From a six metre steel rod heated up to 1200°C to an elegant and precise golf club ground by eye and hand, our forging process guarantees that the metals natural grain is preserved in every step of the process.

Loading…

The Grain Flow Forging process was patented in 1998 – to create a precise iron head through multiple forging stages from a single billet of steel. Begin exploring what makes Grain Flow Forging a unique process…

What is grain flow forged

WHAT IS GRAIN FLOW FORGING?

  • Grain Flow Forging allows for a highly precise iron head to be crafted through multiple forging stages from a single billet of steel.
  • The method uses the metal's natural grain to enhance the head's integrity, consistency and durability.
  • Mizuno is the only company to arrange and control this flow to pass on a performance benefit to the golfer.

CAST VS. FORGED

Cast Head

Cast or ‘form forged’ head with loss of internal grain structure

Forged Head

Mizuno Grain Flow Forged with tight, reinforced grain structure.

ONE PIECE & MULTI‐PIECE CONSTRUCTION

One piece Grain Flow Forging
Neck and head are forged from the same single billet of steel, ensuring continuous grain through the head.

Competitor forged iron with welded neck
Unlike a Mizuno Grain Flow Forged iron the iron is made with two parts – with no continuous grain through the head.

Sound Test

Watch the video to hear the difference between cast and forged club heads

Materials

Crucial to the calibre and feedback of Mizuno clubs is the quality of materials selected for their forging…

Dedicated research into continuously improving our golf clubs led to our progression from 1025 Mild Carbon Steel to 1025E Pure Select, as well as the revolutionary introduction of Boron.

1025E PURE SELECT MILD CARBON

The steel behind Mizuno's softest feeling irons. Used in our one piece irons for higher level players seeking the ultimate in precision and feedback. 1025 is used for its balance of strength, bend‐ability and feel. The evolution to 1025E reduces unnecessary elements that occur during the forging process – phosphorus and sulphur.

Boron Infused Steel

Introduced in 2014 to combine the precision of a forged iron with the ball speed of a distance iron. Widely used in other industries, the smallest trace of boron to the steel mix increases its strength during manufacture. Allowing Mizuno to create more complex one piece Grain Flow Forged irons like the MP‐25, for a balance of feel, precision and increased ball speeds.

Boron steel vs 1025E Pure Select Mild Carbon steel

A simple bladed iron like MP‐5 would have identical feel and performance from either a Boron infused or mild carbon steel billet. The Boron is only impactful when a more complex head design is required. Post manufacture both materials behave near identically.

Hiroshima
Hiroshima

In 1968, Mizuno moved the production of its forged irons to the Chuo plant in Hiroshima – on the west coast of Japan.

Still made in the same exclusive plant today, the partnership has allowed Mizuno to evolve and perfect its forging expertise over many years.

Please tour our forging factory and follow the complete process of manufacturing a Grain Flow Forged iron.

Step 1

Uncut Japanese steel rods are delivered into the forging plant – ready to be sheared into single 10 inch billets for every Grain Flow Forged iron.

The six‐metre steel rod are sheared into 10in length.

Billets traveling down a chute.
Dirty billets in a container.

The raw steel rods are abrasion cleaned of any surface weathering prior to heating.

Clean billets in a container.

Buffered billets are ready for heating and bending process.

Step 2

Each Billet gets heated to 1200°C before being stretched and bent to the angle that will roughly form the head and hosel.

The bending stage ensures that the hosel and clubhead are forged from a single billet – to ensure a perfect grain flow throughout.

Step 3

primary forging stage

The bent billet is placed onto a forging mould and hit four times by a 1,000‐ton hammer press to tightly align grains in the metal.

To control the thickness and weight of each clubhead, the hammer operator uses a foot pedal – the process requires Chuo's most experienced staff.

The operators will work for 3 years before allowed onto the Mizuno hammers. Once on the hammers, they work 5 more years under the watch of a master operator until they can work alone.

Every head in each model (both A and B headweights) has its own forging master mould for that specific set of clubs.

Heads immediately after primary forging riding the conveyor during cool down.

Step 4

COOKIE CUTTER STAGE

Cookie cutter roughly trims off the excess metal from the cooled heads, known as the flash…

…before being reheated for the precision forging stage.

Step 5

Precision Forging Stage

Each clubhead is reheated and pressure squeezed to create precise head shape before trimming.

With each stage of precision forging the billet is looking more and more like a useable golf club.

30 pairs of hands and eyes ensure each forged irons quality.

Until ready for grinding and plating.

Step 6

PLATING & GRINDING

Final Grain Flow Forged head ready for stamping, polishing, plating and assembly.

THE FINISHED ARTICLE

After plating the finished clubs are then shipped to their assembly plants ready to be custom assembled.

The finished MP18 club

With our combination of market leading R&D, cutting‐edge technology and stunning craftsmanship, Mizuno can proudly say that we believe we produce some of the best irons in the world. Each and every club is produced with the user in focus.