passes 2–8), rotating the ingot 90° sequentially.

 

Deform analysis software was used to simulate and compare the core forging penetration of the optimized process with that of the process before optimization. The billet dimensions were set at 1230 mm × 1150 mm (square). The selected parameters were as follows:

• Before optimization, the parameters were as follows: anvil width of 900 mm, a 20% reduction, a strain rate of 0.004 s⁻¹, and a deformation temperature of 1100°C.
• After optimization, the anvil width was increased to 1200 mm, while the reduction was adjusted to 15%, with the strain rate and deformation temperature remaining at 0.004 s⁻¹ and 1100°C, respectively.

For billets of the same size, the equivalent stress and strain rate distributions are shown in Figures 4 and 5.

Simulation analysis and comparison demonstrate that the stress and strain conditions at the billet core are similar in both processes, confirming that core forging can be effectively achieved.

 

Through process optimization, a 1200 mm wide anvil was used, and the reduction rate was set to 15%. The results, shown in Figure 6, demonstrate that the surface cracking was effectively addressed. The final product passed flaw detection and met NB/T 47013-2015 Level 1 requirements. The product was successfully delivered.

 

 

(a) Distribution of equivalent stress with a 900mm anvil and 20% compression
(b) Distribution of equivalent stress with a 1200mm anvil and 15% compression

Figure 4: Comparison of equivalent stress distribution

 

(a) Equivalent strain rate with a 900mm anvil and 20% compression
(b) Equivalent strain rate with a 1200mm anvil and 15% compression

Figure 5 Comparison of equivalent strain rates

 

• Optimizing the height-to-diameter ratio of the forging billet after upsetting effectively prevents surface cracking caused by excessive deformation.
• After upsetting, the forging billet is reshaped into a square using upper and lower plates, then briefly reheated in the furnace to raise the surface temperature, facilitating subsequent large deformation during the stretching process.
• The use of wide anvils for stretching forging requires high press tonnage, making the selection of an appropriate press tonnage a critical factor in process optimization.
• During wide-anvil stretching, the reduction must be carefully controlled, particularly in the final stage of the downstroke.
• After process optimization, surface cracks are effectively minimized, and the core compaction requirements of the forging billet are successfully met.

 

Figure 6 Drawing effect after process optimization

 

Ball valve bodies are critical components in valves, traditionally manufactured through casting. However, casting is prone to defects such as porosity, shrinkage, and dendritic formation, which can prevent valves from meeting performance requirements in harsh operating conditions. To enhance the mechanical properties of ball valve bodies, researchers and manufacturers have turned to forging techniques, particularly free forging and die forging. These methods, however, generate substantial material waste and incur high machining costs. Recent advancements in heavy equipment technology have made the multi-directional die forging process widely adopted. This process is characterized by high material utilization, continuous internal fiber alignment, and superior mechanical properties in forged components. This paper introduces two distinct ball valve body forming processes using the multi-directional die forging method.

 

The ball valve body (Figure 1) is a component with flanges at both ends, a smaller central diameter, and larger diameters at the flanges. Symmetrically positioned bosses of varying sizes are present on the ball flange side. Made of carbon steel, the valve body weighs 128 kg, with a designed forging weight of 207 kg and a material utilization rate of approximately 62%.

(a) Ball valve components (b) Forged ball valve bodies
Figure 1: Ball valve body components and forged parts

 

Producing this forged valve in a single operation using conventional forging methods poses significant challenges. Multi-directional die forging technology, in combination with heavy equipment, applies pressure to the blank within a separable die cavity from multiple directions, enabling the production of complex shapes. The primary methods of multi-directional die forging include horizontal splitting, vertical splitting, and combined splitting. This paper introduces two multi-directional die forging schemes—horizontal splitting and vertical splitting—for manufacturing this ball valve body. Both methods meet the required forging quality standards, differing primarily in their equipment load requirements and mold splitting structures.

 

The valve body features large flanges at both ends, a smaller central diameter, and significant size variation along the flange axis. The multi-directional die forging process begins with blanking the material, as shown in Figure 2.

(a) Round bar stock (b) Blanking (c) Multi-directional die-forged parts
Figure 2: Horizontal split die forming process

The horizontal split die method uses multi-directional die forging. In this process, the heated preform is placed in the multi-directional die. Forging occurs within the die cavity, with the die surface aligned to the forging's maximum horizontal projection. Figure 3 shows the structure of the horizontal split die used in multi-directional forging.

