Press hardening

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Hot stamping (also known as press hardening, hot press forming, or hot forming die quenching) is a relatively new technology which allows ultra-high strength steels (typically 22MnB5 boron steel [1] ) to be formed into complex shapes, which is not possible with regular cold stamping operations. [2] This process is commonly used for the production of automotive body in white components because its advantages align with the design criteria of modern passenger vehicles. For high strength aluminium alloys, there is a similar hot forming process, which has different metallurgical transformations - Hot Form Quench [3] .

Contents

Methods

Indirect hotforming sketch Indirect hotforming sketch.png
Indirect hotforming sketch
Direct hot forming sketch, Direct hot forming Direct hot forming sketch, Direct hot forming.png
Direct hot forming sketch, Direct hot forming
Direct Process

The unformed blank is heated in a furnace, formed in hot condition (state 2 in below figure), and quenched in the die to achieve the required properties.

Indirect Process

The blank is formed, trimmed, and pierced in cold condition (i.e., state 1 in below figure). It is later heated and quenched in a die to get high strength properties.

Selection of the process depends on part complexity and blank coating (Zn based coatings typically require indirect process). In either method, the blank is formed in a much softer and formable state and is later hardened in the dies, which have drilled cooling channels. A typical hot stamped components has 1000 MPa (145 ksi) Yield Stress and 1500 MPa (215 ksi) Ultimate tensile strength. [4] [5] The process is undergoing constant refinement with new grades of steel emerging for hot and cold forming. [6]

Advantages

Higher strength steels may help reducing the weight by downgauging (i.e., use of thinner sheets), while increasing the crashworthiness. [7] However, one problem with many high strength steels is that their formability is generally lower than milder grades. In addition, springback and die wear also cause problems as the forming stresses and contact pressures are higher. [8]

Related Research Articles

<span class="mw-page-title-main">Metallurgy</span> Field of science that studies the physical and chemical behavior of metals

Metallurgy is a domain of materials science and engineering that studies the physical and chemical behavior of metallic elements, their inter-metallic compounds, and their mixtures, which are known as alloys.

<span class="mw-page-title-main">Stainless steel</span> Steel alloy resistant to corrosion

Stainless steel, also known as inox, corrosion-resistant steel (CRES) and rustless steel, is an alloy of iron that is resistant to rusting and corrosion. It contains at least 10.5% chromium and usually nickel, as well as 0.2 to 2.11% carbon. Stainless steel's resistance to corrosion results from the chromium, which forms a passive film that can protect the material and self-heal in the presence of oxygen.

Beryllium copper (BeCu), also known as copper beryllium (CuBe), beryllium bronze, and spring copper, is a copper alloy with 0.5–3% beryllium. Copper beryllium alloys are often used because of their high strength and good conductivity of both heat and electricity. It is used for its ductility, weldability in metalworking, and machining properties. It has many specialized applications in tools for hazardous environments, musical instruments, precision measurement devices, bullets, and some uses in the field of aerospace. Beryllium copper and other beryllium alloys are harmful carcinogens that present a toxic inhalation hazard during manufacturing.

<span class="mw-page-title-main">Forging</span> Metalworking process

Forging is a manufacturing process involving the shaping of metal using localized compressive forces. The blows are delivered with a hammer or a die. Forging is often classified according to the temperature at which it is performed: cold forging, warm forging, or hot forging. For the latter two, the metal is heated, usually in a forge. Forged parts can range in weight from less than a kilogram to hundreds of metric tons. Forging has been done by smiths for millennia; the traditional products were kitchenware, hardware, hand tools, edged weapons, cymbals, and jewellery.

