How to control the annealing temperature and process time of seamless pipes?

As a key material in industrial production, the performance and quality of seamless pipes (SMLS) directly affect the overall performance of the product. Annealing treatment, as an important link in the production process of seamless pipes, plays a significant role in improving the organizational structure of materials, eliminating internal stress, and improving plasticity and toughness. So, how should the annealing temperature and process time of seamless pipes be determined?

1. Selection of annealing temperature

Annealing temperature is one of the key factors affecting the annealing effect of seamless pipes. Generally speaking, the selection of annealing temperature needs to consider factors such as the material, wall thickness, use requirements and subsequent processing of seamless pipes. For common carbon steel seamless pipes, the annealing temperature is usually set between 700-900℃. This temperature range can effectively eliminate the internal stress in the material, avoid excessive grain growth, and maintain good comprehensive performance. For alloy steel seamless pipes, due to the addition of alloy elements, the annealing temperature often needs to be appropriately increased, generally between 900-1200℃, to ensure that the alloy elements can be fully diffused and optimize the organizational structure of the material.

2. Control of process time
In addition to annealing temperature, control of process time is also crucial. The length of process time is directly related to the adequacy of annealing effect and the level of production efficiency. Generally speaking, annealing time needs to be comprehensively considered according to the size, wall thickness and annealing temperature of seamless pipe. At lower annealing temperature, in order to ensure the adequacy of annealing effect, annealing time may need to be appropriately extended; at higher annealing temperature, efficiency can be improved by shortening annealing time. At the same time, it is also necessary to avoid problems such as excessive annealing time leading to grain growth and performance degradation of materials.

3. Optimization of annealing process
In order to further improve the annealing effect and production efficiency of seamless pipes, the annealing process can also be optimized. For example, the use of rapid heating and cooling technology can shorten the annealing cycle and improve production efficiency; by accurately controlling the temperature and time parameters in the annealing process, the performance of seamless pipes can be precisely controlled; in addition, different annealing media and atmosphere conditions can be used according to the specific use requirements of seamless pipes to meet different performance requirements.

Conclusion:

The annealing temperature and process time of carbon steel seamless pipes need to be accurately set and optimized according to the specific material and use requirements. Through scientific and reasonable annealing treatment, the performance and quality of seamless pipes can be significantly improved, providing more reliable material guarantee for industrial production.

What are the factors that affect the annealing of seamless steel pipes?

Annealing conditions are a key issue that directly affects product quality and performance, and there are many influencing factors. The following are 9 key factors:

1. Annealing temperature.
Whether the required temperature is reached. Temperature is a key factor. Too high or too low will affect the structure and performance of the steel pipe. Too high temperature may cause coarse grains, and too low temperature will not be fully softened. The heat treatment process of steel generally adopts heat treatment + tempering heat treatment process, which is what we usually call "annealing", with a temperature range of 1040 ~ 1120℃ (Japanese standard).

2. Holding time.
The holding time affects the uniformity of the organization and the grain size. Too long time may cause coarse grains, and too short time may cause insufficient organization transformation.

3. Annealing atmosphere.
The annealing atmosphere generally uses pure hydrogen, and the atmosphere purity is above 99.99%. If the other part of the atmosphere is a rare gas, the purity can be lower, but it cannot contain too much CO2 and water vapor.

4. Furnace wall air tightness.
The seamless steel pipe furnace should be closed and isolated from the outside gas; if radon gas is used as the protective gas, only one exhaust pipe is opened (for igniting the exhausted radon gas). The inspection method can be applied with soap liquid in the gaps of each joint of the annealing furnace to see if there is any gas escaping; the area where the gas is very easy to escape is the area where the annealing furnace enters the pipeline and the area where the pipeline exits. Especially the sealing ring in this place is very easy to wear and tear, so it should be checked and replaced frequently.

5. Working pressure of protective gas.
In order to better avoid micro-leakage, the protective gas in the furnace should maintain a certain positive pressure. If it is radon protective gas, it is generally stipulated to be above 20kBar.

6. Water vapor in the furnace.
On the one hand, check whether the raw materials of the furnace wall are dry. When the furnace is loaded for the first time, the raw materials of the furnace wall must be air-dried; on the other hand, whether there are too many water marks on the seamless steel pipe entering the furnace, especially if there are holes on the top of the pipe, do not let water penetrate, otherwise you will destroy the atmosphere in the furnace.

7. Cooling rate
The cooling rate affects the final organization and performance. Too fast may lead to too high hardness, too slow may produce undesirable organization.

8. Steel pipe material
Steel pipes of different materials have different organizational transformation temperatures and speeds during annealing, which affects the formulation of annealing process.

9. Operation process
Operation processes such as furnace loading method and stacking density will also affect the annealing effect.

Read more: Types of seamless carbon steel pipes or Carbon steel pipe (CS pipe) material and classification