{"id":9456,"date":"2026-08-14T10:43:53","date_gmt":"2026-08-14T03:43:53","guid":{"rendered":"https:\/\/giaanh.vn\/?post_type=kien-thuc&p=9456"},"modified":"2026-10-15T08:57:26","modified_gmt":"2026-10-15T01:57:26","slug":"part-1-cutting-and-forming","status":"publish","type":"kien-thuc","link":"https:\/\/giaanh.vn\/en\/knowledge\/cutting-and-forming\/","title":{"rendered":"Part 1: Cutting and Forming"},"content":{"rendered":"

The way a material plate is cut at the beginning can directly affect the operations that follow.<\/p>\n

Thermal cutting creates a heat-affected zone at the edge. Mechanical cutting leaves cold deformation, while waterjet cutting does not affect the material structure through the same mechanism as thermal cutting.<\/p>\n

For this reason, the cutting method should be selected as part of the entire fabrication sequence, especially when the component will later be bent, drilled or further formed.<\/p>\n

With high-hardness steel, an unacceptable cut edge, untreated burrs or an unsuitable bending radius may not cause immediate failure in the workshop. These areas can later become initiation points for microcracks or cracking during forming or after a period of operation.<\/p>\n

1. Explanation of key technical terms used in this article<\/span><\/h2>\n

Before examining individual cutting and forming methods, several terms should be clearly understood because they appear throughout fabrication drawings, technical guidelines and workshop inspection activities.<\/p>\n

Five terms related to cutting and bending<\/p>\n\n\n\n\n\n\n\n\n\n
Technical term<\/strong><\/th>\nMeaning<\/strong><\/th>\n<\/tr>\n<\/thead>\n
Burr<\/strong><\/td>\nA sharp metal projection remaining on the edge after cutting<\/td>\n<\/tr>\n
Microcrack<\/strong><\/td>\nA very small crack at the edge root that requires close inspection to detect<\/td>\n<\/tr>\n
Rolling direction<\/strong><\/td>\nDirection of the steel grain, which affects the bending radius<\/td>\n<\/tr>\n
Cold deformation<\/strong><\/td>\nChange in steel caused by deformation at room temperature<\/td>\n<\/tr>\n
Preheating for thermal cutting<\/strong><\/td>\nHeating the steel before thermal cutting to control the cooling rate<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Two additional concepts also need to be noted:<\/p>\n\n\n\n\n\n\n
Technical term<\/strong><\/th>\nMeaning<\/strong><\/th>\n<\/tr>\n<\/thead>\n
Heat-affected zone (HAZ)<\/strong><\/td>\nThe band of material adjacent to the cut that is affected by the thermal cycle<\/td>\n<\/tr>\n
Minimum bending radius<\/strong><\/td>\nThe smallest permissible radius for the specific grade, thickness and rolling direction<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

In this article, preheating for thermal cutting<\/strong> refers to heating performed before thermal cutting. Preheating for welding<\/strong> is part of the welding process and is discussed in \u00a0Part 2: Welding high-hardness steel<\/strong><\/a><\/span>.<\/p>\n

2. The cutting method determines the edge condition and affects subsequent operations<\/span><\/h2>\n

\"\"<\/p>\n

Different cutting methods leave different edge conditions. These conditions directly affect bending and forming in the next stage.<\/p>\n\n\n\n\n\n\n\n
Cutting method<\/strong><\/th>\nResulting edge condition<\/strong><\/th>\nEffect on subsequent operations<\/strong><\/th>\n<\/tr>\n<\/thead>\n
Thermal cutting<\/strong><\/td>\nA heat-affected zone is created, and the edge structure has been thermally affected<\/td>\nGreater attention is required if the edge will later be bent<\/td>\n<\/tr>\n
Waterjet cutting<\/strong><\/td>\nDoes not create a heat-affected zone through the same mechanism as thermal cutting<\/td>\nMore favorable when the component needs to be formed close to the edge<\/td>\n<\/tr>\n
Mechanical cutting: shearing, punching<\/strong><\/td>\nThe edge is subjected to cold deformation<\/td>\nThe edge may be more prone to cracking during subsequent bending<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

The cutting method should therefore not be selected independently of the work that follows.<\/p>\n

If the component still needs to be bent, drilled or further formed, the material grade, thickness, cutting method and requirements of the next operation should be considered together.<\/p>\n

