Mild Steel Tubing (1010)

The term "mild steel tubing" refers to tubing that has been produced by the electric resistance welding (ERW) process. It is provided in the state in which it leaves the welder, with only minimal downstream processing such as stress-relieving or annealing to meet particular customer specifications.

The lack of additional processing such as cold drawing makes as-welded tubing a cost-effective product for many mechanical applications. It is produced in a wide variety of sizes with close tolerances that allow the tubing to be used in mechanical parts with little or no metal removal or machining.

Some of the principal benefits you can expect from as-welded tubing in mechanical applications:

• Uniformity - As-welded tubing has uniform wall thickness and concentricity, as well as uniform mechanical properties.
• Strength - Cold forming gives as-welded tubing a higher yield and tensile strength than the steel from which it is made.
• Less Processing - The close dimensional tolerances of as-welded tubing allows its use for mechanical parts with minimal downstream processing.
• Cost-Effectiveness - Because it undergoes less processing than other types of mechanical tubing, as-welded tubing can provide cost advantages for less-demanding applications.
• Wide Size Range - As-welded tubing is available in an exceptionally broad range of OD and wall thickness dimensions.
• Variety of Shapes - As-welded tubing is produced in round, square and rectangular shapes and in a variety of special shapes to meet the needs of individual applications.

Chromoly (4130)

Chromoly is an abbreviation for "chromium-molybdenum steel".  It is not as lightweight as some steel alloys, but has the advantages of high tensile strength – 90-95 ksi [ksi = 1000 pounds per square inch] in the normalized condition – and malleability. It is also easily welded and is considerably stronger and more durable than standard (1020) steel tubing.

Chromoly is often called "4130" because the carbon content is nominally 0.30%. With this relatively low carbon content the alloy is excellent from the standpoint of fusion welding .

The alloy can be hardened by heat treatment or "normalizing". This is a process of taking 4130 tube up to a prescribed temperature and cooling it at a precise rate. This removes all strain created in the tube manufacturing process and allows the homogenization of the steel's grain structure.

Here are the principal benefits you can expect from Chromoly tubing in mechanical applications:

• Strength - Normalizing gives Chromoly high yield and tensile strength.
• Uniformity - Chromoly has uniform wall thickness and concentricity, as well as uniform mechanical properties.
• Close Tolerances - Chromoly offers exceptionally close tolerances for OD, ID and wall thickness dimensions.
• Surface Quality - OD and ID surfaces of Chromoly are free of oxide and scale and have a smooth, dense finish with no trace of the weld.
• Machinability - Chromoly is easily machined and welded.
• Wide Range of Sizes - Chromoly can be manufactured to an almost infinite range of OD and wall thickness dimensions by varying the size of the dies and mandrels used.

DOM

Drawn Over Mandrel (DOM) refers to high-strength, electrically-welded tubing that has been further processed by cold drawing through dies and over mandrels to improve its uniformity, mechanical properties and surface finish.

To a great extent, DOM tubing is customized to each specific application. This provides further advantages, particularly to high-volume manufacturers. They include a wider range of sizes and tighter dimensional tolerances that allow the tubing to be used in mechanical parts with little or no metal removal or machining. Because of its many advantages, DOM is the material of choice in many of the most demanding applications for tubing, including: hydraulic cylinders, auto and truck components, recreational vehicles and others.

The manufacturing process for DOM tubing begins with coils of steel, which are slit to the proper width for the desired tube size. The strip is cold formed and passed through an electric resistance welder which joins the edges together, under pressure, to complete the tubular shape. After testing the weld's integrity, the tubing is cut to length for further processing.

The cold-drawing process creates a uniform, precision product with substantially improved tolerances, surface finish and tensile strength, increased hardness and good machinability. In this process, the tube is cleaned and annealed, and one end of each length is squeezed to a point so it can be gripped by the drawing mechanism. The tube is then drawn through one or more dies and over mandrels (see drawing).

This reduces the diameter of the tube and thins its walls to the required dimensions in a controlled fashion to provide the qualities desired in the finished product. Metallurgically, drawing improves the tube's concentricity, tensile strength, hardness and machinability. Close dimensional accuracy is achieved through tight control of both outside and inside diameters.

Here are the principal benefits you can expect from DOM tubing in mechanical applications:

• Cost-Effectiveness - Close tolerances allow DOM to be used for mechanical parts with minimal or no downstream processing.
• Strength - Cold-drawing gives DOM high yield and tensile strength.
• Uniformity - DOM has uniform wall thickness and concentricity, as well as uniform mechanical properties.
• Close Tolerances - DOM offers exceptionally close tolerances for OD, ID and wall thickness dimensions.
• Surface Quality - OD and ID surfaces of DOM are free of oxide and scale and have a smooth, dense finish with no trace of the weld.
• Machinability - DOM is easily machined, with only a nominal stock allowance for clean-up.
• Wide Range of Sizes - DOM can be manufactured to an almost infinite range of OD and wall thickness dimensions by varying the size of the dies and mandrels used.

Pipe

The term "Standard Pipe" refers to steel pipe manufactured for use in a wide variety of applications that require strength, durability and ease of fabrication. Because of its many advantages, Standard Pipe is the material of choice in such diverse applications as conveying fluid and gaseous mediums, water wells, fencing, foundation pilings, building and bridge construction and many others.

 Products are produced in a variety of steels including carbon and alloys, galvanized, weathering and HSLA and to meet various ASTM, API, government and customer specifications. Pipe can be supplied with several different types of ends---threaded-and-coupled, beveled or grooved.

Three principal processes - electric resistance welding, butt (continuous) welding and seamless - are used in the manufacture of Standard Pipe.

Aluminum

Alloys

Glossary

Electric Resistance Welding (ERW)
Strip is unwound from coils and side-trimmed to control width and condition the edges for welding. The strip then passes through a series of contoured rolls which progressively cold-form it into a circular shape. The edges are forced together under pressure and welded by heating the steel to temperatures between 2200° F and 2600° F using copper contacts or coil induction.

Weld flash is removed from the the inside and outside surfaces of the newly-formed pipe, and the weld zone is heat treated to ensure homogeneity between the base metal and weld. The weld is subjected to in-line nondestructive testing, and the pipe then passes through a series of sizing rolls to attain its precise finished diameter. It is then straightened and cut to the desired finished length.

Butt (Continuous) Welding
The continuous process produces a full range of pipe sizes from only a few different widths of skelp. The coils of skelp, or strip, are fed into the mill and their ends welded together to provide a continuous flow. The strip passes through a pre-heater and into a furnace. The heated strip is shaped into an arc of about 270° in a forming stand before passing into the welding stand. There a nozzle applies oxygen to the edges to further heat them as they are pressed and welded together.

The pipe's OD and wall thickness are reduced in a stretch-reducing mill. Pipe is then cut to length, reduced to the required size in a sizing mill and water-cooled before being straightened. It is then ready for finishing operations.

Seamless
The production process for seamless pipe begins by heating a steel billet to about 2250° F. The red-hot billet is rotated and drawn by rolls over a piercing rod, or mandrel. The action of the rolls causes the metal to flow over and about the mandrel to create a hollow pipe shell. After reheating, the shell is moved forward over a support bar and is hot-rolled in several reducing/sizing stands to the desired wall thickness and diameter.

The pipe, which has grown significantly in length during the piercing and sizing processes, is then cut into sections and conveyed across a cooling bed to cool slowly in the air. It then receives whatever finishing processes are needed to meet customer requirements.

Measuring Guidelines