The length measurement of steel is the most basic size of all kinds of steel, which refers to the length, width, height, diameter, radius, inner diameter, outer diameter and wall thickness of steel.
The legal measurement units of steel length are meter (m), centimeter (cm) and millimeter (mm).
In the current practice, it can also be expressed in inches (〃), but it is not a legal unit of measurement.
1. Size range of steel
It is an effective way to save materials to specify the size range of steel.
The range scale means that the length or length multiplied by width is not less than a certain size, or length, length by width from how much to how much size range of delivery.
The production unit can produce and supply according to the size requirements.
2. Random length (ordinary length)
Where the product size (length or width) is in the standard range, but does not require fixed size is called indefinite.
Random length is also called normal length (ruler).
Metal materials delivered according to random length can be delivered within the specified length.
For example, if the length of ordinary round steel is not more than 25 mm, which is usually 4-10 m, the round steel within this range can be delivered.
3. Fixed length
Cutting into a fixed size according to the order requirements is called fixed length.
When delivering according to the fixed length, the delivered metal materials must have the length specified by the demander in the order contract.
For example, if it is indicated in the contract that the goods shall be delivered according to the fixed length of 5 m, the delivered materials must be 5 m long, and those shorter than 5 m or longer than 5 m are unqualified.
But in fact, the delivery cannot be 5 m long, so it is stipulated that positive deviation is allowed, but negative deviation is not allowed.
4. Double length
The fixed size cut into integral multiples according to the order requirements is called double length.
When the goods are delivered by double length, the length of the delivered metal materials must be an integral multiple of the length (called single length) specified by the demander in the order contract (plus the saw bite).
For example, in the order contract, if the length of a single length that the demander requires is 2 m, the length is 4 m when it is cut into double length, 6 m when it is cut into three length, and one or two saw bites are added respectively.
The amount of saw bite is specified in the standard.
When double length delivery, only positive deviation is allowed, and negative deviation is not allowed.
5. Short feet
If the length is less than the lower limit of the random length specified in the standard, but not less than the shortest allowable length, it is called short length.
For example, according to the standard of water and gas transmission steel pipe, 10% of 2-4 m short steel pipe is allowed in each batch.
4 m is the lower limit of random length, and the minimum allowable length is 2 m.
6. Narrow rule
A narrow rule is one whose width is less than the lower limit of the width specified in the standard, but not less than the narrowest allowed width.
When the goods are delivered according to the narrow size, attention must be paid to the narrow size ratio and the narrowest size specified in the relevant standards.
The picture shows the steel production process.
Fig. 1 The steel production process.
7. Examples of steel length measurement
7.1 Length dimension of section steel
1) There are two kinds of standard length of railway tracks: 12.5 m and 25 m.
2) The dimensions of round steel, wire rod and steel wire are calibrated in mm of diameter D.
3) The dimension of square steel is calibrated by the millimeter (mm) of side length a.
4) The dimensions of hexagonal and octagonal steel are calibrated by the number of millimeters (mm) of the opposite side distance s.
5) The dimension of flat steel is calibrated by the number of millimeters (mm) of width b and thickness d.
6) The dimensions of I-beam and channel steel are calibrated by the millimeter (mm) of waist height h, leg width b and waist thickness d.
7) The dimension of equilateral angle steel is calibrated by the number of millimeters (mm) of equal side width b and side thickness d.
The size of unequal angle steel is calibrated by the number of mm of side width b, B and side thickness D.
8) The dimension of H-beam is calibrated by the number of mm of web height h, flange width b, web thickness t1 and flange thickness t2.
7.2 Length measurement of steel plate and strip
1) Generally, the thickness of steel plate d is calibrated in mm.
The width b and the thickness d of the steel strip are calibrated in mm.
2) There are different sizes for single steel plate, such as hot rolled steel plate:
1 mm thick steel plate with width of 600 × length of 2000 mm;
650×2000 mm ；
1000×2000 mm, etc.
7.3 Length measurement of steel pipe
1) Generally, the diameter D, inner diameter and wall thickness s of steel pipe are calibrated in mm.
2) Each kind of steel pipe has different sizes, such as seamless steel pipe with outer diameter of 50 mm and wall thickness of 2.5-10 mm;
In other words, there are 29 species with the same wall thickness of 5 mm and outer diameter of 32-195 mm.
Another example is the welded steel pipe with a nominal diameter of 25 mm, including 3.25 mm ordinary steel pipe and 4 mm thickened steel pipe.