I. Steel Length Dimensions
Steel length dimensions are the most fundamental measurements of all types of steel, referring to the length, width, height, diameter, radius, inner diameter, outer diameter, and wall thickness of the steel.
The legal units of measurement for steel length are meters (m), centimeters (cm) and millimeters (mm). In current practice, inches (“”) are also used, but they are not legal units of measurement.
1. Steel strip dimensions
Defining strip dimensions for steel is an effective measure to save materials. Range dimensions mean that the length or product of length and width is not less than a certain size, or that the size is within a certain range for delivery. The production unit can supply according to these dimensional requirements.
2. Undefined length (normal length)
The term “indefinite length” refers to product dimensions (length or width) that are within the standard range but are not fixed. Undefined length is also known as normal length.
For metal materials delivered according to undefined length, delivery is acceptable as long as it is within the defined length range. For example, for common round steel not exceeding 25 mm, the usual length is set between 4 and 10 m. Any round steel within this range can be delivered.
3. Fixed Length
Fixed length refers to cutting into specific sizes according to order requirements. In the case of fixed length delivery, the metal material supplied must be of the length specified in the customer's purchase contract.
For example, if the contract stipulates a fixed delivery length of 5m, then all materials delivered must be 5m long. Anything smaller or larger than 5m is considered unacceptable. However, in reality, not all deliveries can be exactly 5m long, so a positive deviation is allowed, but a negative deviation is not.
4. Multiple Length
Multiple length refers to cutting into integer multiples of a specific size according to order requirements. When delivering in multiple length, the length of the metal material supplied must be an integer multiple (plus the saw cut) of the length (called single length) specified in the customer's purchase contract.
For example, if the customer contract requires a single length of 2m, then when cut to double length the length will be 4m; when cut to triple length it will be 6 m, each with one or two amounts of saw cutting added. The amount of saw cutting is stipulated in the standard. When delivering in multiple length, only one positive deviation is allowed; a negative value is not acceptable.
5. Short length
Short length refers to a length that is less than the lower limit of the standard undefined length, but not less than the shortest length allowed.
For example, in the standard for steel pipes for water and gas transmission, it is allowed to have 10% (calculated by the root number) of short length steel pipes of 2 to 4 m in length in each batch. Here, 4m is the lower limit of undefined length and the shortest length allowed is 2m.
6. Narrow width
Widths less than the lower limit specified by the standard, but not less than the narrowest width allowed, are called narrow widths. When delivering according to narrow widths, attention should be paid to the standard regulations regarding the proportion of narrow widths and narrowest width.
II. Examples of Steel Length Dimensions
1. Length dimensions of structural steel
a) The standard lengths for railway tracks are 12.5m and 25m.
b) The dimensions of round steel, wire rod and steel wire are marked by diameter (d) in millimeters (mm).
c) The square dimensions of the steel are marked by the side length (a) in millimeters (mm).
d) The hexagonal and octagonal dimensions of the steel are marked by the distance between the corners (s) in millimeters (mm).
e) The dimensions of flat steels are marked by width (b) and thickness (d) in millimeters (mm).
f) The dimensions of the I-beam and steel channel are marked by waist height (h), leg width (b) and waist thickness (d) in millimeters (mm).
g) Equal angle steel dimensions are marked by equal side width (b) and side thickness (d) in millimeters (mm). The dimensions of unequal angle steel are denoted by the side widths B, b and side thickness (d) in millimeters (mm).
h) The dimensions of the H beam are marked by the height of the web (h), width of the flange (b), thickness of the web (t1) and thickness of the flange (t2) in millimeters (mm).
2. Dimensions of steel plates and strips
⑴ The thickness 'd' of steel plates is normally indicated in millimeters (mm). Strips, on the other hand, are described by both width 'b' and thickness 'd' in millimeters (mm).
⑵ Individual steel plates come in specific dimensions. For example, hot rolled steel plates include: 1mm thick plates measuring 600×2000mm, 650×2000mm, 700×1420mm, 750×1500mm, 900×1800mm, 1000×2000mm and so on against.
3. Dimensions of steel pipes
⑴ The outer diameter 'D', inner diameter and wall thickness 'S' of steel pipes are generally marked in millimeters (mm).
⑵ Each type of steel tube has defined dimensions. For example, seamless steel tubes with an outer diameter of 50 mm come in 15 variations with wall thicknesses ranging from 2.5 to 10 mm. Alternatively, for tubes with the same wall thickness of 5 mm, the outer diameter can vary from 32 to 195 mm in 29 variants.
Similarly, welded steel tubes with a nominal diameter of 25 mm are available with a standard wall thickness of 3.25 mm or a thicker variant with a wall thickness of 4 mm.
