FAQ

H13 tool steel is mainly supplied as round bar and steel plate. DIN 1.2344 & ASTM H13 are equivalent material. This article we introduce H13 hardness.

H13 is a typical chromium-molybdenum tool steel widely used in hot work and cold work tooling applications. H13 usually are delivered in annealing condition. H13 Harness after annealing is max 235 HB.

Common H13 heat treatment and hardness regulations as follow

• H13 Annealing hardness: 235 HB
• H13 Cold drawn hardness: 262 HB
• Preheat temperature: 788°C
• Quenching temperature | Salt bath: 996°C
• Quenching temperature | Controlled atmosphere furnace: 1010°C
• Austenitiz-ing time:  5 – 15 minutes
• Quench Medium: Air
• Tempering temperature: 552°C
• H13 Tempering hardness: Min 52 HRC

Air Hardening Steel refers to as self- hardening steel. A steel that becomes fully hardened when cooled in air from above its critical point and does not require rapid quenching by oil or water. The risk of distortion is greatly reduced by air hardening. Some common air hardening steel grades are like d2, A2, A6 steel.

What does Quenching mean?

Quenching is a stage of material processing through which a metal is quickly brought down to room temperature from a high temperature by rapid cooling. Quench hardening is a mechanical process in which steel and cast-iron alloys are strengthened and hardened. Quenching and tempering provides steel with high strength and ductility.

During quenching, the following media are used to rapidly cool material:

• Air/argon/nitrogen
• Liquid polymers
• Oil
• Water

The slower the quench rate, the longer thermodynamic forces have to alter the microstructure, which is in some cases desirable, hence the use of different media. Sometimes multiple media are used. For example, metal may be air cooled and then dipped in a water bath to complete the quenching process.
Quenching can lead to warping/cracking and other issues with the material, even when it is done properly. Using water as a quench media, for instance, can cause the material to warp as it cools. It is crucial to control the environment in which the quenching is done to minimize the risk of damage to the material. When done properly, the material is harder and more durable, making it suitable for a wide range of uses. Extremely rapid cooling can prevent the formation of a crystal structure, resulting in amorphous metal or “metallic glass.”

Four types of furnaces are commonly used in quench hardening:

• Salt bath furnace
• Continuous furnace
• Box furnace
• Vacuum furnace

The type of furnace used depends on what other processes or types of quench hardening are being done on the different materials.

The quenchant is determined by the steel

In tool steels we have a letter prefix .A-2 is an Air hardening steel, O-1 is an Oil hardening steel and W-1 is a Water hardening steel !! A quenchant for a steel should be fast enough to fully harden the steel but no faster. A faster quench will produce unnecessary stresses in the steel and may lead to things like quench cracks.You can edge quench in oil, this is common for knives.Or you can fully quench in oil. You can edge quench in water which is usually done with clay or you can fully quench in water. It all depends on the steel and what you want to achieve.

The more complex the alloy the more care needs to be taken with the specific quenchant. Simple steels are more foregiveing and different quenchants can be used. A certain amount of expermentation may be required to attain the best mixture of hard, tough, edge retention etc IMHO. The 10XX series is about as simple as you can get and can be quenched in oil or water as needed for the specif blade configuration.

What is bearing steel ?

Bearing steel refers to steel materials which are mainly used for bearings. Some steel standards are for bearing steel, like ASTM A295, DIN 17230, JIS G4805 etc. The common steel grades are like SUJ2, 52100, 100Cr6 etc.

Generally speaking, steel is an alloy of iron that has enhanced chemical and physical properties. Steel has been used since ancient times but it was produced inefficiently and expensively until the mid of 19th Century, when the Bessemer process was invented. Since then, steel has been mass produced in many forms, including metal foil, steel plate and steel sheet.

Steel Sheet vs Steel Plate vs Steel Foil

• Metal Foil

Metal foil is a very thin sheet of metal that has been hammered or rolled flat. Metal foils can be made from any type of metal, although the most commonly found foils are aluminum foil and gold foil. Aluminum foil typically has a thickness of .03mm, although any sheet of metal with a thickness of less than 0.2mm is considered a foil.

• Steel Sheet

Steel Sheet is any metal that is thicker than a foil and thinner than 6mm, the thickness of a metal plate. Steel Sheet is often used for building structures that do not require durability. It is also often corrugated or diamonded for additional strength without increasing weight. Corrugation is the creasing of the metal at regular intervals to form ridges, and diamonding is the addition of diamond ridges that add structure to the metal.

• Steel Plate

Once the steel is more than 6mm thick it is known as steel plate. Steel Plate is used in applications where durability is more important than saving weight. It is used in automobiles where durability is required to pass crash testing.

The Difference

The only difference between sheet and plate steel is the gauge (thickness) of the metal. They both have very different uses, depending on the varying durability and weight requirements for different projects.

Source: www.ehow.com

The comparision between wrought and forged steel product is as follow:

• Wrought steel material refers to product forms (forged, rolled, ring rolled, extruded…), while forging is a subset of wrought product form.
• The main difference between wrought and forged steel is strength. Forged steels are tougher than wrought steels as they begin as a casting which is then forged which adds to its durability. Wrought steel is less likely to be used in high-tension applications and it may be harder and more brittle than forged steel.
• Forged steel is more durable in certain applications because, although it begins life as a casting as well, it is hammer forged using large hydraulic hammers that force the atoms and molecules of the steel into alignment as they hit it. Wrought steel does not undergo this same process, which makes forged steel harder and less likely to crack when struck, when compared between wrought and forged steel. Striking tools and axes are often made of forged steel because they are used to hit things, and the brittle nature of a cast steel would lead them to breaking rapidly if they were not forged.
• Wrought is any hot or cold working of metal, and is therefore a description under which you would find forging, rolling, heading, upsetting, drawing, etc.
• Forging is the open (including hammer and anvil or closed die forming of metal heated to forging temperatures.

