Stainless steel forging pipe plate deep hole processing

In 2010, our company was tasked with manufacturing a reflux condenser for the 400,000-ton urea plant of Shandong Runyin Biochemical Co., Ltd. The key component of the device was the tube sheet, which had an outer diameter of 1,960 mm and a thickness of 150 mm, made from 00Cr17Ni14Mo2 material. According to the engineering drawings, the tube sheets were required to be manufactured and accepted in accordance with Class II forgings as specified in JB4728-2000 "Stainless Steel Forgings for Pressure Vessels." The equipment included two tube sheets and nine baffles, each with a size of φ1,790 mm × 20 mm. Each tube sheet featured 2,576 tube holes, arranged in an equilateral triangular pattern, as shown in Figure 2. The design specifications demanded that 96% of the hole bridge width must be at least 5.77 mm after drilling, with a minimum allowable width of 3.48 mm. Additionally, the tube holes needed to be strictly perpendicular to the sealing surface, with a perpendicularity tolerance of 0.08 mm. Given the length-to-diameter ratio of the tube holes being 6, this fell into the category of deep-hole drilling. At the time, we didn’t have CNC or deep-hole drilling machines, so we relied on the existing Z3080 radial drilling machine. This posed significant challenges, especially regarding the accuracy of hole spacing, diameter tolerance, verticality, and surface roughness—factors that directly impacted the assembly and performance of the heat exchanger. The risks involved in using conventional machinery were high, as even minor deviations could lead to oversized holes. To ensure high-quality drilling under these constraints, we conducted a thorough analysis of the processing challenges and developed a detailed plan to address them. ### 1. Analysis of Processing Difficulties (1) The large number of tube holes and strict requirements for hole bridge width demanded extremely precise scribing. (2) The tube sheet's thickness and the deep-hole nature of the drilling made maintaining verticality very challenging. Any slight deviation during drilling would result in significant errors on the backside. (3) With multiple baffle layers, ensuring the concentricity between the tube sheet and the baffle holes was critical. Failure to maintain this could greatly increase the difficulty of inserting the heat transfer tubes. (4) The material used, 00Cr17Ni14Mo2 (Grade II forging), is highly plastic and has strong cutting resistance. Its compact structure during forging increased its toughness, and it also exhibited work hardening, making drilling more difficult and causing rapid wear on the drill bits. (5) The chips produced from stainless steel are typically long and stringy, making them hard to break and prone to wrapping around the drill bit, potentially scratching the inner walls of the holes and affecting surface finish. ### 2. Processing Plan and Precautions To overcome these challenges, we adopted a two-step approach: first drilling, then reaming. (1) **Scribing:** To ensure accurate alignment between the tube sheet and the baffle, we used a scribe line on the baffle plate. After testing, we drilled locating holes with a φ6 mm drill bit and used the baffle as a template for the other components. We scribed from the outside inward to minimize cumulative error. By carefully drawing crosshairs and calculating the center points of the hexagonal pattern, we ensured precise positioning of all tube holes. The final position error was controlled within 0.2 mm, and sharp tools were essential to reduce any potential mistakes. (2) **Drilling:** Before drilling, the baffle was fixed as a mold on the tube sheet, and concentricity was checked. A φ6 mm drill bit was used to create positioning holes, followed by a φ23 mm taper shank twist drill. The tube sheet was placed on a stable workbench, and verticality was strictly maintained. Drilling was done in multiple passes to aid chip removal and cooling. (3) **Reaming:** After the initial drilling, a φ25.4 mm reaming drill was used to improve the surface quality of the holes. The small amount of material removed during reaming helped maintain precision and surface integrity. (4) **Cutting Fluid Selection:** Due to poor thermal conductivity of stainless steel, heat dissipation was a major concern. We used a 10% emulsion as the cutting fluid to help cool the drill bit and extend its life while improving the surface finish of the holes. (5) **Cutting Parameters:** Optimal cutting speed and feed rate were crucial for both drilling and reaming. We set the drilling speed at 105 r/min with a feed rate of 0.32–0.4 mm/r, and the reaming speed at 200 r/min with a feed rate of 0.45–0.6 mm/r. These settings improved efficiency without compromising quality. ### 3. Conclusion Through careful planning and execution, the tube holes met all technical specifications. Key considerations during the process included: (1) Shortening the drill bit length as much as possible to increase rigidity. (2) Ensuring the drill bit was properly installed, kept sharp, and replaced when dull. (3) Monitoring chip discharge during drilling and retracting the tool immediately if clogging occurred. This project demonstrated our ability to handle complex machining tasks with limited equipment, delivering high-quality results through meticulous planning and attention to detail.

Wall Concealed Shower Mixer

The Wall Concealed Shower Mixer, also known as the wall concealed shower Mixer, is a high-end, sophisticated and minimalist design of bathroom equipment. It is cleverly hidden in the wall and does not take up floor space, which enhances the cleanliness of the bathroom while showing a minimalist aesthetic style. Typically made of high-quality stainless steel or copper, these shower mixers are durable and easy to clean.

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Overall, the Wall Concealed Shower Mixer is a beautiful, practical and high-tech shower solution that adds comfort and convenience to the modern bathroom and is ideal for the pursuit of high quality of life and design.

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