Possible causes of soft parts during induction heat treating

The process of induction hardening is based on the same principles as any other heat treating operation designed to harden parts. The process is dependant on several factors to be successful, bringing the material to the proper temperature, cooling the material rapidly to allow the transformation of martensite to occur, and finally the general chemistry and ability of the material to harden properly. When one or more of these critical factors are not present, the material may end up with soft spots or remain soft entirely.

The factors that we as heat treaters have the most control over are the heating and quenching of the parts.

It is important to bring the materials to the proper temperatures in order for the austenitic phase to occur. In some cases, based on the material, it may be necessary to hold the temperature for a fixed amount of time to allow all the material to fully transform and avoid undesirable by-products that that can later reduce the materials hardness.

It is just as important to quench a material properly to produce the desired hardness. Improper quenching can occur if a part is quenched too slowly by using the wrong quenchant for a certain material, or not using enough quenchant to remove the heat quickly enough. Also, most water based quenchants use additives such as a polymer to slow down the cooling to prevent cracks; the addition of too much of this substance (polymer) reduces the ability to remove the heat quickly enough and can cause soft parts. Care must also be taken to cool the part sufficiently to prevent residual heat from tempering the part.

One of the most important factors to allow proper hardness to be achieved is one that we have very little control over, the basic chemistry and properties of the steel. It is important to understand that modern steels, while very tightly controlled in their composition, still do have a tolerance for how much carbon and various other alloying agents that promote hardenabilty are present.

It is important to understand and design around these tolerances.  Doing so could help to prevent a situation where a heat of steel can be on the low side of the carbon and alloy range, and would not be able to achieve the hardness if it was designed around the high side of the range.

Also during manufacturing or subsequent operation, steel can loose carbon on the surface, also known as decarburization. This will sometimes result in localized soft spots or a hardened layer below the softer decarb area.

These are just a few of the common things that will cause your parts to be on the low side of your hardness tolerances.

 

Lou Ghinga

Estimator

Zion Industries, Inc.

Choosing the Right Induction Machine for the Job

When determining the proper Induction Machine for your job, several things to consider including the case depth and surface area of the part to be hardened.

            First let’s talk about induction machines in general.  Each induction machine is characterized by its output power (kW) and its output frequency (kHz).  When choosing your equipment, these are the most important numbers you will need to know.  At Zion we have induction machines ranging in power from 5 – 300 kW and frequencies from 3 – 450 kHz.  Not every machine can operate at every power level and every frequency.  Typically the frequencies are fixed and the power outputs are stated as maximums.  A typical machine rating would be 100kw and 10kHz, where the power level is a maximum and the frequency is fixed.

            Knowing what your case depth requirements are will help you choose the correct machine frequency (kHz).  The following table can be used as a guideline to determine the correct frequency for your required case depth.

Frequency (kHz)	Required Case Depth (inches)
1	.250 – .370
3	.130 – .250
10	.060 – .130
450	.015 – .060

            Determining your power (kW) requirements takes slightly more math.  First you must determine the surface area (in^2) of the part to be hardened.  For a simple shaft with a diameter (D) of 1” and a hardened length (L) of 2”, the surface area is D x π x L or 6.28”.  Once you have determined your surface area, you simply multiply this by a power density factor of 10 kW/in^2.  For our example, this gives you a value of 62.8 kW required to effectively heat up this shaft.

            So in a nutshell you can see that there is much to determining the right induction machine for the job.  Each induction machine can be different and can provide different results for your induction hardening requirements.  We would be happy to talk with you about any of your induction equipment questions.

 

Bob Puls Jr.

President

Zion Industries, Inc.

Total vs. Effective Case Depth

One of the benefits of induction hardening is the ability to selectively apply a surface hardness or case hardness to steel materials. The case hardness will allow the piece to have superior wear and strength characteristics at the surface, but allow the interior of the piece to remain flexible. 

Case hardness is defined as the outer surface that has been made harder than the interior, or core. The term case depth refers to the depth of the case, or hardened layer of a piece of material. Case depth is typically measured as “total” or “effective”. The two terms are sometimes misunderstood, but are different and it is important to understand those differences.