Figure 3: Horizontal split die structure

Figure 4: Metal flow and cavity filling during forging

 

Round bar stock is selected for free forging. After heating the billet, an infrared thermometer is used to measure its surface temperature. If the billet’s temperature falls below 850°C, it is returned to the furnace for reheating and holding before proceeding with multi-directional die forging. If the temperature exceeds 1050°C, multi-directional die forging can proceed immediately.

 

Horizontal punches on both sides compress the preform within the closed mold cavity, causing the metal to flow and fill the cavity. The final forming takes place at the larger convex region of the valve body. The forging produced by multi-directional die forging demonstrates excellent surface quality, with a fully formed metal structure and no defects, such as folding in the inner hole or surface irregularities.

 

Numerical simulations of the forming force help determine the load required for plastic forming, providing valuable insights for production tests. This study used a comprehensive three-dimensional mold model for numerical simulation analysis (Figure 5). The maximum horizontal forming load was 66.4 MN, while the maximum clamping load reached 65.2 MN.

(a) Horizontal punch load (b) Upper and lower clamping load
Figure 5: Die force analysis during forging

(a) Round bar material (b) Blanking (c) Multi-directional die-forged components
Figure 6: Horizontal split die forming

 

The valve body features large flanges at both ends, with significant size variations between the central section and the flanges. The blank must be selected according to the dimensions of the valve's smallest section. Upsetting the flange on one side can result in folding defects and instability in the inner hole of the flange. In the vertical split die forming scheme, the process begins with upsetting and consolidating the bar material, followed by extrusion to shape the concave hole.

 

The initial step involves upsetting and consolidating the bar material, followed by extrusion to form the desired shape. The next step involves upsetting, consolidation, and deep-hole forming using the vertical split die with multi-directional forging equipment. Figure 7 illustrates the deep-hole forming process in the second step.

 

Due to the large flanges on both sides of the ball valve body, additional metal must be added, increasing the complexity of the filling process. The original bar is first forged into a blank to form a flange on one side, then placed in the cavity of the multi-directional die for forging. Throughout the process, the temperature of the preform must be closely monitored. If the temperature drops below 850°C, the preform is returned to the furnace for reheating and holding. If the preform temperature exceeds 1050°C, forging can proceed directly without reheating.

Figure 7: Deep-hole forming process in the vertical split die scheme

(a) Blank (b) Upsetting the aggregate material (c) Forming the concave hole (d) Clamping (e) Multi-directional die forging (f) Final forging
Figure 8: Process flow for forming the ball valve body

(b) Final forging upper punch load (b) Preform upper punch load (c) Left and right clamping load
Figure 9: Die force analysis during the forging process

 

Figure 8 depicts the forming process flow for the ball valve body in the vertical split die scheme, requiring two sets of concave dies. The process begins with upsetting and consolidating the bar material, followed by forming the concave hole at the base of the flange, as shown in Figures 8(b) and 8(c). The preform is positioned within the multi-directional forging die cavity, aligning the concave hole at the flange base with the convex portion of the lower ejection die. The left and right dies are then clamped together. The preform is upset and consolidated by the upper punch, and subsequently, the blank is extruded and shaped using the forming punch, as depicted in Figures 8(d), 8(e), and 8(f). The forming process employs a total of four upper punches. As the upper punches play a critical role, prompt replacement during production is essential to maintain the quality of the forged part. A flexible and automated mechanism for upper punch replacement is required to ensure continuous production.

 

The initial pre-forging load is 43.7 MN, as illustrated in Figure 9(a). The extrusion load for the punch during multi-directional forging is 47 MN, which forms the large end flange and the convex joint on the valve body, as shown in Figure 9(b). The maximum left and right clamping load for the vertical split die is 54.2 MN, ensuring the stability of the valve body during forming and optimal forging quality, as shown in Figure 9(c).

 

• Die Splitting Structure: In the horizontal splitting scheme, the splitting surface is oriented horizontally, while in the vertical splitting scheme, it is oriented vertically.
• Different Forming Steps: To achieve consistent forging dimensions in both splitting schemes, the preform in the vertical splitting scheme requires multiple upsetting and consolidation steps. Consequently, the vertical splitting scheme involves more steps than the horizontal scheme does.
• Different Forming Loads: Simulation results show that the mold load in the horizontal splitting scheme is higher than that in the vertical scheme. In the vertical scheme, the blank undergoes roughening and consolidation before flange formation on both sides, which reduces resistance during the later stages of metal flow.
• Forming Challenges: The side boss area of the ball valve body presents the greatest challenge during forging, as it is difficult to achieve full metal filling. This area also experiences high resistance to metal flow.

