CLASSIFICATION

ítuf-CuSnC electrodes are used primarily to surface bearing surfaces where the lower hardness of these alloys is required, for surfacing corrosion resistant surfaces, and, occasionally, for applications requiring wear resistance.

Applications & Properties

Hot Hardness: The copper-based alloy filler metals are not recommended for use at elevated temperatures. Mechanical properties, especially hardness, will tend to decrease consistently as the temperature increases above 205°C.

Impact: In general, as the aluminum content increases, impact resistance decreases rapidly. The impact resistance of deposits made by using ECuAl-A2 electrodes will be the highest of the copper-base alloy classifications. Deposits made using ECuSi electrodes have good impact properties. Deposits made using ECuSn electrodes have low impact values.

Oxidation Resistance: Weld metal deposited by any of the ECuAl family of electrodes forms a protective oxide coating upon exposure to the atmosphere. Oxidation resistance of the copper-silicon deposit is fair, while that of copper-tin deposits is comparable to the oxidation resistance of pure copper.

Corrosion Resistance: Several copper base alloy filler metals are used rather extensively to surface areas subject to corrosion from reducing type acids, mild alkalies, and salt water. They should not be used in the presence of oxidizing acids, such as HNO3, or when sulfur compounds are present. Filler metals producing deposits of higher hardness may be used to surface areas subject to corrosive action as well as erosion from liquid flow for such applications as condenser heads and turbine runners.

Abrasion: None of the copper-base alloy deposits is recommended for use where severe abrasion is encountered in service.

Metal-to-Metal Wear: Copper-aluminum deposits with hardness of 130 to approximately 320 HB are used to overlay surfaces subjected to excessive wear from metal-to-metal contact. For example, ECuAl-E electrodes are used to surface dies, and to draw and form stainless and carbon steels and aluminum. All the copper-base alloy filler metals classified by this specification are used to deposit overlays and inlays for bearing surfaces, apart from the CuSi filler metals. Silicon bronzes are considered poor bearing alloys. Copper-base alloy filler metals selected for a bearing surface should produce a deposit of 50–75 HB under that of the mating part. Equipment should be designed so that the bearing will be worn in preference to the mating part.

Mechanical Properties in Compression: Deposits of the ECuAl filler metals have high elastic limits and ultimate strengths in compression ranging from 172–448 MPa and 827–1179 MPa, respectively. The elastic limit of ECuSi deposits is around 152 MPa with an ultimate strength in compression of 414 MPa. The ECuSn deposits will have an elastic limit of 76 MPa and an ultimate strength of 221 MPa.

Machinability: All these copper-based alloy deposits are machinable.

Heat Treatment: Ordinarily, no heat treatment is needed in surfacing with copper-based alloy filler metals.

Welding Characteristics: To minimize dilution from the base metal when surfacing with copper base electrodes, the first layer should be deposited using as low amperage as practical. Excessive base metal dilution can result in reduced machinability and service performance. The manufacturer should be consulted for specific welding parameters.

Preheat: Generally, preheat is not necessary unless the part is exceptionally large. In such a case, a 93°C preheat may be desirable to facilitate the smooth flow of the weld metal. At no time should the preheat temperature be above 205°C when applying the first layer. On subsequent layers, an inter-pass temperature of approximately 93°–316°C will simplify deposition of the weld metal.

Welding Considerations

Role of Hydrogen in Surfacing: Hydrogen can be detrimental to surfacing deposits. The effect varies widely from one alloy type to another. In general, hydrogen’s detrimental effect on microstructure is the most pronounced for martensitic types, with austenitic types being the least affected. Other factors influencing hydrogen’s effect include carbon and alloy contents plus in-service welding variables. In welding there are many sources for hydrogen contamination.

Coating moisture is one of the most important. Most electrodes are manufactured and packaged to control moisture. When received, consideration must be given to proper storage to prevent moisture pick-up. During use, improper regard to welding procedure and environmental variables can result in spalling or “hydrogen-induced” (under bead) cracking.

Low equipment cost, great versatility, and general convenience make manual shielded metal arc welding very popular. The welding machine, which is essentially a power conversion device, is usually the main item of equipment needed.

It may be a motor-generator, transformer, transformer-rectifier combination, or fuel-operated engine combined with a generator. The arc power may be either direct or alternating current. The filler metal is in the form of covered electrodes. (Bare electrode arc welding is a rarity today, though it is feasible with austenitic manganese steel electrodes). Welding can be done in almost any location and is practicable for a variety of work, ranging from very small to quite large. For some applications, it is the only feasible method; and, for many others (especially where continuous methods do not offer significant benefits), it is the economical choice. The operation is under the observation and control of the welder, who can easily cover irregular areas and often correct for adverse conditions. It is also helpful if the welder exercises judgment in other matters, such as holding the arc power down to minimize cracking; keeping a short arc and avoiding excessive puddling to minimize the loss of expensive alloying elements in the filler metal; minimizing dilution with base metal; and restricting hydrogen pickup. This process is used extensively for hard facing, buttering, buildup, and cladding. Surfacing of carbon and low-alloy steels, high-alloy steels, and many nonferrous metals may be done with the shielded metal arc process. Base metal thicknesses may range from below 6–450 mm or more. The surfacing metals employed include low- and high-alloy steels, stainless steels, nickel-base alloys, cobalt-base alloys, and copper-base alloys. The welding conditions for surfacing are not fundamentally different from those used in welding a joint. The arc and weld pool are shielded by the slag or the gases, or both, produced by the electrode. The type of covering on the electrode has considerable effect on the characteristics of the weld metal. Surfacing can be done on work ranging in size from very small to quite large.

Various shielded metal arc process variables affect the three most important surfacing characteristics: dilution, deposition rate, and deposit thickness.

These factors may make it unwise to change only the indicated variable; this in turn may mean that the desired change in dilution, deposition rate, or deposit thickness may not be achieved. For example, a given welding procedure with a small electrode diameter may produce high dilution.

This indicates that a change to a large size electrode will decrease dilution. This is true, however, only if the amperage, travel speed, position, etc., also remain constant. In many cases, a larger amperage value must be used with the larger electrode size to obtain acceptable weld quality. In this case, the dilution may remain constant or even increase with the change to the larger electrode size. The process usually achieves a deposition rate from 0.5–2 kg per hour at dilution levels from 30–50%.

Holding Ovens: 30°C-140°C above ambient temperature. Drying Conditions: 260°C-425°C for 1-2 hour prior to use.

CHEMICAL COMPOSITION OF UNDILUTED WELD METAL, %

Single values shown are maximum percentages. Rem = Remainder.

*Includes cobalt.

#These elements must be included in “Others (Oth)”

APPROXIMATE WELD DEPOSIT HARDNESS (As-welded condition) on Brinell at 500 Kg Load: 85-100

EFFECT OF SMA VARIABLES ON THE THREE MOST IMPORTANT CHARACTERISTICS OF SURFACING

 

SIZES & CURRENT CONDITIONS (AC or DCEP or DCEN)

WARNING: Safety and health information is available from many sources, including, but not limited to Safety and Health Fact Sheets listed in A11.3, ANSI Z49.1 Safety in Welding, Cutting, and Allied Processes published by the American Welding Society, 8669 Doral Blvd., Suite 130, Doral, FL 33166., and applicable federal and state regulations. The Safety and Health Fact Sheets are revised, and additional sheets added periodically.