During this production step, by using the cold heading technology, a head and a body of the bolt are formed from a steel wire cut. The wire is initially unwinded from the coil and enters the machine, then it is straightened and cut to a defined length. Afterward, this wire cut is transferred in a system of dies and blows which continuously form the requested shape. The particular number of dies and blow strokes is defined by the actual part-shape complexity.
The company currently has 29 cold heading machines that cover a wide range of shapes and sizes based on their production possibilities.
The point of this process is to roll a thread of the semifinished product manufactured during the cold heading process. These special machines use linear or rotary thread rolling dies which act as a negative of the future thread. The semifinished product is moved by the feeding mechanism in the thread rolling die and then the thread is rolled by a one-way movement on the body of the semifinished product. During this process washers are also assembled, it happens right before rolling the thread. Washers can freely rotate, but are still held in place and can not be removed from the bolt.
The company currently has 31 thread rolling machines that cover a wide range of shapes and sizes based on their production possibilities.
Heat treatment is usually the following step after the thread rolling process. The basic principle of heat treatment is to achieve the desired strength and hardness based on the customer’s request. For this purpose, we currently use two basic heat treatment technologies. The first one is quenching and tempering, the second one is stress-relief annealing. We also have a dephosphating process available.
Our company currently has 5 continuous furnaces for quenching and tempering and 1 continuous furnace for stress-relief annealing.
The semifinished part gets its corrosion resistance and friction coefficient specifications during this production process. The ACZ can apply two base coats. The first one is galvanic zinc plating with chromate passivation in black color or clear, with the option of applying dehydrogenation process. The second base coat is the dip-spin coating Geomet® 720. On top of that, we are able to apply a variety of top coats that stabilize the friction coefficient or improve the corrosion resistance.
Additional Production and Non-production Processes
We have some additional specific production machines on top of the four basic production steps. Specifically, we are able to do the pointing process of bolts’ tip end (according to ISO 4753, etc.), touch roll process to remove any dents that naturally occur during the production process, degreasing and preservation by oil. Manual or machine sorting based on defined specifications are the additional non-production processes we can offer to our customers. The matter of course is to meet all customer requirements also in terms of packaging. Last but not least, the company ACZ has completely equipped chemical and metrological laboratories, enabling us to do in-house salt spray testing (SST).