<span class="mw-page-title-main">Heat treating</span> Process of heating something to alter it

Heat treating is a group of industrial, thermal and metalworking processes used to alter the physical, and sometimes chemical, properties of a material. The most common application is metallurgical. Heat treatments are also used in the manufacture of many other materials, such as glass. Heat treatment involves the use of heating or chilling, normally to extreme temperatures, to achieve the desired result such as hardening or softening of a material. Heat treatment techniques include annealing, case hardening, precipitation strengthening, tempering, carburizing, normalizing and quenching. Although the term heat treatment applies only to processes where the heating and cooling are done for the specific purpose of altering properties intentionally, heating and cooling often occur incidentally during other manufacturing processes such as hot forming or welding.

<span class="mw-page-title-main">Carbon steel</span> Steel in which the main interstitial alloying constituent is carbon

Carbon steel is a steel with carbon content from about 0.05 up to 2.1 percent by weight. The definition of carbon steel from the American Iron and Steel Institute (AISI) states:

<span class="mw-page-title-main">Extrusion</span> Process of pushing material through a die to create long symmetrical-shaped objects

Extrusion is a process used to create objects of a fixed cross-sectional profile by pushing material through a die of the desired cross-section. Its two main advantages over other manufacturing processes are its ability to create very complex cross-sections; and to work materials that are brittle, because the material encounters only compressive and shear stresses. It also creates excellent surface finish and gives considerable freedom of form in the design process.

<span class="mw-page-title-main">Maraging steel</span> Steel known for strength and toughness

Maraging steels are steels that are known for possessing superior strength and toughness without losing ductility. Aging refers to the extended heat-treatment process. These steels are a special class of very-low-carbon ultra-high-strength steels that derive their strength not from carbon, but from precipitation of intermetallic compounds. The principal alloying element is 15 to 25 wt% nickel. Secondary alloying elements, which include cobalt, molybdenum and titanium, are added to produce intermetallic precipitates. Original development was carried out on 20 and 25 wt% Ni steels to which small additions of aluminium, titanium, and niobium were made; a rise in the price of cobalt in the late 1970s led to the development of cobalt-free maraging steels.

<span class="mw-page-title-main">Sheet metal</span> Metal formed into thin, flat pieces

Sheet metal is metal formed into thin, flat pieces, usually by an industrial process.

<span class="mw-page-title-main">Case-hardening</span> Process of hardening the surface of a metal object

Case-hardening or Carburization is the process of introducing carbon to the surface of a low carbon iron or much more commonly low carbon steel object in order to enable the surface to be hardened.

In metallurgy and materials science, annealing is a heat treatment that alters the physical and sometimes chemical properties of a material to increase its ductility and reduce its hardness, making it more workable. It involves heating a material above its recrystallization temperature, maintaining a suitable temperature for an appropriate amount of time and then cooling.

<span class="mw-page-title-main">Magnesium alloy</span> Mixture of magnesium with other metals

Magnesium alloys are mixtures of magnesium with other metals, often aluminium, zinc, manganese, silicon, copper, rare earths and zirconium. Magnesium alloys have a hexagonal lattice structure, which affects the fundamental properties of these alloys. Plastic deformation of the hexagonal lattice is more complicated than in cubic latticed metals like aluminium, copper and steel; therefore, magnesium alloys are typically used as cast alloys, but research of wrought alloys has been more extensive since 2003. Cast magnesium alloys are used for many components of modern automobiles and have been used in some high-performance vehicles; die-cast magnesium is also used for camera bodies and components in lenses.

6061 aluminium alloy is a precipitation-hardened aluminium alloy, containing magnesium and silicon as its major alloying elements. Originally called "Alloy 61S", it was developed in 1935. It has good mechanical properties, exhibits good weldability, and is very commonly extruded. It is one of the most common alloys of aluminium for general-purpose use.

AerMet alloy is an ultra-high strength type of martensitic alloy steel. The main alloying elements are cobalt and nickel, but chromium, molybdenum and carbon are also added. Its exceptional properties are hardness, tensile strength, fracture toughness and ductility. Aermet is weldable with no preheating needed. AerMet alloy is not corrosion resistant, so it must be sealed if used in a moist environment. AerMet is a registered trademark of Carpenter Technology Corporation.

