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Stainless Steel Technical Guide
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Stainless Steel Technical Guide
Welding Stainless Steels with Hobart Electrodes and Wires
Introduction
This publication is not intended to be a welding engineering or technique manual. Its purposes are as follows:
- Review the basics of stainless steel metallurgy
- Discuss the industry’s most popular stainless steel alloys
- Provide reference material for guidance
- Provide detailed information on Hobart stainless steel electrodes and wires, including suggested parameters for customer applications
Hobart Brothers Co. is proud of its excellent reputation in the stainless steel market. Products are well established in the marketplace, well accepted by end users and, when properly used, result in consistently high-quality weldments and customer satisfaction.
THE RESPONSIBILITY OF THE WELDING PRODUCTS MANUFACTURER IS TO SUGGEST FILLER METAL COMPOSITIONS FOR WELDING STAINLESS STEEL BASE METALS ALREADY SPECIFIED BY DESIGN AND/OR CORROSION CONSULTANTS. STAINLESS STEEL ELECTRODE AND WIRE GRADES MAY BE SUGGESTED FOR CUSTOMER USE BASED ON THE INFORMATION RECEIVED, BUT THE RESPONSIBILITY FOR RESULTS AND WELDMENT PERFORMANCE IN SERVICE RESTS WITH THE FABRICATOR.
After you invest the time necessary to study this publication, keep it in a prominent place for continued reference. Your inquiries for additional technical information or availability of Hobart® standard or special products will be sincerely appreciated.
NOTE: The following is in reference to the typical properties listed in this publication for Hobart. The information contained herein is based on data and information developed in the laboratories of Hobart (“Seller”), but is presented without guarantee or warranty. The Seller makes no recommendation for and disclaims any liability incurred from any use thereof, including without limitation, any use in a commercial process not controlled by the Seller and any use in violation of any existing patent, foreign or domestic, or of applicable laws and regulations.
THE SELLER MAKES NO WARRANTIES, EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, EXCEPT AS EXPRESSLY STATED IN SELLER’S SALES CONTRACT OR SALES ACKNOWLEDGMENT FORM.
Hobart
Hobart has a rich and diverse history. The company was incorporated in 1917 by Charles Clarence (C.C.) Hobart, along with his wife, Lou Ella, and their three sons, Edward, Charles and William.
The company began its manufacturing endeavors with a variety of products, including generators (Dynamos), metal office furniture and air compressors. In 1925, it produced its first welder, which started Hobart on the path to becoming a preeminent company in the welding industry. It also became a prominent supporter of welding education with the establishment of the Hobart Institute of Welding Technology in 1930. The school became a separate non-profit entity in 1940 and has since trained more than 90,000 welders.
In 1937, Hobart turned its attention to the production of stick electrodes and shortly thereafter, began serving an active role in manufacturing during the turbulent years of World War II. It produced more than 100,000 welders and approximately 45,000 generators to support the war effort, and received the Army/Navy E Award for excellence for its contribution.
In the mid-1940s, Hobart launched what is now known as Hobart® Ground Power after being approached by American Airlines to design a generator specifically to start large aircraft engines.
By 1958, Hobart began manufacturing solid wires, which led to the development and production of tubular wires in the mid-1960s — both under the Hobart® brand.
Hobart purchased Tri-Mark® and Corex® in 1986, adding metal-cored wire development to its capabilities.
The acquisition of McKay® in 1993 added hard surfacing and stainless steel filler metal options to its growing capability list; the addition of MAXAL in 2011 allowed the company to offer aluminum filler metals.
Hobart was family-owned and operated until its acquisition by Illinois Tool Works (ITW) in 1996. ITW is a multinational manufacturer of a diversified range of value-adding and short lead time industrial products and equipment, and is also the parent company of Miller Electric Mfg. Co., Bernard, Tregaskiss and Jetline.
In May 2013, the company consolidated all of its brands under a single Hobart® brand in order to simplify its filler metal offering and provide a full product line to distributors and end users. The Hobart® brand signifies collaboration, innovation and expertise, and is a recognized leader in the industry.
Today, Hobart continues to develop and manufacture Hobart tubular wires (metal-cored and flux-cored), solid wires and stick electrodes for distribution to a diverse customer base around the globe. Each of its products has been carefully formulated to offer the highest- quality results, improve productivity for end users and help reduce operation costs.
