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    • 金属板材硬度的现场检测方法
    • 本站编辑:莱州市试验机金刚石工具厂发布日期:2018-12-13 14:01 浏览次数:


    1、无缝钢管常用的硬度指标

    无缝钢管一般常用布氏、洛氏、维氏三种硬度指标来衡量其硬度。

    1) 布氏硬度在无缝钢管标准中,布氏硬度用途最广,往往以压痕直径来表示该材料的硬度,既直观,又方便。但是对于较硬的或较薄的钢材的钢管不适用。

    2)洛氏硬度无缝钢管洛氏硬度试验同布氏硬度试验一样,都是压痕试验方法。不同的是,它是测量压痕的深度。洛氏硬度试验是目前应用很广的方法,其中HRC在钢管标准中使用仅次于布氏硬度HB。洛氏硬度可适用于测定由极软到极硬的金属材料,它弥补了布氏法的不足,较布氏法简便,可直接从硬度机的表盘读出硬度值。但是,由于其压痕小,故硬度值不如布氏法准确。

    3) 维氏硬度无缝钢管维氏硬度试验也是一种压痕试验方法,可用于测定很薄的金属材料和表面层硬度。它具有布氏、洛氏法的主要优点,而克服了它们的基本缺点,但不如洛氏法简便,维氏法在钢管标准中很少用。

    2、无缝钢管硬度检测方法

    不锈钢的硬度检测要考虑到它的力学性能,这关系到以不锈钢为原料而进行的变形、冲压、切削等加工的性能和质量。因此,所有的无缝钢管要进行力学性能测试。力学性能测试方法主要分两类,一类是拉伸试验,一类是硬度试验。

    拉伸试验是将无缝钢管制成试样,在拉伸试验机上将试样拉至断裂,然后测定一项或几项力学性能,通常仅测定抗拉强度、屈服强度、断后伸长率和断面收缩率。拉伸试验是金属材料最基本的力学性能试验方法,几乎所有的金属材料,只要对力学性能有要求,都规定了拉伸试验。特别是那些形状不便于进行硬度试验的材料,拉伸试验成为weiyi的力学性能检测手段。

    硬度试验是将一个硬质压头按规定条件缓慢压入试样表面、然后测试压痕深度或尺寸,以此确定材料硬度的大小。硬度试验是材料力学性能试验中最简单、最迅速、最易于实施的方法。硬度试验是非破坏性的,材料硬度值与抗拉强度值之间有近似的换算关系。材料的硬度值可以换算成抗拉强度值,这一点具有很大的实用意义。

    由于拉伸试验不便于测试,并且由硬度换算到强度很方便,因此人们越来越多地只测试材料硬度而较少测试其强度。特别是由于硬度计制造技术的不断进步和推陈出新,一些原来无法直接测试硬度的材料,如无缝钢管、不锈钢板和不锈钢带等,现在都已经可能直接测试硬度了。所以,存在一个硬度试验逐渐代替拉伸试验的趋势。

    在不锈钢材料的国家标准中大多数都同时规定了拉伸试验和硬度试验。对于那些不便于进行硬度试验的材料,例如无缝钢管就只规定了拉伸试验。在不锈钢标准中,一般都规定了布、洛、维三种硬度试验方法,测定HB、HRB(或HRC)和HV硬度值,规定三种硬度值只测其一即可。特别是本公司新型研制的便携式表面洛氏硬度计、管材洛氏硬度计,可以对薄至0.05mm的不锈钢板、不锈钢带以及细至¢4.8mm的无缝钢管进行快速、准确的硬度检测,使得过去在国内难以解决的问题迎刃而解。

     

    3、无缝钢管硬度检测工具

    无缝钢管的内径在6.0mm以上,壁厚在13mm以下的退火无缝钢管材,可以采用W-B75型韦氏硬度计,它测试非常快速、简便,适于对无缝钢管材做快速无损的合格检验。无缝钢管内径大于30mm,壁厚大于1.2mm的无缝钢管,采用洛氏硬度计,测试HRB、HRC硬度。无缝钢管内径大于30mm,壁厚小于1.2mm的无缝钢管,采用表面洛氏硬度计,测试HRT或HRN硬度。内径小于0mm,大于4.8mm的无缝钢管,采用管材专用洛氏硬度计,测试HR15T硬度。当无缝钢管内径大于26mm时,还可以用洛氏或表面洛氏硬度计测试管材内壁的硬度。

    二、焊管的硬度检测

    焊管是用钢板或钢带经过弯曲成型,然后经焊接制成。按焊缝形式分为直缝焊管和螺旋焊管。按用途又分为一般焊管、镀锌焊管、吹氧焊管、电线套管、公制焊管、托辊管、深井泵管、汽车用管、变压器管、电焊薄壁管、电焊异型管和螺旋焊管。 一般焊管:一般焊管用来输送低压流体。用Q195A、Q215A、Q235A钢制造 。也可采用易于焊接的其它软钢制造。钢管要进行水压、弯曲、压扁等实验,对表面质量有一定要求,通常交货长度为4-10m,常要求定尺(或倍尺)交货。焊管的规格用公称口径表示(毫米或英寸)公称口径与实际不同,焊管按规定壁厚有普通钢管和加厚钢管两种,钢管按管端形式又分带螺纹和不带螺纹两种。

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    Record: 1. Hardness Testing Method of Seamless Steel Pipe 2. Hardness Testing Method of Welded Pipe 3. Hardness Testing Method of Tin Matte

    4. Testing methods for die hardness and die steel hardness 5. On-site testing methods for strip steel hardness 6. Testing methods for hardness of heat-treated workpieces

    7. Testing methods for hardness of aluminium profiles 8. Testing methods for hardness of castings 9. Testing methods for hardness of stainless steel strips 10. Testing methods for hardness of stainless steel plates 1. Testing methods for hardness of seamless steel tubes

    1. Hardness Index of Seamless Steel Pipe

    The hardness of seamless steel pipe is generally measured by three hardness indexes, Brinell, Rockwell and Vickers.

