What is a Flat Bar? Material Selection and Availability

Here.What is a Flat Bar? Material Selection and Availability"　Notes on the following.

I use flat bars (FB) a lot in mechanical design,Flat bars come in many materials (types), and it is sometimes difficult to decide which one to choose when there are similar materials available.

A wide variety of flat bars exist, from the common SS400 to special materials, as defined by JIS standards.　Selecting the wrong material for your application can lead to insufficient strength and increased costs, which can cause failure and regret.　In this article, we note the characteristics and distribution of each material in as much detail as possible so that you can use it as a reference for your selection.　(This memo is summarized from the basics so that it is easy to understand for the general reader.)

What is a flat bar?

Definition of Flat Bar (Flat Steel)

As the name suggests, a flat bar is a plate- or bar-shaped steel material with a rectangular cross section.Name "Hirako" in the Japanese Industrial Standards (JIS)　and is widely used in machinery and buildings around us.

A key feature of this material is its production method.Flat bars are made by rolling them on rollers while all four sides are hot.　This is clearly distinguished from a member that is cut from a large sheet of steel (steel plate) to the required width.

With the method of cutting from steel plates, warping and distortion are likely to occur due to the heat generated during cutting, which can be time-consuming to correct later,Flat bars are manufactured in predetermined widths from the start, eliminating the need for a cutting processIt is.　This has the advantage of low warpage and distortion and high dimensional accuracy, which leads to reduced machining costs.　This stable quality is one of the reasons why our products are trusted by many designers and manufacturing sites.

Importance in Machine Manufacturing

Flat bars have established themselves as an indispensable basic material in modern machine manufacturing due to their ease of fabrication and dimensional stability.　　Its applications are extremely wide-ranging and include structural frames that form the backbone of machinery, components that support parts, moving parts that require high precision, jigs used in assembling products, and base plates used to install machinery.

This versatility, where a single material can be used in a wide variety of fields, is what makes flat bars so important.This ease of use is the reason why it is treated as a basic procurement item in any manufacturing industry, rather than a special material　It is.

Steel] Typical types of flat bars

SS400｜The cheapest and most commonly distributed steel material

SS400 is the most common flat bar material and widely distributed in the market.SS400" is the standard material used in mechanical design and construction, so much so that it is called "SS400" unless otherwise specified.

The greatest advantage of this material is its low price and availability.SS400 is a type of "rolled steel for general structural purposes" as defined in JIS G 3101, and is only guaranteed to have a tensile strength of 400 N/mm² or higher.　It is.

No strict regulations on chemical composition, such as carbon content, making it suitable for mass production and keeping costs low　It is.　　For this reason, it is widely used in general structural members where strength is the only requirement, such as machine racks, base plates, and architectural brackets.

However, there are some points to note in the selection process.Since the chemical composition is not guaranteed, weldability and increased hardness (hardenability) by heat treatment cannot be expected.　Welding may cause instability in strength,Avoid use for critical components that require high reliability　It is.

Difference in surface finish

SS400 flat bars are available in two main surface finishes.

• Black skin (black leather)Hot-rolled: Still hot-rolled, with a black oxide film on the surface. It is the least expensive, but the surface is rough, and when painted, this film may peel off and the paint may peel off with it,Surface preparation required　will be.
• Polished: Black-finish material finished by cold drawing or other processes, characterized by smooth surfaces and high dimensional accuracy.　It is suitable for parts where appearance is important, but costs are higher.

S45C/S50C｜Carbon steel for machine structural use with increased strength through heat treatment

S45C and S50C are very commonly used flat bars as materials for machine parts along with SS400　They are.　　These are classified as "carbon steel for machine structural use (S-C material)," and the biggest difference from SS400 is that the chemical composition, especially carbon content, is strictly controlled by JIS G 4051.

Due to this characteristic,Hardness and strength of S45C and S50C can be greatly improved by heat treatment (quenching and tempering)　It is　　It is suitable for machine parts that require high strength and wear resistance that SS400 cannot handle, such as shafts, gears, jigs, and parts of molds.S45C in particular is a material that is widely distributed and easy to obtain　It is.

On the other hand, S50C has more carbon than S45C, resulting in higher hardness after heat treatment.　However, on the other hand, toughness (tenacity) is reduced to the extent that it becomes harder, and it tends to be harder to cut and has worse weldability.It is important to decide which material to choose, taking into consideration the balance between the hardness required for the part and the ease of machining.　However, I think S45C is used in many cases.

