Compared to 12CrMoV steel, 12Cr1MoV alloy steel pipe offers superior oxidation resistance and thermal strength. This makes it a preferred choice in high-temperature applications where durability and performance are critical.
One of the key features of this steel is its close relationship between creep limit and permanent strength, allowing it to maintain good plasticity even under prolonged stress. It also exhibits excellent workability and weldability, though it requires preheating to 300°C before welding, followed by stress relief to ensure structural integrity.
This steel grade is widely used in high-pressure, ultra-high-pressure, and subcritical power plant boilers for superheaters, headers, and main steam pipelines. At 580°C, it retains high thermal strength, oxidation resistance, and good permanent plasticity. The production process is relatively simple, and the welding performance is favorable. However, it is sensitive to the cooling rate during normalization. Prolonged exposure at 580°C may lead to pearlite spheroidization. A major advantage of 12Cr1MoV is its 100% recyclability, aligning with national environmental protection and resource conservation strategies. Domestic policies actively encourage expanding its application fields.
Currently, China's consumption of 12Cr1MoV alloy steel pipe is only about half that of developed countries. Expanding its use provides significant growth opportunities for the industry. According to research from the 12Cr1MoV Alloy Steel Pipe Branch of the China Special Steel Association, demand for high-pressure long products made from this material is expected to grow by an average of 10–12% in the coming years.
**Process Overview**
Due to different manufacturing methods, 12Cr1MoV alloy steel pipes are categorized into hot-rolled (extruded) seamless pipes and cold-drawn (rolled) seamless pipes. Cold-drawn tubes can be further divided into round and special-shaped types.
**Hot Rolling (Extruded Seamless Steel Pipe):**
Round tube billet → Heating → Piercing → Three-roll skew rolling, continuous rolling, or extrusion → Tube removal → Sizing (or diameter reduction) → Cooling → Billet tube → Straightening → Hydrostatic test (or flaw detection) → Marking → Storage.
**Cold Drawn (Rolled) Seamless Steel Pipe:**
Round tube billet → Heating → Piercing → Heading → Annealing → Pickling → Oiling (copper plating) → Multi-pass cold drawing (cold rolling) → Billet → Heat treatment → Straightening → Hydraulic test (flaw detection) → Marking → Warehousing.
**Three Characteristics of Microstructure Strengthening in 12Cr1MoV Alloy Steel Pipe**
The microstructure of the alloy steel pipe determines its mechanical properties, but microstructure strengthening plays a crucial role in shaping these properties. After cold rolling, changes in the cooling environment cause transformations in bainite, martensite, and other structures, significantly altering the mechanical behavior of the pipe. This allows for the production of steel pipes with varying strength levels to meet different performance needs.
1. **Parent Phase Requirement:** For microstructure strengthening, the parent phase must be present within the steel composition.
2. **Microstructure Strengthening Process:** This involves both deformation and diffusion mechanisms. In low-temperature environments, non-diffusion processes dominate, while in high-temperature conditions, diffusion plays the primary role.
3. **Key Factors:** Tissue strain and environmental cooling are critical. Temperature changes influence the energy state of the structure, shifting it from low to high. Additionally, the presence of fine particles in the alloy enhances its structural adaptability.
**Hardenability of 12Cr1MoV Alloy Steel Pipe**
Hardenability primarily depends on the critical cooling rate, which is influenced by the stability of the supercooled austenite. Several factors affect this stability:
1. **Chemical Composition:** Carbon content significantly impacts hardenability. When carbon content is below 1.2%, increasing C% reduces the critical cooling rate and shifts the C curve to the right, enhancing hardenability. Above 1.2%, the opposite occurs. Most alloying elements, except cobalt, improve hardenability by shifting the C curve to the right.
2. **Austenite Grain Size:** Larger grains shift the C curve to the right, reducing the critical cooling rate but increasing the risk of deformation and cracking.
3. **Uniformity of Austenite:** A more uniform austenite composition delays pearlite nucleation, extending transformation incubation time and improving hardenability.
4. **Original Structure:** The original microstructure affects the final properties of the steel.
5. **Alloying Elements:** Elements like Mn and Si enhance hardenability but may introduce other negative effects.
Common Mold frame: an important tool on the construction site
In the construction site, we often see a variety of tools and equipment, one of the most common is the ordinary mold. As an important construction auxiliary tool, the common die frame has been widely used in the construction industry. This paper will introduce in detail the related issues of the common die frame, including its background, composition, assembly, use and maintenance.
A common mold frame is a formwork used for concrete placement, which is composed of profiles and accessories that can be combined into formwork of different shapes and sizes according to different needs. In the construction site, the ordinary mold frame is mainly used for the pouring of concrete structures such as walls, beams and slabs. Due to its characteristics of reusable, convenient assembly and low cost, ordinary die frames have become important tools in construction sites.
The basic components of a common mold holder include profiles and accessories. Profiles are usually made of steel or wood and are used to form the frame and support structure of the template. Accessories mainly include bolts, nuts, washers, latches, etc., used to connect and fix profiles to ensure the stability and reliability of the template.
The assembly process of the ordinary mold frame is relatively simple, but some details need to be paid attention to. First, it is necessary to determine the shape and size of the required template according to the construction drawings, and then select the appropriate profiles and fittings. In the assembly process, it is necessary to follow a certain sequence and steps,
In the construction site, we often see a variety of tools and equipment, one of the most common is the ordinary mold. As an important construction auxiliary tool, the common die frame has been widely used in the construction industry. This paper will introduce in detail the related issues of the common die frame, including its background, composition, assembly, use and maintenance.
A common mold frame is a formwork used for concrete placement, which is composed of profiles and accessories that can be combined into formwork of different shapes and sizes according to different needs. In the construction site, the ordinary mold frame is mainly used for the pouring of concrete structures such as walls, beams and slabs. Due to its characteristics of reusable, convenient assembly and low cost, ordinary die frames have become important tools in construction sites.
The basic components of a common mold holder include profiles and accessories. Profiles are usually made of steel or wood and are used to form the frame and support structure of the template. Accessories mainly include bolts, nuts, washers, latches, etc., used to connect and fix profiles to ensure the stability and reliability of the template.
The assembly process of the ordinary mold frame is relatively simple, but some details need to be paid attention to. First, it is necessary to determine the shape and size of the required template according to the construction drawings, and then select the appropriate profiles and fittings. In the assembly process, it is necessary to follow a certain sequence and steps,
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