Definition and Origin of Stainless Steels
Definition
Stainless steels are defined as iron base alloys containing relatively low carbon and a minimum of about 11 percent chromium (some put the minimum at 10 percent and others at 12 percent). Most commercial grades are higher than 11 percent chromium and contain up to about 0.08 percent carbon. Some may go to 0.2 percent carbon or even to 1 percent carbon. For increased corrosion resistance or for manufacturing requirements in specific applications, chromium may be increased and other elements such as nickel or molybdenum may be added as required. The effects of alloying elements and impurities in stainless steels and high-strength, heat-resisting alloys are shown in the section “Effects of Alloying Elements and Impurities in Stainless Steels and High Strength Heat-Resisting Alloys” on page 32. Stainless steels are sometimes called stain-resisting steels, since the term stainless may suggest non-staining. However, stainless is a correct designation; it does not mean non-staining in all environments, but less staining or less resistant to corrosive attack when compared with steels containing under about 11 percent chromium. When the total alloy content exceeds about 50 percent, the designation “heat-resisting” is more applicable than “stainless.”
Origin
There is an old story about stainless steel being discovered shortly after World War I by a European scrap dealer. After noticing one shiny cannon barrel in a pile of rusty scrap cannon barrels, he had it analyzed and found its chromium level to be quite high. While that event may have occurred, the claim to original “discovery” is considered fictional. Somebody must have known something to produce a superior artillery piece.
Another legend has it that stainless steels were discovered by Harry Brearley, an English metallurgist. In the early 1900s he made a series of experimental steels with 6–16 percent chromium for gun barrels. In a discarded heap he observed that some barrels had not rusted like the rest of the heap.
During the century preceding World War I, extensive research with chromium alloy steels was conducted in Europe, England and the U.S. Unfortunately, many of the early metallurgists studied alloys of unfavorable composition, e.g., chromium too low or too high and carbon too high (likely due to difficulty in obtaining low carbon-level alloys.) To make matters worse, early experiments were limited to exposure in sulfuric acid, completely overlooking the significance of resistance to attack by nitric acid.
“Discovery” of stainless steels having compositions within the ranges of the three major classes recognized today (martensitic, ferritic and austenitic) occurred progressively during the productive period of about 1905–1915 in three distinct directions: constitution, corrosion resistance and industrial applications. In 1905–1906, Leon Alexandre Guillet (France) was the first to produce and explore stainless steels metallurgically and mechanically in compositions falling within the three major classes. However, he did not discover the phenomenon of passivity, the remarkable resistance of stainless steels to most corrosive chemical solutions, which would readily attack ordinary steels. Passivity is a relative term, since a stainless steel may be passive, e.g., inert (corrode at very low rates) in one medium, and active (corrode at high rates) in another.
From 1908–1910, the research of Phillip Monnartz (Germany) disclosed the ‘stainlessness’ of stainless steel as a function of passivity. If any one person can be given the credit for discovery of the stainless phenomenon of the steels described as stainless, it should be Monnartz. He noted the significance of the minimum level of about 11 percent chromium, the need for low carbon, the fact that carbon could be stabilized, and the contribution of molybdenum in enhancing corrosion resistance.
As it pertains to industrial usefulness or commercial applications, history records that Benno Strauss and Eduard Maurer promoted austenitic grades in Germany in the 1909–1912 time frame. In the U.S. (1911- 1914), Frederick Becket and Christian Dantsizen were conducting work with ferritic grades. In addition, Harry Brearley introduced cutlery steels (Type 420, martensitic) in England (1913–1916).
In summary, we can say that the discovery of stainless steels followed the cumulative efforts of many investigators during the century preceding 1915, with full revelation occurring in the productive decade of discovery between 1905 and 1915. Within another 10–15 years, stainless steels were well recognized and widely in use in a large variety of applications.
Since the 1905–1915 glory years of discovery, many new grades of stainless steel have been developed. The American Iron and Steel Institute (AISI) now lists 60 standard types. Many proprietary grades are also in use commercially. In recent years, the precipitation hardening (PH) stainless steels have emerged as the fourth class. More recently, duplex stainless steels, containing approximately 50 percent ferrite and 50 percent austenite, are being promoted for aggressive environments where resistance to stress corrosion cracking is of paramount importance.