Although it is more expensive than SS400, it is a very important choice in the design of mechanical parts because of its great advantage in adjusting performance through heat treatment　The first two are the following.

SM and SN materials｜Special steel materials for weldability and earthquake resistance

SM and SN materials are flat bars for more specialized requirements that SS400 cannot meet.　They are rarely found in general home centers or online stores and are used primarily in large buildings and infrastructure facilities.

SM material is "rolled steel for welded structures (JIS G 3106)," which, as the name implies, is a steel material specialized in guaranteeing the performance of welded parts　It is　　Unlike SS400, its chemical composition is strictly controlled, so its strength does not deteriorate easily even when welded, and its quality remains stable. Because of these characteristics, SS400 is used as an important material for large structures such as bridges, ships, and industrial machinery, where welding is frequently used.

On the other hand, SN material is called "Rolled steel for building structure (JIS G 3136)", which is a material with even stricter regulations for SM material, with particular emphasis on earthquake resistance performance.　It is.　To prevent buildings from collapsing in the event of an earthquake, they must be able to absorb energy and deform flexibly, so special provisions are made, such as an upper limit on the yield point.

The main consideration in selecting these materials is distributability.SM and SN materials are not general-purpose stock items like SS400 and S45C, but are basically "made-to-order" products manufactured by steelmakers based on the design specifications of a specific project　This will be the case.　Therefore, procurement is often accompanied by long delivery times and minimum order lot constraints.

Tool steel｜Hard steel used for molds and blades

Tool steel is a special steel material with extremely high hardness and wear resistance used as a "tool" for pressing and cutting other metal materials　It is.　It is supplied in the form of flat bars as material for products such as molds, drills, and blades.

Tool steels are classified into several types according to JIS standards based on the components they contain.

• Carbon tool steel (SK material):It is a basic tool steel whose hardness is adjusted by the amount of carbon (JIS G 4401).
• Alloy tool steels (SKS material, SKD material, etc.)This is a steel material to which alloying elements such as chromium and tungsten are added to further improve wear and impact resistance (JIS G 4404). SKD11, especially for cold dies, is widely used.

A major characteristic of the tool steel market is that not only JIS-standard materials are distributed, but also steel manufacturers develop and sell many branded steel products with their own added value.　It is.　　For example, Daido Steel's "NAK55Products such as "DC53" and "DC53" are preheated (prehardened steel) or have improved machinability, which greatly reduces the time and labor required to make the molds.

Of course, these high-performance materials are extremely expensive and procurement is limited to suppliers specializing in specialty steels.　However, in many cases, the benefits can be significant when viewed in terms of total cost, as they can extend the life of molds and shorten processing time.　Materials should be selected from the perspective of improving product productivity, rather than being compared based on simple price alone, as is the case with general-purpose steels.

Nonferrous Metals] Typical Types of Flat Bars

SUS304｜Typical stainless steel with excellent corrosion resistance

SUS304 is the most typical and widely used stainless steel material.Classified as an austenitic stainless steel with chromium and nickel added to iron, its greatest feature is excellent corrosion resistance, or "rust resistance.　The following is located in the

Taking advantage of this rust-resistant property, it is widely used in environments where it is exposed to water and moisture, such as kitchen equipment, food processing machinery, chemical plant parts, outdoor railings, and the interior and exterior of buildings.　It is also used for ornaments and household items that require design due to its beautiful silver luster.It has a very large distribution volume and, like SS400, is readily available as a common material.　It is.

However, it is not a universal solution.　First, it is more expensive than ferrous materials.　Also, because it is a very sticky material, tool edges wear easily during cutting, and machinability may be perceived as poor.

To improve this drawback, some manufacturers have developed proprietary steels such as "SUS303," which is easier to machine by adding free-cutting components, and "304Mac," which maintains the JIS standard but improves drill workability and other properties.In addition, a wide variety of surface finishes are available for stainless steel flat bars　It is.The matte "COLD (2B)" finish is the most common, but "Hairline (HL)" with a polished grain in one direction and "#400" finish with a quasi-mirror-like luster are also available, and can be selected according to the design.