The term total case depth refers to the depth of hardness where the hardened layer reaches the same hardness and properties as the base or core material. Total case depth is typically measured by sectioning the work piece and polishing and etching with an acid solution to reveal the depth of the hardened layer. The measurements can then be taken visually and measured using a calibrated eyepiece or scale to qualify the total depth.

The term effective case depth refers to the depth where a hardness measurement drops below a specified point. The hardness will then continue to decline until the “total” case depth is reached. The hardness at the effective depth is specified based on the characteristics required and the hardenabiltiy of the material. For example, high carbon steel that may have a minimum surface hardness of 60 HRc may call for an effective case depth of 0.120” at 50 HRc. The method of determining effective case depth involves sectioning the piece and polishing the surface. Measurements of the hardness are then taken at regular depth intervals until the hardness drops to the specified range. This distance from the surface is then measured to determine the effective depth.

 At Zion Industries we work with our customers to make sure that we understand their requirements, and when necessary can help clarify the requirements that may be on a third party print. It is important to understand that the measurement method called for on the print was established at the engineering stage, and the design intent must be followed as the method of measurement is determined.

Lou Ghinga

Estimator

Zion Industries, Inc.

Success Story: Back Up Supplier

If you’ve been reading our other recent blogs, hopefully by now you’re getting a better understanding of what Zion Industries is about and how diverse our capabilities are.

We have enjoyed numerous successes with many of our partners in a wide variety of challenges. There are a lot of things that make us very different from what you may be use to in working with some of our competitors out there, but I’ll save that for another article.

We are diversified in working with partners from numerous industries including automotive, aerospace, military, lawn and garden, off road vehicles, powdered metals, mining and a lot more. If you drive a Ford, GM, Chrysler, Toyota, Lexus, Honda, Audi, BMW, VW or Harley Davidson – some of the parts that we work on are found on those vehicles and a lot of other brands too.

Some of our partners do their own induction heat treating in – house. But what happens if they experience a critical breakdown or significant quality problem that takes time to fix ? How happy does that make their customers ? Have you ever had the pleasure of being the one that gets to explain to your customer why you have to hold up production of their products because of a problem that you have ? That’s always fun. However, things happen and sometimes problems arise that take time to fix.

Another good problem that some of our partners experience from time to time is that they can’t keep up with the demand for their products – and that’s a good problem to have I would say. One of our partners has just that kind of a problem sometimes. And that’s where we’ve been able to lend a helping hand.

While the economy has been having fits and flutters affecting us all in one way or another, some businesses have been experiencing steady or even surging production such as this particular company that we partner with. When they are faced with production overloads, we are called in to help them get caught up. Overflow work is sent to us and we process their parts quickly and efficiently to their required heat treating specifications to help them keep up with their demand as it fluctuates. When business is normal for them, they do all the parts themselves.

By working together in this way, we are providing a back up resource for their needs when they need us.  When we’re not needed, we are in ready standby for them at all times. They have never had a back-up partner before working with us in any aspect of their operations but we have proven to them that our reliability, availability and consistency of quality can actually enhance their operations and add value to their demanding customers.

I guess you could say that we’re really their insurance partner. They know we can be relied on for help at a moment’s notice. Have you ever considered back up help ? What would you do if your induction heat treater had a problem that was affecting you ? Wouldn’t it be nice to have a back up plan ?  

John Bode

Sales

Zion Industries, Inc.

Ever want to be a STAR?

Zion Industries values their employees and wants to show appreciation for good works.  We have a program called STARZ … each of our three plants participates in this employee driven system.  Management appreciation is typically slow in coming and sometimes misses the most worthy.

The STARZ program accepts nominations from our workers’ peers.  The criteria are revolved around the core values which Zion Industries hold dear.  Those core values are: Devoted to Honesty, Passionate for the Customer, Committed to Quality, and Dedicated to Family.  Each team member can nominate another for a single act or continuous efforts related to those core values.  The system rewards the winner of the month’s STARZ award for each plant.