 

Research on the ball valve body forging process indicates that achieving the same forging size with the vertical splitting scheme requires multiple material consolidation steps before the punch can form a deep hole. Directly upsetting and compressing the original blank may cause folding inside the hole, resulting in scrap. Trial production results align with the simulation outcomes. Thus, the ball valve forging described in this study should utilize the horizontal splitting scheme. This scheme conserves raw materials and simplifies the forming process, while imposing greater demands on the equipment's load capacity.

This report presents an ultra-high-pressure forged pre-start multi-stage adjustable self-sealing control valve, focusing on its structural features and operating principles. A comparative analysis of the product structure, manufacturing process, and overall performance was conducted. The design improvements for the steam control valve include integral forgings for pressure-bearing components and a multi-stage sleeve with a pre-start auxiliary valve core, featuring an adjustable self-sealing balanced pressure reduction structure. This design enhances the valve’s efficiency and performance.

 

In response to national initiatives for energy conservation, emission reduction, and industrial transformation, the steam control valve plays a critical role in steam turbine bypass systems and temperature/pressure reduction devices. It is widely used in industries such as power generation, petrochemicals, textiles, heating, refrigeration, large-scale cogeneration, and military vessels. The valve directly influences the performance of steam turbine bypass systems and temperature/pressure reduction devices. Traditional steam control valves are prone to damage and vibration, often leading to leakage. The increasing variability in large-scale operating conditions and complex process parameters often causes issues with regulation, safety, and reliability in these systems. This report introduces a super-high-pressure pre-start multi-stage adjustable self-sealing balanced pressure reduction forged control valve. The valve features significant improvements in structure, manufacturing technology, reliability, and cost efficiency, and is specifically designed to meet the demands of large-scale, variable operating conditions and complex process parameters.

 

Figure 1 illustrates the composition of the ultra-high-pressure forged pre-start multi-stage adjustable self-sealing control valve. The design of this valve integrates multi-stage pressure reduction and noise attenuation, combined with a cage sleeve structure and both main and auxiliary valve cores. This enables efficient multi-stage pressure reduction with a pressure reduction ratio as low as 0.3, achieving a precision of 1% under ultra-high temperature, high-pressure, and significant pressure differential conditions.

 

The valve body and bonnet are forged from high-temperature, high-pressure-resistant materials, ensuring a uniform, dense structure, enhanced structural integrity, and superior reliability under extreme operating conditions. Additionally, the forged valve body is available in various configurations, including straight-through (flat-in/flat-out), top-entry/bottom-exit, and angled types, to meet specific installation requirements. Its compact design and efficient layout reduce space requirements and installation costs.

 

A metal-elastic Wood seal structure is used between the valve body and bonnet, ensuring a secure connection and enhancing the seal's lifespan and reliability under ultra-high-pressure conditions. The sleeve and valve core feature a high-efficiency cage sleeve structure. Compared to traditional plunger control valves, this design offers superior noise reduction and pressure attenuation. Optimal internal component alignment and precision manufacturing technology regulate the outlet steam flow rate, mitigate cavitation risk, and minimize noise and vibration during operation. Under high-temperature, high-pressure conditions, the valve operates with minimal vibration, and the overall noise level remains below 85 dB(A). Figure 4 illustrates the theoretical simulation results for vibration and noise reduction.

1. Valve body 2. Valve seat 3. Multi-stage sleeve 4. Main valve core 5. Carbon ring seal 6. Lower positioning ring 7. Lower four-opening and closing ring 8. Valve bonnet 9. Upper four-opening and closing ring 10. Sealing packing 11. Guide frame 12. Actuator 13. Insulation frame 14. Packing pressure plate 15. Support plate 16. Gasket 17. Wood seal pair 18. Fastening butterfly nail 19. Balance hole seat 20. Pre-start auxiliary valve core 21. Disc spring

Figure 1 Ultra-high pressure forged self-sealing pre-start multi-stage adjustable control valve

 

1. Lower valve bonnet 2. Valve body 3. Lower guide bushing 4. Valve seat 5. Valve core 6. Pin shaft 7. Valve stem 8. Four-opening and closing ring 9. Support plate 10. Clamp 11. Clamp plate 12. Lever 13. Packing pressure plate 14. Sealing packing 15. Sealing ring 16. Throttle screen

Figure 2 Traditional self-sealing high-pressure control valve

 

The sleeve, valve core, and other components are made from Cr-Mo-V or Cr-W-V alloys, which exhibit outstanding resistance to both high temperatures and high pressures. Advanced processing techniques are employed to significantly enhance surface hardness, improving the valve's operational stability and extending its service life.