Tool steels refers to a variety of carbon and alloy steels that are particularly well-suited to be made into tools. Their suitability comes from their distinctive hardness, resistance to abrasion and deformation and their ability to hold a cutting edge at elevated temperatures. As a result tool steels are suited for their use in the shaping of other materials.

There are six groups of tool steel:

1. water-hardening tool steels,
2. cold-work tool steels,
3. shock-resisting tool steels,
4. high-speed tool steels,
5. hot-work tool steels,
6. special purpose/plastic mold tools steels.

You have full details of six groups tool steel here: What Is Tool Steel ? (Six Groups With Details)

Case hardening steel or surface hardening steel is the steel process of hardening the surface of a metal object while allowing the metal deeper underneath to remain soft, thus forming a thin layer of harder metal (called the “case”) at the surface. For iron or steel with low carbon content, which has poor to no hardenability of its own, the steel case hardening process involves infusing additional carbon into the case. Steel Case-hardening is usually done after the part has been formed into its final shape, but can also be done to increase the hardening element content of bars to be used in a pattern welding or similar process. The term face hardening is also used to describe this technique, when discussing modern armour.

Case hardening steel is done through a simple method of hardening steel. It is less complex than hardening and tempering. This techniques is used for steels with a low carbon content. Carbon is added to the outer surface of the steel, to a depth of approximately 0.03mm. One advantage of this method of hardening steel is that the inner core is left untouched and so still processes properties such as flexibility and is still relatively soft.

STAGE ONE:
The case hardening steel is heated to red heat. It may only be necessary to harden one part of the steel and so heat can be concentrated in this area.

STAGE TWO:
The case harden steel material is removed from the brazing hearth with blacksmiths tongs and plunged into case hardening compound and allowed to cool a little. The case hardening compound is high in carbon.

STAGE THREE:
The case harden steel material is heated again to a red colour, removed from the brazing hearth and plunged into cold, clean water.

Because hardened metal is usually more brittle than softer metal, through-hardening (that is, hardening the metal uniformly throughout the piece) is not always a suitable choice for uses where the metal part is subject to certain kinds of stress. In such circumstances, case-hardening can provide a part that will not fracture (because of the soft core that can absorb stresses without cracking) but also provides adequate wear resistance on the surface.

Bright steel is usually a carbon steel alloy which has had the surface condition improved by drawing, peeling or grinding over the hot rolled finish supplied by the steel mill.

Bright steel is essentially black steel material that has had further processing. The bright steel is processed further in cold reduction mills, where the material is cooled (at room temperature) followed by annealing and/or tempers rolling. This process will make steel with closer dimensional tolerances and a wider range of surface finishes. The term bright drawn is mistakenly used on all products, when actually the product name refers to the rolling of flat rolled sheet and coil products.

When referring to bright steels bar products, the term used is “cold finishing”, which usually consists of cold drawing and/or turning, grinding and polishing. This process results in higher yield points and has four main advantages

• Cold drawing increases the yield and tensile strengths, often eliminating further costly thermal treatments.
• Turning gets rid of surface imperfections for bright steels material.
• Grinding narrows the original size tolerance range.
• Polishing improves surface finish.
• All cold products provide a superior surface finish, and are superior in tolerance, concentricity, and straightness when compared to black steel.

Cold finished bright steel bars are typically harder to work with than black steel due to the increased carbon content. However, this cannot be said about bright drawn sheet and black steel sheet. With these two products, the bright drawn product has low carbon content and it is typically annealed, making it softer than black steel sheet.

Uses: Any project where tolerances, surface condition, concentricity, and straightness are the major factors.

Die Steel referes to Plain carbon steel or alloy steel used in making tools for cutting, machining, shearing, stamping, punching, and chipping. Common die steel grades like O1, O2 etc.

1. High Speed Steel (HSS or HS) is a subset of tool steels, commonly used in tool bits and cutting tools.

HSS steel is often used in power-saw blades and drill bits. It is superior to the older high-carbon steel tools used extensively through the 1940s in that it can withstand higher temperatures without losing its temper (hardness). This property allows High Speed Steel to cut faster than high carbon steel, hence the name high-speed steel. At room temperature, in their generally recommended heat treatment, High speed steel grades generally display high hardness (above HRC60) and abrasion resistance (generally linked to tungsten and vanadium content often used in HSS) compared with common carbon and tool steels.

A sample of alloying compositions of common high speed steel

2. The second meaning is HSS-hollow structural section, which is a type of metal profile with a hollow tubular cross section. The term is used predominantly in USA, or other countries which follow US construction or engineering terminology.

HSS members can be circular, square, or rectangular sections, although other shapes are available, such as elliptical. Hollow structural section is only composed of structural steel per code.

HSS is sometimes mistakenly referenced as hollow structural steel. Rectangular and square HSS are also commonly called tube steel or structural tubing. Circular hollow structural section are sometimes mistakenly called steel pipe though true steel pipe is actually dimensioned and classed differently from HSS. (hollow section dimensions are based on exterior dimensions of the profile, while pipes are essentially dimensioned based on interior diameters, as needed to calculate areas for flow of liquids.) The corners of HSS are heavily rounded, having a radius which is approximately twice the wall thickness. The wall thickness is uniform around the section.