Here in North Carolina we have modified this approach and called it “Employee of the Month”.  This modification adds a reward to the normal half of a day off with pay. North Carolina added designating a special parking place, closest to the door and when selected we arrange for a catered lunch to be provided at award time for that special employee.

We strive to show appreciation, as the core value of Dedicated to Family keeps us looking out for each other.  The customer benefits by the continuous improvements that are a fall out of this recognition program.

Gary Wolf

Plant Manager,

North Carolina Plant

Success Story: Controlling the Induction Hardening Process

At Zion Industries we are always interested in partnering with our customers to help them overcome difficult heat treating challenges. Recently Zion Industries started working on a project with a major manufacturer of material handling equipment. During our initial meetings it was evident that this customer was deeply concerned with the quality of their products, and we were excited about the opportunity to work with them to help them develop a superior product.

 The heat treat supplier that had been supplying the induction hardening process did not seem to have a reliable repeatable process. This posed many challenges to the equipment maker who was always trying to work around inconsistencies in the process. During heat treat operations, the dimensions of the piece can and do change. The supplier did not appear to have reliable process controls in place, as their amount of variance from lot to lot caused excessive, unreliable dimensional changes, even though the heat treat parameters appeared to be met.

 At Zion Industries we approached this challenge as we do any new project. After careful consideration and engineering of the tooling and process parameters we felt confident that we could provide a reliable and repeatable process. We processed our first batch of parts and the results were extremely favorable as all of the heat treat parameters were met, and the amount of distortion in the parts had been reduced by a factor of 6! After our first trials we were excited, as was the user, but the repeatability of the process had yet to be proven. After we processed several more batches with minimal distortion and met all of the parameters, the customer felt confident enough to purchase new tooling for their ID spline processes and moved the work to Zion Industries to begin production.

We were extremely pleased to be able to help this customer with their heat treating problem. The customer’s desire to partner with us through the development process proved extremely beneficial. Working together we were able to provide a superior product. We look forward to seeing your difficult application. 

Lou Ghinga

Estimator

Zion Industries, Inc.

Core Values

When you think about values one of the first words that often come to peoples minds is morals.  However, values are more than just morals.  Values are the convictions that people hold and they are the reasons we make the decisions that we make.  Very simply, Values are the deep convictions and guiding principles that guide our everyday life.  A business has values as well.  Businesses values will guide their decisions as well as provide a filter for formulating strategy.

As we defined our Core Values at Zion, there were several things that we tried to keep in mind.  First of all, the values that we identified needed to be a core belief of the organization.  Second, the list of values that we identified needed to be held to 3-5 values that could be easily memorized and understood by all employees.  We needed these values to become so deeply engrained throughout the organization that they became not just words on the wall but a way of life.

After a process in which we received input from various stakeholders throughout the organization, we came up with the 4 Core Values of Zion; Devoted to Honesty, Passionate for the Customer, Committed to Quality, Dedicated to Family.

 

Bob Puls Jr.

President

Zion Industries, Inc.

Case Study: Underground Mining Application

Recently Zion Industries was involved in a development project for an underground mining application. Working together with a forging supplier to the mining industry, we developed the tooling and the process to achieve the required hardness and depth. Additionally the project also involved close tolerances of certain features after heat treat, Zion was able to meet and exceed the requirements for this phase of the project as well. 

The product was launched successfully and soon put into service. After a few months of service it was evident that the original engineering specifications would not prove adequate for the severe duty that these products would encounter in the field. The mining equipment manufacturer realized that the hardness and depth would need to be increased to provide an adequate life span for this particular product. New specifications were drafted and provided to Zion Industries.

Zion Industries was once again called upon to develop a new process, one that would allow the current parts to be reworked to the new specifications. Using a few test pieces, Zion was able to take the existing parts, and achieve a depth of over 3X the previous specification. This was not without challenges, as critical alloying agents that would have increased hardenability and the depth of hardness, were not added to the original material specifications. The process was developed and submitted to the customer for approval. The new process was found to be completely satisfactory and the decision was made to process all of the existing components to the new specifications.

