Challenges and Considerations of AHSS Metal Stamping

Designing and producing lighter-weight vehicles is a primary goal of some automobile manufacturers. Less weight allows for improved performance, safety and fuel economy while also reducing material costs. Advanced high-strength steel (AHSS) alloys represent a strong candidate for use in structural components of automobiles. They also present new difficulties in alloy composition; OEMs should pay attention to ongoing research in their formation, properties and effective stamping of these metal parts.

Observed Advantages of AHSS

Conventional mild steels have low carbon content and minimal blending elements which result in simple microstructures. AHSS alloys use carefully controlled additions of alloying elements to produce complex multi-phase structures with unique mechanical properties. There are a variety of AHS steel compositions and their properties provides considerable versatility. Dual-phase (DP) steels and transformation-induced plasticity (TRIP) for example, already see considerable use in vehicles. DP steels are highly resistant to fractures and necking. TRIP steels demonstrate a capacity for high energy absorption under sudden strain, excellent for the “crumple zones” of vehicles.

Formability Concerns of AHSS

Formability – the ability of a piece of metal to undergo plastic deformation without sustaining damage – is a critical trait for automotive alloys to ensure that parts do not fracture within metal forming presses. AHSS alloys, however, exhibit issues with formability as it relates to springback during some more complex precision metal stamping processes. Assessing the related mechanical properties of AHSS, in turn, is difficult with usual testing because the multi-phase structure leads to non-constant strain hardening. The viscous pressure bulge (VPB) test has shown promise, though, in constructing flow stress curves for AHSS samples.

Effective Modeling of Fracture States

The forming limit curve (FLC) is a standard in predicting the forming behavior of sheet metal to illustrate stress states that result in fracture. Traditionally, this involves a series of tests at varying ratios of shear and strain to determine when fracture occurs, but the variability of AHSS responses to strain make this especially costly in time and materials. The Center for Precision Forming at Ohio State University, however, has demonstrated a “three-point technique” for approximating the FLC with just three tests: pure shear, pure strain and biaxial tension. This can provide a more time- and cost-effective method for OEMs and their progressive metal stamping companies they work with.

The advances made in newer metal forming presses allow sheet metal stampers in PA to make fine adjustments to speed and force when forming critical shapes. There is great promise for precision metal stamping in the automobile industry. Further research in controlling the properties and performing effective testing and working will help manufacturers realize goals of more efficient automotive design.

How Are High Pressure Vessels for Compressed Gas Made?

If you are a buyer of pressurized gas for your business, you may be curious about how a commercial metal forming company produces high pressure vessels suitable for containing compressed gas. There are several steps involved in making pressure vessels that can withstand up to 1000 times more pressure than other more basic containers that may be used for storing dry goods under normal pressure.

Heat Treated Metal and Chemical Baths

Metals such as the steel alloy chromoly are often used for high-pressure vessels. These metals are initially treated at a temperature near 1300 degrees Fahrenheit for 36 hours before being immersed in the first of a series of chemical baths intended to allow the metal to flex and be capable of safely storing compressed gas. Once dried, the metal is moved over a hydroforming press to be formed into the shape outlined by the designer. Often there is a deep draw die that is made based upon the specifications provided by the client.

A Series of Presses

Several different types of powerful presses are used to shape compressed gas vessels. A mandrel pressor hydroforming sheet metal press applies up to 800 tons of force before another type of press may be used to continue refining the vessel shape with up to 150 tons of force while using a coolant to prevent overheating. Several presses may be employed to stretch the metal until the closed bottom end of the vessel is shaped and reinforced.

Finishing the Top and Exterior

In order for a commercial metal forming company to complete a pressure vessel, it is necessary to create a leak-proof neck and valve connection. First, a band saw is used to slice off the top of the container following pressing. A torch then heats the edge to more than 1500 degrees Fahrenheit for 90 minutes before the vessel is returned to yet another chemical bath for several minutes. The vessel is finally reheated to a slightly lower temperature around 1200 degrees Fahrenheit for 90 minutes before being left to cool for several hours. The surface is smoothed by shot blasting and the finished container is tested by being filled with and submerged in water.

All of the transitions between extreme heat and cooling involved in the production of a high-pressure vessel temper the metal and allow it to flex enough to safely contain pressurized gases. There are several major types of pressured vessels that that can be created by shaping deep drawn aluminum, specialty alloys and carbon steel. There are only a handful of hydroforming companies in USA that specialize in making pressure vessels for the compressed gas market.

Everything You Need To Know About Hydroforming

As a purchasing agent, you need understand what you can about many different types of manufacturing processes so you can make the right decision for the parts that you are going to have produced. If you are looking for a symmetrically round metal part to be made, then it helps to learn about what hydroforming is and what can be done with this type of process. There are only a few hydroforming companies in the USA because the equipment being used is highly specialized.

What Is Hydroforming?

Hydroforming is a technology for forming and creating metal parts. It allows for precision shaping of metal parts that are drawn to a depth more than 5 inches deeper than the previous formation. Most deep draw metal stamping machines do not have the capability to go deeper than 4 inches. In this hydroforming process, a pressurized fluid is used to form the metal pieces around a mold or die. The metal materials being formed often start out as a flat sheet or occasionally a tube.

Hydroforming sheet metal starts off as an approximately cut flat sheet of metal that is pushed around a die form with the pressurized water or oil to form the shape. Hydroforming is most often used when the production runs fall below 2500 pieces and not often used in longer runs. Some of the products that lend themselves best to hydroforming sheet metal are seamless vats, vessels, tanks, cooking pans and other types of metal containers. Many of the metal forming manufacturers that include deep draw metal forming in their offerings also include seam welding services, so they can bring two haves of a vessel together.Many times, hydroforming sheet metal creates seamless parts that get attached to other metal components with the aid of gaskets and fasteners.

The Process

The actual process of hydroforming starts with tooling that is made according to a CAD diagram. The tool goes into a tray with the metal placed over the form. Everything is moved into the chamber for forming. The machine fills with the water or a specially oil and begins the process of lifting, stretching and shaping the metal using a tremendous amount of force. The fluid is then extracted back into its reservoir and the chamber opens with the completed part.

Using Hydroforming

Hydroforming can be used in many applications with various types of metal. It is great for parts that have 90-degree bends or dramatic shaping requirements. It is ideal if the part needs to be lightweight, and it also costs less than typical deep draw stamping processes, which is perfect if you are looking for lower part costs on shorter production runs.

Materials can be anything from titanium, stainless steel, various carbon steel grades, aluminum to and even copper.