Inspecting Hot Rolled Seamless Tubing

Inspecting a Hot Rolled Seamless tube? Of course!

In our prior posts we've outlined the melt and production processes responsible for making a hot rolled seamless tube. While the overall production process is certainly complex, each process has detailed operational processes. This ensures that we can provide a fantastic product to meet our customer's needs.

To ensure that traceability is maintained from billet to tube, each products is individually?stenciled with?a series of?recorded information. This helps with tracking of all operations and tests done along the way as one complete record.

The final piece of information that is critical to understand are the various methods of inspection happening along the way. The most used, and often the best, is each technicians vast experience and their ongoing visual inspection. However, that is not the only method employed. There are many options and the ASTM standards specify a few for A519 compliance.

Metallurgical Testing

Samples are taken from each lot to test for chemical composition and hardness. This ensures each sample meets the specifications requirements. For example, 1026 grade tubing must maintain the following range of required elements. Each grade has its own recipe!

Excerpt from ASTM A519A519M - 23 Table 2

Visual Inspection

Visual inspection of hot rolled seamless tube sounds simple enough; however, it can be a lengthy and laborious process. Mill technicians must perform key steps in the process to ensure that the tube meet customers' exacting standards.

• External Inspection: In this piece of the process, operators look over the tubes for any sign of cracking, erosion, corrosion, debris, grinding, scouring, manufacturing defects, discoloration, and the state of the finish coating.
• Dimensional Inspection: The outside diameter and walls are verified. Hot rolled seamless mechanical tubing is produced to two dimensions, and outside diameter and a wall thickness. This is where really understanding the total tolerance and required clean up can make or break a part design. See ASTM A519 Table 6 & 7 to reference these key production tolerance requirements. For calculation of the full machining clean up allowance it's important to include Appendix X1. There is a lot to consider in calculating the correct size.

Excerpt on tolerances from ASTM A519/A519M - 23 Tables 6 & 7

NDT Inspection

Taking Inspection to the next level, the following are methods that mills can employ to inspect for defects. Many tests have been added to the inline process for efficient consistency.

Ultrasonic Inspection

Ultrasonic Inspection (UT) is a non-destructive testing technique that is used to determine the thickness of the tube. It can also be used to test the internal structure of the tube. In a fascinating application of science, (UT) equipment uses high-frequency sound waves to 'bounce' around the tube. The returning sound waves will tell the machine the thickness of the test piece, deformities, cracks, inclusions, lack of fusions, and corrosion. (UT) is widely because it is a highly portable technology.

Eddy Current Testing

Eddy Current Testing (ECT) is another non-destructive process that is widely used to test tubing. This test uses electromagnetic induction to identify defects in the material. A probe is first put into the tube and pushed through its entire length. Currents are created by electromagnetic coils on the probe, which helps it detect surface defects on the tube.

(ECT) is one of the fastest testing technologies in a mills playbook; however, it is a highly specialized skill and requires a trained technician to properly utilize the technology. Most commonly, (ECT) is used to detect corrosion, pitting, cracks, and erosion.

From the selecting scrap metal, to dialing in the chemistry, and every step along the way, the final steps of inspection ensure the best products to exceed our customer's needs!

Process control, inspection, and testing methods are the tools used to ensure material is within the required ASTM standards. These procedures and processes ensure that our customers receive the best possible product every time!

This includes:

1. Dimensional inspection.
2. Metallurgical inspection.
3. Various non-destructive tests.

These Hot Rolled A519 Seamless Tubes are now ready to be bundled, stenciled, and tagged with identifying heat lot. From machining a complex automotive part, simple bushing, to everything in between, there is nothing simple about this work horse of a tube. Contact your steel solution partner at Marmon/Keystone for help finding the right tube to meet your design needs.