Microalloyed steel is a type of alloy steel that contains small amounts of alloying elements, including niobium, vanadium, titanium, molybdenum, zirconium, boron, and rare-earth metals. They are used to refine the grain microstructure or facilitate precipitation hardening.

<span class="mw-page-title-main">Mangalloy</span> Alloy steel containing around 13% manganese

Mangalloy, also called manganese steel or Hadfield steel, is an alloy steel containing an average of around 13% manganese. Mangalloy is known for its high impact strength and resistance to abrasion once in its work-hardened state.

Hot metal gas forming (HMGF) is a method of die forming in which a metal tube is heated to a pliable state, near to but below its melting point, then pressurized internally by a gas in order to form the tube outward into the shape defined by an enclosing die cavity. The high temperatures allow the metal to elongate, or stretch, to much greater degrees without rupture than are possible in previously utilized cold and warm forming methods. In addition, the metal can be formed into finer details and requires less overall forming force than traditional methods.

Caldie is a chromium-molybdenum-vanadium alloyed tool steel manufactured by Uddeholms AB. It is intended for cold work processes, such as blanking and piercing, applied to difficult materials such as advanced high strength steel, where compressive strength and chipping and cracking resistance are important.

Boron steel refers to steel alloyed with a small amount of boron, usually less than 1%. The addition of boron to steel greatly increases the hardenability of the resulting alloy.

<span class="mw-page-title-main">Hot form quench</span> Aluminium forming technique

Hot Form Quench (HFQ®) - a lightweighting technology - is an industrial forming process for the production of deep drawn, precise and complex geometry ultra-high strength aluminium sheet components. It is the aluminium hot stamping process for age-hardening grades of sheet and has similarities to the press hardening of ultra-high strength steels. HFQ, the original aluminium hot stamping process, exploits viscoplasticity of aluminium at high temperatures to facilitate the production of lightweight structures, often replacing steel, composites, castings, extrusions or multiple cold formed pressings.

References

  1. Hickey, Kate (2021-09-22). "Press Hardened Steels". AHSS Guidelines. Retrieved 2024-03-12.
  2. So, H., D. Faßmann, H. Hoffmann, R. Golle & M. Schaper. "An investigation of the blanking process of the quenchable boron alloyed steel 22MnB5 before and after hot stamping process", Journal of Materials Processing Technology 212, 437-449 (2012).
  3. Scharifi, Emad; Yardley, Victoria A.; Weidig, Ursula; Szegda, Damian; Lin, Jianguo; Steinhoff, Kurt (August 2023). "Hot Sheet Metal Forming Strategies for High-Strength Aluminum Alloys: A Review—Fundamentals and Applications". Advanced Engineering Materials. 25 (16). doi:10.1002/adem.202300141. ISSN   1438-1656.
  4. Kurz, T., "New Developments in Zinc Coated Steel for Press Hardening", in Insight Edition Conference, September 20–21, Gothenburg, Sweden (2011).
  5. Watkins, J., "Material Development", in AP&T Press Hardening, Next Step Seminar, Novi, MI, October, (2011).
  6. Billur, Eren; Berglund, Göran; Gustafsson, Tord (2019), Billur, Eren (ed.), "History and Future Outlook of Hot Stamping", Hot Stamping of Ultra High-Strength Steels: From a Technological and Business Perspective, Cham: Springer International Publishing, pp. 31–44, doi:10.1007/978-3-319-98870-2_3, ISBN   978-3-319-98870-2, S2CID   116476501 , retrieved 2024-03-07
  7. Smith, D. "2011 Grand Cherokee", Presented in Great Designs in Steel, May 18th, Livonia, MI, (2011)
  8. Billur, E. & T. Altan, "Challenges in Forming Advanced High Strength Steels", in Proceedings of New Developments in Sheet Metal Forming 2010, pp285-304, May 2–4, Stuttgart, Germany (2010).