Is it possible for seamless tubes and pipes to have insufficient hardness? Well, the answer is yes. However, there are some steps that the manufacturers need to follow to the T to ensure that the pipes are correctly hardened. Pipes and tubes with insufficient hardness can be dangerous to use as they may lack the properties for which they are known, such as strength and lastingness.
Even the leading manufacturers need help with the insufficient hardness of the seamless pipes and tubes. If the pipes need to be more challenging, they can cause the projects they are used to fail. Also, the failure of the project can dissatisfy the customers.
However, the manufacturers can avoid unwanted situations by keeping tabs on the things that may go wrong and avoiding those to ensure the quality of the pipes.
Here, we will discuss the five primary reasons that can cause insufficient hardness of the seamless tubes and pipes so that manufacturers can avoid them when producing the pipes.
- Exposing the steel billets to too much heat:
The manufacturers start producing seamless pipes by choosing solid steel billets that can pierce and create hollow pipes. In order to pierce the billets, they first need to heat the billet. The ideal heat in which the billets become malleable is 2000°F. When the solid bars reach the ideal temperature, the manufacturers should stop exposing them to heat further. In case they keep increasing the heat, the billets become more pliable. While the additional heat may seem okay, more flexibility may cause the billets to lose shape. Also, the pipes will not reach their desired hardness when you cool them after piercing.
So, the manufacturers should use dedicated software to control the temperature. They should also make sure to calibrate the software to the desired heat threshold to avoid any disruption in the manufacturing process.
1. Shorter cooling times make weak seamless tubes and pipes:
When the manufacturers are done heating and piercing the solid steel bars, they need to cool down the pipes. The pipe producers use cooling beds to air-cool the pipes. However, sometimes the manufacturers need to cool down the pipes for an adequate time. If the manufacturers do not cool down the pipes correctly, the pipes remain heated after the heat treatment. When the pipes should become cold, they hold on to the heat even without the manufacturers heating the pipes additionally. As a result, the standard value of the pipes becomes less than what it usually should be.
The manufacturers should have a dedicated cooling bed to air-cool the pipes for extended periods. Also, they must keep checking the temperature of the pipes before moving to the following procedure. Even when they are sure the pipes are cool, they must keep them on the cooling bed for even more time.
In case the seamless tube manufacturers need to make the process faster, they can use refrigeration to bring down the temperature of the pipes. However, refrigeration should be the last resort as it may cool down the pipes inconsistently. Therefore, you should use refrigeration only after air-cooling the pipes if they have not reached the desired temperature.
2. Longer cooling time than required:
If a shorter cooling time is a problem and causes insufficient hardness of the pipes, so happens if it takes longer than required to cool. Sometimes, the manufacturers face problems when the pipes take longer than usual to cool down completely. For example, if the fabricators do not use a refrigeration system and rely entirely on air cooling, it may take longer than usual, depending on the weather. It will take longer to cool the pipes in warmer temperature areas. Therefore, the producers need to release the pipes and insert them in the tank as quickly as possible. The sooner they grasp the refrigeration characteristics of the seamless tubes and pipes, the better it is for the cooling of the pipes.
Also, the temperature of the refrigeration elements rises when you expose them to continuous heat, for instance, by inserting heated pipes in them. For example, the water temperature used in the refrigeration process needs to be around 30°C. However, when you constantly submerge heated pipes into the refrigeration system, the water temperature rises to 60°C-70°C. As a result, the refrigeration system takes longer than usual to cool down the pipes.
To avoid such scenarios, the manufacturers need to increase the amount of refrigeration material if they have a large number of pipes to be cooled. Also, they must keep checking the temperature of the refrigeration material so that they can pay attention to the rise in the temperature, which can delay the cooling process.
3. Over-quenching:
As the seamless tube manufacturers know, quenching is the process using which they treat heated metal pipes. The process involves cooling the heated pipes rapidly so that they can change the mechanical properties of the metal. The pipe producers heat the steel billets above their recrystallization temperature. First, however, they make sure that the metal pipes do not start melting. Once the pipes reach a specific temperature, they use a medium, such as oil, brine, etc., to quench the metal pipes. Quenching in oil allows the manufacturers to modify the mechanical properties of the pipes without causing any cracks or warps.
Sometimes the manufacturers may need to deal with over-quenching of the metal pipes. Overquenching occurs when the pipe fabricators use too high a temperature for quenching or when there is a stark difference in a temperature control system. The manufacturers can adjust the temperature using a temperature control software system. They must repair and calibrate the software to ensure that the quenching material’s temperature is maintained correctly so that the seamless tubes and pipes are not over-quenched.
4. Carburization:
Seamless pipes and tubes may lack hardness if there is a residual carburized layer. It is because raw material residue due to heat treatment causes carburization. To avoid the issue, the manufacturers may use protective atmosphere heating, introduce salt baths with proper oxidation, and use annealing and box furnaces. Also, pipe manufacturers should use protection for box furnaces to avoid carburization. They can also use vacuum heating quenching.
The final words:
Even though the manufacturers may think they follow proper manufacturing procedures, they sometimes have to deal with specific problems. The problems are avoidable if they pay attention to details. For example, seamless tubes and pipes may need more hardness if the manufacturers expose the steel billets to extreme heat and maintain proper cooling temperature, quenching method, or carburization. The pipe manufacturers can ensure proper hardening of the pipes if they follow the proper processes.