Working closely with our customer, Zion was able to meet the requirements of the new process. The customer was able to save untold thousands of dollars and countless months that would have been involved in forging and machining new components. We look forward to working with you on your challenging application. Contact Zion Industries today to see how we can help. 

Lou Ghinga

Estimator

Zion Industries, Inc.

Use of Sensors in Induction Systems

              In today’s manufacturing process many different devices are used to measure temperature, pressure, voltage, flow and rotation. These devices are called sensors. A sensor is a device that measures a physical quantity and converts it into a signal which can be read by an observer or by an instrument. For example, a mercury thermometer converts the measured temperature into expansion and contraction of a liquid which can be read on a calibrated glass tube.

             Sensors can be mechanical like the thermometer or electrical like the thermostat that controls the temperature in your house. Many new sensors are being manufactured every day to help process information for quality purposes.

            The proximity sensor can be used to tell if a part is in the correct location. This same sensor can be used to count the number of parts that have passed a location. This data can then be turned into information that tells how many parts per minute are being manufactured or rpm of the line.

            At Zion Industries we use the latest pressure, flow and temperature sensors to name a few that help assure consistent quality on all parts that are heat treated or tempered. These sensors along with our recording instruments allow repeatability in all aspects of manufacturing.

Ed Wichmann

Engineer

Zion Industries, Inc.

Benefits of Induction Heat Treating!

Dish Rags, Pretzels and Bullets – (don’t forget about the plumbing either)

Or, why would I want to choose induction heat treating and what would the benefits be ?

Hi everyone ! I just wanted to take a few minutes to explain more about the benefits of induction heat treating and why you would want to choose induction heat treating. First of all, there are a lot of different kinds of heat treating that are done in a variety of different ways. “But how can I figure out what kind of heat treating I’ll need ?”  – you say. Most of the time, the material that you are working with will dictate the type of heat treating that is needed – but not always. An equally weighted factor is also what the end user (your customer?) needs. That’s where our decades of experience comes in – we can look at what you have and will be happy to tell you what you might need.

The biggest difference between induction heat treating and all the other types of heat treating out there is that with induction, you can focus the heat treatment to a specific area of a part, while leaving the rest of the part physically and metallurgically unchanged. Huh ?

I know what you’re thinking…”What is this guy talking about ? If I’m going to get a part heat treated, why wouldn’t I want the whole piece treated ?”  ( I can read minds ya know – so be careful). And no, it’s not time for coffee yet.

Let’s look at a simple axle shaft for an example. Now an axle shaft will have all kinds of forces acting on it. There will be rotational torque loads on the shaft, residual surface stresses, it will want to flex – kind of like wringing out a sponge or your favorite dish rag (c’mon – admit it – I know you have one !) and it will even have frictional wear areas. With induction heat treating, you can strengthen the specific areas most important to increasing the longevity of the shaft while still allowing it to do all the other normal things that shafts do. Or think of it another way – what lasts longer ? – a dish rag that you twist and can go back to it’s original shape or a pretzel rod that is hard all the way through and if pressured too much – will snap ?

Did you know that with induction heat treating, we can even soften particular areas of metal ? Also known as induction annealing. Why would you want to do that ? Well, say you’re the military and you’re making ammo for some kind of gun. With induction annealing, we can soften one end of the casing so you can crimp in the projectile in while still allowing the rest of the casing to maintain the desired rigidity. Pretty neat stuff.

It really depends on a variety of factors as to why induction heat treating can be beneficial. It may or may not be what you need – that’s the real key here. Maybe you need a dish rag or maybe your application calls for a pretzel. Heck maybe you need a hard and crunchy cookie (gears ?) or you really need a cookie soft on the edges for those of you with teething issues. (sorry another crude attempt at making a gear joke) Well what happens if you accidentally drop all those things down the sink while you’re drinking that coffee you got after you started reading this and now you’ve got to do some plumbing work ? No problem – with induction brazing – we can help you reconnect those fittings too ! Did I mention leak free ?

 

John Bode

Sales

Zion Industries