A6063｜Lightweight, easy-to-process aluminum alloy

A6063 is the most standard aluminum alloy flat bar material in circulation.Its greatest advantage over steel and stainless steel is its lightness. With a specific gravity that is about one-third that of steel, it is the best choice when weight reduction of products is required　The first two are the following.

This material is an aluminum alloy with magnesium and silicon added, providing an excellent balance of strength and corrosion resistance.　It is also suited to a processing method called extrusion molding, which allows for the efficient manufacture of products with complex cross-sectional shapes. Its applications include window sashes and door frames for construction, safety covers for machinery, and heat sinks for heat dissipation.

It also has good workability, allowing for easy cutting, bending, and drilling.　In addition, the product can be used in a wide range of applications, such asAn anodic oxidation treatment called "anodizing" can form a hard, transparent film on the surface.　This improves corrosion and abrasion resistance, and at the same time allows for a greater degree of freedom in design, as it can be colored in a variety of colors.

One caveat is that it is less strong than steel materials.　Since it may not be suitable for structural members subject to large loads, the necessary strength should be fully considered when designing. This material shows its true value when there is a clear objective of weight reduction.

Other nonferrous metals｜SUS316, brass, etc.

In addition to SUS304 and A6063, various nonferrous metal flat bars are used for specific applications and environments. Here are some typical examples.

SUS 316

SUS316 is a stainless steel in which the element molybdenum is added to SUS304 to further improve corrosion resistance　It is　　In particular, it has strong resistance to chloride ions contained in seawater and sea breeze, and is resistant to localized corrosion called "pitting corrosion.　Although more expensive than Type 304, it is the material of choice in situations where high reliability is required.

Brass

Brass is an alloy of copper and zinc, and is characterized by its beautiful golden glow.　The type called "free-cutting brass," which is easy to process and especially easy to cut, is often used as a material for precision machine parts such as bolts, nuts, and valves. It is also widely used for architectural hardware, ornaments, and musical instrument parts because of its beautiful appearance.

These materials are less widely distributed than SUS304 and A6063, and are specialized materials. However, they are important choices to meet special requirements such as "higher corrosion resistance" and "excellent machinability" that cannot be met by common materials. The most appropriate material must be selected by clarifying the project's required specifications and balancing them with cost and availability.

Specialty Flat Bar Types

Overall view of available flat bar materials

In addition to the typical materials introduced so far, there are a great many other types of flat bars.　The following table provides a comprehensive list of materials available on the Japanese market.　This includes items that are readily available through online stores as well as items that require an order from a specialized trading company or manufacturer.

This table shows how many options are available.　However,In the actual design and procurement process, it is important to understand how these materials are "marketed".　Not all materials are equally available, so considering distributability is key to realistic material selection　The first two are the following.

How to choose materials for ease of distribution

Know the three levels of marketability

When choosing a flat bar material, it is extremely important to understand not only its technical performance, but also its "availability," or marketability　It is.　　The market is divided into three main levels, depending on the material.

Level 1: Commodity (Immediate delivery)

Four materials belong to this level: SS400, S45C, SUS304, and A6063.These are "standard stock items" that most steel dealers and online stores keep in stock at all times.　This is the most suitable option for prototype production, urgent repairs, or when you need to obtain small quantities with a short delivery time.

Level 2: Specialty Inventory

General tool steels such as S50C, SUS316, and SKD11 fall into this level. Although not as high as Level 1, there is a certain demand for these steels, so dealers specializing in specialty steels keep them in stock.¹²The material is used in the following cases. Often chosen when general-purpose materials do not perform as well, but are not that special.Procurement requires several days of lead time. Need to anticipate several days lead time for procurement.　There are

Level 3: Made-to-order products

Most high-performance alloy steels such as SM, SN, and SCM materials (chrome molybdenum steel) and special tool steels are at this level.These are materials designed for specific products or projects for which there is little or no general demand, so market inventories are essentially non-existent.　Orders must be placed directly with the steel manufacturer, and delivery times in weeks to months and minimum production quantities are usually set.

Thus, knowing that availability varies greatly by material, we can have a realistic viewpoint at the design stage, such as "Is this material readily available?" and "How long will it take to deliver?" This will enable smooth development without rework.

Types and Roles of Suppliers

There are many different companies involved in the process of obtaining a flat bar that play different roles. Knowing what company to buy from will make the procurement process easier.

