Seamless Steel Pipe Wall Thickness Variation Control Technology

Reducing the amount of variation, or achieving more wall thickness consistency, can be the difference between meeting a customer’s requirements or not. It also helps to reduce or even may eliminate the customer’s need for subsequent processes such as machining.

无缝管通常是在两卷式穿孔磨机上制造的。在某些情况下，仅此步骤就足以生产满足客户要求的管子。但是，如果穿刺后需要进一步改进墙壁厚度，则管生产商可以使用其他设备和过程步骤。两种类型的设备是交叉摇动的延伸器磨坊（通常以其商品名称而闻名，例如Assel或Diescher Mill）和冷水台。

Overview of the Three Process Steps

无缝的管制造通常始于穿孔厂中的热交叉。刺穿是用高质量墙壁制造管子的第一个过程步骤。此步骤通常是一个或多个伸长过程，可以提高壁质量，同时也可以增加管子长度。管离开无缝的磨坊并冷却后，它可以在冷拉台上完成，作为提高墙壁公差的第三步。

Piercer Mill.Most attention about seamless wall quality is directed at the piercer mill. This attention is justified because the piercer mill has the largest effect on wall variation. Tubing produced by a piercer mill can be optimized to 7 to 10 percent wall variation.

尽管刺穿的壳可能的壁变化可能小于10％，但对于相对较厚的墙壁，这种量的变化量。例如，实现±10％的壁耐力会产生一个管子厚度为13.5 mm（0.531英寸）至16.5 mm（0.650英寸）或更高的管子时，或以15毫米（0.590英寸）订购时。对于更严格的客户需求，可能需要通过延伸器磨坊进行进一步处理。

延伸器磨坊。管子生产工业中使用了五种主要类型的延伸厂：Mandrel Pipe Mill，推杆，插头厂，伸展式降低厂和交叉摇动的延伸器磨坊。五十年的整个行业用途表明，在这些延伸器磨坊中，交叉延伸的延伸器可在钢铁厂生产的管子的壁耐受性方面取得最大的改善。交叉滚动延伸器磨机使用OD上的工作卷和ID上的mandrel（请参阅Figure 1).

Cold Draw Bench.在长凳上绘制的是一种冷饰面方法，可改善无缝的管墙尺寸。在绘制的台式过程中，首先将管子松散地螺纹到连接到杆上的mandrel上。然后，钳子组件将管子握住，并将其拉到固定的碳化物或工具钢模中。结果是具有非常好的尺寸控制的定制管。典型的OD耐受性为±0.1 mm（±0.004英寸），大约是典型热填充无缝管的十分之一。

绘图过程带来的其他好处包括增强的表面饰面，提供ID公差的能力以及改进的机械性能。管produced with this process require minimal or additional processing and are considered value-added products.

Guidelines for Cross-roll Elongation

对于交叉延伸，两个主要要求与壳壳有关。这些将驼峰高度部分填充到其设计的80％至90％，并最大化入口侧握把。这两种要求都与Assel Mill中的卷通过设计有关。3

Figure 2
卷驼峰位于工作卷的中间。重要的是要将管道段与工作卷的设计功能相匹配。由俄亥俄州谢尔比·科波韦尔德（Copperweld）绘制。
Filling the Hump.驼峰是工作卷中部附近地区的一般术语，其中包含凸起的轮廓（请参阅Figure 2). Filling the hump is a matter of measuring the as-pierced wall and then comparing it to the known hump dimension from the print. The piercer mill is then adjusted to get the proper value. For example, if the hump design is 8 mm (0.315 in.), the as-pierced shell should measure 7 mm (0.276 in.) more than the customer size (because 7 is 90 percent of 8).

