Showing posts with label welding. Show all posts
Showing posts with label welding. Show all posts

Saturday, November 10, 2018

Mobile Generator and Power Console Trailers by Hotfoil-EHS

Hofoil-EHS manufactures mobile generator trailers for welding heat treating power and temperature control. Custom designed from large to small, Hotfoil-EHS will build to your specification.


Thursday, October 11, 2018

The ICE Advanced Heat Treatment Control System

The ICE IS System, is developed for precise, reliable and efficient heat treatment control. It consists of IS controllers and ISPort software. With ISPort software you can define process parameters as temperatures, rates, tolerances etc; operate and control one or many processes from one or several controllers; edit PID values; fill in needed information, ex. customer info, work info etc.; print all work documents and heat treatment certificates. For more information contact Hotfoil-EHS,

Friday, May 25, 2018

Hotfoil-EHS Manufacturing and Distribution Facilities

Hotfoil-EHS, Inc. is an organization with over 70 employees and an impressive engineering capability. Through continued re-investment of profits, Hotfoil-EHS acquired additional large fabrication facilities and today is a full-service engineering, design, and manufacturing company of industrial heating equipment. Their Hamilton, NJ headquarters provides 68,000-square-feet of manufacturing space, with other manufacturing and distribution facilities located in Chattanooga, TN, LaPorte, TX, and Birmingham, England.


Wednesday, May 16, 2018

The Importance of Post-weld Heat Treatment for Welding Repairs

Welding is the process of melting two metals together. During the welding process, the metal is exposed to very high temperatures and undergoes a phase change, first from solid to liquid, then back to solid as it cools.

During welding, residual stresses are formed in an area referred to as "the heat affected zone" or HAZ. In the HAZ, differential contractions occur as the metal heats, liquifies and then cools to ambient.

Residual stresses have a significant impact on the performance of a weld and their reduction is highly desirable. The undesirable impact of residual stresses in welded metal structures involve fatigue performance and corrosion resistance.

heat treating furnace
Heat treatment furnace.
pwht with resistance heaters
PWHT with resistance heaters
Welding repairs are increasingly a structural integrity concern for aging  equipment such as pressure vessels, piping systems and other large steel systems. The make up of residual stresses near repair welds can be drastically different from those residual stresses of the original weld.  Post-weld heat treatment (PWHT) is used to reduce residual stress in steel and and should be used for welding repairs ( as well as on new welds).

PWHT is proven very effective in reduction of high residual stress around the weld repair. Conventional PWHT can be done by combustion furnace, induction heaters or electric resistance heaters (ceramic pad heaters). Accurate ramp and soak times, as well as data recording can be done with modern power console systems. It is strongly recommended to apply PWHT for all original and repair welds.

Wednesday, November 29, 2017

Custom Generator Trucks for Mobile Heat Treating

Hotfoil-EHS designs and manufactures custom Generator Trucks for remote heat treating applications. These truck-based, mobile heat treating systems are also know as Mobile Heat Treating Rigs.

Hotfoil-EHS will custom build a generator truck to your specification, with everything you need for a mobile, in-the-field heat treating system. Custom designs include a variety of generator sizes, power consoles, interior workspaces and layouts, air conditioning, and easy access to all electrical components. 

For more information, visit or call 609.588.0900.

Wednesday, October 18, 2017

Plasma Arc Welding: The Basics

Preliminaries: What is an arc? 

Inert gases used in welding, helium and argon, are made up of loose atoms flying around and banging against themselves and the walls of their container. At high temperatures the atoms speed up and negatively charged electrons are knocked off the atoms. A plasma is  a kind of soup of little, fast-moving, negative electrons, neutral atoms, and big, slow-moving, positively charged ions (what's left of an atom after electrons have been knocked off). Plasmas are neutral because the charge of the ions and electrons balance, but because the electrons and the ions can move independently, plasmas conduct electricity like metals. Plasmas can be started by applying a high electric field to a gas. The electric field (volts per distance) picks up a stray electron and slams it into a neutral atom hard enough to knock out more electrons. An electron avalanche takes place and starts a plasma. This happens when an arc is struck. A high frequency current can do it, too.