    1) Brinell hardness is the most widely used standard for seamless steel pipe. It is often expressed by indentation diameter, which is both intuitive and convenient. But it is not suitable for steel pipes with harder or thinner steel.

    2) Rockwell hardness test of seamless steel pipe with Rockwell hardness is the same as Brinell hardness test, which is indentation test method. The difference is that it measures the depth of indentation. Rockwell hardness test is a widely used method at present. HRC is second only to Brinell hardness HB in steel pipe standard. Rockwell hardness can be applied to the determination of metal materials from very soft to very hard. It makes up for the shortcomings of the Brinell method. It is simpler than the Brinell method and can read the hardness value directly from the dial of the hardness machine. However, because of its small indentation, the hardness value is not as accurate as that of Brinell method.

    3) Vickers hardness test of seamless steel pipe with Vickers hardness is also an indentation test method, which can be used to measure the hardness of very thin metal materials and surface layer. It has the main advantages of Brinell's method and Rockwell's method, and overcomes their basic shortcomings, but it is not as simple as Rockwell's method, and Vickers method is seldom used in steel pipe standards.

    2. Hardness Testing Method of Seamless Steel Tube

    Hardness testing of stainless steel should consider its mechanical properties, which is related to the properties and quality of deformation, stamping and cutting of stainless steel as raw materials. Therefore, all seamless steel tubes should be tested for mechanical properties. There are two kinds of testing methods for mechanical properties, one is tensile test and the other is hardness test.

    Tensile test is to make seamless steel tubes into specimens. The specimens are pulled to fracture on a tensile testing machine, and then one or several mechanical properties are measured. Usually, only tensile strength, yield strength, elongation after breaking and section shrinkage are measured. Tensile test is the most basic test method of mechanical properties of metal materials. Almost all metal materials, as long as the mechanical properties are required, have stipulated the tensile test. Especially for those materials whose shape is not easy to carry out hardness test, tensile test has become a means of Weiyi's mechanical properties testing.

    Hardness test is to determine the hardness of the material by slowly pressing a hard indenter into the surface of the sample under specified conditions and then testing the indentation depth or size. Hardness test is the simplest, quickest and easiest method in material mechanical property test. Hardness test is non-destructive, and there is an approximate conversion relationship between hardness and tensile strength. The hardness value of the material can be converted into the tensile strength value, which has great practical significance.

    Due to the inconvenience of tensile test and the convenience of conversion from hardness to strength, more and more people only test the hardness of materials and less test their strength. Especially due to the continuous progress and innovation of hardness tester manufacturing technology, some materials which could not directly test hardness, such as seamless steel pipe, stainless steel plate and stainless steel strip, are now possible to directly test hardness. Therefore, there is a tendency that the hardness test will gradually replace the tensile test.

    Tensile test and hardness test are stipulated in most national standards for stainless steel. For materials that are not easy to carry out hardness tests, such as seamless steel tubes, only tensile tests are required. In the standard of stainless steel, three hardness test methods of cloth, lol and vitamin D are generally stipulated. The hardness values of HB, HRB (or HRC) and HV are determined. It is stipulated that only one of the three hardness values can be measured. In particular, the company's new portable surface Rockwell hardness tester, pipe Rockwell hardness tester, can be thin to 0.05mm stainless steel plate, stainless steel strip and fine to 4.8mm seamless steel tube for rapid and accurate hardness testing, making the past difficult problems in China to solve.

    3. Hardness Testing Tool for Seamless Steel Pipe

    W-B75 type Wechsler hardness tester can be used for annealed seamless steel pipe whose inner diameter is more than 6.0 mm and wall thickness is less than 13 mm. This tester is very fast and simple, and is suitable for rapid and non-destructive inspection of seamless steel pipe. Seamless steel tubes with inner diameter greater than 30 mm and wall thickness greater than 1.2 mm are tested by Rockwell hardness tester for HRB and HRC hardness. Seamless steel tubes with inner diameter greater than 30 mm and wall thickness less than 1.2 mm are tested by surface Rockwell hardness tester for HRT or HRN hardness. Seamless steel pipe with inner diameter less than 0 mm and larger than 4.8 mm is tested by Rockwell hardness tester. When the inner diameter of seamless steel tube is larger than 26 mm, Rockwell hardness tester or surface Rockwell hardness tester can also be used to test the hardness of the inner wall of the tube.

    Hardness Testing of Welded Pipe

    Welded pipe is made of steel plate or strip after bending and welding. According to the weld form, it can be divided into straight welded pipe and spiral welded pipe. According to its use, it can be divided into general welded pipe, galvanized welded pipe, oxygen-blowing welded pipe, wire sleeve, metric welded pipe, idler pipe, deep well pump pipe, automobile pipe, transformer pipe, welded thin-walled pipe, welded special-shaped pipe and spiral welded pipe. General welded pipe: General welded pipe is used to transport low-pressure fluid. Using Q195A and Q2