The valve stem is made from imported high-chromium, heat-resistant stainless steel, which prevents electrochemical reactions with graphite packing, thereby avoiding corrosion and surface pitting. Additionally, the surface undergoes an electrostrictive metal finishing process to enhance hardness and surface smoothness, thereby reducing friction and minimizing leakage.

 

The pre-start auxiliary valve core incorporates advanced technology, enabling precise control during operation. During valve operation, the auxiliary valve core opens first, followed by the main valve core once pressure equilibrium is achieved. This process effectively reduces unbalanced forces during operation, lowering actuator shaft thrust, minimizing energy consumption, and improving the cost-effectiveness of the control valve. Figure 5 illustrates the design principle.

 

The control valve seal is designed for zero leakage, with the sealing surface coated with an imported hard alloy. The single-seat tapered seal pair enhances the resistance to erosion at the valve port, ensuring reliable sealing when the valve is closed. Figure 6 illustrates the design principle.

Figure 3 Pressure Reduction Design

 

Figure 4 Theoretical Simulation of Vibration and Noise Reduction

Figure 5 Schematic Diagram of the Pre-Start Auxiliary Valve Core Structure

Figure 6 Tapered Seal Pair Diagram of the Valve Core and Valve Seat

 

The control valve sealing material is made from high-performance reinforced flexible graphite to prevent leakage from the valve stem during operation. Additionally, the sealing ring is constructed from high-quality imported materials, ensuring reliable sealing performance under high-temperature and high-pressure conditions. The valve seat features an inlaid split structure, effectively preventing deformation caused by thermal stress. The valve core and stem are designed as a single integrated unit, which simplifies both disassembly and reassembly, improving on-site maintenance efficiency. All wear parts are replaceable, with an efficient and simplified replacement process.

 

The valve seat and body are precision-ground before assembly, with a stainless steel sealing gasket installed between them. Three carbon ring seals are used at the dynamic seal between the valve core and sleeve, preventing internal leakage and minimizing the potential for valve body erosion. The valve’s thermal insulation frame incorporates four high-strength steel columns, reducing weight, enhancing vibration resistance, and preventing fatigue-induced cracking of the casting bracket. This structure minimizes heat transfer from the valve body to the actuator, thereby enhancing valve reliability.

 

The control valve opens, adjusts, or closes in response to a pressure signal applied to the rear of the valve. The signal activates the actuator, which, in turn, drives the valve stem connected to the valve core. As the valve core moves vertically within the valve seat and multi-stage sleeve, it modifies the flow area of the medium, thereby controlling throttling. Inlet steam first passes through the sleeve in the upper chamber, where primary throttling and decompression occur. Secondary throttling and decompression take place at lower flow rates. The steam then flows through the main valve core within the valve seat for further throttling and decompression, followed by tertiary throttling and decompression at even lower flow rates, before entering the lower chamber.

 

The main valve core is adjusted vertically within the multi-stage sleeve to control the flow area of the first sleeve, thereby achieving primary throttling and decompression. Simultaneously, the main valve core is adjusted within the valve seat to control the number of throttling holes at its lower end, modifying the flow area to achieve secondary throttling and decompression.

 

All valve materials undergo precision machining, with the inner surfaces of the multi-stage sleeve and valve stem precisely ground to tight tolerances. After grinding, the valve stem undergoes an electrochemical finishing process, improving its corrosion resistance and reducing friction between the stem and packing. Stud holes on the valve body and corresponding holes on the valve cover are machined with high precision to ensure alignment. Before assembly, the valve seat and core are precision ground, and three sets of sealing rings are installed between the valve core and multi-stage sleeve to prevent internal leakage and mitigate the risk of valve body wear. The inner surfaces of the multi-stage sleeve, valve seat, packing pad, and packing gland are nitrided to enhance surface hardness, reduce wear between moving parts, and extend the valve's service life.