Manufacturer

Companies such as Nippon Steel, JFE Steel, and Kobe Steel, Ltd. have been working on all kinds of steel products.The "Maker" as a source　It is. Huge facilities produce steel products to meet large-scale demand.Orders for made-to-order items, for example, are placed directly with the manufacturer or through a trading company as described below.

trading company

Specialized trading companies" such as Metal One Corporation and Marubeni-Itochu Steel Inc. stand between manufacturers and users, providing logistics, inventory management, and information.In particular, it plays a central role in the planned procurement of large quantities of steel materials and in arranging made-to-order products.

Distributors and processors

Distributors and processors" purchase large quantities of steel from manufacturers and trading companies, cut and process it according to the user's requirements, and sell it.　 This includes steel stores in town and online stores that specialize in specific processes.Often able to accommodate small-lot orders, making them accessible to designers　It is.

E-commerce platform

Online suppliers such as MISUMI and Monotaro are modern forms of distribution that utilize information technology to meet the needs for high-mix, small-lot, and short delivery times.Particularly useful in prototyping and R&D situations, as the aforementioned "commodity (ready-to-ship)" level materials are readily available, even from a single unit　It is.

Which supplier to choose depends on the type of material needed, the quantity, the processing, and the urgency of the delivery date.　It is good to understand this relationship.

Strategic Material Selection Points

As we have seen, flat bars come in a wide variety of materials and with different distribution characteristics.　With this information in mind, here are some strategic points for selecting the best material for each purpose.

General structural components where cost is the highest priority

For machine frames, girders, brackets, etc., where strength requirements are not so stringent, SS400 "black-dyed leatherThe "material" is the first choice.　This is the case.　The overwhelming advantage of this product is its low price and ease of availability. However, if painting is required, the cost of surface preparation must also be taken into account.

Machine parts that require strength and hardness

For parts that are subject to wear or high forces, S45C or S50C "polished" materials should be selected for heat treatment.　It is. Cold-finished materials have a smooth surface and high dimensional accuracy, which reduces the need for additional labor. It is important to include the heat treatment process and associated costs in the planning at the design stage.

Environments where rust resistance is required

The first basic material is SUS304　It is　It is sufficiently corrosion resistant in a typical environment.　If,For parts that require a lot of cutting, it is worth considering the use of SUS303 or the manufacturer's proprietary free-cutting steel (e.g., 304 Mac), which is easier to machine, to reduce machining costs.　Furthermore, in harsh environments such as coastal areas or where chemicals are handled, it is wise to specify SUS316, which is more corrosion resistant.

When weight reduction is a top priority

If you have a clear objective of making your product lighter, the aluminum alloy A6063 is the standard choice. It is the most readily available of the aluminum alloys and can meet many weight reduction needs.

Please use these points to organize your project's requirements (performance, cost, and delivery date) and select the most appropriate material. And remember to always check with your supplier for availability, price, and exact delivery date before making a final decision.

Related Sites

Finally, the following are five websites that we consulted in preparing this summary article.

• Japanese Standards Association (JSA)
  • URL:. https://www.jsa.or.jp/
  • Rationale: This organization establishes and publishes JIS (Japanese Industrial Standards) such as SS400 and S45C, which define the materials of flat bars. It is the most basic source of information and the highest authority on steel standards.
• Japan Iron and Steel Federation (JISF)
  • URL:. https://www.jisf.or.jp/
  • Reason: It is the leading organization representing the Japanese steel industry and is involved in the drafting of statistical data and JIS standards related to steel. The site is very reliable for obtaining trends and official information on the industry as a whole.
• Nippon Steel Corporation
  • URL:. https://www.nipponsteel.com/
  • Rationale: We are the largest steel manufacturer in Japan and produce a wide variety of steel materials described in the article. Product catalogs and technical documents are authoritative sources of information on the specific properties and applications of each steel material.
• Daido Steel Co.
  • URL:. https://www.daido.co.jp/
  • Rationale: We are a leading company in the field of special steels, including tool steels and stainless steels. We provide primary information on proprietary steel products such as 304 Mac, which is mentioned in the article, and on high-performance mold steels.
• MISUMI Corporation (meviy)
  • URL:. https://jp.meviy.misumi-ec.com/
  • Rationale: As an online procurement site for machine parts, it is used by a very large number of design and manufacturing engineers. It is a reliable source of information from the user's point of view, with a wealth of practical information such as the distributability of each material, actual machining services, and standard sizes.

That's it.