Welding-Tool-Steel:

SOLUTIONS with Effective, Practical Advice

Welding-Tool-Steel, repair welding, rebuilding worn or broken tools, tool assembly, crack repair, crack prevention, salvaging unusable costly tools, hardness testing, heat treatments explained, filler of same composition for annealed steel, different for hardened tools, welding tips, repair questions needing answers: these are some of the subjects of this page for information of interested readers.

What is in here for me?

An overview is presented here of the problems of Welding-Tool-Steel, the challenges and the solutions for saving by weld repair the investment in expensive tools now unusable for any one of many causes.

How to prepare a plan of action for deciding what is needed, how to select the material, the process and the heat treatments.

See our New Page on Metals Knowledge for assembling at no cost an Encyclopedia Online, a rich collection of valuable information on Metals, from expert Internet sources.

	Web www.welding-advisers.com

Welding-Tool-Steel is generally required for the following purposes:

• Assembly of a composite tool made of simpler elements
• Modification of a tool to suit different requirements or to repair mismachining
• Rebuilding of a worn out surface or edge
• Repair of a broken, cracked or damaged tool
• Improvement of properties on a specific location of a tool built of a simple steel.

Tool steels...

Tool steel are usually grouped according to their most important function like:

• Cold work tool steel, used for punches, shearing blades, forming tools, may be made of any one of the tool steels identified by the quenching medium used to develop hardness, listed here in the order of increasing hardenability:

  • Water hardening tool steels, (Wx, where x is a serial number)
  • Oil hardening tool steels, (Ox, as above)
  • Air hardening tool steels (Ax and Dx as above).

• Shock resisting tool steels, used for hammers, chisels (Sx, where x is a serial number)
• Hot work tool steels, used for dies for casting and forging (Hx)
• High speed steels, used for machining tools (Tx for Tungsten based and Mx for Molybdenum based, x is a serial number).
• Other special purpose tool steels

Welding-Tool-Steel is preferably performed in annealed conditions which is the softest and best adapted to massive machining. Tool steels are later processed by heat treatment to develop their most useful characteristics for the purpose intended.

Hardenability...

One of the most important characteristics to remember when selecting a tool steel for a specific application is its hardenability meaning the capability of displaying the required properties (hardness, toughness, wear resistance etc.) upon heat treatment. Different materials reach their optimum qualities at different quenching speeds from the hardening temperature.

That is to mean that the size of the tool imposes limits to the attainable speed of cooling from austenitizing temperature and to the corresponding microstructures obtained. Therefore a material perfectly adequate for a small tool may be unsuitable for building a massive tool, because it may be impossible to treat it to the required properties using standard heat treatment.

Weldability...

Tool steels include a variety of different compositions with most varied types of weldability that is the ease or the difficulty with which they can be welded. However as tool steels are mostly highly alloyed with considerable amounts of Carbon, Welding-Tool-Steel procedures require application of preheating and postheating in order to reduce internal stresses, to eliminate crack formation, and need welding skill.

It is generally preferable to weld tool steels in annealed condition, although sometimes it may be impractical to perform an annealing treatment as a preparation for welding.

Shielded Metal Arc Welding-Tool-Steel is the preferred process because of its advantages, like the large selection of available filler materials, the fact that the process is most versatile and the solid slag shielding provides more protection than gas shield (unreliable if drafts are in the area) and may retard cooling which is viewed as a favorable feature.

Among the disadvantages we list the frequent interruption for changing electrode, (even more if using a thinner one), the need of slag chipping and cleaning, the difficulty of maintaining preheat temperature, the peening requirement and the variability of results.

Practical advice.

For shielded metal (SMAW) arc Welding-Tool-steel one should follow the recommendations listed hereafter.

• The smallest size electrode suitable for the job should be selected.
• The surface should be prepared by machining or by grinding, with rounded sides grooves presenting a joint angle of at least 30^o and such that the width at the bottom be greater than the electrode diameter.
• If a crack has to be repaired, stop holes should be drilled at both ends and all the cracked portion should be machined away, with smooth transitions.
• For edge building or rebuilding it may be advantageous to use a support copper or graphite bar to contain the molten filler metal.
• Absolute cleanliness is most important for the work and electrodes as it is dryness of electrode cover.
• The lowest heat input possible should be used, and should be decreased for successive passes.
• If possible the work should be positioned at a slight uphill inclination so that the weld penetration be improved.
• Preheating should always be performed, possibly in a furnace or in a specially built insulated preheat box, at a suitable temperature before attempting to weld.
• Narrow beads should be deposited and then slag is to be removed by chipping and brushing between passes.
• Peening lightly is recommended on the hot weld to relieve stresses.

Generic advice.

For selecting the most appropriate filler Welding-Tool-Steel one should consider the base metal composition, commonly given by the tool steel designation, the condition of the tool if annealed or hardened, and the service requirements of the welded area.

The importance of selecting a filler composition similar to that of the base metal for Welding-Tool-Steel is greater for annealed tool steels, generally to be welded during the tool manufacturing process, so that the weld will respond equally to heat treatment providing comparable hardness.

For Welding-Tool-Steel in hardened condition the selection is more difficult, however the range of possible materials is larger. It is not recommended to repeat the hardening and tempering cycle, because of the risk of cracking.