 

In response to the leakage and vibration issues experienced by traditional control valve structures during system operation, the causes of these issues have been analyzed. Based on this analysis, a structural improvement design was developed and verified by multiple users. The high-pressure forged pre-start multi-stage adjustable self-sealing control valve offers a more rational structure and improved adjustment performance, ensuring the reliable operation of the system.

The manufacturing process of forged valve bodies is a complex and precise engineering task that involves several critical steps. Each step plays a vital role in determining the performance and reliability of the final product. The valve body is the core component of the valve, designed to withstand fluid pressure and temperature. Therefore, the manufacturing process must ensure high strength, durability, and the ability to adapt to harsh conditions. Below is a detailed overview of the manufacturing process for forged valve bodies.
The first step in manufacturing a forged valve body is selecting the appropriate metal or alloy. Common materials include carbon steel, stainless steel, and alloy steel. The choice of material depends on the application and operational conditions of the valve; some applications may require higher corrosion resistance or high-temperature performance. After selecting the material, it undergoes strict quality inspection to ensure its chemical composition, physical properties, and mechanical performance meet relevant standards, preventing defects during the manufacturing process.
Once the material passes inspection, it is heated to a specific forging temperature. This temperature typically falls within the recrystallization range of the material, ensuring good plasticity and reducing the risk of cracking during forging. Proper heating time and temperature control are key to maintaining the metal's performance.
The heated metal is then flattened into a disc-shaped blank, bringing it closer to the final shape of the valve body. This process usually involves pressing the metal using specialized molds, forming the initial contours of the valve body, including the cavity and connection parts. This step not only provides a basic shape for subsequent processing but also improves production efficiency.
After preliminary shaping, the valve body is placed into a final forging mold and subjected to high-pressure pressing to achieve a more precise finished shape. At this stage, the design details of the valve body are further defined to ensure that its dimensions and surface quality meet design requirements. Fine forging enhances the physical properties of the valve body and improves its internal structure, increasing its strength and toughness.
After forging, excess material (flash) forms on the valve body and needs to be removed through machining or manual finishing. This process ensures the final shape and dimensions of the valve body are correct and prepares it for further finishing and surface treatment. After removing the flash, the valve body appears smoother and lays the groundwork for subsequent inspections and treatments.
Following forging, the valve body undergoes a controlled heating and cooling process known as heat treatment. This process aims to enhance the strength, toughness, and wear resistance of the valve body, ensuring reliable performance under high pressure and extreme conditions. Common heat treatment methods include quenching, tempering, and normalizing, with the specific choice depending on the material properties and application requirements.
After heat treatment, the metallic surface of the valve body needs to be cleaned to remove oxidation, debris, and impurities generated during forging and heat treatment. This process ensures a clean surface for subsequent inspections and coating treatments. Good surface cleaning not only enhances the appearance of the valve body but also helps prevent corrosion issues in later treatments.
Once cleaned, the valve body undergoes non-destructive testing methods, such as ultrasonic testing, radiography, and magnetic particle testing, to ensure there are no internal defects. Non-destructive testing is a critical step in ensuring the quality and safety of the valve body, allowing for the timely detection of minor cracks or other defects that could affect performance. This step is especially crucial for valve bodies that will endure high pressure and extreme conditions.
Throughout the manufacturing process, strict quality control measures must be implemented to ensure that each step meets established technical specifications. Detailed inspection standards and procedures are put in place to guarantee product consistency and reliability. During the final inspection, quality control personnel check the dimensions, materials, and performance parameters of the valve body to ensure compliance with all standards and requirements.
While machining and finishing are not always essential components of the forging process, they are typically performed to achieve specific features and surface finishes required for the valve body in its intended application. The finished valve body may undergo processes like sandblasting, polishing, or coating treatments to enhance its corrosion resistance and wear resistance. Additionally, to prevent damage during transportation, the valve body is stored properly and protected appropriately.
The manufacturing process of forged valve bodies is a complex and systematic operation, encompassing every stage from material selection to the final shipment of the product. This precise process ensures that the valve bodies perform excellently and reliably under high pressure and harsh conditions. As a mature and widely used production method, forging technology continues to evolve alongside new technological advancements, providing robust support and assurance across various industries. With its detailed production processes, forged valve bodies are designed to perform optimally even in extreme conditions while contributing positively to the sustainable development of the industry.