As plasma cools off, the electrons move more slowly and are recaptured, and the plasma is no more unless the energy loss to its surroundings is replenished. A voltage imposed on a plasma accelerates the conducting charges and can maintain a plasma indefinitely. A welding arc is a plasma maintained between oppositely charged electrodes. In the GTA (gas, Tungsten, arc) process one electrode is a tungsten rod; the other is the workpiece.

The arc column itself is hot, say 10,000 to 20,000 °C. A voltage drop of around one volt per millimeter is typical for an arc column. Thus if the arc is conducting a 100 amp current, about 100 watts of power is needed to maintain a millimeter of arc column, around the same as a light bulb. The really important voltage drops, through which the electrodes are heated, occur at the electrodes. This will be discussed below.

How a PAW Torch Works 

A plasma torch is like a little rocket engine. The plasma is initiated by a high frequency AC voltage in a chamber inside the torch in an inert "plasma gas." As the plasma gas is fed into the chamber it heats up and expands as well as ionizes. The hot gas rushes out through a water-cooled nozzle as a plasma jet.

The plasma jet can be used directly as a heat source, but usually the arc is transferred to the workpiece. The internal "pilot arc" is no longer necessary once the transference takes place. The transferred arc still heats the plasma gas inside the torch and the plasma gas still rushes out as a plasma jet.


The plasma jet makes a particularly stable arc with less tendency to wander erratically and somewhat greater concentration than a GTAW arc. It is not so sensitive to standoff distance as is a GTAW torch. But especially useful is the ability to operate in the "keyhole" mode.

The plasma jet has kinetic energy that produces a pressure when it impinges against a weld pool. The pressure is enough to push a centimeter or two into a pool of liquid metal, so that a plasma arc can penetrate into the workpiece like an electron beam or a laser, although the penetration mechanism is not the same. Hence plasma arc welds can be deeper and narrower than GTA welds. The number of weld passes can be reduced in changing from GTAW to PAW.

When the PAW process is operated with the arc penetrating all the way through the workpiece the operation is said to be in the "keyholing" mode. The arc impinges on the forward surface of the "keyhole." Melted metal flows around the sides of the keyhole and the streams join behind the keyhole. (The flow of metal is driven by variations in surface tension with temperature, i.e. thermocapillary forces.)

In metals that form tenacious oxides, or sometimes due to contamination in spite of the shield gas used to envelope and protect the keyhole, an oxide layer reminiscent of plastic wrap covers the converging streams of molten metal. A lumpy non-weld results.

But keyholing has a tendency to blow away weld seam contaminants. Where weld seam contamination is a problem PAW in the keyholing mode might be considered. Porosity in aluminum alloys might be reduced in this way. In the latter case special measures need to be taken to avoid problems from the tenacious oxide on the surface of aluminum.

Polarity and Why It Matters 

At the cathode or negative electrode the temperature must be high enough so that the electron emission process keeps the arc supplied. Otherwise the arc goes out. The needed heat is generated when the cooled end of the arc increases in resistance and produces a voltage drop. The heat replenishes the heat conducted away by the electrode metal, the energy required to pull each electron out of the metal, and the energy required to heat each electron to the plasma temperature.

The energy to pull an electron out of a metal is expressed as a voltage drop called the "work function." At the anode or positive electrode the heat that must be supplied to maintain equilibrium is approximately (neglecting thermal radiation effects) the heat conducted away by the electrode metal. Besides heat generated by the higher resistance of a locally cooled plasma, heat is brought to the surface by the amount of the energy gained when an electron enters the electrode metal (work function) and by the greater plasma temperature of the entering electrons.

Because the electrons extract heat from the cathode and deliver heat to the anode, the welding process is considered to be more efficient when operated in "straight polarity," when the torch electrode is negative, the workpiece positive, and electrons flow to the workpiece. Unless there's a reason not to, welding torches are operated in the straight polarity mode.

