The Classic: Stainless Steel Comparison
"Titanium Enhanced" Stainless Steel
Central Boiler SCL models are manufactured using "Titanium Enhanced" Stainless Steel.

"Titanium Enhanced" Stainless Steel is the stainless alloy of choice based on its ability to withstand the stress, corrosive environment, and high temperatures that are exerted on your firebox during operation. Carbon steel (used in Central Boiler CL models) also has all the characteristics that you are looking for when deciding on a durable firebox material.

Other stainless steel alloys simply fall short of what it takes to withstand the stresses and corrosive environment that outdoor wood furnace metals are exposed to while they are in use.

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Stress Corrosion Cracking
Stress Corrosion Cracking (SCC) is defined as: the failure induced by the combined influences of tensile stress and a corrosive environment. Combinations of the following conditions can cause SCC: (1) presence of halide ions (generally chloride), (2) residual tensile stresses, and (3) temperatures in excess of about 120°F (49°C).
 
Below are two graphs that illustrate how three outdoor wood furnace metals (Carbon Steel, "Titanium Enhanced" Stainless Steel, and 304L Stainless Steel) react to the high temperatures exerted on them during operation.
Thermal Expansion
Thermal expansion is the expansion in metal resulting from an increase in temperature. The greater the expansion rate, the greater the chance of SCC (Stress Corrosion Cracking) to occur in the metal.

304L Stainless Steel has nearly double the expansion that "Titanium Enhanced" Stainless Steel and Carbon Steel have.
This graph reflects the expansion amount on a 4'x 4' sheet of metal.
References: Mechanics of Materials, Beer and Johnston
Material Property Data, MatWeb
   
Thermal Conductivity
Heat is normally conducted by atoms literally bumping into each other. Metal electrons add to this flow of heat, which is why metals tend to be good conductors of heat. The measure of how good a material is at conducting heat is known as its thermal conductivity. Thermal conductivity is defined as the rate at which heat flows through material.

A firebox material with higher thermal conductivity will boost the efficiency of your outdoor wood furnace by transferring more Btu's into the water jacket, instead of out your chimney.

References: MStandard Handbook for Mechanical Engineers, Baumeister & Marks
National Physical Laboratory, Internet
   
Ferritic Stainless Steel
"Titanium Enhanced" Stainless Steel
Ferritic stainless steels have very useful corrosion resistant properties, such as resistance to chloride SCC, corrosion in oxidizing aqueous media, oxidation at high temperatures, and pitting and crevice corrosion in chloride media.

Resistance to stress-corrosion cracking is the most obvious advantage of the ferritic stainless steels. Ferritic steels, particularly those that are nickel-free, resist chloride and SCC very well.

References: Technical Data Blue Sheet, Allegheny Ludlum
Chemical Engineering, Oct 18, 1982
Austenitic Stainless Steel
304L Stainless Steel
Type 302, 304, 304L and 305 alloys are the most susceptible of all the Austenitic Stainless Steels to SCC.
References: Technical Data Blue Sheet, Allegheny Ludlum
Chemical Engineering, Oct 18, 1982
 
This is actual Low Carbon Austenitic Stainless Steel cut out of a wood furnace that failed due to Stress Corrosion Cracking.
   
Browse our furnace models to find which SCL "Titanium Enhanced" Stainless Steel model will best fit your application.

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A safe, efficient outdoor furnace that can provide 100% of your heating needs.Outdoor Boilers of Europe distributes the Classic Outdoor Wood Furnace. Heats multiple buildings, hot tubs, pools, greenhouses, domestic water and more.

While burning wood indoors can mean many problems, there is an alternative... The Classic outdoor wood furnace from Outdoor Boilers of Europe. The Classic eliminates the problems associated with indoor burning and allows you to get even more benefits from wood heat. This outdoor furnace can actually improve the indoor environment in your home or business, while eliminating the time-consuming chore of tending a traditional wood stove. In addition, tests show that the Classic is the most efficient outdoor wood furnace, with the fewest emissions.