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Steel engineer Stig Rubæk loves mechanical defects because it is almost always an opportunity to learn something that can then be prevented in the future.

With over 40 years of experience in steel manufacturing, Stig Rubæk is Moller International’s key engineering partner when it comes to advising agricultural components manufacturers on materials choices for the manufacturing of agricultural parts.

Specifications in the purchase order determine the quality of the component

The final quality of the manufactured component starts well before the contract for the purchase of the material for the components is signed.

“It is a major mechanical challenge to produce a component like a plough share for tillage equipment as there are so many variables to consider,” says Rubæk.

A plough share must be hard enough to endure - over its intended lifetime - the continual pulling forces as well as the associated vibrations required for hard tillage work in the field. You need to find the right compromise between robustness and hardness, if you like, or technically speaking between brittleness and fatigue,” adds Rubæk.

Additionally, the weight of the component should be minimised, as this could affect fuel consumption and, of course, the impact on the soil.

“But in the metal itself it is necessary to know in intricate detail what the material properties are. These cover a range of variables which are yield and tensile strength but also ductility and toughness, and of course fatigue strength. These remain important factors that can affect positively as well as negatively a product’s final performance on the field,” comments Rubæk with a passion that is contagious.

It goes without saying that the product needs to withstand a potentially harsh outdoor environment which obviously field work is,” says Rubæk.

These are already a lot of factors to consider on the field, so let’s go back to how it all starts when a manufacturer puts in a purchase order for steel before it even enters into manufacturing” says Rubæk.

The properties of the metal used for the components can change in the manufacturing process

When deciding on the purchase of material, it is necessary to analyse in advance what the end product should be able to do and, above all, for how long.

A plough share or any other component in order to be fit for purpose should have the right mechanical properties which primarily include hardness and wear-resistance. It is important for a manufacturer to analyse what changes may take place in the steel during the manufacturing process, since this will ultimately affect the end product and its quality.

“When buying steel, the quality i.e. the specification of the steel therefore needs to be determined according to the manufacturing processes it needs to go through. Steel changes its structure when it is forged and then changes again if it undergoes heat treatment. It is perfectly possible to buy high quality steel that then fails, when used to manufacture a ploughshare, because the steel could lose some of properties through the manufacturing process. Unfortunately, often such a mistake is not discovered until the final customer finds out about it,” adds Rubæk.

Essentially the grade of steel for a product like a plough share is measured by its tensile and yield strength, ductility and hardness,” says Rubæk.

Advice for manufacturers of agricultural metal parts: Reference to standards!

The steel selected for a component must have the right grade of metal that will enable it to cope with all of the intended manufacturing processes in order to result in the pre-dermined quality for the component. If the steel purchased also includes pre-treatment and/or a coating this should also be considered too and should be specified exactly in the purchasing order.

Not only should components manufacturers specify the precise grade of the steel but also references to standards. A manufacturer of agricultural parts usually receives exactly what he orders and not more than that.

“I recommend references to standards, whenever possible. For example, referring to EN 10083, part 1-3, which is a classical standard for construction steel specifying steel for quenching and tempering, technical delivery conditions for alloy steel”

My best advice is: Be as exact as possible. It will eliminate possible and costly mistakes later,” concludes Rubæk

Rubæk has personally translated over 300 technical standards for steel into both English and Danish and knows from experience that specifications using international standards will help eliminate unintentional errors from suppliers.

Steel engineer Rubæk has personally visited over 50 different steel manufacturing plants (Steelworks) in his long career around the word. 

With a mechanical engineering degree, majoring in metallurgy from the Technical University of Denmark, Rubæk spent 10 year at Danish Steel Works with various technical responsibilities including in continuous casting, metallographic laboratory and welding technology. Following that, Rubæk taught metallurgy as associate professor at the Engineering college of Copenhagen and later University of Southern Denmark, alongside providing consultancy services to the steel industry. 

In 2001. Rubæk established his own metallurgical company, Metal-Consult, which he has managed full-time since 2007.

Rubæk has been a steel consultant for a major windmill producer since 2007 concerning steel for windmill towers. In this role he has been involved in description, Quality Assurance (QA) and opportunities for a range of steelworks in China and Europe and North America.

He has also been involved in conducting numerous metallurgical failure analyses on delivered steel plates, ready for manufacturing.

Moller International and its team members have worked with Stig Rubæk for several decades in the areas of components installed in tillage equipment used globally for arable farming.

Moller International works with a global team of experts that together offer its manufacturing clients a complete service package, which includes analysis of the requirements as well as the specifications for purchasing orders from suppliers in any part of the world, including China and India. Moller International also offers engineering drawings expertise for components as well as technical advice on manufacturing processes, machining and tools.

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