But there is a reason to weld in "reverse polarity," where the electrons flow away from the workpiece: the cathodic cleaning effect. A high speed movie of the vicinity of a GTA weld pool in the reverse polarity mode will reveal a display of sparkling points of light, miniature explosions continually occurring all over the surface. This is thought to be caused by electrostatic breakdown of a thin surface oxide layer. The positive ions in the arc accumulate on the surface of the oxide layer and induce a balancing negative charge. If the oxide layer is thin, it doesn't take a lot of charge to produce an electric field (volts per distance) big enough to cause the oxide layer to break down in a mini-explosion. Cleaned surface is distinct and visible around the crown of a weld made in reverse polarity.  But to get the cleaning necessary to weld aluminum alloys one takes a hit in power available for welding, and the effective capability of the machine is reduced.

Abstracted from a 2004 NASA document by Arthur Nunes.

Thursday, August 31, 2017

Custom Mobile Heat Treating Trucks

Hotfoil-EHS designs and manufactures custom mobile rigs for remote heat treatment applications.

Custom designs include a variety of generator sizes, power consoles, interior workspaces and layouts, air conditioning, and easy access to all electrical components. For more information, visit or call 609-588-0900.

Wednesday, July 12, 2017

Induction Heating Basics

Induction Heating
Induction heating coils
around large pipe for
pre-weld heat treatment.
Induction heating occurs when passing alternating magnetic fields through conductive materials. This is accomplished by placing an alternating current carrying coil around or in close proximity to the materials. The alternating fields generate eddy currents in the materials. These currents interact with the resistance of the material to produce heat. There is a secondary heating process called hysteresis. This disappears at the temperature at which the material loses its magnetic properties.

Direct Induction
Direct induction heating occurs when the material to be heated is in the direct alternating magnetic field. The frequency of the electromagnetic field and the electric properties of the material determine the penetration depth of the field, thus enabling the localized, near-surface heating of the material. 

Comparably high power densities and high heating rates can be achieved. Direct induction heating is primarily used in the metals industry for melting, heating, and heat treatment (hardening, tempering, and annealing).

Indirect Induction
With indirect induction heating, a strong electromagnetic field generated by a water- cooled coil induces an eddy current into an electrically conducting material (susceptor), which is in contact with the material to be treated. Indirect induction heating is often used to melt optical glasses in platinum crucibles, to sinter ceramic powders in graphite crucibles, and to melt materials in crucibles prior to drawing crystals. Indirect induction is also used to heat susceptors used for joining operations.

Tuesday, June 27, 2017

Quick Facts About Welding as a Profession

Welding is the most common way of permanently joining metal parts. In this process, heat is applied to metal pieces, melting and fusing them to form a permanent bond. Because of its strength, welding is used in shipbuilding, automobile manufacturing and repair, aerospace applications, and thousands of other manufacturing activities. Welding also is used to join steel beams in the construction of buildings, bridges, and other structures and to join pipes in pipelines, power plants, and refineries.

Welders work in a wide variety of industries, from car racing to manufacturing. The work that welders do and the equipment they use vary with the industry. Arc welding, the most common type of welding today, uses electrical currents to create heat and bond metals together—but there are more than 100 different processes that a welder can use. The type of weld normally is determined by the types of metals being joined and the conditions under which the welding is to take place.

Welders, cutters, solderers, and brazers typically do the following:
  • Study blueprints, sketches, or specifications
  • Calculate dimensions to be welded
  • Inspect structures or materials to be welded
  • Ignite torches or start power supplies
  • Monitor the welding process to avoid overheating
  • Maintain equipment and machinery

The median annual wage for welders, cutters, solderers, and brazers was $39,390 in May 2016. The median wage is the wage at which half the workers in an occupation earned more than that amount and half earned less. The lowest 10 percent earned less than $26,800, and the highest 10 percent earned more than $62,100.

In May 2016, the median annual wages for welders, cutters, solderers, and brazers in the top industries in which they worked were as follows:
  • Specialty trade contractors - $42,900
  • Repair and maintenance - $39,340
  • Manufacturing - $38,200
  • Merchant wholesalers, durable goods - $37,790
Wages for welders, cutters, solderers, and brazers vary with the worker’s experience and skill level, the industry, and the size of the company.

Most welders, cutters, solderers, and brazers work full time, and overtime is common. Many manufacturing firms have two or three 8- to 12-hour shifts each day, allowing the firm to continue production around the clock if needed. As a result, welders, cutters, solderers, and brazers may work evenings and weekends.