The same material can have different edge conditions depending on how it is cut. A method that is convenient for cutting is not necessarily the most suitable for the next forming operation.<\/p>\n

3. Thermal cutting: controlling temperature and cut-edge quality<\/span><\/h2>\n

Thermal cutting heats a narrow zone of the material to a high temperature while the surrounding steel remains at a lower temperature.<\/p>\n

After cutting, the surrounding material draws heat away from the heated zone, causing it to cool rapidly. Where the technical documentation requires preheating, heating helps control the temperature difference and cooling rate.<\/p>\n

Cracks may not appear immediately after cutting. Therefore, a freshly cut edge that looks intact is not sufficient to confirm that all fabrication conditions were appropriate.<\/p>\n

3.1. Preheating according to the correct grade and thickness<\/span><\/h3>\n

Where the applicable documentation requires preheating, the temperature needs to be controlled before ignition and during the cutting process.<\/p>\n\n\n\n\n\n\n\n\n\n
Control item<\/strong><\/th>\nRequirement<\/strong><\/th>\n<\/tr>\n<\/thead>\n
Equipment<\/strong><\/td>\nHeating equipment and a contact thermometer, not only temperature crayons<\/td>\n<\/tr>\n
Method<\/strong><\/td>\nHeat both sides evenly around the cutting line<\/td>\n<\/tr>\n
Temperature threshold<\/strong><\/td>\nRefer to the correct material grade and thickness range<\/td>\n<\/tr>\n
Before cutting<\/strong><\/td>\nMeasured temperature on both sides meets the requirement<\/td>\n<\/tr>\n
After an interruption<\/strong><\/td>\nIf the temperature falls below the required level, reheat before continuing<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

There is no single preheating temperature that applies to all high-hardness steels.<\/p>\n

Before starting a fabrication batch, the correct material grade, thickness and applicable technical documentation need to be identified. A parameter used for a previous batch remains valid only if the current batch still falls within the same scope of application.<\/p>\n

3.2. Preheating must remain within the permitted temperature range<\/span><\/h3>\n

Preheating is not simply about reaching a minimum temperature.<\/p>\n

The temperature must remain within the range appropriate for the specific grade, thickness and fabrication method. A temperature below the requirement will not provide the intended cooling-rate control, while a temperature above the permitted range may affect the material condition.<\/p>\n

Therefore, the required value should be taken from the current technical documentation rather than from a single memorized value applied to several steel grades.<\/p>\n

3.3. Preheating requirements vary by cutting technology<\/span><\/h3>\n

Thermal-control requirements do not apply in the same way to every cutting method.<\/p>\n

For laser cutting and nitrogen plasma cutting, preheating may reduce cut quality. These methods do not use preheating in the same manner as conventional thermal cutting.<\/p>\n

Before applying any temperature requirement, the cutting technology and its corresponding technical guidance need to be clearly identified.<\/p>\n

3.4. Inspecting the edge after cutting<\/span><\/h3>\n

The surface and edge quality of the steel should be inspected before the component moves to the next operation.<\/p>\n\n\n\n\n\n\n\n\n
Item<\/strong><\/th>\nMethod<\/strong><\/th>\n<\/tr>\n<\/thead>\n
Inspection method<\/strong><\/td>\nVisual inspection, hand inspection and appropriate measuring tools<\/td>\n<\/tr>\n
Acceptable condition<\/strong><\/td>\nClean edge, no scale or deep burn marks, no detectable sharp projection by touch<\/td>\n<\/tr>\n
Condition requiring correction<\/strong><\/td>\nRough edge, grooves or microcracks at the edge root<\/td>\n<\/tr>\n
Action when unacceptable<\/strong><\/td>\nRework the edge; if cracking remains, remove the cracked area<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

An unacceptable cut edge may not cause an immediate problem at the cutting stage.<\/p>\n

Damage may only appear when the component is bent or after a period of operation. At that point, the original cause may be difficult to trace if the edge condition was not inspected and recorded earlier.<\/p>\n

4. Mechanical cutting and punching must remain within the permitted range<\/span><\/h2>\n

Shearing and punching can only be used within certain hardness and thickness ranges. Outside the permitted range, cracking may occur at the edge.<\/p>\n

The applicable range must be checked against the exact material grade. Where mechanical cutting is unsuitable, other methods such as thermal cutting or waterjet cutting should be considered according to the applicable technical documentation.<\/p>\n

Before selecting a method, determine:<\/p>\n