Otherwise if the volume required for Welding-Tool-steel is limited, one prefers to use directly a filler material, whose composition may be quite different from the base metal, but which is self hardening upon cooling. If the weld is needed in a non working area, then there is a wider selection either of low alloy steels or of stainless steels.

Specific filler selection.

All this said and explained we are still left with the all important task of selecting a suitable filler material for Welding-Tool-Steel without having a comprehensive Table showing us which is which and when to pick what. The problem is that most tool steels are specific development of individual manufacturers who may not be ready to disclose all they know about their products, but we may still know or inquire which general class our steel belongs to.

Also the large variety of applications and of requirements means that different Welding-Tool-Steel solutions may be required in different situations, even with the same tool steel. The same problem we face with electrode manufacturers, where the issues are possibly even more complicated by the limits imposed by the cover materials of electrodes.

An Article on the Selection of Filler Metals for welding Tool Steels is published in the August 2006 issue of Practical Welding Letter No. 36.
To read the article click on PWL#036.

An Article on Preheating Alloy and Tool Steels was published in Section 2 of Issue 37 of Practical Welding Letter for September 2006. To read the article click on PWL#037.

An Article on Cryogenic Processing was published (7) in Issue 57 of Practical Welding Letter for May 2008. To read the article click on PWL#057.

To read all the Articles as they are published please Subscribe. You will also receive a bonus book on Practical Hardness Testing Made Simple.
It may be helpful.

Requesting help.

Tip!:The best course of action would then be to try to recruit the services of the professional personnel (metallurgical experts) of the two sources (steel and filler) and let them come up with their proposal for specific Welding-Tool-Steel.

We should know the name or at least the class of the tool steel and where it was purchased. If we do not know, then we should obtain its chemical composition by proceeding with Material Identification, submitting the tool or a small chip thereof (inquire on the size needed) to a suitably equipped Laboratory for identification.

We should also determine the Vickers or Rockwell hardness of the tool we are going to weld unless we know for sure that the material is still in the annealed state (as purchased). Let us remind you that you are entitled to a FREE download of our book on PRACTICAL HARDNESS TESTING MADE SIMPLE, as explained further down in this page.

Then the filler metal supplier of our choice should be asked with which of his materials he/she would propose for Welding-Tool-Steel, obtaining also the maximum of informations available. If possible we should make a weld test on a small specimen reproducing the original material and condition and the proposed filler electrode. The result will tell if the choice was adequate or not.

Heat Treatments.

Preheating temperature to prepare for Welding-Tool-Steel should be selected with care, with reference to the original tool steel and to the condition, if annealed or hardened. As a matter of orientation it could be similar to the suggested tempering temperature for the steel. Thin materials require lower temperatures than thick ones. If Welding-Tool-Steel is performed in several passes, the preheat temperature should be maintained and restored as necessary between passes.

Any visual defects like arc strike marks or end crater, appearing on the surface upon completing the weld must be repaired immediately, before the tool cools down and before post heating is applied.

For Welding-Tool-Steel on annealed materials, one should soften the weld by annealing at the recommended temperature for the steel (and then furnace cooling) or subcritical annealing (that is keeping it for quite a long time at a temperature just below that of austenite transformation and cool in air) before performing machining and finishing. Full heat treatment as required for the tool steel involved will follow.

Post weld heat treating is performed after Welding-Tool-Steel to relieve stresses. Usually the heat is applied again after letting the work cool uniformly somewhat, but before it reaches room temperature. Postheat should not exceed the tempering temperature for the steel.

Find some interesting links in a special Mid Month Bulletin Page of our PRACTICAL WELDING LETTER, designed to offer you, our interested readers, the opportunity to search the web quickly and effectively on the subject of Steel and welding Steel. We urge you to explore this rich source of essential knowledge. Online Resources on Steel and Steel Welding , presenting Downloads, Previews, Links and Information is now available by clicking on PWL#044B.

Looking for more Online Reference Links?
Click on Welding Resources

Any questions or comments or feedback? Write them down and send them to us by e-mail. Click on the Contact Us button in the NavBar at top left of every page.

Let us offer you a FREE subscription to our Practical Welding Letter with items written for you at your request, and also a FREE book in pdf format to download to your computer on PRACTICAL HARDNESS TESTING MADE SIMPLE. Act now and you will enjoy receiving informative and useful tips and knowledge for your continuing education and progress. Click on Subscription!

To reach a Guide to the collection of the most important Articles from Past Issues of Practical Welding Letter, click on Welding Topics

Back Home
Site Map
MATERIALS

For anyone of the following subjects, click on the underlined item.
Cast Iron Welding
Steel Welding
Alloy Steel Welding
Stainless Steel Welding
Aluminum Welding
Magnesium Welding
Titanium Welding
Copper Welding
Heat Resisting Alloys Welding
Joining Lead Tin Zinc
Refractory Metals
Precious Metals.

POWERED BY:

Click on this Logo NOW!

Copyright (c) 2003, 2004, 2005, 2006, 2007, 2008 by
Elia E. Levi and
www.welding-advisers.com
All Rights Reserved

Welding-Tool-Steel is the economic solution to scrapping expensive tools when damaged or broken, but it may not be easy to perform, unless you know how to...