In recent years, the increasing demand for energy has brought with it significant changes in the materials used for welding applications, as well as an ongoing effort among companies serving this sector to maintain control of their costs and increase their productivity. The goal for these companies is the same: to secure a competitive edge in a growing market.

From the construction of offshore oil platform jack-up rigs to the fabrication of boiler or pressure vessel and process piping, labor is always a key consideration. The faster a job can be completed, of course, the better the bottom line. In that respect, the impact welding has on these applications cannot be ignored. Nor can the filler metals used to complete them.

Many applications in today’s energy sector require materials capable of withstanding extremely high temperatures, while others use high strength materials that are subject to low temperatures. Recently, multiple advancements have been made in filler metal technologies — specifically flux-cored welding wires — that can help companies address the needs of both. In particular, these filler metals offer both the chemical and mechanical composition necessary to match the materials, and also the characteristics needed to help companies improve weld quality, reduce costs (particularly for labor and rework) and increase their productivity.

Following is a discussion of some of these filler metal technology advancements.

Addressing the Extremes of High-Temperature Applications
Various grades of chrome-moly steel are common in the fabrication of pressure vessels and boiler piping, and are also used for fittings and valves. This material offers the high-temperature strength and the corrosion resistance needed for each of these applications and it requires filler metals capable of providing the same characteristics. Chrome-moly applications like these also require a low X-factor. X-factor is a formula that measures a weldment’s resistance to temper embrittlement (the loss of toughness that occurs when the weldment is held or slowly cooled through a temperature range of approximately 850 to 1100 degrees Fahrenheit). It is a component that filler metal manufacturers pay close attention to during the development of products for chrome-moly applications in the energy sector. 
In past years, fabricators typically relied on stick electrodes to provide them with the mechanical and chemical composition necessary to weld chrome-moly boiler and pressure vessel piping that will be subject to high-temperature service environments. Today, there are two new T-5 gas-shielded flux-cored wire options available that can meet those requirements, while also helping companies increase their productivity.  The interesting aspect about these wires is their ability to weld out of position.

Most flux-cored wires with a T-5 or basic slag system are typically not recognized for out of position performance, as the slag has a low melting point and creates a puddle that is too fluid and difficult to control unless in the flat or horizontal position. Both the AWS E81T5-B2M H8 and AWS E91T5-B3M H8 wires, however, are readily able to weld out of position, particularly vertical up and vertical down. This characteristic makes them usable for welding on both existing, installed piping systems and in a shop environment, allowing companies the versatility to weld on multiple applications without incurring the cost or time associated with process changeovers. It also eliminates part movement and the downtime associated with it. Theses wires operate with mixed shielding gases (argon and CO2), so they have a more stable arc and create less spatter than standard T-5 wires that use straight CO2.

Unlike other T-5 wires, these products operate on DC current, negative polarity (DCEN).

The AWS E81T5-B2M H8 wire (Hobart® FabCO® XTREME® B2) is designed for welding on 1-1/4 percent chrome/1/2 percent molybdenum steels, including ASTM A335 Grade P11 piping. In addition to providing reliable toughness properties, this wire offers a low X-factor (8 to 13) and low diffusible hydrogen levels (less than 6 millileters per 100 grams of weldment) to reduce the chance of temper embrittlement and crack susceptibility, respectively. The wire also offers a tensile strength of more than 86 ksi, along with yield strength of nearly 69 ksi. The Charpy V-notch impact values exceed those of a comparably classified stick electrode (such as an E8018-B2), which many fabricators have used in the past for boiler and pressure vessel applications. The impact values for this wire fall into the range of 91.25 ft-lb (123 joules) at -40 degrees Fahrenheit (-40 degrees Celsius) in the post-weld heat treated (PWHT) condition and 50.2 ft-lb (68 joules) in the “as welded” condition. The wire is usable for single and multiple passes.