Friday, June 23, 2017

Process Heating: Induction

Induction Heater
Induction heating coils around large pipe
in preparation of welding.
The principles of induction heating have been applied to manufacturing operations since the 1930s, when the first channel-type induction furnaces were introduced for metals melting operations. Soon afterward, coreless induction furnaces were developed for melting, superheating, and holding. In the 1940s, the technology was also used to harden metal engine parts. More recently, an emphasis on improved quality control has led to increased use of induction technology in the ferrous and nonferrous metals industries.

In a basic induction heating setup, a solid state power supply sends an alternating current (AC) through a copper coil, and the part to be heated is placed inside the coil. When a metal part is placed within the coil and enters the magnetic eld, circulating eddy currents are induced within the part. These currents ow against the electrical resistivity of the metal, generating precise and localized heat without any direct contact between the part and the coil. 

An induction furnace induces an electric current in the material to be melted, creating eddy currents which dissipate energy and produce heat. The current is induced by surrounding the material with a wire coil carrying an electric current. When the material begins to melt, electromagnetic forces agitate and mix it. Mixing and melting rates can be controlled by varying the frequency and power of the current in the wire coil. Coreless furnaces have a refractory crucible surrounded by a water-cooled AC current coil. Coreless induction furnaces are used primarily for remelting in foundry operations and for vacuum refining of specialty metals.

Induction heating power console
Induction heating power console (Hotfoil-EHS)
Channel furnaces have a primary coil wound on a core. The secondary side of the core is in the furnace interior, surrounded by a molten metal loop. Channel furnaces are usually holding furnaces for nonferrous metals melting, combined with a fuel- red cupola, arc, or coreless induction furnace, although they are also used for melting as well.

The efficiency of an induction heating system for a specific application depends on several factors: the characteristics of the part itself, the design of the induction coil, the capacity of the power supply, and the degree of temperature change required for the application.

Induction heating works directly with conductive materials only, typically metals. Plastics and other nonconductive materials often can be heated indirectly by first heating a conductive metal medium that transfers heat to the nonconductive material.

With conductive materials, about 80% of the heating effect occurs on the surface or “skin” of the part. The heating intensity diminishes as the distance from the surface increases, so small or thin parts generally heat more quickly than large thick parts, especially if the larger parts need to be heated all the way through.

Induction heating can also be used to heat liquids in vessels and pipelines, primarily in the petrochemical industry. Induction heating involves no contact between the material being heating and the heat source, which is important for some operations. This lack of contact facilitates automation of the manufacturing processes. Other examples include heat treating, curing of coatings, and drying.

Induction heating often is used where repetitive operations are performed. Once an induction system is calibrated for a part, work pieces can be loaded and unloaded automatically. Induction systems are often used in applications where only a small selected part of a work piece needs to be heated. Because induction systems are clean and release no emissions, sometimes a part can be hardened on an assembly line without having to go to a remote heat treating operation.

Wednesday, May 31, 2017

Resistor Controlled Welding Machines

resistor controlled welding machines
Resistor controlled welding machines by AFTEK.
Resistor control has been used in multi-operating welding systems in shipyards and heavy construction for decades. In the heyday of nuclear power plant construction in the USA, nearly all were built using multiple-operator systems. From the thirties until about 1990, nearly all multiple-operator systems were the designed similarly. They used a large bulk power supply with “grids” connected by cables to form a system of distributed power. This system minimized the use of high voltage primary power, distributing 75-80 volts of secondary voltage instead.

As these systems grew in popularity, the concept of “packs” became popular. These packs provided 2, 4, 8, and 16 arcs in a steel rack, and all being connected to a separate power supply. A now defunct company named Big Four developed the concept of connecting multiple-operator systems in a loop arrangement, which resulted in greatly improved voltage stability. In 1990, this loop concept was further refined into integrated, modular welding packages. These newly designed systems provided an internal power supply sufficiently sized to provide power to all the arcs without any interference.

Loop systems are still being used today. They are viewed as a very economical welding alternative. For example, for a loop that needs twenty MIG arcs, it is possible to use (4) 500-amp power supplies connected to a single 500 MCM cable which circles the work space. Twenty control modules can be connected wherever needed on the closed loop of cable. A huge cost savings is realized in having to establish just four (4) primary connections instead of twenty (20).

