Cold Drawn Tee

Cold Drawn Tee is a T-shaped pipe fitting formed through cold processing technology (applying external force to metal billets at room temperature for stretching and extrusion), widely used in low-pressure, medium and small diameter pipeline systems to achieve the diversion or merging of media. Its process does not require high temperature heating, relies on the cold plastic deformation of metals, and has the characteristics of high dimensional accuracy and good surface quality. The following provides a detailed analysis from the aspects of process principles, characteristics, and applications:

1、 Principle of Cold Drawing Forming Process

The manufacturing core of cold drawn tees is to utilize the plasticity of metal at room temperature, and force the billet to deform into a "T" - shaped structure through molds and external forces. The specific steps are as follows:

Preparation of billets: Seamless steel pipes are selected as billets (mostly made of metals with good plasticity such as low carbon steel and stainless steel), cut into specific lengths according to the size of the tee, and the diameter of the billet is usually slightly larger than the diameter of the main pipe.

Pre treatment: Remove rust and lubricate the surface of the billet (such as applying lubricants or phosphating) to reduce friction between the billet and the mold during cold drawing and avoid surface scratches.

Cold drawn forming:

Fix the billet in a dedicated mold, which includes a main pipe cavity and a branch pipe core;

Apply axial tension or radial pressure to the billet through a hydraulic press or specialized cold drawing equipment, while using a branch punch to squeeze the billet from the side, forcing the metal to flow towards the branch at room temperature, gradually forming the contours of the main and branch pipes;

If it is a reducing cold drawn tee, the shrinkage of the branch pipe is controlled by the mold to make the diameter of the branch pipe smaller than that of the main pipe (usually the diameter of the branch pipe is not less than 1/2 of the diameter of the main pipe, otherwise it may cause uneven deformation).

Subsequent processing: After forming, the tee is shaped, the ports are cut, burrs are removed, and if necessary, low-temperature annealing is performed (to eliminate internal stress caused by cold processing). Finally, quality is ensured through size inspection and hydrostatic testing.

2、 The core characteristics of cold drawn tees

Compared to hot pressed tees (high-temperature forming) or welded tees, the unique advantages of cold drawn tees are reflected in:

High dimensional accuracy: During the cold drawing process, the mold has strong constraints on the billet, and the diameter deviation of the main and branch pipes of the tee is small (usually up to ± 0.1mm), with good wall thickness uniformity, suitable for pipeline systems with high dimensional accuracy requirements.

Excellent surface quality: Processing at room temperature avoids problems such as oxidation and decarburization caused by high temperatures, with high surface smoothness (low Ra value), and can meet hygiene requirements without additional polishing (such as in the food and pharmaceutical industries).

Mechanical performance improvement: Cold working refines the internal grain size of the metal, producing a "work hardening" effect. The tensile strength and hardness of the tee are significantly improved (by 10% -30% compared to the raw material), but the plasticity slightly decreases.

Simple process and low cost: no need for heating equipment and complex heat treatment processes, short production cycle, suitable for mass production of small and medium-sized tees (such as DN15-DN100), with lower cost than hot pressing or forging tees.

3、 Classification and specifications

Cold drawn tees can be classified into the following types based on their structure and application scenarios:

According to the diameter relationship:

Equal diameter cold drawn tee: The main and branch pipes have the same diameter (such as DN50 × DN50), suitable for equal diversion scenarios;

Reducing cold drawn tee: The diameter of the branch pipe is smaller than that of the main pipe (such as DN80 × DN50), used for connecting pipes of different diameters. It is important to note that the diameter of the branch pipe should not be too small (usually not less than 1/3 of the main pipe, otherwise it is prone to cracking).

According to pressure level:

Mainly suitable for low-pressure pipeline systems (such as PN10-PN40), due to the decrease in metal plasticity after cold drawing, it is difficult to withstand high pressure (usually not exceeding 10MPa), avoiding fracture caused by brittleness.

By material:

Low carbon steel (such as Q235, 10 # steel) and stainless steel (such as 304, 316) are mainly used, while high carbon steel or high alloy steel is difficult to cold draw due to poor cold plasticity.