For welding on ASTM A387 Grade P21 and P22 pipe composed of 2-1/4 percent chrome/1 percent molybdenum, an AWS 91T5-B3M H8 wire (Hobart FabCO XTREME B3) is a good alternative to E8018-B3 stick electrodes, particularly in terms of its ability to improve productivity. This flux-cored wire provides a tensile strength of approximately 105 ksi with a yield strength of 88 ksi using a shielding gas mixture of 70 to 80 percent argon and 20 to 25 percent CO2 at 35 to 50 cubic feet per hour (cfh). Like the AWS E81T5-B2M H8 wire, this wire provides excellent toughness properties, along with low diffusible hydrogen levels (less than 6 milliliters per 100 grams of weldment). The wire works well for welding boiler and pressure vessel piping, fittings and valves and has a low X-factor of 8-13 to reduce the risk of temper embrittlement. Its Charpy V-Notch impact properties are 110 ft-lb (149 joules) at -40 degrees Fahrenheit (-40 Celsius).

Meeting the Needs of Offshore Applications

Offshore applications, such as the building of jack-up oil rigs present their own unique set of challenges when it comes to filler metals, particularly because these applications use high-strength materials and require welds that can withstand extremely low temperatures.

For offshore applications, one new filler metal option is the AWS E121TG-GC H4 gas-shielded flux-cored wire. This wire has been designed to produce welds in the 120 to 130 ksi tensile strength range, making it particularly well-suited for offshore applications that require high-strength, defect-free welds with good impact properties. It can also weld materials including A514, Le Tourneau N25HN, WeldTen 710 and 780, HY100 and other similarly high-strength steels. This wire offers a highly basic slag system that is unique to this particular wire, as well as an operating range that is comparable to flux-cored wires featuring a rutile (T-1) slag system; it also has equally low spatter levels and an equivalent type of slag removal.  The AWS E121TG-GC H4 wire provides Charpy impact properties of 74.7 ft-lb (101.2 joules) at -76 degrees Fahrenheit (-60 degrees Celsius) and operates with 100 percent CO2.

The AWS E121TG-GC H4 wire, as well as the aforementioned AWS E81T5-B2M H8 and AWS 91T5-B3M H8 wires are a unique step in providing companies in the energy sector with options beyond stick electrodes for welding demanding and critical applications — and improving their productivity by using a flux-cored process. It is certain, however, that with the increasing demands for energy and the emergence of new, high-strength materials that filler metal manufacturers will continue to be challenged with even more new product developments.

What Else Is New?
In addition to the products mentioned in this article, there are other newer flux-cored wires available for offshore applications, as well as transmission pipelines.

AWS E111T-1-GM H4 ― Designed for jack-up rig building (including cantilever or rack and chord welding) and for overmatched API X80 pipeline welding, this all-position gas-shielded flux-cored wire offers good impact toughness with a tensile strength ranging from 110 to 130 ksi and low diffusible hydrogen levels (4 milliliters per 100 grams of weldment). It offers low spatter levels, easy-to-remove slag and a smooth, stable arc. It can also be used on high-strength steels such as Riverace 710, WelTen 710, ABS EQ56, A514 and other similar HSLA steels. The wire operates with a shielding gas mixture of 75 to 80 percent argon/20 to 25 percent CO2 and is recommended for single- and multiple-pass welding.

AWS E81T8-Ni2 J ― Designed primarily for X80 pipeline applications, this self-shielded flux-cored wire can also be used for offshore drilling rigs. Some contractors use the wire for non-energy related applications including ship and barge building, along with general structural and fabrication applications. It is well-suited for applications requiring high tensile strength (it offers 94 ksi) and low temperature CVN impact toughness [107 ft-lb (138 joules) at -20 degrees Fahrenheit (-29 degrees Celsius) and 96 ft-lb (134 joules) at -40 degrees Fahrenheit (-40 degrees Celsius)] and performs particularly well in all positions as it has a fast-freezing slag.