这种关系在薄壁管产生中很重要，因为机械管的壁耐受性是基于百分比的（每个ASTM标准A519）。薄壁管的公差很难实现，因为例如，5毫米（0.197英寸）的5％比10 mm的5％（0.394英寸）更紧密。试管生产商必须了解，如果磨坊能力为壁变化的1 mm（0.040英寸），则可以代表中壁部分的商业公差一半（CP值为2.0），而薄壁的耐受性变化不耐受。部分（CP小于1.0）。

穿孔厂的外壳需要减少壁厚，以确保适当的驼峰高度填充。对于非常薄壁的管道，制造商可能会发现，如果不能实现的话，交叉卷磨机的质量提高可能很难，因为刺穿的壳体的变化太大。对于某些管子尺寸，壁变化的百分比可能会增加，而不是在齿球厂中减少。通过仔细计算确定变异百分比。尽管总尺寸变化减少了分子，但分母以更大的速率降低，因为交叉延伸延伸器磨机的管的壁厚度比齿球磨机的管要比壁厚少50％至75％。

Cross-rolling Grip.The second requirement is to maintain the best grip in the cross-rolling process. Grip is defined as the number of tube spirals before the hump centerline in the cross-rolling elongator mill roll pass design—in simple terms, the pierced shell should contact the roll face early in the process so tube feed is established before it encounters the work zone in the hump section. The work done in the hump section requires an extreme amount of energy, up to several thousand horsepower. The work force is applied in a very short section, usually 15 to 25 mm (less than 1 in.) wide. If the tube is not gripped properly, it will spin rather than feed, or it may feed irregularly through the work zone, creating variation.

In most cases the best condition for the pierced shell is achieved by producing the maximum outside diameter that will properly fit into the cross-rolling elongator mill roll face. Usually this relationship is resolved by adjusting the piercer mill setup to produce the correct tube dimension. But in some cases it may be necessary to increase or decrease slightly the divergent angle of the elongator mill to ensure that the shell will fit and grip properly.

直接从延伸厂采集的管的壁质量进行的实验用于确定管子是否具有比通过尺寸磨坊或延伸降低磨坊进一步处理的试管更好的壁质量。据确定，在尺寸降低过程中，纵向和压缩力在壁上起作用，并可以增加壁变化。直接从交叉延伸延伸器磨机中取出的管具有较高的壁厚稠度和更好的表面质量，因为它们不暴露于尺寸磨坊中的滚动条件。但是，通过尺寸磨坊的管子可以通过在拉动长凳上的冷绘图来减少壁变化。

Guidelines for Cold Drawing

处理冷的无缝管的成功取决于从无缝热磨机中维持高壁质量，并正确选择了冷水台工具（Mandrel和Die Sets）。

Three main points that concern drawing pierced tube are:

• 需要减少一些墙壁，以确保在抽签开始时壁上咬在墙壁上，然后在抽签期间正确地坐在模具轴承中。如果传入的墙太不规则或太轻，则曼德尔将不会前进到模具轴承中，并且所得管将没有良好的外部尺寸，内部尺寸和壁厚的公差。
• Bench drawing is limited to a maximum 40 percent reduction in area. If the incoming wall is too heavy, it may cause the metal to fail rather than yield during drawing, especially for work-hardening alloy steel grades.
• 图是一个纵向过程。纠正严重纵向壁变化的潜力有限，因为模具和mandrel是自由浮动的，并且会遵循壁变化而不是纠正它。

可以通过选择最合适的模具配置文件来优化冷图（请参阅Figure 3). No single design works best for all seamless tubes because the design depends on many factors, such as wall thickness, steel grade, pass reduction requirements, and draw bench limitations.

Figure 3
Three main cold-drawing die profiles are radius, straight, and straight/radius blend, or combination

Three die profiles are:

• 半径模具 - 死亡入口是一个没有锐角或平坦表面的弧。
• Straight die—the die inlet has a flat, angular surface, typically 10 to 20 degrees per side.
• Combination die—the die inlet combines flat surfaces and radius blends.

For each production order drawn, a statistical control chart or Student t-test method can be completed and used to optimize the die profile and die dimension as a permanent record.

For most seamless tubes, a radius die produces the best wall quality. Because the radius die has a more gradual inlet profile and smooth blend into the bearing section, the tube draw is more consistent and results in higher-quality dimensions. But there is a drawback to this type of die: Because of the gradual inlet profile, only a small OD reduction can be made on the tube. The seamless tube must be customized to use this sort of die, adding changeover expense.

一致地实现一致性

实现一致性需要从完成到开始分析过程。成品的客户指定的墙壁厚度为通过Draw板台处理的管子提供了最终尺寸，该板将导致模具和Mandrel选择。此选择确定了从无缝磨机中的适当尺寸管，这决定了适当的设置和操作参数。