 

 
Forged steel gate valves are essential components in various piping systems due to their excellent sealing performance, high-temperature, and high-pressure resistance. They are a popular choice for fluid control. There are two main types of forged steel gate valves, classified by their sealing surface configurations: wedge gate valves and parallel gate valves. This article will explore the structural features, advantages and disadvantages, applicable scenarios, and working principles of these two types, helping users better understand their applications.
In parallel forged steel gate valves, the sealing surfaces remain parallel to the vertical centerline, ensuring a tight seal between the valve body and the gate. The design and performance of this type of valve are highlighted in several key areas.
Double Gate Design: Most parallel forged steel gate valves feature a double gate structure. By inserting a double-sided thrust wedge between the two gates, the gates can tightly contact the valve body sealing surface when closed. This design helps distribute pressure and reduce localized wear.
Spring Assistance: Some parallel forged steel gate valves are equipped with springs between the two gates to provide additional preload. This design not only enhances sealing performance but also helps prevent seal failure due to prolonged use.
Wear Resistance: The sealing surfaces of parallel forged steel gates experience relatively less wear, making them suitable for medium- to low-pressure environments. This reduces maintenance and replacement frequency, thereby lowering operating costs.
Fluid Compatibility: These forged steel valves are suitable for various non-corrosive fluids, such as water, steam, and oil. They are particularly effective for low-pressure and small-diameter applications (DN40—300mm).
Parallel forged steel gate valves are commonly used in urban water supply, wastewater treatment, and chemical plants due to their simple structure and reliable sealing performance. They excel in low-flow systems, effectively controlling fluid movement.
Wedge forged steel gate valves have sealing surfaces angled to the vertical centerline, forming a wedge shape. Their design features and applications are as follows.
Sealing Surface Angle: The sealing surface angles of wedge forged steel gate valves typically range from 2°52', 3°30', 5°, 8°, to 10°. The choice of angle primarily depends on the temperature of the medium. Generally, higher working temperatures require a larger sealing surface angle to reduce the wedging phenomenon caused by temperature changes.

Single and Double Gate Design: Wedge forged steel gate valves can be designed with either a single gate or a double gate. Single gate structures are simpler and more reliable but have stricter precision requirements for the sealing surface angle. In contrast, double gate designs, while more complex, are less likely to experience wedging under temperature variations.
In this part, we will mainly talked about the major advantages and disadvantages of wedge forged steel gate valves.
High Temperature and Pressure Resistance: Wedge forged steel gate valves can operate stably at high temperatures and pressures, making them suitable for hot water, steam, and petrochemical applications.
Compensation Capability: In double gate designs, sealing surface wear can be compensated by adding gaskets, extending the valve's service life.
Complex Structure: Compared to parallel forged steel gate valves, wedge valves have a more complex structure, leading to higher maintenance costs.
Prone to Sticking: In viscous media, double gate structures can easily stick, affecting normal operation and increasing maintenance frequency.
Wedge forged steel gate valves are widely used in industries such as petroleum, chemical, metallurgy, power generation, and water supply, especially in applications where fluid temperature and pressure have strict requirements. For instance, they are commonly used in the petrochemical industry to control high-temperature and high-pressure fluids, ensuring safe and stable system operation.
When choosing forged steel gate valves, users should make informed decisions based on specific operating conditions, medium characteristics, temperature, and pressure requirements. Here are some selection suggestions.
For low-pressure, small-diameter fluid control, parallel forged steel gate valves are recommended due to their simple structure and ease of maintenance, making them suitable for non-corrosive media like water and steam.
In environments with high-temperature and high-pressure fluids, wedge forged steel gate valves are advisable, particularly those with a double gate design, as they can effectively avoid wedging caused by temperature variations.
For viscous or sedimentary media, avoid using double gate wedge forged steel gate valves to reduce the risk of sticking and jamming.
The design and application of forged steel gate valves depend on different operational requirements. Parallel forged steel gate valves, with their parallel sealing structure, are ideal for low-pressure and small-diameter fluid control, ensuring excellent sealing. In contrast, wedge forged steel gate valves, with their unique wedge-shaped sealing design, can operate under higher temperatures and pressures, making them more versatile. By understanding these two types of forged steel gate valves in detail, users can select the appropriate valve for their specific needs, ensuring the efficient and safe operation of their piping systems.