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  • 改善方管带状组织的四种方法
  • 本站编辑:杭州双惠金属材料有限公司发布日期:2019-07-17 10:54 浏览次数:

带状组织是钢材内部的一种缺陷,可分为一次带状组织和二次带状组织。带状组织的存在使钢的组织不均匀,并严重影响方管性能,降低其塑性、冲击韧性、断裂韧性和断面收缩率,造成冷弯不合、冲压废品率高。并且在进行热处理时,方管容易变形、淬火开裂。要改善这一问题,我们可以采取以下四种方法:

The banded structure is a kind of defect in steel, which can be divided into primary banded structure and secondary banded structure. The existence of banded structure makes the structure of steel uneven, and seriously affects the properties of square tube, reduces its plasticity, impact toughness, fracture toughness and section shrinkage, resulting in cold bending incompatibility and high scrap rate of stamping. The square pipe is easy to deform and crack during quenching. To improve this problem, we can adopt the following four methods:

一轧钢工艺

No.1 rolling process

一次带状组织是在连铸过程中出现的,但采用合理的轧钢工艺可有效抑制二次带状组织的出现。轧钢工艺中加热制度、开轧温度、变形量、终轧温度和冷却速度等参数尤为重要。通过铸坯加热,可对铸态组织的成分偏析起到均匀化作用,也可以方管降低轧制过程的变形抗力。在允许的条件下,都尽可能采用较高的加热温度,而且还要保证足够的加热时间。

The primary strip structure occurs in the continuous casting process, but the secondary strip structure can be effectively restrained by adopting reasonable rolling process. The parameters such as heating system, start-up temperature, deformation, final rolling temperature and cooling rate are particularly important in rolling process. By heating the billet, the composition segregation of as-cast structure can be homogenized, and the deformation resistance of square tube during rolling can also be reduced. Under permissible conditions, higher heating temperature should be adopted as far as possible, and enough heating time should be ensured.

二钢种成分

Composition of No.2 Steel

钢种成分设计的方面,要妥善处理升高转变温度的元素和降低转变温度的元素之间的关系。合金元素对转变温度是相互作用、相互影响的,如果能使几种元素的影响相互抵消,减小枝晶间和枝晶内转变温度的差异,就能减轻方管的带状组织。

In the aspect of steel grade composition design, the relationship between elements that increase transformation temperature and elements that decrease transformation temperature should be properly handled. The effect of alloying elements on transformation temperature is interaction and interaction. If the influence of several elements can be counteracted and the difference of transformation temperature between dendrites and within dendrites can be reduced, the banded structure of square tubes can be alleviated.

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三热处理工艺

THREE HEAT TREATMENT TECHNOLOGY

方管在退火过程中,由于随炉冷却,使先共析铁素体析出充分,加重带状组织级别。在正火过程中,冷速较快,可以减轻带状组织。采用等温正火工艺时,将钢材加热保温一段时间,快速冷却到珠光体转变区的某一温度,然后进行保温使其完成铁素体和珠光体的均匀转变,随后在空气中进行冷却。

In the annealing process of square tubes, the pre-eutectoid ferrite precipitates sufficiently and the banded structure grade is aggravated due to furnace cooling. In the normalizing process, the cooling rate is faster, which can reduce the banded structure. When isothermal normalizing process is adopted, the steel is heated and heated for a period of time, and rapidly cooled to a certain temperature in the pearlite transition zone. Then the uniform transformation of ferrite and pearlite is completed by thermal insulation, and then cooled in air.

四连铸工艺

Four Continuous Casting Process

钢材轧后出现的带状组织主要来源于连铸坯中产生的枝晶偏析,控制连铸坯的枝晶偏析和促进元素的均匀分布是减轻或消除带状组织的有效方法。从连铸工艺来看,扩大等轴晶区的范围和获得细小的二次枝晶能有效控制枝晶偏析。通过合理控制浇注温度并保持恒定的速度浇注,能有效增大等轴晶区域。另外,采制定合理的二冷工艺,控制二冷区各段冷却水量的大小,可以控制方管表面温度,使其冷却均匀,也可以得到大区域的等轴晶。

The strip structure of steel after rolling mainly comes from dendrite segregation in continuous casting slab. Controlling dendrite segregation in continuous casting slab and promoting the uniform distribution of elements are effective ways to reduce or eliminate strip structure. From the point of view of continuous casting technology, the dendrite segregation can be effectively controlled by enlarging the equiaxed zone and obtaining fine secondary dendrites. By controlling the pouring temperature reasonably and keeping constant pouring speed, the equiaxed grain region can be effectively enlarged. In addition, reasonable secondary cooling technology is adopted to control the cooling water volume in each section of the secondary cooling zone. The surface temperature of square tubes can be controlled to make the cooling uniform, and the equiaxed crystals in large areas can also be obtained.