Most conventional arc weld­ers use a transformer-like device called a reactor to control the "heat" of the welding arc. If you examine the Voltage/Amperage (V/A) curve for a con­ventional constant current (or constant voltage) welding power supply, you’ll see spikes. This is inherent in the design of conventional arc weld­ers. The V/A curve of a resistor controlled arc welder, on the other hand, is a straight line.

Resistor controlled arc systems provide more consistency of power - if you shorten the arc, thus lowering the arc voltage, the current will increase, and maintain virtually the same power (heat). If you lengthen the arc, you raise the voltage, but the power remains virtually constant. Why is this important? In any welding process, increasing the amperage increases penetration and increasing the voltage widens and flattens the head (and reduces penetration). With a resistor controlled arc, if you are welding along the seam and it closes, shortening the arc length will increase penetration. If the weld opens, lengthening the arc will lessen the penetration and widen the weld. This provides excellent control right in the electrode holder.

AFTek, a US manufacturer located in Chattanooga, TN and division of Hotfoil-EHS, is the sole remaining manufacturer of resistor controlled welding machines in the USA. Their resistance welders are an acknowledgement of the superior design Big Four developed years ago, while improving performance with edge-wound coils for better heat dissipation (thus better current control) and rotary switches for current selection, even under load.

Wednesday, May 3, 2017

Custom Built Heat Treat Furnaces

Custom Built Heat Treat Furnaces
 15'x15'x60' Custom Furnaces
Hotfoil-EHS has extensive heat treating furnace design and fabrication experience. From small, low-throughput furnaces, to much larger high yield furnaces, to rail-driven furnaces, Hotfoil-EHS Design Engineers and Fabrication Shop have done it all.

 Heat Treat Furnace
Capable of handling 45,000 lbs.
Recently Hotfoil-EHS provided a customer with a heat treat furnace that is 15'x15'x60' that accommodates up to 45,000 pounds of material. Two, 5 million BTU burners heat the furnace to 1650 deg. F. The furnace travels on a track, back and forth, to accommodate two beds for greater production.

 Heat Treat Furnace
Rail system with (2) beds

For more information, visit or call 609.588.0900.

Sunday, April 16, 2017

A Better Choice in Heat Treatment Control Systems

ICE Star Heat Treatment Controllers
Ice Star, a Finnish company, engineers and manufactures heat treatment controllers for electric and gas furnaces, as well as for induction and resistive heating consoles. The company manufactures the most advanced metal heat treatment control system available today. Since 1984, they have been laser-focused on the development and advancement of industrial heat treatment controllers and software.

ICE Star Model ISG Heat Treatment Controllers
ICE Star
Model ISG
Heat Treatment Controller
Ice Star’s founder, Esa Santala, has decades of knowledge and experience in the heat treatment industry. He developed one of the first processor controlled multi-channel controllers and has since been building even more innovative products.

Ice Star controllers do not require a separate recorder. Ice Star controllers monitor all critical heat treatment variables - temperature, time, soak, upsets, diagrams, events, alarms etc. - and then provide extremely detailed records for each. Additionally, with ISPort software, you can monitor and control the heating processes directly from remote process displays and computers.

For more information about Ice Star in North America, visit Hotfoil-EHS or call 609.588.0900.

Monday, February 27, 2017

The Hotfoil-EHS Fusion 45 Induction Heating Console

Induction heating can improve your bottom line by decreasing weld failures, and decreasing setup and tear down times. The technology allows for accurate temp control, without heavy electrical service or complicated controls. The portability and ease of use will allow you to heat more welds faster.

For more information call Hotfoil-EHS at 609.588.0900 or visit

Sunday, February 26, 2017

Induction Heating Provides Welders Uniformity and Shortens Welding Time

Welder’s must pay strict attention when it comes to preheating, interpass temperature control and stress relieving. Torches takes too long and make it difficult to maintain heating uniformity. Plus there’s the issue with open flames and the expense of fuel.

Ovens are great for uniformity and control, but require transport and time. They're certainly not convenient.

A great alternative, one that provides excellent uniformity, control, and convenience, is induction heating.

Induction heating is unique because it uses molecular excitation as its source of heat, as opposed to open flames or external electric elements.

Induction heating works very quickly, and since there is no contact with the target piece, there are far less concerns about part contamination.  Many industrial processes use induction heating when very high temperatures and uniform control is desired.

Its important to note that the heat is created from inside the object itself, with no open flame or external electric heat source.

Induction heating is used to heat conductive materials. Developed in the early 20th century, it quickly became a popular choice for hardening military equipment parts during wartime. Because of induction heating’s controllability, speed and consistent output, its popularity continued to grow as new manufacturing and production methodologies were developed. Today, induction heating has become a popular technology for the welding industry to provide pre and post-weld stress relief.

Induction heaters provide temperatures and cycle times hard to achieve otherwise. By virtue of their high temperature capabilities, very fast heat up times, precise application of heat, excellent controllability, and ease of setup / breakdown, the use of induction heating has been know to cut 30% to 50% of total weld cycle time in real-life welding applications.

Induction heaters consist of a few primary components: An electromagnet and an electronic oscillator that passes a high-frequency alternating current (AC) through the electromagnet. RF (radio frequency) energy is transferred into the workpiece via electromagnetic waves. These alternating magnetic waves penetrate the object, creating electric eddy currents. These eddy currents (Foucault currents) flow through the target piece and produce heat.

Pre and post-weld heat treating (stress relieving) is a growing market for induction heating systems because it offers significant benefits such as excellent heat placement and distribution, lower cycle times, safety, ease of use, and efficiency.

For more information about induction heaters for pre and post-weld heat treating visit HotfoilEHS at or call 609.588.0900.

Monday, November 21, 2016

All Stainless Heat Treat Power Consoles

Hotfoil-EHS Stainless Steel Power Consoles
Hotfoil-EHS Stainless Steel Power Consoles
Power consoles are standardly offered in 6, 9, 12, 18, and 24 zone configurations with a variety of control and recording systems. All Hotfoil-EHS Power Consoles are available in Stainless Steel and can be customize to your requirements.

With decades of experience in challenging applications, and thousands of successful installations, Hotfoil-EHS maintains their well deserved reputation as the highest quality and most competitively priced manufacturer of heat treat power consoles in the world.

Thursday, September 29, 2016

Fusion45: New Rugged Induction Heater Improves Weld Quality

Welding Induction Heater
New Welding Induction Heater
Heat treating isn’t done in a laboratory, or a clean room. Applications are out in the real world, where dirt, grease and grime are normal. Hotfoil’s new induction heater is designed to work in the toughest conditions, and continue to run shift after shift.

Induction heating works very quickly, and since there is no contact with the target piece, there are far less concerns about part contamination. Many industrial processes use induction heating when very high temperatures and uniform control is desired.

Pre and post-weld heat treating (stress relieving) is a growing market for induction heating systems because it offers significant benefits such as excellent heat placement and distribution, lower cycle times, safety, ease of use, and efficiency.

Induction heating can improve your bottom line by decreasing weld failures, and decreasing setup and tear down times. The technology allows for accurate temp control, without heavy electrical service or complicated controls. The portability and ease of use will allow you to heat more welds faster.

Check out the new Hotfoil-EHS Fusion45 Induction Heater:

Thursday, September 22, 2016

Diagram of Equipment for Typical Weld Heat Treating

weld preheat console in use
Weld preheat
console in use
Weld preheating involves heating a section of, or the entire part, to a specific desired temperature, generally referred to as the preheat temperature.

The heating may or may not continue during welding, dependent on the heat generated by the arc. The goal is to maintain a certain temperature from the first weld pass to the last.

Preheating produce several very beneficial effects, including producing a more ductile metallurgical structure that cracks less, helps in releasing trapped hydrogen, and reduces stress cracking during cooling.

It is always recommended that you should consult with weld heating experts and learn the fundamentals of this process in order to avoid costly errors in preparation or wasting money on the using the wrong equipment.

Here is a very general diagram of the typical welding pre-heat equipment layout.

For more information, visit or call 609.588.0900